# Force on wire

## Homework Statement

A stiff wire 50cm long is bent at a right angle in the middle. One section lies along the z axis and the other is along the line y=2x in the xy plane. A current of 20A flows in the wire down the z axis and out the line in the xy plane. The wire passes through a uniform magnetic field give by B=.318i. Determine the magnitude and direction of the total force on the wire.

F=BILsin(theta)

## The Attempt at a Solution

For the z axis part of the wire, I get F=(20)(.25)(.318)
For the xy plane part of the wire I get (20)(.25)(.318)(.447)
Now when i square these forces take the sum and square root the answer, I don't get the magnitude I should. This problem is pretty straight forward, not quite sure why I cant get it.

Thanks guys

## Answers and Replies

SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
0.447 ≈ cos(θ), where θ is the angle the xy-plane portion of the wire makes with the x-axis (also the direction of the B field.

sin(θ) = 2/√(5) .