Question

at 20 c a length of copper wire has a resistance of 5.0. What is its resistance when the wire is heated to 80c? let a=.0004 at 20c.

Answer 1

Answer:

$R=5.12\ \Omega$

Explanation:

Electric Resistance and Temperature

For some materials, resistivity is linearly related to the temperature. The function that relates them is

$R=R_o[1+\alpha (T-T_o)]$

Where Ro is the electric resistance at 20°C, $\alpha$ is the temperature coefficient of the conductor, T is the actual temperature at which we want to compute R, and To is the initial temperature, usually 20°C.

The problem gives us the following values

$R_o=5\ \Omega,\ T_o=20^oC,\ \alpha=0.0004\ ^oC^{-1},\ T=80^oC$

Thus

$R=5[1+0.0004 (80-20)]=5.12\ \Omega$

$\boxed{R=5.12\ \Omega}$