Electrician Trade (ALP)

Electrician trade covers electrical wiring, motors, transformers, safety standards.

Basic concepts:

• Voltage (V), Current (I), Resistance (R), Power (P).
• Ohm's law: V = IR.
• Power: P = VI = I²R.

AC vs DC:

• DC: unidirectional. Battery, solar.
• AC: alternating. Indian mains: 230 V, 50 Hz, single-phase. 415 V, 50 Hz, three-phase.

Earthing:

• Provides safety path for fault currents.
• Types: plate, pipe, strip, rod.
• Earth resistance: ≤ 1 Ω (preferably).

Wiring:

• Materials: copper (best), aluminium.
• Insulation: PVC, XLPE.
• Color code:
  • Live: red / brown.
  • Neutral: black / blue.
  • Earth: green / green-yellow.
• Wiring systems: cleat, casing-capping, conduit (concealed/surface), tray, busbar.

Protective devices:

• Fuse: melts on overload.
• MCB: Miniature Circuit Breaker, reusable.
• MCCB: Moulded Case Circuit Breaker.
• RCCB / RCD: Residual Current Device, for shock prevention.
• ELCB: Earth Leakage Circuit Breaker.

Motors:

• Single-phase induction motor: uses capacitor for starting.
• Three-phase induction motor: most common in industry.
• DC motor: for variable speed.
• Starter: for motor (DOL, star-delta, soft starter).

Transformers:

• Step up / step down voltage.
• Distribution transformers: 11 kV / 415 V.

Switchgear:

• Switches, isolators, contactors, MCCBs.

Lighting:

• Incandescent (old).
• Fluorescent (CFL).
• LED (most common now, efficient).

Indian Electrical standards:

• IS 732: code of practice for electrical wiring.
• IS 3043: earthing.
• CEA regulations.

Safety:

• Always switch off before working.
• Test with neon tester.
• Never work alone on live circuits.

RRB ALP focus: Ohm's law, motor types, fuses vs MCB, wiring color code.