Q20 of 41 Page 461

A wire of given material having length l and area of cross-section A, has a resistance of 2 Ω. Find the resistance of another wire of same material having length 2l and are of cross-section A/2.

Given

Resistance (R) = 2Ω


Area of cross-section = A


Length = l


We know that


⇒ (1)


New Area = A/2


New Length = 2l


New Resistance = R’


⇒


⇒


⇒


⇒ from (1).


Hence the new resistance will be four times the previous resistance i.e. 8Ω.


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