Describe the forces between magnetic poles and between magnets and magnetic materials, including the use of the terms north pole (N pole), south pole (S pole), attraction and repulsion, magnetised and unmagnetised

Magnetic Poles

Every magnet has two poles: a north pole (N) and a south pole (S). Think of them as the two ends of a stick that can stick to each other like a pair of oppositely charged magnets.

• 🔵 N pole is the end that points to the geographic North.
• 🔴 S pole is the end that points to the geographic South.

Forces Between Poles

When two magnetic poles are brought close together, they either attract or repel. The rule is simple:

1. Opposite poles attract: N ↔ S (like a magnet’s north end to another magnet’s south end).
2. Like poles repel: N ↔ N or S ↔ S (the same ends push away).

Mathematically, the force between two poles can be expressed (in a simplified form) as:

\$F = k \frac{p1 p2}{r^2}\$

where \$p1\$ and \$p2\$ are the pole strengths, \$r\$ is the distance between them, and \$k\$ is a constant.

Magnetised vs Unmagnetised Materials

Materials can be magnetised (have their own north and south poles) or unmagnetised (no permanent poles).

• 🔧 Magnetised materials: iron, steel, nickel, cobalt. They can stick to a magnet because they become temporary N and S poles.
• 🧪 Unmagnetised materials: plastic, wood, glass. They don’t stick to a magnet unless the magnet is very strong.

When a magnet touches an unmagnetised iron object, the iron becomes temporarily magnetised. The magnet’s field aligns the tiny magnetic domains inside the iron, creating opposite poles on the iron’s ends.

Exam Tips for 4.1

• Remember the Opposite = Attract, Like = Repel rule.
• Use the symbols N and S when writing short answers.
• When explaining why a magnet sticks to a metal object, mention temporary magnetisation and the alignment of magnetic domains.
• Practice drawing a simple diagram: two magnets with arrows showing the direction of the magnetic field lines (from N to S).
• Check that you use the correct terminology: magnetised vs unmagnetised, attraction vs repulsion.