# Magnetism Questions Help

1. Apr 26, 2013

### silentcoder

1. The problem statement, all variables and given/known data
1. Determine the magnetic force acting on an proton (m = 1.67 x 10-27 kg) moving at 2.9 x 106 m/s in a magnetic field of 6.8 T. The proton is moving south. The magnetic field points straight down.

2. A 6.0 m long wire with 7.0A of current flowing through it experiences a force of 12 N. Determine the magnitude of the magnetic field. You may assume that the current and the magnetic field are 90° to one another.

2. Relevant equations
1. Fm = qvbsinƟ
2. Fm = IlBsinƟ

3. The attempt at a solution
1. There was no charge given so is it alright to use charge of 1.6x10^-19?
Fm = qvbsinƟ
Fm = (1.6x10^-19 C)(2.9x10^6 m/s)(6.8T) sin 90
Fm = 2.53 x 10^-12 N

2. No magnetic field strength is given so how can i figure out the magnetic field strength?

Thanks

2. Apr 26, 2013

### SC400slide

I would love to know as well...

3. Apr 26, 2013

### rude man

Yes. A proton has charge = electron but + instead of -.
What is the force on a wire of length L in a B field if the B field is orthogonal to the wire? Very basic formula ...

4. Apr 26, 2013

### silentcoder

For number 1 i get: Fm = -3.15x10^-12 N[South]

For number 2 I am having hard time understanding what you are trying to say.

5. Apr 26, 2013

### rude man

If you'll try to answer my question ... I should have added, the wire has a current i flowing thru it.

Last edited: Apr 26, 2013
6. Apr 26, 2013

### silentcoder

The formula will be F = ILB SinƟ

This is what I get:
F = ILB sin 90
12 N = (7.0 A)(6.0 m)B sin 90
12 N/(7.0 A)(6.0 m) = B sin 90
2/7 = B sin 90
B = 2/7 T
B = 0.29 T

Last edited: Apr 26, 2013
7. Apr 26, 2013

### rude man

Looking good ...

8. Apr 26, 2013

### silentcoder

Thanks so were those 2 questions correct?

9. Apr 26, 2013

### rude man

I did not check your numbers but the formulas were correct.