Page 102 - Physics_Form_2

Physics for Secondary Schools

of electromagnets and transformers. Brass, copper, tin, zinc and aluminium are non-
magnetic materials. These materials are not attracted by a magnet. Non-metals, for
example, plastic, rubber, water, wood and ceramics are also non-magnetic. These
materials cannot be magnetised.

Types of magnets
FOR ONLINE READING ONLY
Magnets are categorised according to their sources of magnetism. They include:
1. Temporary magnets. These acquire magnetism due to an applied external magnetic
field but lose their magnetism when the external field is removed. These magnets
retain magnetism in a short time (i.e., the time during which the magnetising field
is present). For example, the magnetism that is induced in iron is temporary and
is lost once the external magnet is withdrawn. Iron nails and paper clips shown in
Figure 3.3 (a) are good examples of objects that can be temporarily magnetised. An
electromagnet used in magnetic cranes, as shown in Figure 3.3 (b), is an example
of a temporary magnet.

Electromagnet

(a) Iron paper clips and nails (b) Magnetic crane

Figure 3.3: Temporary magnets

Other examples of temporary strong, controllable magnetic fields, such as
magnetism are electromagnets. These railroad tracks, electric motors, microphones,
are temporary magnets created by an hard drives, MRI machines, security
electric current flowing through a coil, systems, cranes, and various computer and
often with an iron core to enhance the television hardware.
magnetic field. They can be quickly
turned on and off, and their magnetic
strength can be adjusted by changing
the current. However, they require a
continuous power supply to maintain
magnetism, which disappears when
the current stops. Electromagnets are
widely used in applications needing Figure 3.4: Electric Motor

96
Student’s Book Form Two

Physics Form 2 Final.indd 96 25/10/2025 10:26