# Unit 5: Magnetism and Electromagnetism

## Concepts

**Magnetism** - The study of magnetic fields and their relationship with electric current. Can also be referred to as electromagnetism.

**Magnetic fields** - Fields that create forces which act on ferromagnetic substances. They're represented visually with magnetic field lines. These lines point from north to south. When represented visually, lines that go into the page are drawn as x's, while lines going out of the page are drawn as dots.

**Electromagnetic induction** - A changing magnetic field induces an emf, or electric motive force. This emf produces an induced current.

**Lenz' Law** - A current produced by an induced emf moves in a direction so that the magnetic field created by that induced current opposes the original change in magnetic flux.

**Dot product and cross product ** - Two ways that vectors can be multiplied. Dot product only gives the magnitude, while cross product gives the magnitude and the direction of the resultant vector.

**Faraday's law of induction** - States that if the magnetic flux in a coil changes, an emf is induced in that coil.

## Formulas

**F = Iℓbsinθ** - The force on an electric current in a magnetic field. The force on the electric current = (current)(length of the wire the current is flowing through)(the strength of the magnetic field)sin(the angle between the vectors of the electric current and the magnetic field).

**F = qv x B** - The direction and magnitude of the force from a magnetic field on a charge. Vector of the force = (charge)(velocity of the charge) x (vector of the magnetic field).

**Φ = BAcosθ** - Used to find magnetic flux in some area. Magnetic flux = (strength of the magnetic field)(area)cos(angle between the magnetic field and the area).

**ε = -(△Φ/△t)** - Faraday's law of induction as a formula. Induced emf = -(change in flux/change in time).

**ε = Bℓv** - Another formula for induced emf, used when a rod is traveling through a magnetic field. Induced emf = (strength of magnetic field)(length of the rod)(speed of the rod).