Cracking the SAT Physics Subject Test

Loop seen from side

The most effective airflow is when the loop is completely perpendicular, as in the
situation to the left. The least effective is when the airflow and loop are in the
situation to the right.

We can apply this idea to a magnetic field passing through a loop. The magnetic
flux, ΦB, through an area A is equal to the product of A and the magnetic field

perpendicular to it.

ΦB = B ┴ A = BA cos θ

Magnetic Flux Units

The SI unit for magnetic

flux is called the weber

(Wb), which is equivalent

to a tesla meter squared

(T×m^2 ).

Magnetic flux measures the density of magnetic field lines that cross through an
area. (Note that the direction of A is taken to be perpendicular to the plane of the
loop.)