Basic Electronics and Electrical Fundamentals
What this domain tests
Basic Electronics and Electrical Fundamentals checks whether you can reason with voltage, current, resistance and simple semiconductor behaviour, not just recall symbols. Expect Ohm's law, series and parallel circuits, resistor colour codes, continuity and diode tests, capacitors, and transistors used as switches.
Core rules
- Ohm's law: V = I × R; power P = V × I = I²R. Keep units consistent: 220 Ω, not 220 kΩ, unless stated.
- Series: current is the same, voltages add, R_total = R1 + R2. Parallel: voltage is the same, currents add, 1/R_total = 1/R1 + 1/R2.
- A silicon diode drops about 0.6–0.7 V forward; an LED may drop 1.8–3.3 V depending on colour. A transistor needs base-emitter bias to conduct.
- Test continuity and resistance only with power removed. Discharge capacitors before measuring.
- Resistor colour code: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9; gold tolerance ±5%, silver ±10%.
Worked example
A 4.2 V battery feeds a red LED through 220 Ω. The LED drops 2.0 V. The resistor sees 4.2 − 2.0 = 2.2 V, so I = 2.2/220 = 0.010 A = 10 mA. Resistor power is I²R = 0.01² × 220 = 0.022 W, so a 0.125 W part is adequate. If the resistor were 100 Ω, current would be 22 mA, possibly overdriving a small LED; the calculation explains why the value matters.
Traps
Measuring resistance in a live circuit gives false readings. Mixing series and parallel rules causes wrong totals. Reading a resistor from the wrong end reverses the first two bands. Assuming a battery is exactly 4.2 V ignores its state of charge.