# What is the current in the current loop?

• ksmith159

## Homework Statement

It is important to be completely isolated from any magnetic field, including the Earth's field. A 1.00m diameter current loop with 200 turns of wire is set up so that the field at the center is exactly equal to the Earth's field in magnitude but opposite in direction. What is the current in the current loop?

## Homework Equations

I=B2r/mew(naught)

## The Attempt at a Solution

The part of the question that states "wire is set up so that the field at the center is exactly equal to the Earth's field in magnitude but opposite in direction" makes me think that we set B=0 rather than using the Earth's magnetic field because opposing fields cancel. If this the the case the current would be zero correct?

If this is not the case then the question is trivial (just plug and chug).

Which way is correct?

## Answers and Replies

B = μο*N*I/2r.
Set the coil such that the plane of the coil is in east-west direction. Set the magnitude and the direction of the current in the coil such that the field at the center is equal B(E) and direction is towards south.