Magnetism and Matter

Notes

1.1 Magnetism

Magnetism is the phenomenon associated with the force of attraction or repulsion produced by magnets and magnetic materials.

A magnet is a material or object that produces a magnetic field.

Every magnet has two poles:

North Pole (N)

South Pole (S)

Basic Properties of Magnets

Like poles repel each other: N–N or S–S.

Unlike poles attract each other: N–S.

A freely suspended magnet approximately points in the north-south direction.

Magnetic poles always occur in pairs.

An isolated north or south magnetic pole has not been observed.

Breaking a magnet produces smaller magnets, each having both N and S poles.

1.2 Bar Magnet

A bar magnet is a rectangular magnetic material having a north pole at one end and a south pole at the other.

Magnetic Field Lines

Magnetic field lines are imaginary curves used to represent a magnetic field.

Outside a bar magnet:

N → S

Inside the magnet:

S → N

Therefore, magnetic field lines form continuous closed loops.

Simple Diagram

Properties of Magnetic Field Lines

They form continuous closed curves.

Outside the magnet, they travel from north to south.

Inside the magnet, they travel from south to north.

The tangent at any point gives the direction of magnetic field at that point.

Two magnetic field lines never intersect.

Closer field lines represent a stronger magnetic field.

Field lines are crowded near the poles because the field is stronger there.

Board Tip: The properties of magnetic field lines are a common short-answer question.

1.3 Bar Magnet as an Equivalent Solenoid

A current-carrying solenoid produces a magnetic field similar to that of a bar magnet.

One end of the solenoid behaves as a north pole and the other as a south pole.

Therefore:

A bar magnet can be considered equivalent to a current-carrying solenoid.

The magnetic field patterns of a bar magnet and solenoid are similar.

1.4 Magnetic Dipole

A system consisting of two equal and opposite…