Basic Electrical and Electronic Fundamentals
What this domain tests
Basic Electrical and Electronic Fundamentals underpins every fault-finding decision in radio and colour TV servicing. The exam checks Ohm's law, power, series and parallel networks, Kirchhoff's laws, AC waveform values, reactance and impedance, resonance, and basic decibel ideas.
Core rules
- Ohm's law: V=IR; power P=VI=I²R=V²/R.
- Series: same current, resistances add, voltages divide. Parallel: same voltage, conductances add; two resistors R1R2/(R1+R2).
- KCL: currents into a node equal currents out. KVL: algebraic sum of voltages around a loop is zero.
- For a sine wave: Vrms=Vpeak/√2; Vpeak=1.414Vrms; Vpp=2Vpeak.
- Capacitive reactance Xc=1/(2πfC); inductive reactance XL=2πfL; impedance Z combines resistance and reactance vectorially.
- Series resonance: XL=XC, impedance is minimum and current is maximum.
Worked example
A 12 V DC supply feeds a 4 Ω resistor in series with a parallel pair of 6 Ω and 3 Ω. The parallel pair is (6×3)/(6+3)=18/9=2 Ω. Total resistance is 4+2=6 Ω. Supply current is 12/6=2 A. The series 4 Ω drop is 2×4=8 V. The parallel section drop is 2×2=4 V. Branch currents are 4/6=0.667 A and 4/3=1.333 A, summing to 2 A, which confirms KCL.
Traps
Do not mix RMS and peak when calculating power; use RMS for resistive power. In parallel networks use the reciprocal sum, not simple addition. A capacitor blocks DC but passes AC, so a DC open-circuit test can mislead. At resonance, voltages across L and C can be much larger than the source voltage.