# magnitude of magnetic field problem?

Determine the magnitude of the magnetic field midway between two long straight wires separated by a distance d if one carries current I1 when the other carries I2. Assume I1 > I2.

A. Assume these currents are in the same direction. Express your answer in terms of the variables d, I1, I2, and appropriate constants.

B. Assume these currents are in opposite directions. Express your answer in terms of the variables d, I1, I2, and appropriate constants.

### 1 Answer

- nyphdinmdLv 71 month agoBest Answer
A. Amperes law tells you that B = u0*I/(2*i*r) where r = distance from current I. Set r = d/2. Note that by the right hand rule, B(I1) is in the opposite direction from B(I2) at r = d/2 so the total B field magnitude is

B = B(I1) - B(I2)= uo/(pi*d) * (I1 - I2)

B. If I2's direction is reversed then B(I1 and B(I2) are in teh same direction at r = r/2 so

B = B(I1) + B(I2)= uo/(pi*d) * (I1 + I2)