1. If two bulbs are connected in parallel and one bulb blows out, what happens to the other bulb?
(A) The other bulb blows out as well
(B) The other bulb continues to glow with the same brightness
(C) The other bulb glows with increased brightness
(D) The other bulb stops glowing
Answer: (B) The other bulb continues to glow with the same brightness
Explanation:
If one bulb blows out, it acts as an open circuit. Current does not flow in that branch but it continues to flow in the other branch of the parallel circuit. Hence the other bulb continues to glow. Also the voltage across other bulb remains the same due to which power delivered to it remains the same so it continues to glow with the same brightness.
2. In a parallel circuit, with a number of resistors, the voltage across each resistor is ________
(A) The same for all resistors
(B) Is divided equally among all resistors
(C) Is divided proportionally across all resistors
(D) Is zero for all resistors
Answer: (A) The same for all resistors
Explanation:
In parallel circuits, the current across the circuits vary whereas the voltage remains the same.
3. The current in each branch of a parallel circuit is proportional to _________
(A) The amount of time the circuit is on for
(B) Proportional to the value of the resistors
(C) Equal in all branches
(D) Proportional to the power in the circuit
Answer: (B) Proportional to the value of the resistors
Explanation:
I=V/R. In a parallel circuit, the voltage across each resistor is equal, hence the value of the current is proportional (inversely) to the value of the resistance.
4․ If 1 A current flows in a circuit, the number of electrons flowing through this circuit is
(A) 0.625 × 1019
(B) 1.6 × 1019
(C) 1.6 × 10-19
(D) 0.625 × 10-19
Ans: (C) 1.6 × 10-19
Explanation:
The charge of one electron is 1.6 × 10-19 coulomb. Again 1 A current means transferring of 1 coulomb charge per one second.
5. The currents in the three branches of a parallel circuit are 3A, 4A and 5A. What is the current leaving it?
(A) 0A
(B) Insufficient data provided
(C) The largest one among the three values
(D) 12A
Answer: (D) 12A
Explanation:
The total current leaving a node is the same as the current that enters it. Total I=I1+I2+I3=3+4+5=12A.
6․ The resistivity of the conductor depends on
(A) area of the conductor.
(B) length of the conductor.
(C) type of material.
(D) none of these.
Ans: (C) type of material.
Explanation:
The resistivity is a property of a material, defined as the resistance between two opposite faces of a cube of a material of unit volume. That is why resistivity is only the unique property of a material and it does not depend upon the dimension of any piece of material.
The same can also be explained as
Where, ρ is the resistivity; m and e is the mass and charge of an electron; T is the relaxation time. All these are properties of a material and independent of length and cross-sectional area.
7․ The resistance of a conductor of diameter d and length l is R Ω. If the diameter of the conductor is halved and its length is doubled, the resistance will be
(A) R Ω
(B) 2R Ω
(C) 4R Ω
(D) 8R Ω
Ans: (D) 8R Ω
Explanation:As per law of resistance, the resistance of the conductor is inversely proportional to its cross-sectional area i.e. it is inversely proportional to the square of the diameter of the cross-sectional area of the conductor. As per same law of resistance, the resistance of the conductor is directly proportional to the length of the conductor.
8. It is preferable to connect bulbs in series or in parallel?
(A) Series
(B) Parallel
(C) Both series and parallel
(D) Neither series nor parallel
Answer: (B) Parallel
Explanation:
Bulbs are connected in parallel so that even if one of the bulbs blow out, the others continue to get a current supply.
9. Batteries are generally connected in______
(A) Series
(B) Parallel
(C) Either series or parallel
(D) Neither series nor parallel
Answer: (A) Series
Explanation:
Batteries are generally connected in series so that we can obtain the desired voltage since voltages add up once they are connected in series.
10. In a _________ circuit, the total resistance is greater than the largest resistance in the circuit.
(A) Series
(B) Parallel
(C) Either series or parallel
(D) Neither series nor parallel
Answer: (A) Series
Explanation:
In series circuits, the total resistance is the sum of all the resistance in the circuit, hence the total is greater than the largest resistance.
11․ How many coulombs of charge flow through a circuit carrying a current of 10 A in 1 minute?
(A) 10
(B) 60
(C) 600
(D) 1200
Ans: (C) 600
Explanation:
1 Ampere current means flowing of 1 Coulomb charge per second. That means 10 A current in 1 minute or 60 seconds implies 10 × 60 = 600 coulombs.
12․ A capacitor carries a charge of 0.1 C at 5 V. Its capacitance is
(A) 0.02 F
(B) 0.5 F
(C) 0.05 F
(D) 0.2 F
Ans: (A) 0.02 F
Explanation:
The capacitance of a capacitor is expressed by Q/V. Where Q is the charge of the capacitor and V is the voltage across the capacitor.
13. In a ____________ circuit, the total resistance is smaller than the smallest resistance in the circuit.
(A) Series
(B) Parallel
(C) Either series or parallel
(D) Neither series nor parallel
Answer: (B) Parallel
Explanation:
In a parallel circuit, the equivalent resistance=1/sum of the reciprocals of all the resistances in the circuit. Hence it is smaller than the smallest resistance in the circuit.
14. Which is the most cost efficient connection?
(A) Series
(B) Parallel
(C) Either series or parallel
(D) Neither series nor parallel
Answer: (A) Series
Explanation:
The advantage of series connections is that they share the supply voltage, hence cheap low voltage appliances may be used.
15. What is the value of current if a 50C charge flows in a conductor over a period of 5 seconds?
(A) 5A
(B) 10A
(C) 15A
(D) 20A
Answer: (B) 10A
Explanation:
Current=Charge/Time.
Here charge = 50c and time = 5seconds,
so current = 50/5 = 10A.
16. KCL deals with the conservation of?
(A) Momentum
(B) Mass
(C) Potential Energy
(D) Charge
Answer: (D) Charge
Explanation:
KCL states that the amount of charge entering a junction is equal to the amount of charge leaving it, hence it is the conservation of charge.
17․ To obtain a high value of capacitance, the permittivity of the dielectric medium should be
(A) low
(B) zero
(C) high
(D) unity
Ans: (C) high
Explanation:
The expression of capacitance is given as
Where ε is the permittivity of the medium. Hence it is seen that the capacitance of a capacitor is directly proportional to the permittivity of the medium used as the dielectric. Therefore, to obtain a high value of capacitance, the permittivity of the dielectric medium should be high.
18․ Four capacitors each of 40 µF are connected in parallel, the equivalent capacitance of the system will be
(A) 160 µF
(B) 10 µF
(C) 40 µF
(D) 5 µF
Ans: (A) 160 µF
Explanation:The impedance of a capacitor is inversely proportional to its capacitance value. Reciprocal of equivalent impedance of parallel connected circuit elements is sum of reciprocal of impedance of each of the elements.
19. KCL is applied at _________
(A) Loop
(B) Node
(C) Both loop and node
(D) Neither loop nor node
Answer: (B) Node
Explanation:
KCL states that the amount of charge leaving a node is equal to the amount of charge entering it, hence it is applied at nodes.
20. KCL can be applied for __________
(A) Planar networks
(B) Non-planar networks
(C) Both planar and non-planar
(D) Neither planar nor non-planar
Answer: (C) Both planar and non-planar
Explanation:
KCL is applied for different nodes of a network whether it is planar or non-planar.
