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

Total Questions: 50

31. A particular house consumes 100 units in 5 days, what will be the energy if converted into joules? [RRB Group D 03/10/2018 (Evening)]

Correct Answer: (d) 3. 6 × 10⁸ J
Solution:

Given, E = 100 units = 100 kWh.
Converting it into joules,
E = 100 × 3.6 × 10⁶ J
(1 kWh = 3.6 × 10⁶ J) ⇒ E = 3.6 × 10⁸  J.

32. How much work is done in moving a charge of 2 C across two points having a potential difference of 10 V ? [RRB Group D 05/10/2018 (Morning)]

Correct Answer: (b) 20 J
Solution:

Given, Q = 2 C and V = 10 V
Work=Charge(Q)×potential difference(V) ⇒ Work = 2 × 10 = 20 J.

33. A current of 0.8A is drawn by a filament of an electric bulb in 5 minutes. Find the amount of electric charge flowing through the circuit. [RRB Group D 05/10/2018 (Afternoon)]

Correct Answer: (a) 240 C
Solution:

Given that, Current (I) = 0.8 A, Time (t) = 5 min or 300 sec.
∵ Q = I × t ⇒ Q = 0.8 × 300 = 240 C.

34. How much work is required to transfer a charge of 5 C across two points with a potential difference of 10 V? [RRB Group D 05/10/2018 (Evening)]

Correct Answer: (b) 50 J
Solution:

Given, Charge (Q) = 5 C, Potential Difference (V) = 10 V.
Work Done = Q × V = 5 × 10 = 50 J.

35. Calculate the potential energy acquired by a 20 kg hammer when it is raised to a height of 15 m (given g=10ms⁻²). [RRB Group D 05/10/2018 (Evening)]

Correct Answer: (a) 3000 J
Solution:

Given, Mass = 20 kg, Height = 15 m.
Potential Energy = m × g × h = 20 × 10 × 15 = 3000 J.

36. An electrical gadget draws a current of 0.6 A in 10 minutes. Find the amount of electric charge flowing through the circuit. [RRB Group D 08/10/2018 (Morning)]

Correct Answer: (c) 360 C
Solution:

Given that, Current (I) = 0.6 A, Time (t) = 10 × 60 = 600 s.
Net charge (ΔQ) = ?
∵ ΔQ = I × t
⇒ ΔQ = 0.6 × 600 = 360 C.

37. If the potential difference and current flow in a circuit are doubled, the resistance of the circuit is: [RRB Group D 09/10/2018 (Morning)]

Correct Answer: (b) will remain the same
Solution:

38. A current of 0.9 A is received by a filament of an electric bulb for two minutes. The charge flowing through the circuit is : [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (c) 108 C
Solution:

Given : Current (I) = 0.9 A, Time (t) = 2 minutes = 2 × 60 s = 120 s.
∵ Q = I × t
Using the formula : Q = 0.9 A × 120 s ⇒ Q = 108 C.

39. How much current will an electric heater coil draw from a 220 V source if the resistance of the coil is 100 ohms? [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (b) 2.2 A
Solution:

Given : Voltage (V) = 220 V, Resistance (R) = 100 Ω
The current drawn by the electric heater coil can be calculated using Ohm's law :
I = V/R ⇒ I = 220 𝑉/100 Ω = 2.2 A.

40. The charge flowing through a circuit in 10 minutes is 300 C. Find the current drawn by the circuit. [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (b) 0.5 A
Solution:

Given, Charge (Q)= 300 C, Time (t)= 10 minutes = 10 x 60 = 600 seconds.
∵ Charge (Q) = Current (I) x Time (t)
Current (I) = charge(q)/time(t) = 300/600 = 0.5 A.