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

Total Questions: 50

31. The equivalent resistance between points A and B shown in the figure below: [RRC Group D 18/08/2022 (Morning)]

Correct Answer: (a) 2 Ω
Solution:

32. Two wires A and B are made of the same material and have the same length but different cross-sectional areas. If the resistance of wire A is 9 times the resistance of wire B, the ratio of the radius of wire A to that of wire B is: [RRC Group D 18/08/2022 (Afternoon)]

Correct Answer: (d) 1 : 3
Solution:

33. The current across the 3 ohm resistance in the given circuit is: [RRC Group D 18/08/2022 (Evening)]

Correct Answer: (a) 5/7 A
Solution:

34. A metallic wire of resistance 100 Ω is bent into a circle having circumference equal to the length of the wire. The equivalent resistance between two diametrically opposite points of the circle is: [RRC Group D 22/08/2022 (Morning)]

Correct Answer: (d) 25 Ω
Solution:

Resistance of wire= 100 Ω. The upper semicircle will be 50 ohm and the bottom will be 50 ohm. Now, these two are in parallel to each other. So, the equivalent resistance = 1/50 + 1/50 = 1/25 . Hence, Equivalent resistance = 25Ω.

35. The ratio of a field produced due to a current carrying circular coil of n turns, to that of a field produced due to a single circular loop of the same radius carrying the same current is: [RRC Group D 22/08/2022 (Morning)]

Correct Answer: (b) n : 1
Solution:

The magnetic field produced by a current-carrying wire at a given point depends directly on the current passing through it. Therefore, if there is a circular coil having “‘n” turns, the field produced is “n” times as large as that produced by a single turn. The magnetic field is produced by current carrying wire at the centre is given by,

36. An electric heater rated 1000 W and an electric geyser rated 2000 W are used for 4 hours daily. The energy consumed in 10 days (in kWh) is [RRC Group D 22/08/2022 (Evening)]

Correct Answer: (a) 120
Solution:

Total energy consumed (KWh) in 10 days
=  (1000 + 2000) W × 4 hrs × 10 days/1000
= 120. (As, 1 KW = 1000 W)

37. A wire of a given material has length ‘l’ and resistance ‘R’. Another wire of the same material having nine times the length and the same area of cross section will have a resistance equal to: [RRC Group D 23/08/2022 (Morning)]

Correct Answer: (c) 9R
Solution:

Resistance of Wire, R = ρ 𝑙/A. Material of another wire is the same, so ρ = constant. Length of another wire = 9l. Area of cross-section is also the same. Therefore, resistance of another wire

38. Two resistors of 4𝛺 each are connected in parallels to a 5V battery source. The total current in the circuit is: [RRC Group D 23/08/2022 (Morning)]

Correct Answer: (d) 2.5 A
Solution:

To obtain equivalent resistance of two resistors of 4Ω each connected in parallel.

39. Three bulbs A, B and C rated 40 W, 60 W and 100 W respectively are connected in parallel to a voltage source of 220 V. the bulb that glows with maximum brightness is: [RRC Group D 23/08/2022 (Afternoon)]

Correct Answer: (b) bulb C
Solution:

40. An electric heater of rating 1000 W is used daily for 5 hours. Find the total cost (in Rs) of running the equipment for the month of September, based on a unit cost of Rs 6.00. [RRC Group D 23/08/2022 (Evening)]

Correct Answer: (d) 900
Solution:

Energy consumption (E) = P × t Where P, t is the power and the time respectively. On substituting the given values,
we get E = 1000 × 5 × 30 (in september - 30 days)
⇒ E = 150000 Wh ⇒ E = 150 kWh
Since, 1 unit is 1 kWh and therefore energy consumed is equal to E = 150 units The energy consumed by heater is 150 unit and hence the cost of energy (C) is equal to Total unit consumed × cost per unit that is C = 150 × 6 = Rs.900.