Railway Science (Physics-Electric Current and its Effects) (Part-VI)

Total Questions: 50

1. Two resistances A and B of 12Ω and 24Ω respectively are connected in series with a 6 V battery. The total heat dissipated in the resistors in 1 second will be ______. [RRC Group D 26/08/2022 (Afternoon)]

Correct Answer: (c) 1.0 J
Solution:

2. A wire of length L and area of cross-section A has a resistance of 0.5Ω. The resistance of a wire of same length (L) and area of cross-section 2A, made of the same material, will be ______. [RRC Group D 26/08/2022 (Afternoon)]

Correct Answer: (b) 0.25 Ω
Solution:

3. Two resistances A and B of 6 Ω and 12 Ω respectively are connected in parallel with a battery of 3 V. The total energy supplied by the battery to the circuit in 1 second will be ___________. [RRC Group D 26/08/2022 (Evening)]

Correct Answer: (b) 2.25 J
Solution:

4. The resistance of a wire of length L and area of cross-section A is 0.2 Ω. The resistance of a wire of the same material, but of length 2L and area of cross-section 4A will be: [RRC Group D 29/08/2022 (Morning)]

Correct Answer: (d) 0.1Ω
Solution:

5. A 200 W bulb is connected to a 220 V source. The current through the bulb is: [RRC Group D 29/08/2022 (Morning)]

Correct Answer: (d) 0.91 A
Solution:

Power, P = 200 W.
Voltage, V = 220 V
Now, Power = Voltage × Current ⇒ 200 = 220 × I ⇒ I = 200/220 = 0.91 A

6. Three identical bulbs are connected in parallel to a battery of 6 V. If the current in the circuit is 0.6A, the power dissipated by the battery is: [RRC Group D 29/08/2022 (Afternoon)]

Correct Answer: (b) 3.6 W
Solution:

Given, V = 6 V and I = 0.6 A
Power = Voltage × Current
P = V × I = 6 × 0.6 = 3.6 W. Hence, power dissipated by the battery is 3.6 W.

7. Two resistors, A (20 Ω) and B (40 Ω), are connected in parallel. The combination is connected to a 6 V battery. The currents in A and B are respectively _________. [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (d) 0.3 A and 0.15 A
Solution:

Given, R₁ = 20 Ω, R₂ = 40 Ω, and V = 6 V
When the resistances are arranged in parallel, the voltage applied is the same but the current gets divided. So, using Ohm’s Law, V = IR ⇒ I₁ = V / R₁ = 6 / 20 = 0.3 A. And, I₂ = V / R₂ = 6 / 40 = 0.15 A.

8. A current of 0.2 A is maintained in a resistor of 10 Ω. The heat produced in the resistor in 1 second is: [RRC Group D 30/08/2022 (Afternoon)]

Correct Answer: (d) 0.4 J
Solution:

Given, I = 0.2 A,
R = 10 Ω, t = 1 sec
Now, Heat = 𝐼²Rt = (0.2)² (10) (1) = 0.4 J

9. Three wires, A, B and C, of the same length and the same thickness have resistances of 1Ω, 0.5Ω and 0.25Ω, respectively. Their resistivities are ________. [RRC Group D 30/08/2022 (Evening)]

Correct Answer: (c) in the ratio of 4 : 2 : 1
Solution:

10. Consider two wires, A and B, of some thickness but lengths L and 4L, respectively. If the resistances of A and B are 0.5 Ω and 2.0 Ω, respectively, the ratio of the resistivity of A to the resistivity of B is: [RRC Group D 30/08/2022 (Evening)]

Correct Answer: (a) 1
Solution: