# Homework Help: Magnetic Forces on Current-Carrying Wires (in magnetic fields). Is answer correct?

1. Feb 3, 2008

### predentalgirl1

1. A horizontal magnetic field of 1.0 x 10^-4 T is at an angle of 30 degrees to the direction of the current in a straight, horizontal wire 75 cm long. If the wire carries a current of 15 A, what is the magnitude of the force on the wire?

2.B be the magnetic field = 1.0 x 10-4 T

Θ be the angle between the magnetic field and current = 300

L be the length of the wire = 75 cm = 0.75m

I be the current in the wire = 15 A

F be the force in the wire ?

From basic magnetic force

F = qvB sin Θ

F = q(L/t)B sin Θ

F = (q/t)LB sin Θ

F = I L B sin Θ

3. F = 15 x 0.75 x 1.0x10-4 sin 300

F = 11.25 x 10-4 sin 300

F = 11.25 x 10-4 (1/2)

F = 5.625 10-4 N

F = 0.5625mN

(Ans)

2. Feb 3, 2008

### Mindscrape

Your algebra is fine, so as long as you didn't make a mistake punching in the numbers it looks good to me.

3. Jan 15, 2009

### psykatic

Re: Magnetic Forces on Current-Carrying Wires (in magnetic fields). Is answer correct

It should be $$sin\theta$$ i.e $$sin~{30^\circ}$$, you've made a typo. Otherwise, the answer is correct!