# Electromagnetism

See magnetism first!

Ensure you understand what 'magnetism' is before you start on electromagnetism... domains, field lines, poles etc

Take a minute to think about that....

Electrons, protons, ions, alpha particles and beta particles are all charged.

When stationary they have no magnetc field around them, but when they move they have! Wow!

It also follows that all electrical wires have a magnetic field around them (but only when the current flows).

### How to draw a representation of a current carrying wire

The field lines form a concentric circle pattern around the wire.

The symbol for the current carrying wire itself is a section through the wire (as shown below). The field lines are then drawn around it.

You are used to the idea that the scientific symbol for a current in a wire is an arrow.

You usually draw a side-on view of a wire - a line, but in this case you are drawing a section through the wire - a circle - and you therefore draw a section through the arrow too!

A current carrying wire has either the arrow tip (current coming out of the page at you) or the cross of the tail feathers of the arrow (current going into the page away from you) shown within the circle that represents the section of the wire.

NB Don't treat the circle that represents the edge of the wire as a field line.... if you put an arrow on it your wire section disappears!!

### The Right Hand Grip Rule

The direction of the field lines can be found using the right hand grip rule.

You must know this at GCSE level (and at A level of course!)

Grip a pencil in your right hand.

Hold it so that your thumb points in the same direction as the pencil tip and your fingers curve around it. (see the diagram).

The pencil represents the current and its tip the direction of the current arrow.

When determining the direction of field lines, place the pencil on the page (tip into or away from page as required) and then your will fingers point in the direction of the field lines.