Current Electricity Class 12 Physics MCQs Pdf
31. There are n similar conductors each of resistance R. The resultant resistance comes out to be x when connected in parallel. If they are connected in series, the resistance comes out to be ________ .
Answer/Explanation
Answer:
Explaination:
n²x
In parallel, x = \(\frac{R}{n}\) or R = nx n
In series, R + R + R …. n times = nR = n(nx) = n²x
32. In the circuit shown, potential difference between X and Y is ________ and across
40 Ω is ________ .
Answer/Explanation
Answer:
Explaination: 120 V, 0 V [In open circuit of a cell V = E for XY and no current
flows though 40 Ω]
33. The figure below shows currents in a part of electric circuit. The current i is
________ .
Answer/Explanation
Answer:
Explaination: 1.7 A
34. A wire is stretched so as to change its length by 0.1%, the percentage increase in its resistance will be _______ .
Answer/Explanation
Answer:
Explaination:
35. The current in the given circuit will be ________ .
Answer/Explanation
Answer:
Explaination:
36. A cell of emf E is connected with an external resistance R, then p.d. across cell is V. The internal resistance of cell will be ________ .
Answer/Explanation
Answer:
Explaination:
37. The figure shows a network of current and the magnitude of current. The current I
will be ________ .
Answer/Explanation
Answer:
Explaination: 23 A, using KirchhofTs law 7=15 + 5 + 3 = 23 A
38. When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction? [NCERT Example; Delhi 2012]
Answer/Explanation
Answer:
Explaination: No. As the collision is a random process, the electrons cannot get
deflected in the same direction.
39. A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor: current, current density, drift speed and electric field?
Answer/Explanation
Answer:
Explaination: Current, because in series, the current is same throughout the
wire.
40. The electron drift arises due to the force experienced by electrons in the electric field inside the conductor. But force should cause acceleration. Why then do the electrons acquire a steady average drift speed?
Answer/Explanation
Answer:
Explaination:
An electron does accelerate but loose its drift speed during the subsequent
collisions with a positive ion of the metal. Therefore, it is the average drift
speed which is acquired by the electron.