Electrical and Electronic Fundamentals
Core concepts
A candidate must be fluent with Ohm's law (V = IR), power relationships (P = VI = I²R = V²/R), and Kirchhoff's voltage and current laws. Series and parallel resistor combinations, voltage dividers, and the difference between ideal and real sources matter. Understand capacitance (Q = CV, energy ½CV²) and inductance (V = L di/dt, energy ½LI²), plus the time constants RC and L/R. Know AC fundamentals: RMS versus peak (V_rms = V_peak/√2 for a sine), phase, impedance of R, L and C, and resonance at f = 1/(2π√(LC)). Familiarity with semiconductor basics-diode forward drop, BJT current gain, MOSFET threshold-is expected.
Traps
Questions often mix peak and RMS values, or ask for power using the wrong form. Remember DC power uses average values while AC power with reactive loads needs power factor. Another trap: assuming a real source has zero internal resistance, which changes terminal voltage under load. Watch units-milliamp versus amp-and sign conventions in Kirchhoff loops. Thevenin equivalents are frequently tested; a common error is forgetting to remove the load before finding R_th.
Worked example
A 12 V source with 2 Ω internal resistance feeds a 10 Ω load. Total resistance is 12 Ω, so current is 1 A. Terminal voltage is 12 − (1 A × 2 Ω) = 10 V, and load power is I²R = 10 W. Rule of thumb: when a load equals source resistance, maximum power transfer occurs, but efficiency is only 50 percent-do not confuse the two ideas.