Question

6. A copper wire has diameter 0.5 mm and resistivity of 1.6 x 10-22 m. What will be
the length of this wire to make its resistance 10 22? How much does the resistance
change if the diameter is doubled?​

Answer 1

Answer:

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=ρl/A = πd 2 /4 ρl ⟹l= 4ρ Rπd 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

Hope that helps you