Magnetic Fields Around Current-Carrying Wires

What happens when an electric current flows through a wire?

A magnetic field is produced around the wire.

What is the shape of the magnetic field around a straight current-carrying wire?

Concentric circles centred on the wire.

What determines the direction of the magnetic field around a straight wire?

The direction of the current.

How can the direction of the magnetic field around a wire be determined?

Using the right-hand grip rule.

How is the right-hand grip rule used for a straight wire?

Point the right thumb in the direction of conventional current; curled fingers show the magnetic field direction.

What happens to the magnetic field when the current is reversed?

The direction of the magnetic field reverses.

What happens to magnetic field strength when current increases?

The magnetic field becomes stronger.

What happens to magnetic field strength as distance from the wire increases?

It decreases.

How can the magnetic effect of a current be demonstrated?

Place a compass near a current-carrying wire and observe the needle deflect.

Why does a compass needle deflect near a current-carrying wire?

The wire's magnetic field exerts a turning effect on the compass needle.

What happens to the compass when the current is switched off?

It returns towards the direction of Earth's magnetic field, assuming no other significant magnetic fields.

Why should the current direction be shown on a magnetic field diagram?

It determines the direction of the field lines.

What does a dot in a circle represent on a wire diagram?

Current travelling out of the page towards the observer.

What does a cross in a circle represent on a wire diagram?

Current travelling into the page away from the observer.

What happens to the magnetic field if the current in a wire is doubled?

At the same distance, the field becomes stronger, approximately doubling for a long straight wire.

Can an electric current produce a magnetic field without a permanent magnet?

Yes, a current-carrying conductor produces its own magnetic field.

Why is the magnetic field around a straight wire not uniform?

Its strength changes with distance from the wire.