# Homework Help: Current carrying wire in uniform magnetic field; where is net magnetic field 0?

1. Mar 17, 2012

### mm2424

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

A long wire carrying 100 A is perpendicular to the magnetic field lines of a uniform magnetic field of magnitude 5.0 mT. At what distance from the wire is the net magnetic field equal to zero?

2. Relevant equations
B = iμo/2∏R

3. The attempt at a solution

I reasoned that in order for the net magnetic field at some point outside the wire to be 0, the magnetic field from the current in the wire must cancel out the uniform magnetic field (B = 5.0 mT).

So, I used B = iμo/2∏R

B = 5.0 x 10^-3 T = 100Aμo/2∏R

R = 4 mm

Is this reasoning sound?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Mar 18, 2012

### Redbelly98

Staff Emeritus
Looks good