21. KVL deals with the conservation of?
(A) Mass
(B) Momentum
(C) Charge
(D) Energy
Answer: (D) Energy
Explanation:
KVL states that the sum of the potential energy and taken with the right sign is equal to zero, hence it is the conservation of energy since energy doesn’t enter or leave the system.
22. The sum of the voltages over any closed loop is equal to __________
(A) 0V
(B) Infinity
(C) 1V
(D) 2V
Answer: (A) 0V
Explanation:
According to KVL, the sum of the voltage over any closed loop is equal to 0.
23․ Five capacitors each of 5 µF are connected in series, the equivalent capacitance of the system will be
(A) 5 µF
(B) 25 µF
(C) 10 µF
(D) 1 µF
Ans: (D) 1 µF
Explanation:
When numbers of circuit elements are connected in series, the impedance of equivalent combination is sum of impedance of all elements in series. Again, capacitance is inversely proportional to impedance. Hence, when capacitors are connected in series
(A) 1 ohm of resistance
(B) ratio of 1 V to 1 C
(C) ratio of 1 C to 1 V
(D) none of these
Ans: (C) ratio of 1 C to 1 V
Explanation:
1 Farad capacitance is defined as the capacity of dielectric medium to store 1 Coulomb charge when 1 Volt potential difference is applied across it. Thus, capacitance is expressed as the ratio of charge to voltage (Q = CV).
25. What is the basic law that has to be followed in order to analyze the circuit?
(A) Newton’s laws
(B) Faraday’s laws
(C) Ampere’s laws
(D) Kirchhoff’s law
Answer: (D) Kirchhoff’s law
Explanation:
Kirchhoff’s laws, namely Kirchhoff’s Current Law and Kirchhoff’s Voltage law are the basic laws in order to analyze a circuit.
26. Every____________ is a ____________ but every __________ is not a __________
(A) Mesh, loop, loop, mesh
(B) Loop, mesh, mesh, loop
(C) Loop, mesh, loop, mesh
(D) Mesh, loop, mesh, loop
Answer: (A) Mesh, loop, loop, mesh
Explanation:
According to Kirchhoff’s Voltage Law, Every mesh is a loop but every loop is not a mesh. Mesh is a special case of loop which is planar.
27. KVL is applied in ____________
(A) Mesh analysis
(B) Nodal analysis
(C) Both mesh and nodal
(D) Neither mesh nor nodal
Answer: (A) Mesh analysis
Explanation:
Mesh analysis helps us to utilize the different voltages in the circuit as well as the IR products in the circuit which is nothing but KVL.
28. Which of the following is not an expression power?
(A) P=VI
(B) P=I2R
(C) P=V2/R
(D) P=I/R
Answer: (D) P=I/R
Explanation:
Power is the product of voltage and current. Writing I in terms of V, we get P=V2/R and writing V in terms of I, we get P=I2r.
29․ The unit of resistivity is
(A) Ω.
(B) Ω - metre.
(C) Ω / metre.
(D) Ω / m².
Ans: (B) Ω – metre
Explanation:
(A) Ω.
(B) Ω - metre.
(C) Ω / metre.
(D) Ω / m².
Ans: (B) Ω – metre
Explanation:
30․ Instantaneous power in inductor is proportional to the
(A) product of the instantaneous current and rate of change of current.
(B) square of instantaneous current.
(C) square of the rate of change of current.
(D) the temperature of the inductor.
Ans:(A) product of the instantaneous current and rate of change of current.
Explanation:
The instantaneous voltage across the inductor is expressed as the product of inductance and rate of change of current through it. Power is expressed as the product of current and voltage. Hence instantaneous power in an inductor is proportional to the product of instantaneous current and rate of change of current through it.
31․ The voltage induced in an inductor is represented as,
(A) product of its inductance and current through it.
(B) ratio of its inductance to current through it.
(C) ratio of current through it to its inductance.
(D) product of its inductance and rate of change of current through it.
Ans: (D) product of its inductance and rate of change of current through it.
Explanation:
The instantaneous voltage across the inductor is expressed as the product of inductance and a rate of change of current through it as it doesn't allow any certain change of current through it. Voltage induced in an inductor is written as
32. Which of the following statements are true?
(A) Power is proportional to voltage only
(B) Power is proportional to current only
(C) Power is neither proportional to voltage nor to the current
(D) Power is proportional to both the voltage and current
Answer: (D) Power is proportional to both the voltage and current
Explanation:
Power is proportional to both voltage and current.
33. A 250V bulb passes a current of 0.3A. Calculate the power in the lamp.
(A) 75W
(B) 50W
(C) 25W
(D) 90W
Answer: (A) 75W
Explanation:
Here, V = 250v and I = 0.3A.
P=VI.
Which implies that,
P=250*0.3=75W.
34. Kilowatt-hour(kWh) is a unit of?
(A) Current
(B) Power
(C) Energy
(D) Resistance
Answer: (C) Energy
Explanation:
Power is the energy per unit time. That is, P=E/t. If the unit of power in kW and the unit of time is an hour,
then the unit of energy=unit of power*unit of time=kWh.
35. Calculate the work done in a resistor of 20 ohm carrying 5A of current in 3 hours.
(A) 1.5J
(B) 15J
(C) 1.5kWh
(D) 15kWh
Answer: (C) Energy
Explanation:
To find power: P=I2R=52*20=500W=0.5kW.
To find Work done: W=Pt=0.5*3=1.5kWh.
36. The SI unit of power is?
(A) kW(kilo-watt)
(B) J/s(joules per second)
(C) Ws(watt-second)
(D) J/h(joules per hour
Answer: (B) J/s(joules per second)
Explanation:
Power = energy/time
SI unit of power = SI unit of energy/SI unit of time = joule/second.
37․ Absolute permittivity of dielectric medium is represented as
(A) ε0
(B) εr
(C) εr/ε0
(D) εrε0
Ans: (D) εrε0
Explanation:
The relative permittivity (εr) of the medium is defined as the ratio of actual permittivity of the medium to the absolute permittivity of air or vacuum. Absolute permittivity of air or vacuum is expressed as ε0. Hence the absolute permittivity of dielectric medium is represented as the product of relative permittivity of the medium and absolute permittivity of air or vacuum.
(A) ε0
(B) εr
(C) εr/ε0
(D) εrε0
Ans: (D) εrε0
Explanation:
The relative permittivity (εr) of the medium is defined as the ratio of actual permittivity of the medium to the absolute permittivity of air or vacuum. Absolute permittivity of air or vacuum is expressed as ε0. Hence the absolute permittivity of dielectric medium is represented as the product of relative permittivity of the medium and absolute permittivity of air or vacuum.
38․ Magnetic flux has the unit of
(A) Newton
(B) Ampere turn
(C) Weber
(D) Tesla
Ans:(C) Weber
Explanation:
The unit of magnetic flux is called Weber in honor of famous scientist Wilhelm Eduard Weber (1804 – 1891). Magnetic flux has also another unit named Maxwell. 1 Maxwell = 10-8 Weber.
