Question:
a piece of wire of resistance 20 ohm is drawn out so that its length increased twice its original length .calculate the resistance of the wire in the new situation
Answer:
Given,
R=20 Ω
Let,Length of wire is L and when it drawn out, its new length is 2L
The volume of wire in both the situations remains constant.So, it the length of wire doubled, the area of cross section of wire becomes half.
So, the new resistance of wire-
Rnew = 2l/(A/2)
=4L/A
=4×Old resistance of wire (Because, R=L/A)
=4×20 = 80 Ω
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