Question

A wire of resistance 20 ohm is drawn out so that its length is increased to twice its originals length . Calculate resistance in the new situation

Answer 1

if length increases resistance also increases

So,it is increased to twice its originals length, area of cross decreases

20*4=80ohm

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Answer 2

Given resistance = R1 = 20 ohm

Let length of the wire = L

Therefore, new length of the wire = 2L

Since, when the length is doubled, cross sectional area of the wire becomes half.

Therefore, new resistance = R = 2L/ (A/2) =4L/A

R = 4 x 20 (since, L/A = resistance)

R = 80 ohm.