Basic Electronics
Basic Electronics is the foundation domain of the ETA CETa exam. It checks whether you can apply DC and AC fundamentals, passive-component behavior, circuit laws, and correct meter use to simple circuits, rather than memorized pinouts or advanced troubleshooting.
Core rules and concepts
Current is charge flow; voltage is potential difference; resistance opposes current. Conventional current flows from positive to negative, opposite electron drift. Use Ohm’s law V = IR and power P = VI = I²R = V²/R, keeping volts, amps, ohms, and watts consistent.
Series: one path, same current, voltages add, R_eq = R1 + R2 + ... . Parallel: same voltage, currents add, 1/R_eq = 1/R1 + 1/R2 + ... ; for two resistors R_eq = (R1R2)/(R1+R2). Kirchhoff’s current law sums currents at a node to zero; voltage law sums loop voltages to zero.
Capacitors store charge Q = CV; series capacitance uses reciprocals, parallel capacitances add. Inductors oppose current change; series inductances add, parallel inductances use reciprocals. Reactance depends on frequency: X_C = 1/(2πfC), X_L = 2πfL. For a sine wave, V_rms = V_peak/√2.
Connect an ammeter in series, a voltmeter in parallel, and an ohmmeter only to an unpowered component.
Worked example
A 12 V source feeds 6 Ω in series with a parallel pair of 12 Ω and 24 Ω. First find the parallel pair: (12×24)/(12+24) = 288/36 = 8 Ω. Add the series resistor: R_total = 6 + 8 = 14 Ω. Main current I = V/R = 12/14 = 0.857 A. The parallel-pair voltage is I × 8 = 6.86 V, so the 12 Ω branch draws 6.86/12 = 0.572 A and the 24 Ω branch draws 6.86/24 = 0.286 A; they sum to 0.858 A within rounding. Total power is P = VI = 12 × 0.857 = 10.3 W.
Traps that cost marks
Do not use the product-over-sum shortcut for three or more parallel resistors. Do not add parallel resistances directly or forget the final reciprocal. Keep peak and RMS values separate; a 120 V RMS sine has about 170 V peak. Never connect an ammeter across a supply or use an ohmmeter on a live circuit. Check whether a question asks for total current, branch current, or component voltage before calculating.