How does the resistance of a wire change when:
its diameter is tripled?
where l = length of wire
A= area of cross-section of the wire
When the diameter is tripled, d' = 3d Radius, r' = 3r
Area of cross-section, `A=Api^2=A(3pi)^2=9Api^2=9A`
Thus, the area of cross-section will become nine times.
Then the new resistance,
Thus, the resistance will be reduced by nine times.