A coil has N turns enclosing an area of A . In a physics laboratory experiment,

Question

A coil has N turns enclosing an area of A. In a physics laboratory experiment, the coil is rotated during the time interval t from a position in which the plane of each turn is perpendicular to Earth's magnetic field to one in which the plane of each turn is parallel to the field. The magnitude of Earth's magnetic field at the lab location is B.

What is the magnitude initial of the magnetic flux through the coil before it is rotated? (Units of  

Tm^2)

Hint:

The formula for the magnetic flux (1) through one wire loop is

1=B A =BAcos(),

where B  is the magnetic field through the loop, A  is the area vector of the loop, and is the angle between the magnetic field and the area vector.

Note that the area vector of the loop is normal to the plane of the loop. As a result, there are two possible initial orientations with respect to the magnetic field (parallel and antiparallel). Either choice is acceptable, as long as one maintains consistency throughout the problem. In this problem we will deal with magnitudes, so the initial orientation will not be an issue.

Hint:

The initial angle between the magnetic field and the area vector can be taken to be either 0 degrees (area vector parallel to the magnetic field) or 180 degrees (area vector antiparallel to the magnetic field), since the plane of the coil is perpendicular to the magnetic field. Either number is correct as long as one maintains consistency with the choice of area vector.

Explanation / Answer

flux = BA cos(0)

= BA for 1 turn

for N turn =

flux = NBA ( T- m2)

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