39․ If all the elements in a particular network are linear, then the superposition theorem would hold, when the excitation is
(A) DC only
(B) AC only
(C) Either AC or DC
(D) An Impulse
Ans:(C) Either AC or DC
Explanation:
Superposition theorem can be applied for both AC as well DC excitation to calculate the voltage or current calculations. It holds for both DC and AC excitation, if the circuit is linear. But superposition theorem is not applicable for power calculations.
40․ In balanced bridge, if the positions of detector and source are interchanged, the bridge will still remain balanced. This can be explained from which theoem
(A) Reciprocity theorem
(B) Thevinin's theorem
(C) Norton's theorem
(D) Compensation theorem
Ans: (A) Reciprocity theorem
Explanation:
When response to excitation is constant even though we interchange the excitation and responses then the reciprocity theorem is verified for the given network.
41. Which among the following is a unit for electrical energy?
(A) V(volt)
(B) kWh(kilowatt-hour)
(C) Ohm
(D) C(coloumb)
Answer: (B) kWh(kilowatt-hour)
Explanation:
Kilowatt is a unit of power and hour is a unit of time. Energy is the product of power and time, hence the unit for Energy is kWh.
42. A bulb has a power of 200W. What is the energy dissipated by it in 5 minutes?
(A) 60J
(B) 1000J
(C) 60kJ
(D) 1kJ
Answer: (C) 60kJ
Explanation:
Here, Power = 200w and time = 5min.
E=Pt => E= 200*5= 1000Wmin=60000Ws= 60000J= 60kJ.
43. Out of the following, which one is not a source of electrical energy?
(A) Solar cell
(B) Battery
(C) Potentiometer
(D) Generator
Answer: (C) Potentiometer
Explanation:
Solar cell converts light energy to electrical energy. Battery converts chemical energy to electrical energy. Generator generates electrical energy using electromagnetic induction. A potentiometer is an instrument used for measuring voltage and consumes electrical energy instead of generating it.
44. Which among the following is an expression for energy?
(A) V2It
(B) V2Rt
(C) V2t/R
(D) V2t2/R
Answer: (C) V2t/R
Explanation:
Expression for power = VI, substituting I from ohm’s law we can write, P=V2/R. Energy is the product of power and time, hence E=Pt = V2t/R.
45. A battery converts___________
(A) Electrical energy to chemical energy
(B) Chemical energy to electrical energy
(C) Mechanical energy to electrical energy
(D) Chemical energy to mechanical energy
Answer: (B) Chemical energy to electrical energy
Explanation:
A battery is a device in which the chemical elements within the battery react with each other to produce electrical energy.
46․ If P is the power of a star connected system then what will be the power of an equivalent delta connected system?
(A) P
(B) 3P
(C) P/3
(D) None of the above
Ans: (A) P
47․ Which of the followings is/are active element?
(A) Voltage source
(B) Current source
(C) Both
(D) None of these.
Ans:(C) Both
Explanation:
Active elements are capable of delivering energy independently for long time or ideally infinite time. Both voltage and current source are active element and they can change energy level of a circuit.
48․ Which of the following are the passive elements?
(A) Resistor
(B) Bulb
(C) Both
(D) None of these.
Ans: (C) Both
Explanation:
When the element is not capable of delivering energy independently, are called as passive element. Both resistor and bulb are the passive elements and they can't increase the energy level of a circuit.
49․ Power dissipation in ideal inductor is
(A) Maximum
(B) Minimum
(C) Zero
(D) A finite value
Ans:(C) Zero
Explanation:
Internal resistance of ideal inductor is zero. As there is no resistance, there should not be any dissipation of power. Pure inductor has no resistive component, so it active power dissipation is zero.
50․ Inductor does not allow the sudden change of
(A) current
(B) voltage
(C) power
(D) None of the above
Ans: (A) current
Explanation:
Voltage developed across an inductor is expressed by
(A) P
(B) 3P
(C) P/3
(D) None of the above
Ans: (A) P
Explanation:
The power in both of the connections is same either it is connected in Star or Delta.
47․ Which of the followings is/are active element?
(A) Voltage source
(B) Current source
(C) Both
(D) None of these.
Ans:(C) Both
Explanation:
Active elements are capable of delivering energy independently for long time or ideally infinite time. Both voltage and current source are active element and they can change energy level of a circuit.
48․ Which of the following are the passive elements?
(A) Resistor
(B) Bulb
(C) Both
(D) None of these.
Ans: (C) Both
Explanation:
When the element is not capable of delivering energy independently, are called as passive element. Both resistor and bulb are the passive elements and they can't increase the energy level of a circuit.
49․ Power dissipation in ideal inductor is
(A) Maximum
(B) Minimum
(C) Zero
(D) A finite value
Ans:(C) Zero
Explanation:
Internal resistance of ideal inductor is zero. As there is no resistance, there should not be any dissipation of power. Pure inductor has no resistive component, so it active power dissipation is zero.
50․ Inductor does not allow the sudden change of
(A) current
(B) voltage
(C) power
(D) None of the above
Ans: (A) current
Explanation:
Voltage developed across an inductor is expressed by
Sudden change of current means di will change at dt → 0 (dt tends to zero), so sudden change of current means infinite voltage. Therefore it is not possible.
51. A current of 2A flows in a wire offering a resistance of 10ohm. Calculate the energy dissipated by the wire in 0.5 hours.
(A) 72Wh
(B) 72kJ
(C) 7200J
(D) 72kJh
Answer: (B) 72kJ
Explanation:
Here I (current) = 2A and Resistance(R) = 10ohm.
Power = I2R = 22*10=40.
Energy = Pt = 40*0.5*60*60 = 72000J=72kJ.
52. Practically, if 10kJ of energy is supplied to a device, how much energy will the device give back?
(A) Equal to10kJ
(B) Less than 10kJ
(C) More than 10kJ
(D) Zero
Answer: (B) Less than 10kJ
Explanation:
Practically, if 10kJ of energy is supplied to a system, it returns less than the supplied energy because, some of the energy is lost as heat energy, sound energy etc.
53. Materials which easily allow the passage of electric current are known as ______
(A) Insulators
(B) Conductors
(C) Dielectrics
(D) Semi-conductors
Answer: (B) Conductors
Explanation:
Conductors are materials(mostly metals), which freely allow the passage of electrons through it. If electrons can flow freely through a material, it implies that even current can flow freely through that material since current is the rate of flow of electrons.
54. A wire of length 2m and another wire of length 5m are made up of the same material and have the same area of cross section, which wire has higher resistance?
(A) Both have equal resistance
(B) The 2m wire has higher resistance
(C) The 5m wire has higher resistance
(D) The value of resistance cannot be determined from the given data
Answer: (C) The 5m wire has higher resistance
Explanation:
Resistance is directly proportional to the length of the wire, hence as the length of the wire increases, resistance increases.
55. A wire having an area of cross section = 10sqm and another wire having an area of cross section= 15sqm, have the same length and are made up of the same material. Which wire has more resistance?
(A) Both have equal resistance
(B) The 10sqm wire has higher resistance
(C) The 15sqm wire has higher resistance
(D) The value of resistance cannot be determined from the given data
Answer: (B) The 10sqm wire has higher resistance
Explanation:
Resistance is inversely proportional to the area of cross-section. As an area of cross-section increases, resistance decreases. Hence the 10sqm wire has a higher resistance than the 15sqm wire.
