Answer questions about magnetism and center of gravity.

Here are the solutions to the questions:

13 (a) State the basic law of magnetism.

• The basic law of magnetism states that like poles repel each other, and unlike poles attract each other.

13 (b) The figure below shows how magnets are stored in pairs with keepers at the ends.

• i) Identify poles A and B. When soft iron keepers are placed across the poles of magnets, they become induced magnets.

  • Pole A is adjacent to the South poles of the bar magnets, so it will be an induced North pole.
  • Pole B is adjacent to the North poles of the bar magnets, so it will be an induced South pole. Therefore, A is the North pole and B is the South pole.

• ii) Explain why soft iron keepers are suitable for storing magnets. Soft iron is a ferromagnetic material that is easily magnetized and demagnetized. When soft iron keepers are placed across the poles of a magnet, they become induced magnets and form a closed magnetic circuit. This prevents the magnetic field lines from spreading out into the air, which significantly reduces the demagnetizing effect on the permanent magnet, helping it retain its magnetism over a longer period.

14 (i) Define the term center of gravity of a body.

• The center of gravity (C.o.g.) of a body is the point through which the resultant gravitational force (or weight) of the body acts, regardless of the body's orientation. It is essentially the average position of all the mass that makes up the object.