A straight segment of wire 35.0 cm long carrying a current of 1.40 A is in a uniform magnetic field. The segment makes an angle of 53∘ with the direction of the magnetic field.

Question

If the force on the segment is 0.200 N, what is the magnitude of the magnetic field? 

Answer 1

The key equation here is: F = I L . B

Applying the dot product, the equation becomes: F = I L B cos(x)

We want to find B. So our equation becomes:

B = F / I L cos (x)

We know that:

F = 0.200N; I = 1.40A; L = 0.350m; Angle (x) = 53∘

My calculator tells me that: cos (53∘) = 0.602

Therefore: B = 0.200 / (1.40 * 0.350 * 0.602)

Which means that: B = 0.0678T