MCQ-1 The length of wire having a resistance of 2 ohm/m in a heater rated at 2000 W and 240 V will be
(A) 57.84 meter
(B) 55.80 meter
(C) 56.20 meter
(D) 50.8 meter
Ans:(A) 57.84 meter
Explanationation :
Here is given that
Resistance = 2 Ohm/ Meter
Heater rating P = 2000 W
Voltage V = 240 V
Length of Heater Wire L=?
Power P = Voltage V * Current I
2000 = 240 * Current I
Current I = 2000 / 240
Current I = 8.3 A
As per Ohm Law
R = V/I
R = 240/8.3
R = 28.92 ohm
Here is given that Resistance is 2 Ohm per meter
So length of wire L = 28.92 * 2
L = 57.84 meter
MCQ-2 The resistance of a lamp rated at 250 V and 80 watts equal to
(A) 782.45 Ohm
(B) 781.25 Ohm
(C) 783.25 Ohm
(D) 756.35 ohm
Ans:(B) 781.25 Ohm
Explanation:
Here is given that
Voltage V = 250 V
Power P = 80 W
Resistance R =?
Power P = Voltage V * Current I
80 = 250 * Current I
Current I = 80 / 250
Current I = 0.32 A
As per Ohm Law
R = V/I
R = 250/0.32
R = 781.25 ohm
Hence the resistance of Lamp is 781.25 ohm.
