Magnetism & electromagnetism

How to draw magnetic field lines using a compass

-Place plotting compass near the magnet
-Mark the direction the needle points
-Move compass to different points in the magnetic field & mark on direction each time
-Join up the lines

4 magnetic metals

Nickel, Iron, Cobalt, Steel

Magnetically hard

Can be permanently magnetised

Magnetically soft

Can only be temporarily magnetised

What is electromagnetism

When a current flows in wire, it creates a circular magnetic field around it

Solenoid

A straight coil of wire which can carry an electric current to create a magnetic field

What is an electromagnet

A solenoid with an iron core to increase the magnetic field strength

How to increase electromagnet strength

Increase current
Add iron core
Increase number of turns in the wire

The motor effect

A wire carrying a current creates a magnetic field which can interact with another magnetic field & cause a force that pushes the wire at right angles.

Fleming’s left hand rule

Thumb- Force
First finger- magnetic field
Second finger- Current

Split ring commutator

Reverses the direction of current every half turn to keep the coil rotating in an electric motor

Generator effect

Moving a magnet into/out of a solenoid induces a pd across the wire- current will only flow if it's a closed circuit