# Flux density and force

1. Jan 13, 2008

### samblue

1. The problem statement, all variables and given/known data

A power line runs along the earths equator where the magnetic flux density, B, points from south to north and has a strength of 50*10-6T. The current in the line is 500A flowing from west to east. Find the magnitude and the direction of the fore acting on eath kilometer of the power line.

2. Relevant equations

F=qvBsintheta

diection is V cross B.

3. The attempt at a solution

I think I have to use the above equations, however i am unsure how to get the 500A cunnent into this? Is there a relationship linkng v and I? Also although i know how to do a cross product i am unsure how you present the direction, I know you have to use the right hand rule but how do you express this in the exam?

Thanks

2. Jan 13, 2008

### Kurdt

Staff Emeritus
I think it would be better to use $F = ILB\sin(\theta)$. To find the direction of the force you need to use Fleming's left hand rule. Your thumb is the direction of the force, your index finger the field and your middle finger the current.

http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/forwir2.html