Magnetism

Magnet

• A magnet is an object that has the ability to attract magnetic materials such as iron, cobalt and nickel.
• A bar magnet has two ends called magnetic poles. They are
• (a) north-seeking pole (north pole)
• (b) south-seeking pole (south pole)
• When the magnet is hung freely from a thread, the north pole will always point to the north of the Earth while the south pole points to the south.
• This property of a bar magnet makes it suitable for use in a compass.
• A compass has a magnetised needle hanging freely inside it.
• The compass is used in the navigation of ships at sea, aeroplanes in the sky and on land vehicles.
• A magnetic field is the region around a magnet in which magnetic forces act.
• The magnetic force of a magnet is strongest at its poles.
• If the magnetic field is strong, the magnetic force is big. If the field is weak, the force is small.

Magnetic Field Lines

• A magnetic field consists of magnetic field lines.
• The stronger the magnetic field, the closer the magnetic field lines.
• Magnetic field lines differ according to the arrangement of the bar magnets.
• Two bar magnets placed with opposite poles (unlike poles) facing each other form different field lines than those with same poles (like poles) facing each other.
• The magnetic field lines always begin from the north pole and end at the south pole.
• If there are many field lines which are close together, this means that the field is strong.
• No two field lines can cross. Each has its own path. a When like poles are near each other, the field lines repel.
• When unlike poles are near each other, the field lines attract.
• When two fields cancel out, there are no field lines. This is called the neutral point. Refer to the spots marked X on Figure X.
• When field lines are spaced equally with all lines pointing to the same direction, it is called a uniform field.