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A wire of a certain material is stretched slowly by ten percent. Its new resistance

A wire of a certain material is stretched slowly by ten percent. Its new resistance and specific resistance become respectively

Options

(a) both remain the same
(b) 1.1 times, 1.1 times
(c) 1.2 times, 1.1 times
(d) 1.21 times, same

Correct Answer:

1.21 times, same

Explanation:

Δl / l = 0.1 , Therefore, l = 1.1 but the area also decreases by 0.1.

mass = ρlA = Vρ. In l + In A = 1n mass.

.·. Δl / l = ΔA / A = 0 ⇒ Δl / l = -ΔA / A

Length increases by 0.1, resistance increases, area decreases by 0.1, then also resistance will increase. Total increase in resistance is approximately 1.2 times, due to increase in length and decrease in area. But specific resistance does not change.

AIPMT2008
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