56. Which of the following statements are true with regard to resistance?
(A) Resistance is directly proportional to a length of the wire
(B) Resistance is directly proportional to an area of cross section of the wire
(C) Resistance is inversely proportional to the length of the wire
(D) Resistance is inversely proportional to the resistivity of the wire
Answer: (A) Resistance is directly proportional to a length of the wire
Explanation:
The expression for resistance is: Resistance=Resistivity*length of wire/ area of cross section of the wire. Hence resistance is directly proportional to length.
57․ Capacitor does not allow the sudden change of
(A) current
(B) voltage
(C) power
(D) None of the above
Ans: (B) Voltage
(A) current
(B) voltage
(C) power
(D) None of the above
Ans: (B) Voltage
Explanation:
The expression of current through a capacitor is
i = C dv/dt.
1. For sudden change of voltage infinite current is required. But practically it is not possible.
2. Practical capacitor circuit has finite value of time constant
58․ Internal resistance of ideal voltage source is
(A) zero
(B) infinite
(C) finite
(D) 100 ohms
Ans: (A) Zero
Explanation:
Ideal voltage source delivers energy at specified voltage, which is independent of current delivered. So voltage drop is zero and then resistance is zero. Its internal series resistance must be minimum to delivered maximum voltage.
(A) zero
(B) infinite
(C) finite
(D) 100 ohms
Ans: (B) Infinite
Explanation:
Ideal current source delivers energy at specified current, which is independent on voltage across the load. The internal resistance must become very high to deliver maximum current.
60. A wire has the same resistance as the one given in the figure. Calculate its resistivity if the length of the wire is 10m and its area of cross section is 2m.
(A) 16 ohm-metre
(B) 8 ohm-metre
(C) 16 kiloohm-metre
(D) 8 kiloohm-metre
Answer: (B) 8 ohm-metre
Explanation:
From the given circuit, R=V/I = 200/5 = 40ohm.
Resistivity= Resistance*Area of cross section/ Length of the wire.
Resistivity= 40*2/10= 8 ohm-metre.
61. Which, among the following is a unit for resistivity?
(A) ohm/metre
(B) ohm/metre2
(C) ohm-metre
(D) ohm-metre2
Answer: (C) ohm-metre
Explanation:
Resistivity = Resistance* Length/area of cross section.
Unit of resistivity = ohm*(m2)/m = ohm-m.
62. What is the resistivity of Copper?
(A) 1.59*10-8ohm-m
(B) 2.7*10-8ohm-m
(C) 7.3*10-8ohm-m
(D) 5.35*10-8ohm-m
Answer: (A) 1.59*10-8ohm-m
Explanation:
Resistivity is a material property. Different materials have different resistivity. Resistivity of copper is 1.72*10-8 ohm-m.
63․ Nodal analysis can be applied for
(A) planar networks.
(B) non planar networks.
(C) both planar and non planar networks.
(D) neither planar and non planar networks.
Ans: (C) both planar and non planar networks.
Explanation:
Nodal analysis is applied at different nodes of an electric network. So there is no problem with the planar or non planar circuits, so this is applicable for both planar and non planar networks.
64․ Mesh analysis is applicable for
(A) planar networks.
(B) non planar networks.
(C) both planar and non planar networks.
(D) neither planar and non planar networks..
Ans:(A) planar networks.
Explanation:
Mesh analysis is nothing but loop analysis, this is applied for different loops in the network and the network should be planar network. Non planar networks can't form loop equation.
65․ Super position theorem is not applicable for
(A) current calculations.
(B) voltage calculations.
(C) power calculations.
(D) None of the above.
Ans: (C) power calculations.
66․ To apply reciprocity theorem response to excitation ratio is
(A) Ohm.
(B) Mho.
(C) No units.
(D) Either Ohm or Mho.
Ans:(D) Either Ohm or Mho.
Explanation:
Conditions to apply reciprocity theorem are
1. Response to excitation ratio should be either Ohm or Mho.
2. Network should consists of one independent source only.
3. When a network have many dependent sources, reciprocity theorem can't be applied.
(A) planar networks.
(B) non planar networks.
(C) both planar and non planar networks.
(D) neither planar and non planar networks.
Ans: (C) both planar and non planar networks.
Explanation:
Nodal analysis is applied at different nodes of an electric network. So there is no problem with the planar or non planar circuits, so this is applicable for both planar and non planar networks.
64․ Mesh analysis is applicable for
(A) planar networks.
(B) non planar networks.
(C) both planar and non planar networks.
(D) neither planar and non planar networks..
Ans:(A) planar networks.
Explanation:
Mesh analysis is nothing but loop analysis, this is applied for different loops in the network and the network should be planar network. Non planar networks can't form loop equation.
65․ Super position theorem is not applicable for
(A) current calculations.
(B) voltage calculations.
(C) power calculations.
(D) None of the above.
Ans: (C) power calculations.
Explanation:
Super position theorem is used for calculation of voltage and currents only. It is not applicable for power calculations. Superposition theorem states that, in any linear bidirectional circuit having more than one independent source, the response in any one of the branches equal to algebraic sum of responses caused by individual sources, while the rest of the sources are replaced by its internal resistance. Therefore superposition theorem is only applicable for linear quantities. Whereas power is a non linear quantity.
P = I2R
So superposition theorem is not applicable for power calculations.
66․ To apply reciprocity theorem response to excitation ratio is
(A) Ohm.
(B) Mho.
(C) No units.
(D) Either Ohm or Mho.
Ans:(D) Either Ohm or Mho.
Explanation:
Conditions to apply reciprocity theorem are
1. Response to excitation ratio should be either Ohm or Mho.
2. Network should consists of one independent source only.
3. When a network have many dependent sources, reciprocity theorem can't be applied.
67. Calculate the ratio of the resistivity of 2 wires having the same length and same resistance with area of cross section 2m2 and 5m2 respectively.
(A) 5:7
(B) 2:7
(C) 2:5
(D) 7:5
Answer: (C) 2:5
Explanation:
Resistivity = R*A/L
Since resistance and length of the two wires are same so resistivity is directly proportional to area of cross section. Ratio of area is 2:5 so the ratio of resistivity is also 2:5.
68. Which of the following statements are true with regard to resistivity?
(A) Resistance depends on the temperature
(B) Resistance does not depend on the temperature
(C) Resistivity depend on the length
(D) Resistivity depend on area of cross section
Answer: (A) Resistance depends on the temperature
Explanation:
Resistivity is material property. It depends only on temperature.
For the same material with different length and area, resistivity remains the same until temperature remains constant.
69. The reciprocal of resistivity is________
(A) Conductance
(B) Resistance
(C) Conductivity
(D) Impedance
Answer: (C) Conductivity
Explanation:
The expression for resistivity is = RA/l. The expression for conductivity = Cl/A; C=1/R => Conductivity = l/(AR) = 1/resistivity. Hence, conductivity is the reciprocal of resistivity.
70. Materials which easily allow the passage of electric current are known as ______
(A) Insulators
(B) Conductors
(C) Dielectrics
(D) Semi-conductors
Answer: (B) Conductors
Explanation:
Conductors are materials(mostly metals), which freely allow the passage of electrons through it. If electrons can flow freely through a material, it implies that even current can flow freely through that material since current is the rate of flow of electrons.
