# Copper wire length, iron wire resistance, cost of hall light

The answers are give but please provide the solutions.

Resistivity Problems:

1. How long should a copper wire 0.4mm in diameter be for it to have a resistance of 10ohms? The resistivity of copper is 1.7 x 10-8 Q-m

Answer: 74m

2. An iron wire has a resistance of 0.20ohms at 20°C and a resistance of 0.30ohms at 110°C. Find the temperature coefficient of resistance of the iron used in the wire.

Answer: 0.0056/°C

Electrical Power Problems:

1. A 75-W hall light is left on continuously. At $0.09 per kilowatt-hour, find the cost per week.

Answer: $1.13

https://brainmass.com/physics/power/copper-wire-length-iron-wire-resistance-cost-hall-light-303254

#### Solution Preview

Resistivity Problems:

1. How long should a copper wire 0.4mm in diameter be for it to have a resistance of 10ohms? The resistivity of copper is 1.7 x 10-8 Q-m

Answer: 74m

Solution:

The resistance and resistivity are related by the following equation:

ρ=R A/l

where is the resistivity in m,

R is the resistance in ,

A is the cross-sectional area in ...

#### Solution Summary

The expert examines the copper wire length, iron wire resistance and the cost of hall light.