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Induced voltage

When a conductor moves across a magnetic field, the charges in the conductor are pushed and a voltage appears. The voltage is largest when the velocity, the field and the conductor are perpendicular to each other. Faraday's law says more generally that the induced voltage equals the change in magnetic flux per time. Lenz's law says that the induced current opposes the change that created it. That is how a generator works.

\varepsilon = vBL

induced voltage in a moving conductor

\varepsilon = -\frac{\Delta\Phi}{\Delta t}

Faraday's law, approximate

Symbols

$\varepsilon$	induced voltage	V
$v$	speed	m/s
$B$	flux density	T
$L$	length	m

Example

A conductor of 0.3 m moves at 4 m/s perpendicular to a field of 0.5 T.

$\varepsilon = 4 \cdot 0.5 \cdot 0.3 = 0.6$ V.

If the conductor is at rest, or moves along the field, the induced voltage is zero.

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Part of Physics 2: Electromagnetism.