71. A wire of length 2m and another wire of length 5m are made up of the same material and have the same area of cross section, which wire has higher resistance?
(A) Both have equal resistance
(B) The 2m wire has higher resistance
(C) The 5m wire has higher resistance
(D) The value of resistance cannot be determined from the given data
Answer: (C) The 5m wire has higher resistance
Explanation:
Resistance is directly proportional to the length of the wire, hence as the length of the wire increases, resistance increases.
72. A wire having an area of cross section = 10sqm and another wire having an area of cross section= 15sqm, have the same length and are made up of the same material. Which wire has more resistance?
(A) Both have equal resistance
(B) The 10sqm wire has higher resistance
(C) The 15sqm wire has higher resistance
(D) The value of resistance cannot be determined from the given data
Answer: (B) The 10sqm wire has higher resistance
Explanation:
Resistance is inversely proportional to the area of cross-section. As an area of cross-section increases, resistance decreases. Hence the 10sqm wire has a higher resistance than the 15sqm wire.
73. Which of the following statements are true with regard to resistance?
(A) Resistance is directly proportional to a length of the wire
(B) Resistance is directly proportional to an area of cross section of the wire
(C) Resistance is inversely proportional to the length of the wire
(D) Resistance is inversely proportional to the resistivity of the wire
Answer: (A) Resistance is directly proportional to a length of the wire
Explanation:
The expression for resistance is: Resistance=Resistivity*length of wire/ area of cross section of the wire. Hence resistance is directly proportional to length.
74․ Which quantity should be measured by the voltmeter ?
(A) Current
(B) Voltage
(C) Power
(D) Speed
(A) Energy
(B) Time
(C) Power
(D) Charge
Ans:(A) Energy
Explanation:
1 kWh is the amount of energy used by a 1 kW (1000 watt) resistance for 1 hour. Energy = Power × Time.
76․ Which of the following has no units?
(A) Permeability
(B) Moment of a magnet
(C) Magnetic susceptibility
(D) Permittivity
Ans: (C) Magnetic susceptibility
Explanation:
Magnetic susceptibility is the degree to which a material is magnetized by an external magnetic field, hence in the SI system it is dimensionless.The magnetic susceptibility of a material, commonly symbolized by χm, is equal to the ratio of the magnetization M within the material to the applied magnetic field strength H, or χm = M/H.
77․ Which of the following quantities consists of SI unit as WATT ?
(A) Force
(B) Charge
(C) Current
(D) Power
(A) Current
(B) Voltage
(C) Power
(D) Speed
Explanation:
Voltmeter is a high resistance device used for measuring potential difference or voltage. It must be connected in parallel for measurement.
(A) Energy
(B) Time
(C) Power
(D) Charge
Ans:(A) Energy
Explanation:
1 kWh is the amount of energy used by a 1 kW (1000 watt) resistance for 1 hour. Energy = Power × Time.
76․ Which of the following has no units?
(A) Permeability
(B) Moment of a magnet
(C) Magnetic susceptibility
(D) Permittivity
Ans: (C) Magnetic susceptibility
Explanation:
Magnetic susceptibility is the degree to which a material is magnetized by an external magnetic field, hence in the SI system it is dimensionless.The magnetic susceptibility of a material, commonly symbolized by χm, is equal to the ratio of the magnetization M within the material to the applied magnetic field strength H, or χm = M/H.
77․ Which of the following quantities consists of SI unit as WATT ?
(A) Force
(B) Charge
(C) Current
(D) Power
Explanation:
The SI unit of power is the watt and it is discovered by the Scottish engineer James Watt. Power is the rate of consumption of electric energy. So, it is equivalent to joules per second.
78. The resistance of pure metals ___________
(A) Increases with an increase in temperature
(B) Decreases with an increase in temperature
(C) Remains the same with an increase in temperature
(D) Becomes zero with an increase in temperature
Answer: (A) Increases with an increase in temperature
Explanation:
In a conductor, the valence band and conduction band overlap each other, there is an excess of electrons in the conduction band. When the temperature increases, there is an overcrowding of electrons in the conduction band hence reducing the mobility and hence resistance increases.
79. The resistance of insulators __________
(A) Increases with an increase in temperature
(B) Decreases with an increase in temperature
(C) Remains the same with an increase in temperature
(D) Becomes zero with an increase in temperature
Answer:(B) Decreases with an increase in temperature
Explanation:
In the case of an insulator, the energy gap between the conduction band and the valence band is very large. When the temperature is increased, the electrons move from the conduction band to the valence band and hence it starts conducting. When conductance increases, resistance decreases, since C=1/R. Thus, when the temperature increases, resistance decreases in insulators.
80. Which of the following statements are true about metals?
(A) Metals have a positive temperature coefficient
(B) Metals have a negative temperature coefficient
(C) Metals have zero temperature coefficient
(D) Metals have infinite temperature coefficient
Answer: (A) Metals have a positive temperature coefficient
Explanation:
The resistance of metals increases with an increase in temperature thus, it has a positive temperature coefficient.
81. Which of the following statements are true about insulators?
(A) Insulators have a positive temperature coefficient
(B) Insulators have a negative temperature coefficient
(C) Insulators have zero temperature coefficient
(D) Insulators have infinite temperature coefficient
Answer: (B) Insulators have a negative temperature coefficient
Explanation:
Insulators have a negative temperature coefficient because as temperature increases, the resistance of insulators decreases.
82. What is the unit of temperature coefficient?
(A) ohm/centigrade
(B) ohm-centigrade
(C) centigrade-1
(D) centigrade
Answer: (C) centigrade-1
Explanation:
R=Reff[1+temp. coeff(T-Teff)].
From the given expression: (R/Reff-1)/(T-Teff) = temp. coeff. Hence, the unit is the reciprocal of that of temperature = centigrade-1.
83. A copper coil has a resistance of 200 ohms when its mean temperature is 0 degree centigrade. Calculate the resistance of the coil when its mean temperature is 80 degree centigrade. Temperature coefficient of copper is 0.004041 centigrade-1
(A) 264.65 ohm
(B) 264.65 kilo-ohm
(C) 286.65 ohm
(D) 286.65 kilo-ohm
Answer: (A) 264.65 ohm
Explanation:
R=R0(1+α dT) = 200(1+ 0.004041*80) = 264.65 ohm.
84. The temperature of a coil cannot be measured by which of the following methods?
(A) Thermometer
(B) Increase in resistance of the coil
(C) Thermo-junctions embedded in the coil
(D) Calorimeter
Answer: (D) Calorimeter
Explanation:
Calorimeter measures the amount of heat and not the temperature of the coil. The temperature of a coil is mainly measured by thermometer. Resistance of coil increase with an increase in temperature of coil so we can measure temperature using this method. Another method is the formation of thermocouple inside coil due to high temperature at one end and low temperature at other ends.
85. The rise or fall in resistance with the rise in temperature depends on ________
(A) The property of the conductor material
(B) The current in the metal
(C) Property of material as well current in that material
(D) Does not depend on any factor
Answer: (A) The property of the conductor material
Explanation:
The rise or fall in resistance with a rise in temperature depends upon the property of the material. Hence it rises with temperature in metals and falls with temperature in insulators and semi-conductors.
