Electronic Components and Identification
This domain tests recognition of common components, reading their markings and checking polarity or value before assembly. Practical identification prevents wrong-part fitting and later troubleshooting.
Fixed and variable components
- Resistors: carbon film, metal film, wirewound and SMD. Four-band code: digit, digit, multiplier, tolerance. Five-band adds a third digit.
- Capacitors: ceramic disc codes such as 104 mean 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. Electrolytics are polarized: the stripe marks the negative terminal.
- Diodes: the band marks the cathode (bar side). LEDs: longer lead is usually anode, but the flat on the body marks cathode.
- Transistors: pin order differs between types; always check the datasheet or printed pinout rather than assuming E-B-C.
- Inductors and transformers: marked by inductance or turns ratio; check continuity of windings.
Worked example
A resistor reads brown, black, red, gold. Brown = 1, black = 0, red = ×100, gold = ±5%. Value = 10 × 100 = 1000 Ω = 1 kΩ, tolerance ±50 Ω. A meter reading of 980 Ω is therefore acceptable. A capacitor marked 104 is 100 nF, not 104 nF.
Traps that cost marks
Reading a colour code from the wrong end; treating the tolerance band as a digit; interpreting capacitor codes as microfarads; fitting an electrolytic capacitor backwards; assuming all transistors of the same package have identical pinouts.
Exam focus
Expect colour-code calculations, capacitor-code conversion and polarity questions. Always state the unit and tolerance.