Question

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

Answer 1

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When length of wire is doubled i.e. 2l

Also it's area of cross section becomes half i.e 2A

Resistance R=

ρl/A=20Ω

New Resistance ,

R′ = ρl′/A'

= ρ(2l)×2/A

=4ρl/A

=4(ρl)/A

=4×20

=80Ω

Answer 2

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Hahaha