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Lesson 4: Electrical Principles

Lesson 4 of 10, syllabus topic T5. The exam asks 4 questions from this topic, one from each of its 4 groups.

Electrical principles come before components and circuits, because both build on voltage, current, resistance and power.

What you will learn

  • T5A Current and voltage: terminology and units, conductors and insulators, alternating and direct current
  • T5B Math for electronics: conversion of electrical units, decibels
  • T5C Capacitance and inductance terminology and units; Radio frequency definition and units; Impedance definition and units; Calculating power
  • T5D Ohm’s Law; Series and parallel circuits

1. Read

  1. Electronics basics: Four quantitiesHelps with T5A
  2. Electronics basics: AC and DCHelps with T5A
  3. Electronics basics: Units and metric prefixesHelps with T5B
  4. Electronics basics: DecibelsHelps with T5B
  5. Electronics basics: Capacitors, inductors and reactanceHelps with T5C
  6. Electronics basics: PowerHelps with T5C
  7. Electronics basics: Ohm’s lawHelps with T5D
  8. Electronics basics: Series and parallel circuitsHelps with T5D
  9. All 50 T5 questions with their answers and explanationsEvery group, with the rule or source behind each answer

2. Explore

  • Ohm's law and power

    Enter 90 volts and 3 amperes. The resistance is 30 ohms. Then double the resistance at the same voltage and the current halves.

    This is exam question T5D04.

  • Decibels

    Find the change from 5 watts to 10 watts: about 3 dB. Every doubling of power adds about 3 dB, and every halving takes about 3 dB away.

    This is exam question T5B09.

3. Practice

Practice one group at a time. A group is ready when you have answered every one of its questions and learned at least 80 percent of them; a question counts as learned when your last three answers to it were correct. To review quickly, go through this lesson’s questions as flashcards.

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