Basic Electrical and Electronic Fundamentals
The Basic Electrical and Electronic Fundamentals domain checks whether you can reason with current, voltage, resistance and power rather than just recite definitions. RBSE Senior Vocational papers in this trade typically ask for numerical work on series and parallel networks, supply-and-load behaviour, and the simple AC quantities that reappear in rectifier and power-supply chapters.
Core rules
- Ohm's law: V = IR; power P = VI = I²R = V²/R.
- Series: current is common, resistances add, voltage divides in the ratio of the resistances.
- Parallel: voltage is common, conductances add, current divides in inverse ratio of resistance.
- KCL: currents at a node sum to zero. KVL: voltages round a closed loop sum to zero.
- Energy in kWh = watts × hours ÷ 1000. The domestic meter bills energy, not power.
- For a sine wave, Vrms = Vp/√2 ≈ 0.707 Vp; the average over a full cycle is zero.
Worked example
A 12 V supply feeds a 6 Ω resistor in series with two 6 Ω resistors that are in parallel with each other. Find total resistance, current and total power.
Reasoning: the parallel pair gives 6 × 6 / (6 + 6) = 3 Ω. Series addition gives 6 + 3 = 9 Ω. Current I = V/R = 12/9 = 1.33 A. Power P = VI = 12 × 1.33 ≈ 16 W, confirmed by P = I²R = 1.33² × 9 ≈ 16 W. Checking by two routes is what earns the second mark.
Traps that cost marks
- Adding parallel resistors directly instead of using product-over-sum or reciprocals.
- Mixing peak and RMS values: 230 V mains is RMS, so its peak is about 325 V.
- Using P = VI with the full supply voltage when the component only sees part of it.