Electromagnetic Induction

Flashcards on Electromagnetic Induction, Faraday's Law and Lenz's Law.

What does it mean to 'induce' in the context of electromagnetism?

To cause.

What is electromagnetic induction?

When a changing magnetic field near a coil of wire causes an electromotive force (EMF) or voltage to appear across the coil.

What happens to the galvanometer reading when a bar magnet is moved towards a coil?

A current is recorded.

What induces a current in a coil?

A changing magnetic field.

What is Magnetic Flux Density, and what are the units used to measure it?

A measure of the strength of the magnetic field at one point, measured in Teslas.

What is magnetic flux?

The total magnetic field passing through an area.

What are the units for Magnetic Flux?

Webers (Wb).

Is magnetic flux a scalar or vector quantity?

Scalar

State Faraday's Law of Electromagnetic Induction.

The size of the induced emf is directly proportional to the rate of change of flux.

According to Faraday's Law, what does the negative sign in the equation E = - dΦ/dt signify?

The emf is in the opposite direction to the flux (Lenz’s Law).

State Lenz's Law.

The direction of the induced current opposes the change that produces it.

What happens when the south pole of a magnet approaches a coil, according to Lenz's Law?

An emf is induced in the coil, and the induced current flows in a direction that opposes the south pole, causing the near end of the coil to behave like a south pole to repel it.

What is special about alternating current (AC)?

Alternating current constantly changes direction.

What is self induction?

When a changing magnetic field induces an emf in the same coil.

What is mutual induction?

When a changing magnetic field in one coil induces an emf in a nearby coil.