Emf

Definition

Electromotive force (emf) is the voltage generated by a source such as a battery or by changing magnetic fields. It is the driving force that causes electrons to move in a circuit.

5 Must Know Facts For Your Next Test

1. Emf is measured in volts (V).
2. According to Faraday's Law, emf is induced when there is a change in magnetic flux through a loop.
3. The formula for emf induced in a coil with N turns is $\mathcal{E} = -N \frac{d\Phi}{dt}$, where $\Phi$ is the magnetic flux.
4. Lenz's Law states that the direction of the induced emf opposes the change in magnetic flux that caused it.
5. A practical example of emf induction is how electric generators convert mechanical energy into electrical energy.

Review Questions

• What are the units used to measure electromotive force?
• How does Faraday’s Law relate to electromotive force?
• Explain Lenz’s Law and its relation to induced emf.

Related terms

Magnetic Flux: A measure of the quantity of magnetism, considering the strength and extent of a magnetic field.

Faraday’s Law: A fundamental law stating that an electromotive force is induced in a conductor when there is a change in magnetic flux through it.

Lenz’s Law: A law stating that an induced current will flow in such a direction as to oppose the change in magnetic flux that produced it.