Electromagnetism

Right hand rule for straight conductors

Hold the wire in your right hand so that your thumb points in the direction of the convectional current

Into page

Cross

Out of page

circle with dot

Magnetic field INSIDE solenoid

South to north

Right hand rule for solenoids

If the solenoid is held in the right hand with your curved fingers pointing in the direction of the convectional current, your thumb points in the direction of the north pole of the solenoid

Dangers of high voltage transmissions

- electrocution

- collisions

Solutions for said dangers

- building lines underground

- lines closer together, these fields interfere with each other and so net effect is less

Electromagnetic induction def

A changing magnetic field causing a changing voltage

Factors that influence magnitude of induced emf / current (3)

1. Strength of magnetic field

2. Number of turns in coil

3. Speed of movement of magnet

Solenoid

a coil of wire with an electric current in it

How to know if emf / current is induced?

Galvanometer needle moves

Magnetic flux

the number of magnetic field lines passing through a surface area bounded by a closed solenoid loop. It is the "flow" of the magnetic field

Magnetic field

the space around a magnet in which magnetic materials will experience a force

Magnetic field lines

The lines that show the magnetic field around a magnet

Magnetic flux density

The amount of magnetic flux through a unit area which is perpendicular to the direction of the flux

Symbol for both magnetic field strength + flux density

B

Unti: Tesla (T)

Magnetic flux formula

Φ=BAcosθ

Magnetic flux symbol

Φ

In Webers

B

Flux density - magnetic field strength

Unit: Tesla (T)

A

Area

Unit: m^2

θ

Angle between magnetic field and normal

Unit: in degrees

What induces an electric current in the conductor?

The cutting of the field lines / flux when a conductor is moved through a magnetic field

Faraday's law formula

E = (-N x change in Φ) / (change it t)

E

Induced emf

N

Number of loops on the coil

Faraday's Law of Electromagnetic Induction

The induced emf in any closed circuit is equal to the rate of change of the magnetic flux through the circuit