Page 106 - Physics_Form_2

Physics for Secondary Schools

3. CRT (Cathode Ray Tube) 4. Speakers and microphones
television and computer monitors These use permanent magnets and current-
These employ an electromagnet in their carrying coils to convert electric energy
inputs to assist in producing an image on into sound and sound energy into electrical
the screen (see Figure 3.13). energy, respectively. For example, hi-fi
stereo speakers (see Figure 3.14) have very
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powerful magnets to produce high-quality
sound and sufficient volume.

Magnet

Figure 3.13: CRT TV screen Figure 3.14: Speaker

5. Electric generators
These use permanent magnets to convert mechanical energy to electrical energy.

6. Transformers
These are used in power transmission and many electronic devices, as shown in
Figure 3.15 (a) and (b).

Transformer

(a): Transformer on electric poles (b): Small transformer in a television set

Figure 3.15: Transformer for power transmission

Transformers are used in electronic devices to reduce the standard 240 V AC
mains voltage to lower levels suitable for operating equipment such as radios,
high fidelity hi-fi systems, computers, televisions, and doorbells
7. Electromagnets. These are used in hospitals when dealing with eye injuries caused
by iron or steel splinters. They are also used in Magnetic Resonance Imaging
(MRI) to diagnose brain tumours, haemorrhage, nerve injury and stroke injury.
Electromagnets are also applicable in steelworks and cranes.

100
Student’s Book Form Two

Physics Form 2 Final.indd 100 25/10/2025 10:26