Q.4
W
A piece of wire of resistance 30 Q 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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Step-by-step explanation:
When length of wire is doubled i.e. 2l
Also it's area of cross section becomes half i.e
2
A
Resistance R=
A
ρl
=20Ω
New Resistance ,
R
′
=
A
′
ρl
′
=
A
ρ(2l)×2
=4
A
ρl
=4(
A
ρl
)
=4×20
=80Ω
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