# Magnetism

 Subject classification: this is a physics resource.

The magnitude induced EMF through a loop of conducting material is equal to the magnitude of the time derivative rate of change of the magnetic flux through that loop.

${\displaystyle \left|{\frac {d\Phi _{B}}{dt}}\right|=\left|e.m.f\right|}$

## Lenz's Law

The polarity of the induced EMF is such that oppose the changes/current that causes it.

${\displaystyle e.m.f=-N{\frac {d\Phi _{B}}{dt}}}$

## Magnetic Field Strength

Magnetic Field Strength is defined as the force on one metre of wire carrying a current of one amp at right angles to the magnetic field. Magnetic Field Strength is also called flux density and is measured in teslas, T.