# Homework Help: Magnetic Help Due Midnight

1. Apr 10, 2004

### phystudent

I need help, I have no idea how to even start?

A 17 A current is directed along the positive x-axis and perpendicularly to a uniform magnetic field. The conductor experiences a magnetic force per unit length of 0:57 N=m in the negative y direction. Calculate the magnitude of the magnetic field in the region through which the current passes. Answer in units of T.

2. Apr 10, 2004

### harsh

Okay, so here, you are given the force per unit length, the current, and the direction. You need to figure out the B-field. Do you know of any formulas that might work here? Be careful of directions!

3. Apr 10, 2004

### phystudent

I have no idea what to do...my teacher gave me nothing If you could give me a formula and tell me what things mean that would be very helpful

4. Apr 10, 2004

### harsh

Okay, so we know that if you have a particle moving in a magnetic field, it will experience a force. The direction of the force is perpendicular to that of the velocity and the magnetic field. Hence, the formula must have a cross-product. A general force equation is F = (q) (v) x (b) where q=charge, v=velocity, and b=magnetic field. In your case, you are given some current wire. Current is dQ/dt, and if you manipulate the above equation correctly, you will get something like: F = (I) (L) x (B). where I= current, L=length and B= b-field. In your case, you are given F/L, so all you need to do is divide the F/L by I and get your B-field.

5. Apr 10, 2004

### harsh

I think that in order to solve any of these problems, you should first try and understand the cross product and the direction. you will encounter them throughout your study of magnetism.

6. Apr 10, 2004