Question

A 10 ohm résistance wire is recasted into a new wire, calculate the new resistance of the wire
1. its length is doubled
2. its cross section is doubled

Answer 1

$\huge\mathfrak{Answer:}$

Let the original length of wire be l

Let the original area of cross section be A

Resistance=ρl/A=10

(1) Its length is doubled

New length=2l

New resistance=ρ2l/A=2(ρl/A)=2(10)=20Ω

(2)Its cross section is doubled

New area of cross section=2A

New resistance=ρl/2A=ρl/A÷2=10÷2=5Ω