# Homework Help: Force in a magnetic field. Need help using the equation

1. Sep 28, 2008

### crh

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

What is the magnitude of the force per meter of length on a straight wire carrying a 6.70-A current when perpendicular to a 0.89-T uniform magnetic field?

What if the angle between the wire and field is 45.0°?

I know how to do the whole thing, I just can't get my answer right. I don't know if I am working the equation out right.

2. Relevant equations

F=IlBsin$$\theta$$

3. The attempt at a solution

Using the above equation. For part A I know that I use it for 90 degrees at 1m

F=(6.70A)(0.89T)sin90=5.9N/m

Part B is the one I can't get the answer to.

F=(6.07A)(0.89T)sin45

**I haven't had a trig class or a physics class for about 7 years so I don't remember how to exactly use sin. For Part A I got the correct answer because I just didn't use the sin. I just took the (6.70A*0.89T). Can someone explain how to use sin or how to get the right answer. I got 5.07 N/m but that is not correct.

Thanks in advance to everyone that helps.

2. Sep 28, 2008