# What is the magnitude of the magnetic field .

1. Apr 6, 2009

### superjen

An overhead electric power line carries a maximum current of 165 A. What is the magnitude of the magnetic field at a point 2.40 m directly below the power line?

Soo...
I = 165A
L = 2.40m

Equations i have learnt areee
(1) F = ILBsin(theta)
(2) F = |q|vBsin(theta)
(3) r = mv / |q|B
(4) B = (constant)I/R

im unsure
. i tried equation 4 . but that didnt work. any help would be awesome!

2. Apr 6, 2009

### LowlyPion

Maybe this will help?
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c3

3. Apr 6, 2009

### superjen

i just tried it, and it doesnt work. :S

4. Apr 6, 2009

### LowlyPion

What units do they want it in? Gauss or Tesla?

5. Apr 6, 2009

Tesla

6. Apr 6, 2009

### LowlyPion

What did you get then?

7. Apr 6, 2009

### superjen

one was
0.0000137T
and
0.0000275T
Neither of them worked.

8. Apr 6, 2009

### LowlyPion

Is it looking for 1.38*10-5 T by any chance because of significant digits issues?

9. Apr 6, 2009

### superjen

ok, that worked :S:S