Electronics Fundamentals and Basic Circuits
Core concepts
Candidates should be fluent with Ohm's law (V = IR), power relationships (P = VI = I²R = V²/R), and the behavior of series versus parallel networks. In series, current is common and voltages divide in proportion to resistance; in parallel, voltage is common and currents divide inversely with resistance. Know the reciprocal rule for parallel resistors and the shortcut for two resistors (product over sum). Understand Kirchhoff's voltage and current laws as conservation statements, and be able to apply them to simple loops and nodes. Recognize reactive behavior: capacitors block DC and pass high frequencies, inductors pass DC and oppose changing current; impedance combines resistance and reactance. Familiarity with diode forward drop, transistor switching, and the idea of a voltage divider is expected.
Traps
Questions often swap series and parallel rules, or ask for total resistance where one branch is open (infinite) versus shorted (zero). Watch units: mA versus A, kΩ versus Ω. A common distractor is applying the voltage-divider formula to a loaded divider without accounting for the load. Another trap is confusing power dissipated by a component with total circuit power.
Worked example
Two resistors, 6 Ω and 3 Ω, in parallel across 12 V. Parallel voltage is 12 V on each. Currents: 12/6 = 2 A and 12/3 = 4 A, total 6 A. Equivalent resistance = 12/6 = 2 Ω, matching product over sum (18/9 = 2 Ω). Total power = 12 × 6 = 72 W, which also equals 144/6 + 144/3 = 24 + 48 W. Rule of thumb: for two parallel resistors, R_eq is always smaller than the smallest branch.