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# Introduction to electromagnetism

## Currents and magnetic fields

Moving charged particles produce magnetic fields .

A current in a wire produces a magnetic field around the wire.

A moving electron also produces a magnetic field.

Similarly, magnetic fields interact with charged particles . A charged particle that moves through a magnetic field will experience a force.

An electron in a magnetic field will follow a curved path!

Electricity and magnetism are fundamentally connected to each other. The relationship between electricity and magnetism is called electromagnetism.

This is a Tesla coil. It uses alternating currents and magnetic fields to produce impressive lightning-like effects.

## Conventions in electromagnetism

Drawing magnetic field patterns and electric currents on a sheet of paper can be complicated because they often involve three dimensions.

Several conventions are used to make things clearer:

• Magnetic fields are represented by the symbol $B$ or $\vecphy{B}.$
• The following symbol means something (a current, field, force etc.) is directed into the page.
• The following symbol means something (a current, field, force etc.) is directed out of the page.

Left: conventional current coming out of the page produces an anticlockwise circular magnetic field. Right: the field is reversed if the current is reversed.