86. If the temperature is increased in semi-conductors such that the resistance incessantly falls, it is termed as _______
(A) Avalanche breakdown
(B) Zener breakdown
(C) Thermal runway
(D) Avalanche runway
Answer: (C) Thermal runway
Explanation:
When the temperature keeps increasing, the resistance keeps falling continuously and hence the current to increase. This causes the heat in the semi-conductor to rise. This causes the temperature to increase further and the resistance to further decrease. This process continues and until there is sufficient heat to destroy the structure of the semi-conductor completely. This is known as a thermal runway.
87․ KCL works on the principle of which of the following
(A) law of conservation of charge.
(B) law of conservation of energy.
(C) both.
(D) None of the above.
Ans:(A) law of conservation of charge.
Explanation:
KCL (Kirchhoff's Current Law) states that in an electrical circuit total current entering in to a node is equal to the total current leaving from node. This works on the principle of law of conservation of charge. As the current is rate flow of charge. So, charge is conserved at a node.
88․ KVL works on the principle of
(A) law of conservation of charge.
(B) law of conservation of energy.
(C) both.
(D) None of the above.
Ans: (B) law of conservation of energy.
Explanation:
KVL (Kirchhoff’s Voltage Law) states that algebraic sum of voltages in a loop is zero. This works on the principle law of conservation of energy. As the voltage is analogous to potential and this law states that total potential gain and total potential drops along a loop are zero.
89․ Super mesh analysis is used in case of
(A) current source branch is common for two meshes.
(B) ideal voltage source is connected between two non reference nodes.
(C) both.
(D) either 1 or 2.
Ans: (A) current source branch is common for two meshes.
Explanation:
When an ideal or dependent current source branch is common for two meshes it is possible to find the solution by using super mesh analysis. Super mesh analysis is a better technique instead of using mesh analysis to analyze such a complex circuit or network where two meshes have a current source as a common element. In super mesh analysis technique, the current source is in the inner area of the super mesh. Therefore, we are able to reduce the number of meshes by one for each current source which is present in the network. Therefore in this case we are using super mesh analysis.
90․ When we use super node technique
(A) current source branch is common for two meshes.
(B) ideal voltage source is connected between two non reference nodes.
(C) ideal voltage source is connected between non reference node and reference.
(D) All of the above.
Ans: (B) ideal voltage source is connected between two non reference nodes.
Explanation:
When ideal voltage source or dependent voltage source is connected between two non reference node, then it not is possible to find the solution by using node analysis technique. Then we apply supernode analysis technique.
91․ Rms value is defined based on which of the following?
(A) Heating effect
(B) Charge transfer
(C) Current
(D) Voltage
Ans:(A) Heating effect
Explanation:
Rms (Root mean square) value is defined based on heating effect of wave-forms. The value at which heat dissipated in AC circuit is same as the heat dissipated in DC circuit is called rms value, provide both AC and DC circuits have equal value of resistance and operated for same time.
92․ Which of the following defined the average value ?
(A) Voltage
(B) Heating effect
(C) Current
(D) Charge transfer
Ans: (D) Charge transfer
Explanation:
Average value is defined based on charge transfer in the circuit. The voltage at which charge transfer in AC circuit is equal to charge transfer in the DC circuit is called as average value of the AC, provided both AC and DC circuits have equal value of resistance and operated for same time.
93․ For symmetrical wave form average value of one full cycle is
(A) 1
(B) 1.11
(C) 2.22
(D) 0
Ans:(D) 0
Explanation:
For symmetrical wave form both positive half cycle and negative half cycles are same. Therefore while finding average value these two half cycles gets cancelled out, so average value for symmetrical wave form is zero. Actually integrating over a full cycle from 0 to 2π is zero.
(A) law of conservation of charge.
(B) law of conservation of energy.
(C) both.
(D) None of the above.
Ans:(A) law of conservation of charge.
Explanation:
KCL (Kirchhoff's Current Law) states that in an electrical circuit total current entering in to a node is equal to the total current leaving from node. This works on the principle of law of conservation of charge. As the current is rate flow of charge. So, charge is conserved at a node.
88․ KVL works on the principle of
(A) law of conservation of charge.
(B) law of conservation of energy.
(C) both.
(D) None of the above.
Ans: (B) law of conservation of energy.
Explanation:
KVL (Kirchhoff’s Voltage Law) states that algebraic sum of voltages in a loop is zero. This works on the principle law of conservation of energy. As the voltage is analogous to potential and this law states that total potential gain and total potential drops along a loop are zero.
89․ Super mesh analysis is used in case of
(A) current source branch is common for two meshes.
(B) ideal voltage source is connected between two non reference nodes.
(C) both.
(D) either 1 or 2.
Ans: (A) current source branch is common for two meshes.
Explanation:
When an ideal or dependent current source branch is common for two meshes it is possible to find the solution by using super mesh analysis. Super mesh analysis is a better technique instead of using mesh analysis to analyze such a complex circuit or network where two meshes have a current source as a common element. In super mesh analysis technique, the current source is in the inner area of the super mesh. Therefore, we are able to reduce the number of meshes by one for each current source which is present in the network. Therefore in this case we are using super mesh analysis.
90․ When we use super node technique
(A) current source branch is common for two meshes.
(B) ideal voltage source is connected between two non reference nodes.
(C) ideal voltage source is connected between non reference node and reference.
(D) All of the above.
Ans: (B) ideal voltage source is connected between two non reference nodes.
Explanation:
When ideal voltage source or dependent voltage source is connected between two non reference node, then it not is possible to find the solution by using node analysis technique. Then we apply supernode analysis technique.
91․ Rms value is defined based on which of the following?
(A) Heating effect
(B) Charge transfer
(C) Current
(D) Voltage
Ans:(A) Heating effect
Explanation:
Rms (Root mean square) value is defined based on heating effect of wave-forms. The value at which heat dissipated in AC circuit is same as the heat dissipated in DC circuit is called rms value, provide both AC and DC circuits have equal value of resistance and operated for same time.
92․ Which of the following defined the average value ?
(A) Voltage
(B) Heating effect
(C) Current
(D) Charge transfer
Ans: (D) Charge transfer
Explanation:
Average value is defined based on charge transfer in the circuit. The voltage at which charge transfer in AC circuit is equal to charge transfer in the DC circuit is called as average value of the AC, provided both AC and DC circuits have equal value of resistance and operated for same time.
93․ For symmetrical wave form average value of one full cycle is
(A) 1
(B) 1.11
(C) 2.22
(D) 0
Ans:(D) 0
Explanation:
For symmetrical wave form both positive half cycle and negative half cycles are same. Therefore while finding average value these two half cycles gets cancelled out, so average value for symmetrical wave form is zero. Actually integrating over a full cycle from 0 to 2π is zero.
94. Materials having resistance almost equal to zero is _______
(A) Semi-conductor
(B) Conductor
(C) Superconductors
(D) Insulators
Answer: (C) Superconductors
Explanation:
When the temperature of the material falls to absolute zero, the resistance falls to zero and hence there are no I2R losses. Since resistance is zero, conductance is almost infinity and hence these materials are known as superconductors.
95. Nodal analysis is generally used to determine______
(A) Voltage
(B) Current
(C) Resistance
(D) Power
Answer: (A) Voltage
Explanation:
Nodal analysis uses Kirchhoff’s Current Law to find all the node voltages. Hence it is a method used to determine the voltage.
