Magnetic Fields

A magnetic field is the region around a magnet (or magnetic material) where a magnetic pole feels a force. Imagine an invisible map around a magnet that shows where a tiny compass would point and how strongly it would be pushed or pulled.

Field Lines and Direction

We draw magnetic field lines to show the field. Outside a bar magnet, lines go from the north pole (N) to the south pole (S). The arrow on a field line shows the direction a north pole would move. Lines close together mean a stronger field; lines far apart mean a weaker field. The field is strongest at the poles. Between opposite poles held close, the lines are straight and evenly spaced (a uniform field).

Attraction and Repulsion

• Like poles repel (N–N or S–S).
• Unlike poles attract (N–S).

These forces happen because the magnetic fields interact.

Seeing Magnetic Fields

• Iron filings: sprinkle on paper over a magnet and gently tap. Filings line up along field lines, showing the pattern (but not the direction).
• Plotting compass: place the compass near the magnet, mark the arrow direction, move along and repeat to trace a line. Arrows show N to S direction.

Magnetic and Non‑magnetic Materials

Magnetic materials include iron, steel, nickel, and cobalt. They can be attracted and can become magnetised. Most other materials (like wood, plastic, aluminium) are non‑magnetic.

Induced Magnetism

A material like soft iron becomes a magnet only while it is in a magnetic field (temporary magnet). Steel keeps its magnetism for longer (permanent magnet). Temporary magnets switch on and off easily; permanent magnets are harder to magnetise but keep their strength.

Fields from Electric Currents (Overview)

• A current in a straight wire makes circular field lines around the wire (stronger when current is bigger).
• A coil of wire (solenoid) makes a field like a bar magnet, with an N and S end. More turns or more current makes a stronger field.

Common Misconceptions

• Field lines are models we draw; they are not physical strings.
• Magnets do not attract all metals; only magnetic materials are attracted.
• Field lines form complete loops: N to S outside, through the magnet from S to N inside.

Real‑world Connections

• A compass aligns with Earth’s magnetic field to show direction.
• Door catches and fridge seals use magnets to hold closed.