Question 15
Rod A is a steel bar XY. It was magnetized using the “stroke” method as
shown in diagram 1 below. Then, a magnet bar WZ was brought near to rod A,
which was tied to a string, as shown in diagram 2. Rod A moved away when the
magnet WZ was brought near it. A candle was placed under end Y of rod A, as
shown in diagram 3. After a while, rod A moved towards the magnet WZ.
a. Fill the name of magnetic pole (North or South) to the table below:
| Name of pole | Name of magnetic pole |
| --- | --- |
| X | |
| Y | |
| Z | |
| W | |
b. Explain why Rod A started to move towards the magnet WZ in diagram 3.
c. One of home applications of magnet is audio speaker, which transforms
electrical signal into an audible sound. Speakers contain: a moving metal coil, a
stationary permanent magnet, and a cone made of a flexible material such as
paper or plastic. These are arranged as shown in the diagram below:
A metal coil, also known as electromagnet, is placed in front of a permanent
magnet. The electromagnet is attached to the cone. Explain how speaker works?
shown in diagram 1 below. Then, a magnet bar WZ was brought near to rod A,
which was tied to a string, as shown in diagram 2. Rod A moved away when the
magnet WZ was brought near it. A candle was placed under end Y of rod A, as
shown in diagram 3. After a while, rod A moved towards the magnet WZ.
a. Fill the name of magnetic pole (North or South) to the table below:
| Name of pole | Name of magnetic pole |
| --- | --- |
| X | |
| Y | |
| Z | |
| W | |
b. Explain why Rod A started to move towards the magnet WZ in diagram 3.
c. One of home applications of magnet is audio speaker, which transforms
electrical signal into an audible sound. Speakers contain: a moving metal coil, a
stationary permanent magnet, and a cone made of a flexible material such as
paper or plastic. These are arranged as shown in the diagram below:
A metal coil, also known as electromagnet, is placed in front of a permanent
magnet. The electromagnet is attached to the cone. Explain how speaker works?