Basic Electrical and Electronic Fundamentals
What this domain tests
Basic Electrical and Electronic Fundamentals covers the quantities and laws behind every circuit: current, voltage, resistance, power, energy, AC/DC, and conductor/insulator behaviour. Numerical questions on Ohm’s law, series/parallel networks and unit prefixes are common.
Core rules
- Ohm’s law: V = IR. Power: P = VI = I²R = V²/R.
- Series: current common, resistances add, voltage divides in proportion to resistance.
- Parallel: voltage common, conductances add, so 1/R_T = 1/R₁ + 1/R₂ + ...
- Convert mA to A (÷1000) and kΩ to Ω (×1000) before calculating.
- Indian AC mains is 230 V, 50 Hz; RMS is used for power, peak = RMS × √2.
Worked example
A 12 V supply feeds 4 Ω and 2 Ω in series. Total R = 6 Ω, so I = V/R = 12/6 = 2 A. Current through both resistors is 2 A. Voltage across the 2 Ω resistor is V = IR = 2 × 2 = 4 V; across the 4 Ω resistor it is 8 V. Check: 4 V + 8 V = 12 V. Power in the 2 Ω resistor is I²R = 4 × 2 = 8 W, so a 10 W resistor is the practical minimum, not a ¼ W type.
Traps
Mixing series and parallel formulas; connecting a voltmeter in series or an ammeter in parallel; using peak voltage where RMS is needed; and ignoring power rating. A correct resistance value can still overheat if its wattage is too small.