# Homework Help: Biot Savart homework question

1. Nov 11, 2007

### krondragon

[SOLVED] Biot Savart homework question

1. The problem statement, all variables and given/known data
What are the strength and direction of the magnetic field at point P in Figure P32.52, in which the current is 4.5 A and d = 2.2 cm?

2. Relevant equations
Mu*I/(4R) <--- Magnetic field for a half loop at center of circle

3. The attempt at a solution
I tried numerous things with this. I know that the straight wires contribute no field so I only had to work with the arcs. I knew that the total magnetic field faces away from you as the magnetic field from the closest wire is stronger and goes into the page. I am at my last submission for this homework problem, so it is a hit or miss =(. My teacher explained it quickly and my text book does not elaborate too far into this law. I have been stuck on this for several hours already. Thanks in advance.

EDIT

I am in no hurry whatsoever. This homework isn't due till thursday and I already have all questions but this one done. Thank you again in advance and answer when it is most convenient for you.

Last edited: Nov 11, 2007
2. Nov 11, 2007

### G01

You are correct that you only have to work with the arcs. Try to use the principle of superposition. Find the field from one loop and add it to the field from the other loop, while keeping track of signs. This should give you the net field. What direction should the net field point? I will need to see more work if I am going to be able to help you further.

3. Nov 11, 2007

### krondragon

Oh my god I found my mistake. It turns out I misread distance d. I thought distance d was the distance between the arcs, not the distance from arc 2 to the point p. I figured it out and was able to obtain the correct answer.

Last edited: Nov 12, 2007
4. Nov 12, 2007