# Homework Help: Resistance help

1. Mar 17, 2007

### CathyLou

Hiya.

I'm currently studying AS Level Physics and I've no idea how to start the following question.

Any help would be really appreciated.

‘Jump leads’ may be used for starting the engine of one car using the battery of another car. One such set of leads is 4 m long, and consists of copper cables with a cross-sectional area of 13.6 mm^2.

(a) What is the voltage drop along the length of one of these cables when it is carrying a current of 100 A?

(b) In practice, such cables are made up of a number of strands of thin copper wire rather than a single strand of thicker wire. Why?

Thank you.

Cathy

2. Mar 17, 2007

### drpizza

What equation for resistance? (Hint, length, cross-sectional area, and resistivity of copper are important)

3. Mar 17, 2007

### marcusl

After figuring out part a using drpizza's hint--part b has little to do with physics, it's a practical usage issue.

4. Mar 17, 2007

### edward

As for part b.

One solid 13.6 mm wire, is fairly stiff sooo