Electrical Fundamentals and Safety
Domain 1: Electrical Fundamentals and Safety
This domain tests the basic electrical relationships and safe working habits a consumer-energy-meter worker uses before touching any installation: Ohm's law, power, energy, AC supply values, earthing and isolation.
Core rules
- Ohm's law: V = I × R; power in a resistive DC circuit: P = V × I = I²R.
- Single-phase AC active power: P = V × I × cos φ; three-phase: P = √3 × V_L × I_L × cos φ.
- Energy is power sustained over time; 1 kWh = 1,000 W for 1 hour.
- Treat every conductor as live until proved dead with an approved tester; isolate, lock off, tag and prove dead before opening a meter terminal cover.
- Earth continuity and neutral integrity are safety-critical; never use the neutral as a test reference without confirming it.
Worked example
A 230 V single-phase load draws 10 A at unity power factor for 8 hours. Power = 230 × 10 = 2,300 W = 2.3 kW. Energy = 2.3 × 8 = 18.4 kWh. If the meter constant is 3,200 imp/kWh, expected pulses = 18.4 × 3,200 = 58,880 impulses. The reasoning links measured current and voltage to power, then power to registered energy, then energy to meter pulses.
Traps that cost marks
- Mixing kW and kWh; kW is demand, kWh is consumption.
- Using V × I for AC inductive loads without cos φ.
- Assuming a switch has isolated the neutral as well as the phase.
- Forgetting that 1 unit on an Indian consumer bill means 1 kWh.