Basic Electrical and Electronic Fundamentals
Domain 1: Basic Electrical and Electronic Fundamentals
This domain tests whether you can apply Ohm's law, series and parallel networks, power ratings, and AC/DC quantities to practical hardware measurements. Questions often use component values with prefixes and expect a numerical answer.
Core rules
- Ohm's law: V = IR; power P = VI = I²R = V²/R. Keep units in volts, amps, ohms, watts; convert mA to A and kΩ to Ω before calculating.
- Series: same current, voltages add, resistances add. Parallel: same voltage, currents add, reciprocal resistance 1/RT = 1/R1 + 1/R2.
- AC sine: Vrms = Vpeak/√2; Vavg for a full sine is 0, but half-wave average is Vpeak/π. Frequency f = 1/T.
- Capacitor impedance Xc = 1/(2πfC); inductor Xl = 2πfL. In DC steady state a capacitor is open and an inductor is a short (ideal).
- Choose a resistor wattage at least twice the calculated dissipation for margin; a 0.25 W part should not run at 0.24 W in a hot enclosure.
Worked example
A 12 V DC supply feeds 220 Ω and 330 Ω in series. Total R = 550 Ω, so I = 12/550 = 0.0218 A = 21.8 mA. The 220 Ω drop is 0.0218 × 220 = 4.8 V; the 330 Ω drop is 7.2 V; sum 12 V. Power in 330 Ω = I²R = (0.0218)² × 330 = 0.157 W, so a 0.25 W resistor is acceptable but a 0.5 W part gives margin. Check: 4.8 + 7.2 = 12 V.
Traps
- Mixing mA and A, or kΩ and Ω, produces answers off by 1000.
- Assuming parallel resistors add directly.
- Using peak voltage where RMS is required for power.
- Forgetting that a capacitor blocks DC in steady state.
- Under-rating a resistor and ignoring ambient temperature.