Q-1. What is the difference between earth and neutral?
Answer:
Neutral is a return current path for equipments and earthing is protection for humans. Earth is a support for neutral. If neutral is not present, the machine we are using will get in full phase and we will get a shock. So earthing is done to avoid such shocks.
Q-2. What is the difference between an Insulator and a Dielectric?
Answer:
Dielectrics are used to store the electric charges, while insulators are used to block the flow of electric charges. All dielectrics are insulators (they don’t allow the flow of electric charges through them) but all insulators aren’t dielectric because they can’t store charges unlike dielectrics.
Q-3. What are the disadvantages of low power factor?
Answer:
- The disadvantages are:
- Large KVA rating of equipment
- Greater conductor size
- Large copper losses
- Poor voltage regulation
- Reduced handling capacity of system
Q-4. Why is earth pin longest and thickest?
Answer:
More the thickness of the wire/conductor less is the resistance. A thick earth pin provides a less resistant path for the current to be grounded. This is for safety so that the leakage current if any will take the less resistant path from earth pin to ground rather than a person operating an appliance
Q-5. What is Hysteresis loss?
Ans. Hysteresis loss is a heat loss caused by the magnetic properties of the armature. When an armature core is in a magnetic field, the magnetic particles of the core tend to line up with the magnetic field. When the armature core is rotating, its magnetic field keeps
changing direction. The continuous movement of the magnetic particles, as they try to align themselves with the magnetic field, produces molecular friction. This, in turn, produces heat. This heat is transmitted to the armature windings. The heat causes armature resistances to increase
To compensate for hysteresis losses, heat-treated silicon steel laminations are used
Q-6. Which is the motor used in fan?
Answer:
Single-phase induction motor is used in fan
Q-7. Why do we use the starter for a DC motor?
Answer:
Large DC motors with field windings instead of permanent magnets have a very heavy load when starting. To prevent fuses blowing, a series of small resistors are sequentially switched in series with the motor. As the motor picks up speed, a back EMF in opposition to the applied voltage limits the maximum current. When the motor reaches its running speed, the ‘starter’ is out of circuit
Large DC motors with field windings instead of permanent magnets have a very heavy load when starting. To prevent fuses blowing, a series of small resistors are sequentially switched in series with the motor. As the motor picks up speed, a back EMF in opposition to the applied voltage limits the maximum current. When the motor reaches its running speed, the ‘starter’ is out of circuit
Q-8. What is Form Factor?
Answer:
The form factor of an alternating current waveform (signal) is the ratio of the RMS (Root Mean Square) value to the average value (mathematical mean of absolute values of all points on the waveform)
Q-9. Which is more dangerous-shock due to AC or DC?
Answer:
Shock due to DC is more dangerous than AC
Q-10. What are the practical applications of variable resistance?
Answer:
Its applications are:
- Volume control
- Fan speed control
- Light dimmer