Q. Resistance of a wire is 50O. If the length of that wire is doubled, keeping the volume same. What will be the new resistance?

A
25O
B
50O
C
100O
D
200O
Solution:

R=?*l/A
where,
R: resistance
?: resistivity
l: length of wire
A: area of wire
R1=50,
l2=2*l
V1=A1*l1,
V2=A2*l2, V1=V2
from this, A2=A1/2
R2=?*2l1/(A1/2)
R2=4*R1
4*50=200

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