Question

A wire as a length of 1.50m, diameter 0.60mm and resistance of 2ohms. calculate the resistance R of a wire of the same materials of length 0.50m and diameter 0.3mm​

Answer 1

1. R=ρ×L/A

ρ=R×A/L

A=pie(r²)=pie(0.6²)=pie(0.36)=1.13

ρ=2ohm×1.13mm²/1500mm

ρ=0.0015ohm.mm

2. we were told that the wires were made of the same substance so the resistivity(ρ)is the same for both wires so:

R=ρ×L/A

R=0.0015ohm.mm×500mm/0.09mm²

R=8.3'ohm

so our resistance for the second wire is :

R=8.3'ohm