# Formula: Induced Voltage Due to Area Change

## Induced voltage

Unit
This voltage is formed, for example, between the end points of a conductor loop when the area $$A$$ enclosed by the conductor loop is changed. Note: Only as long as the temporal change of this area happens, the induction voltage is measurable. As soon as the area is not changed, the voltage at the endpoints of the conductor loop disappears; of course only under the condition that the magnetic field $$\class{violet}{B}$$ is constant.

If the conductor loop is short-circuited, i.e. the two contacts are connected, then an induction current $$I_{\text{ind}}$$ is generated in the conductor loop.

## Area change

Unit
Area $$A$$ enclosed by the conductor loop changed by the value $$\Delta A$$. If this area $$A$$ changes in time, i.e. $$\Delta A \neq 0$$, then an induced voltage or induced current is generated in the conductor loop.

The minus sign in the induction law is justified by Lenz's rule, and must be there to avoid violating conservation of energy.

## Magnetic flux density (B-field)

Unit
Magnetic field passing through the enclosed area of the conductor loop. According to this formula, $$\class{violet}{B}$$ is NOT changed, i.e. the (constant) external magnetic field must not be increased or decreased.

## Time span

Unit
Time, within which, the enclosed area has changed by the value $$\Delta A$$.

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