Magnetism

Question 1

What are the basic properties of magnets?

Answer 1

• Magnets repel like poles and attract opposite poles.
• Magnets attract magnetic materials (e.g., iron, steel, cobalt, nickel).
• Non-magnetic materials (e.g., wood, plastic) are not affected by magnets.

Question 2

What are magnetically hard and soft materials?

Answer 2

• Magnetically hard materials (e.g., steel) retain magnetism permanently.
• Magnetically soft materials (e.g., iron) are easily magnetised and demagnetised.
• Soft materials are used in electromagnets, as they can be turned on and off.
• Hard materials are used in permanent magnets.

Question 3

What are magnetic field lines?

Answer 3

• Magnetic field lines show the direction and strength of a magnetic field.
• They always point from the north pole to the south pole.
• The closer the lines, the stronger the magnetic field.
• Magnetic field lines never cross.

Question 4

What is induced magnetism?

Answer 4

• When a magnetic material is placed in a magnetic field, it becomes temporarily magnetised.
• The induced poles align opposite to the magnet, causing attraction.
• Removing the field causes the material to lose its magnetism (if magnetically soft).

Question 5

How can the magnetic field pattern for a bar magnet be investigated?

Answer 5

Using iron filings:
1. Place a bar magnet under a sheet of paper.
2. Sprinkle iron filings on top and tap the paper gently.
3. The iron filings arrange into the shape of the magnetic field.

Using a plotting compass:
1. Place a bar magnet on paper.
2. Put a small plotting compass near one pole.
3. Mark the direction the compass points, move it, and repeat.
4. Join the arrows to show magnetic field lines.

Question 6

How can two permanent magnets be used to create a uniform magnetic field?

Answer 6

• Place two bar magnets with opposite poles facing each other.
• The field lines between them are parallel and evenly spaced.
• This creates a uniform magnetic field.
• Used in devices like loudspeakers and MRI machines.