Question

A piece of 14-gauge copper wire 0. 163cm in diameter is 1 4.0m long. (a) What is its resistance? (b) If a potential

difference (V) of 1 .00 V is applied across the wire, what current flows in it? (c) What is the electric field in the

wire?

Answer 1

(a) Find the resistance of copper with resistivity 1.724·10^-8 Ohm·m:

$$R=\frac{\rho L}{A}=\frac{4\rho L}{\pi d^2}=0.116\space\Omega.$$

(b) The current is

$$I=\frac VR=8.65\text{ A}.$$

(c) The electric field inside the wire is zero.