Chapter 7. Basic Electrical and Electronic Principles

Electrical safety comes first. Electricity can cause shock, burns and fires. Only qualified, authorized people should work on mains electrical installations. Isolate, lock out and prove dead before working on any circuit. Use residual-current devices (RCDs or GFCIs), fuses and circuit breakers, and follow local wiring regulations [12][13].

Basic quantities

Key laws

Ohm’s law: V = IR

Power: P = VI

Series circuit: R_total = R₁ + R₂ + R₃ (the same current flows through each part)

Parallel circuit: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ (the same voltage across each branch) [12]

DC and AC. Direct current (DC) flows in one direction, as from batteries. Alternating current (AC) reverses direction periodically; mains supply is AC, with voltage and frequency that differ between countries (for example, about 230 V at 50 Hz in many countries and 120 V at 60 Hz in others) [13].

Components. Conductors and insulators, switches, fuses, resistors, capacitors, inductors, diodes, transistors, relays, sensors and integrated circuits.

Wiring. Colour codes for conductors differ among countries and over time; follow the standards that apply where you work and check each installation with a tester [13].

Measuring. A multimeter measures voltage, current and resistance. Connect it in parallel to measure voltage and in series to measure current; set the correct range first.

Motors and transformers. Motors convert electrical to mechanical energy; transformers change AC voltage levels.

Review: What current flows when 230 V is applied across a 46 Ω resistor, and what power is used? (Answer: I = 230/46 = 5 A; P = 230 × 5 = 1,150 W.)