# Homework Help: The Magnetic Field

1. Mar 5, 2008

### cemar.

1. What are the magnetic field strength and direction at points 1 to 3 in the figure?
Okay, sorry, once again i dont know how to get the picture up here so ill describe it!
There are 2 long wires 4 cm apart, the one on top with a current of 10 A in the positive x direction and the one on the bottom with a current of 10 A in the negative x direction.
Point 1 is 2cm above the top wire.
Point 2 in directly in between the two wires.
Point 3 is 2cm underneath the bottom wire.

2. Relevant equations
Okay so here im thinking something along the lines of that B = (u0/4pi)(Is 'r-hat'/r^2)
or maybe i found this equation in my notes that could be helpful and my gut says its the better bet
B = (u0I)/(2pid)

3. The attempt at a solution
Point 1 : (u0*10A)/(2pi*0.02m)
Point 2 : since it is inbetween two wires with opposite currents, so opposite fields (???) my guess is that it is equal to 0???
Point 3 : the opposite of point 1

Im also curious as to whether we assign a negative or positive value to the current??
And also would the bottom wire have an effect on the magnetic field at point 1??

2. Mar 6, 2008

### rl.bhat

You have to decide the direction of the field by right hand clasp rule. Accordingly the field at point 1 due to top wire is coming out of the paper at a distance 2 cm from the wire and field due to bottom wire is going into the paper at a distance 6 cm from this wire. Apply the same rule to the other points.