Question

c) A copper wire has a diameter 0.5 mm and resistivity 1.6 x10-8ohm m.
(i) What will be the length of this wire to make the resistance of 12 Ohm?
(ii) How much will be the resistance of another copper wire of same length
but half the diameter?

Answer 1

Answer:

48.875

Explanation:

d=0.5mm

d=5*10^-4 m

r= 5*10^-4/2

r=2.5*10^-4

R= 12 ohm

formula R= roh * l / A l= R*A/ roh but A = Π *r^2 A= 22/7 * (2.5 * 10^-4)^2 A=22*2.5*2.5*10^-4*10^-4/7 A= 137.5*10^-8/ 7 l= R*A/ roh l= 12*137.5*10^-8/7/ 1.6*10-8 l= 12*1375/16*7 l= 147.321 m ii) R is inversely proportional to the d ^2

then R = 1/d' ^2

R= 1/(1/2d)^2

R= 4/d^2

thus R becomes 4 times than first one.

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