Question

if the length of the wire is tripled and its area of cross section reduces to 5 times , if the initial resistance of the wire is 50 ohm . find the change in resistance of the wire
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Answer 1

Answer:

Let initial resistance = R

length = l

area of cross section = a

its resistivity = e

R = e * l/a

Let final resistance = R'

length = l' = l/3 since wire is tripled

area = a' = a*3 since wire is tripled

R' = e * l'/a'

R' = e * l/a*3*3

R' = e l/9a

R' 1/9 * el/a

but el/a = R

R' = 1/9 R