Magnetism

Alex and his friends make four different electromagnets. Put the electromagnets below in order of strength, starting with the weakest. Write the letter in the correct order.

A. 50 turns, low current, copper core

B. 100 turns, high current, iron core

C. 50 turns, low current, iron core

D. 100 turns, low current, iron core

• A,D,B,C

• A,B,D,C

• A, C, D, B

• A,C,B,D

Which of these field patterns is correct?

• A

• B

• C

• D

How could a student go about demagnetising a piece of magnetised steel?

• Place it inside a coil of wire and pass direct current through the coil.

• Place it near a piece of unmagnetised metal.

• Expose it to temperature below 0 °C for a long period.

• Hit it repeatedly with a hammer.

A student makes a series of statements about a permanent bar magnet. Which of them is true?

• The north pole of a permanent bar magnet will repel the north pole of another magnet.

• A permanent bar magnet must be made from a soft magnetic material.

• A permanent bar magnet can repel a magnetic material.

• The magnetic field lines of a permanent bar magnet cross each other where the field is strongest.

Which of the following choices of metal would be suitable for

• A

• B

• C

• D

A student wants to find out which end is the magnet’s north pole. What could he do to find out?

• Put the magnet under a piece of paper, and sprinkle iron filings on top.

• Put it near to a piece of magnetic material, like a steel paperclip.

• Place a compass near it.

• Put it near a piece of magnetic material.

When two magnets repel each other, which poles are facing each other?

• North and South

• North and North

• East and West

• West and West

What happens to the magnetic force as a non-magnetic material gets further away from the magnetic field?

• The force increases.

• The force stays the same.

• The force decreases.

• There was no force to begin with.

Which statement about the magnetic field around a bar magnet is correct?

• The magnetic field is the same strength all around the magnet.

• The magnetic field is strongest at the poles of the magnet.

• The magnetic field is strongest near the middle of the magnet.

• The magnetic field is stronger at the south pole than the north pole.

Which of the following is not the property of a permanent magnet?

• Like magnetic poles repel each other and unlike magnet.ic poles attract each other.

• It attracts magnetic materials like iron, cobalt, and nickel.

• A freely suspended magnet always points in a north-south direction.

• Its magnetism can be switched on and off.