Basic Electronics and Circuit Fundamentals
Basic Electronics and Circuit Fundamentals is the gateway domain of the ASSEB HS Electronics and Hardware paper. It tests whether you can apply Ohm's law, Kirchhoff's laws, series and parallel networks, power ratings, and basic AC/DC quantities to small circuits rather than merely recall definitions.
Core rules
- Ohm's law: V = IR; power: P = VI = I²R = V²/R.
- Kirchhoff's current law (KCL): current into a node equals current out.
- Kirchhoff's voltage law (KVL): algebraic sum of voltages around a closed loop is zero.
- Series: same current, RT = R1 + R2 + ...; parallel: same voltage, 1/RT = 1/R1 + 1/R2 + ...
- For a sine wave, RMS = 0.707 × peak; the average of a full sine is zero.
Worked example
A 12 V supply feeds 100 Ω in series with a parallel pair of two 200 Ω resistors. The parallel pair is 200 || 200 = 100 Ω, so total resistance is 200 Ω. Supply current I = 12/200 = 0.060 A = 60 mA. The 100 Ω resistor drops V = 0.060 × 100 = 6 V, leaving 6 V across the pair. Each 200 Ω branch carries 6/200 = 30 mA; KCL check: 30 + 30 = 60 mA.
Traps that cost marks
- Mixing milliamps and amps in P = I²R; convert first.
- Writing RT = R1 + R2 for a parallel pair instead of using reciprocals.
- Assuming a real voltmeter has infinite resistance or an ammeter has zero resistance; loading changes the circuit.
- Confusing peak, peak-to-peak and RMS values; a 12 V RMS transformer output has about 17 V peak.