Question

6. A copper wire has diameter 0.5 mm and
resistivity of 1.6 x 10-8m. What will be the
length of this wire to make its resistance
102? How much does the resistance change
if the diameter is doubled ?
TI Τα
Given​

Answer 1

Explanation:

Given, diameter, d=0.5 mm

resistivity, ρ=1.6×10 −8 Ωm

Resistance, R=10 Ω

Let the length of wire be l.

A=πd 2 /4

R=ρ = πd 2 /4ρl

⟹l= 4ρRπd 2

l= 4×1.6×10 −8

10×3.14×(0.5×10 −3 ) 2 l=122 m R∝1/d 2

If the diameter is doubled, resistance will be one-fourth.

Hence, new resistance =2.5Ω