Magnetic Fields & Field Lines

What is a magnetic field?

The region around a magnet or current-carrying conductor where magnetic forces act.

How can a magnetic field be represented?

Using magnetic field lines.

What do magnetic field lines show?

The direction and relative strength of the magnetic field.

In which direction do magnetic field lines point outside a bar magnet?

From the north pole to the south pole.

What does the direction of a magnetic field mean?

The direction in which a north-seeking magnetic pole would experience a force.

What do closely spaced magnetic field lines indicate?

A stronger magnetic field.

What do widely spaced magnetic field lines indicate?

A weaker magnetic field.

Where are magnetic field lines most closely spaced around a bar magnet?

Near its poles.

Can magnetic field lines cross?

No, because the field has only one direction at any given point.

What is a uniform magnetic field?

A magnetic field with constant strength and direction.

How are field lines drawn in a uniform magnetic field?

As straight, parallel, equally spaced lines.

Where can an approximately uniform magnetic field be produced?

Between two close, opposite, flat magnetic poles.

How can a magnetic field be detected?

Using a plotting compass.

What does the north-seeking end of a plotting compass show?

The direction of the magnetic field at that point.

How can iron filings be used to investigate a magnetic field?

They align with the field, revealing its pattern.

Why do iron filings become aligned in a magnetic field?

They become temporarily magnetised and rotate into alignment.

Why is a plotting compass needed to determine field direction?

Iron filings show the pattern, but not which way the field points.

What happens to magnetic field strength as distance from a bar magnet increases?

It generally decreases.

Why is a magnetic field strongest near the poles?

The magnetic field lines are most concentrated there.