96. Mesh analysis is generally used to determine_________
(A) Voltage
(B) Current
(C) Resistance
(D) Power
Answer: (B) Current
Explanation:
Mesh analysis uses Kirchhoff’s Voltage Law to find all the mesh currents. Hence it is a method used to determine current.
97. KVL is associated with____________
(A) Mesh analysis
(B) Nodal analysis
(C) Both mesh and nodal
(D) Neither mesh nor nodal
Answer: (A) Mesh analysis
Explanation:
KVL employs mesh analysis to find the different mesh current
98. KCL is associated with_________
(A) Mesh analysis
(B) Nodal analysis
(C) Both mesh and nodal
(D) Neither mesh nor nodal
Answer: (B) Nodal analysis
Explanation:
KCL employs nodal analysis to find the different node voltages by finding the value if a current in each branch.
99. Mesh analysis employs the method of ___________
(A) KVL
(B) KCL
(C) Both KVL and KCL
(D) Neither KVL nor KCL
Answer: (A) KVL
Explanation:
KVL employs mesh analysis to find the different mesh currents by finding the IR products in each mesh.
100. Mesh analysis is generally used to determine _________
(A) Voltage
(B) Current
(C) Resistance
(D) Power
Answer: (B) Current
Explanation:
Mesh analysis uses Kirchhoff’s Voltage Law to find all the mesh currents. Hence it is a method used to determine current.
101. Mesh analysis can be used for __________
(A) Planar circuits
(B) Non-planar circuits
(C) Both planar and non-planar circuits
(D) Neither planar nor non-planar circuits
Answer: (A) Planar circuits
Explanation:
If the circuit is not planar, the meshes are not clearly defined. In planar circuits, it is easy to draw the meshes hence the meshes are clearly defined.
102. Nodal analysis is generally used to determine_______
(A) Voltage
(B) Current
(C) Resistance
(D) Power
Answer: (A) Voltage
Explanation:
Nodal analysis uses Kirchhoff’s Current Law to find all the node voltages. Hence it is a method used to determine the voltage.
103. If there are 10 nodes in a circuit, how many equations do we get?
(A) 10
(B) 9
(C) 8
(D) 7
Answer: (B) 9
Explanation:
One node is taken as reference node so, the number of equations we get is always one less than the number of nodes in the circuit, hence for 10 nodes we get 9 equations.
104. Nodal analysis can be applied for________
(A) Planar networks
(B) Non-planar networks
(C) Both planar and non-planar networks
(D) Neither planar nor non-planar networks
Answer: (C) Both planar and non-planar networks
Explanation:
Nodal analysis can be applied for both planar and non-planar networks since each node, whether it is planar or non-planar, can be assigned a voltage.
105. How many nodes are taken as reference nodes in a nodal analysis?
(A) 1
(B) 2
(C) 3
(D) 4
Answer: (A) 1
Explanation:
In the nodal analysis, one node is treated as the reference node and the voltage at that point is taken as 0.
106. In superposition theorem, when we consider the effect of one voltage source, all the other voltage sources are ____________
(A) Shorted
(B) Opened
(C) Removed
(D) Undisturbed
Answer: (A) Shorted
Explanation:
In superposition theorem when we consider the effect of one voltage source, all the other voltage sources are shorted and current sources are opened.
107. In superposition theorem, when we consider the effect of one current source, all the other voltage sources are ____________
(A) Shorted
(B) Opened
(C) Removed
(D) Undisturbed
Answer:(A) Shorted
Explanation:
In superposition theorem, whether we consider the effect of a voltage or current source, voltage sources are always shorted and current sources are always opened.
108. In superposition theorem, when we consider the effect of one voltage source, all the other current sources are ____________
(A) Shorted
(B) Opened
(C) Removed
(D) Undisturbed
Answer: (B) Opened
Explanation:
In superposition theorem when we consider the effect of one voltage source, all the other current sources are opened and voltage sources are shorted.
109. In superposition theorem, when we consider the effect of one current source, all the other current sources are ____________
(A) Shorted
(B) Opened
(C) Removed
(D) Undisturbed
Answer: (B) Opened
Explanation:
In superposition theorem, whether we consider the effect of a voltage or current source, current sources are always opened and voltage sources are always shorted.
110. Superposition theorem does not work for ________
(A) Current
(B) Voltage
(C) Power
(D) Works for all: current, voltage and power
Answer: (C) Power
Explanation:
Power across an element is not equal to the power across it due to all the other sources in the system. The power in an element is the product of the total voltage and the total current in that element.
111. The Thevenin voltage is the__________
(A) Open circuit voltage
(B) Short circuit voltage
(C) Open circuit and short circuit voltage
(D) Neither open circuit nor short circuit voltage
Answer: (A) Open circuit voltage
Explanation:
Thevenin voltage is obtained by opening the specified terminals so it is open-circuit voltage. It is not the short circuit voltage because if specified terminals are shorted voltage is equal to zero.
112. Thevenin resistance is found by ________
(A) Shorting all voltage sources
(B) Opening all current sources
(C) Shorting all voltage sources and opening all current sources
(D) Opening all voltage sources and shorting all current sources
Answer: (C) Shorting all voltage sources and opening all current sources
Explanation:
Ideal current sources have infinite internal resistance hence behave like an open circuit whereas ideal voltage sources have zero internal resistance hence behave as a short circuit.
113. Thevenin’s theorem is true for __________
(A) Linear networks
(B) Non-Linear networks
(C) Both linear networks and nonlinear networks
(D) Neither linear networks nor non-linear networks
Answer: (A) Linear networks
Explanation:
Thevenin’s theorem works for only linear circuit elements and not non-linear ones such as BJT, semiconductors etc.
114. In Thevenin’s theorem Vth is __________
(A) Sum of two voltage sources
(B) A single voltage source
(C) Infinite voltage sources
(D) 0
Answer: (B) A single voltage source
Explanation:
Thevenin’s theorem states that a combination of voltage sources, current sources and resistors is equivalent to a single voltage source V and a single series resistor R.
115. Vth is found across the ____________ terminals of the network.
(A) Input
(B) Output
(C) Neither input nor output
(D) Either input or output
Answer: (B) Output
Explanation:
According to Thevenin’s theorem, Vth is found across the output terminals of a network and not the input terminals.
116. Which of the following is also known as the dual of Thevenin’s theorem?
(A) Norton’s theorem
(B) Superposition theorem
(C) Maximum power transfer theorem
(D) Millman’s theorem
Answer: (A) Norton’s theorem
Explanation:
Norton’s theorem is also known as the dual of Thevenin’s theorem because in Norton’s theorem we find short circuit current which is the dual of open circuit voltage-what we find in Thevenin’s theorem.
117. Can we use Thevenin’s theorem on a circuit containing a BJT?
(A) Yes
(B) No
(C) Depends on the BJT
(D) Insufficient data provided
Answer: (B) No
Explanation:
We can use Thevenin’s theorem only for linear networks. BJT is a non-linear network hence we cannot apply Thevenin’s theorem for it.
118. The Norton current is the_______
(A) Short circuit current
(B) Open circuit current
(C) Open circuit and short circuit current
(D) Neither open circuit nor short circuit current
Answer: (A) Short circuit current
Explanation:
Norton current is obtained by shorting the specified terminals. So, it is the short circuit current. It is not the open circuit current because if specified terminals get open circuited then current is equal to zero.
