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 ?
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New resistance is 80ohm
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R= ¶l/A = 20
Given, length is increased to twice its original length..so ne length will be
l+ l=2l
when length is increased twice, area of cross section decreases to half.
so the new area will be
a/2
The new resistance will be: ¶ × 2l
____
a/2
=2×2׶l
_____
a
= 4 ¶l/a
= 4× 20
= 80 ohms
Given, length is increased to twice its original length..so ne length will be
l+ l=2l
when length is increased twice, area of cross section decreases to half.
so the new area will be
a/2
The new resistance will be: ¶ × 2l
____
a/2
=2×2׶l
_____
a
= 4 ¶l/a
= 4× 20
= 80 ohms
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