Electronics: Revision Notes (Form 5 SPM Physics)

What this chapter covers

• 5.1 Electron
• 5.2 Semiconductor Diode
• 5.3 Transistor

Key ideas explained

• What a semiconductor diode does, A diode lets current flow through it in one direction only. This one-way behaviour is used to turn alternating current into direct current, called rectification.
• How a transistor acts as a switch, A small current into the base of a transistor lets a much larger current flow through the main circuit. Removing the small current switches the large one off, so the transistor works as an electronic switch.
• What doping does to a semiconductor, Adding a tiny amount of impurity to pure silicon greatly increases its ability to conduct. Depending on the impurity, it forms n-type or p-type material, the building blocks of diodes and transistors.

Formulas in this chapter

This chapter is concept- and skill-based: the DSKP lists no formula for it, so marks come from definitions, explanations and diagrams rather than calculation.

Terms you must define precisely

• n-type semiconductor, A semiconductor doped so that free electrons are the majority charge carriers.
• p-type semiconductor, A semiconductor doped so that positive holes are the majority charge carriers.
• Semiconductor diode, A component made from a p-n junction that allows current to flow in one direction only.
• Rectification, The process of converting alternating current into direct current, usually using diodes.
• Transistor, A semiconductor device with three terminals used to amplify signals or to act as an electronic switch.
• Light-emitting diode (LED), A semiconductor diode that emits light when a current flows through it in the forward direction.
• Electron, A stable subatomic particle carrying a negative electric charge, found orbiting the nucleus of an atom.
• Thermionic emission, The release of electrons from the surface of a heated metal when it is given enough thermal energy.

A revision order that works

1. Read the 3 standards above and tick the ones you can already explain aloud without notes.
2. Rewrite every definition in one sentence with the correct unit; definitions are the cheapest marks in Paper 2.
3. Derive each formula once from its meaning, then practise rearranging it before substituting numbers.
4. For each experiment, write the manipulated, responding and constant variables from memory, then the graph you would plot.
5. Finish with a timed set of calculations with units on every line.

More Electronics resources

• Chapter overview: Electronics
• Common Mistakes
• Practice Questions
• Paper 2 Answering Guide
• Paper 3 Guide
• Key Terms

Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)