119. Norton resistance is found by?
(A) Shorting all voltage sources
(B) Opening all current sources
(C) Shorting all voltage sources and opening all current sources
(D) Opening all voltage sources and shorting all current sources
Answer: (C) Shorting all voltage sources and opening all current sources
Explanation:
Ideal current sources have infinite internal resistance hence behave like an open circuit whereas ideal voltage sources have zero internal resistances hence behave as a short circuit. So, to obtain Norton resistance, all voltage sources are shorted and all current sources are opened.
120. Norton’s theorem is true for __________
(A) Linear networks
(B) Non-Linear networks
(C) Both linear networks and nonlinear networks
(D) Neither linear networks nor non-linear networks
Answer: (A) Linear networks
Explanation:
Norton’s theorem works for only linear circuit elements and not non-linear ones such as BJT, semiconductors etc.
121. In Norton’s theorem Isc is__________
(A) Sum of two current sources
(B) A single current source
(C) Infinite current sources
(D) 0
Answer: (B) A single current source
Explanation:
Norton’s theorem states that a combination of voltage sources, current sources and resistors is equivalent to a single current source IN and a single parallel resistor RN.
122. Isc is found across the ____________ terminals of the network.
(A) Input
(B) Output
(C) Neither input nor output
(D) Either input or output
Answer: (B) Output
Explanation:
According to Norton’s theorem, Isc is found through the output terminals of a network and not the input terminals.
123. Can we use Norton’s theorem on a circuit containing a BJT?
(A) Yes
(B) No
(C) Depends on the BJT
(D) Insufficient data provided
Answer: (B) No
Explanation:
We can use Norton’s theorem only for linear networks. BJT is a non-linear network hence we cannot apply Norton’s theorem for it.
124. Which of the following is also known as the dual of Norton’s theorem?
(A) Thevenin’s theorem
(B) Superposition theorem
(C) Maximum power transfer theorem
(D) Millman’s theorem
Answer: (A) Thevenin’s theorem
Explanation:
Thevenin’s theorem is also known as the dual of Norton’s theorem because in Norton’s theorem we find short circuit current which is the dual of open circuit voltage-what we find in Thevenin’s theorem.
125․ Form factor is equal to Peak factor in case of
(A) square wave.
(B) triangle wave.
(C) saw tooth wave.
(D) all of the above.
Ans: (A) square wave.
Explanation:
The form factor of an alternating current waveform is the ratio of the rms value to the average value. The peak factor is the peak amplitude of the waveform divided by the rms value of the waveform. For square waveform form factor and peak factor is same and value is one.
(A) square wave.
(B) triangle wave.
(C) saw tooth wave.
(D) all of the above.
Ans: (A) square wave.
Explanation:
The form factor of an alternating current waveform is the ratio of the rms value to the average value. The peak factor is the peak amplitude of the waveform divided by the rms value of the waveform. For square waveform form factor and peak factor is same and value is one.
126․ If a resistor is connected across the voltage source and the frequency of voltage and current wave form is 50Hz, then what is frequency of instantaneous power
(A) 0 Hz.
(B) 100 Hz.
(C) 50 Hz.
(D) 150 Hz.
Ans:(B) 100 Hz.
Explanation:
Therefore, frequency is doubled for the instantaneous power.
(A) 0 Hz.
(B) 100 Hz.
(C) 50 Hz.
(D) 150 Hz.
Ans:(B) 100 Hz.
Explanation:
Therefore, frequency is doubled for the instantaneous power.
127. A voltage source connected in series with a resistor can be converted to a?
(A) Current source in series with a resistor
(B) Current source in parallel with a resistor
(C) Voltage source in parallel with a resistor
(D) Cannot be modified
Answer: (B) Current source in parallel with a resistor
Explanation:
A voltage source connected in series can be converted to a current source connected in parallel using the relation obtained from Ohm’s law, that is V=IR. This equation shows that a voltage source connected in series has the same impact as a current source connected in parallel.
128. A current source connected in parallel with a resistor can be converted to a?
(A) Current source in series with a resistor
(B) Voltage source in series with a resistor
(C) Voltage source in parallel with a resistor
(D) Cannot be modified
Answer: (B) Voltage source in series with a resistor
Explanation:
A current source connected in parallel can be converted to a voltage source connected in series using the relation obtained from Ohm’s law, that is V=IR. This equation shows that a current source connected in parallel has the same impact as a voltage source connected in series.
129. A source transformation is_________
(A) Unilateral
(B) Bilateral
(C) Unique
(D) Cannot be determined
Answer: (B) Bilateral
Explanation:
A source transformation is bilateral because a voltage source can be converted to a current source and vice-versa.
130. In source transformation________
(A) Voltage source remains the same
(B) Current sources remain the same
(C) Both voltage and current source remain the same
(D) Resistances remain the same
Answer: (D) Resistances remain the same
Explanation:
In source transformation, the value of the voltage and current sources change when changed from voltage to current source and current to voltage source but the value of the resistance remains the same.
131. If there are 3 10V sources connected in parallel then on source transformation__________
(A) The effect of all the sources is considered
(B) The effect of only one source is considered
(C) The effect of none of the sources is considered
(D) The effect of only 2 sources is considered.
Answer: (B) The effect of only one source is considered
Explanation:
When voltages are connected in parallel, the effect of only one source is considered because the effect of the voltage remains the same when connected in parallel.
132. Star connection is also known as__________
(A) Y-connection
(B) Mesh connection
(C) Either Y-connection or mesh connection
(D) Neither Y-connection nor mesh connection
Answer: (A) Y-connection
Explanation:
The star connection is also known as the Y-connection because its formation is like the letter Y.
133. Delta connection is also known as____________
(A) Y-connection
(B) Mesh connection
(C) Either Y-connection or mesh connection
(D) Neither Y-connection nor mesh connection
Answer: (B) Mesh connection
Explanation:
Delta connection is also known as mesh connection because its structure is like a mesh, that is, a closed loop which is planar.
134. Does maximum power transfer imply maximum efficiency?
(A) Yes
(B) No
(C) Sometimes
(D) Cannot be determined
Answer: (B) No
Explanation:
Maximum power transfer does not imply maximum efficiency. If the load resistance is smaller than source resistance, the power dissipated at the load is reduced while most of the power is dissipated at the source then the efficiency becomes lower..
135. Under the condition of maximum power efficiency is?
(A) 100%
(B) 0%
(C) 30%
(D) 50%
Answer: (D) 50%
Explanation:
Efficiency=(Power output/ Power input)*100.
Power Output=I2RL, Power Input=I2(RL+RS)
Under maximum power transfer conditions, RL=RS
Power Output=I2RL; Power Input=2*I2RL
Thus efficiency=50%.
136. Name some devices where maximum power has to be transferred to the load rather than maximum efficiency.
(A) Amplifiers
(B) Communication circuits
(C) Both amplifiers and communication circuits
(D) Neither amplifiers nor communication circuits
Answer: (C) Both amplifiers and communication circuits
Explanation:
Maximum power transfer to the load is preferred over maximum efficiency in both amplifiers and communication circuits since in both these cases the output voltage is more than the input.
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