Magnetism and Electromagnetism

• The diagram shows how a steel bar can be magnetized. How can steel bar be demagnetized?

  Use an a.c. supply and gradually decrease the current in the circuit.

  
• A copper wire carrying a current is held between the poles of a Magnet. The current can be reversed. The poles of the magnet can be changed over. In how many of the four directions shown can a force act on the wire?

  2

  
• Which diagram shows the poles of the two magnets?

  A

  
• Three metal bars X, Y and Z, exhibit the following magnetic properties: X is attracted by both ends of Y. Y can be repelled by Z.

  X: Unmagnetized Y: Magnetized Z: magnetized