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Lesson 4: Electrical Principles

Lesson 4 of 10, syllabus topic G5. The exam asks 3 questions from this topic, one from each of its 3 groups.

Electrical principles return with reactance, decibels and power, which the circuit and antenna lessons rely on.

What you will learn

  • G5A Reactance; inductance; capacitance; impedance; impedance transformation; resonance
  • G5B The decibel; current and voltage dividers; electrical power calculations; sine wave root-mean-square (RMS) values; PEP calculations
  • G5C Resistors, capacitors, and inductors in series and parallel; transformers

1. Read

  1. Electronics basics: Capacitors, inductors and reactanceHelps with G5A
  2. Electronics basics: DecibelsHelps with G5B
  3. Electronics basics: PowerHelps with G5B
  4. Electronics basics: Series and parallel circuitsHelps with G5C
  5. All 40 G5 questions with their answers and explanationsEvery group, with the rule or source behind each answer

2. Explore

  • Reactance and resonance

    Raise the frequency and watch inductive reactance rise while capacitive reactance falls. Where the two are equal, the circuit is resonant.

  • Ohm's law and power

    Enter 400 volts across 800 ohms. The load uses 200 watts.

    This is exam question G5B03.

  • Decibels

    Find the power ratio for 20 dB: 100 times. That is the difference between a signal at S9 and one at 20 dB over S9.

    This is exam question G4D05.

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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