Electrical Appliances
What this domain tests
Electrical Appliances tests the operating principles, ratings, circuit requirements and common faults of domestic appliances such as lamps, fans, heaters, irons, geysers, mixers and air-conditioners.
Core rules
- Resistive appliances - heaters, irons, geysers, incandescent lamps - have power factor near 1. Inductive appliances - fans, mixers, compressors - have a lower power factor and often a capacitor.
- A fan capacitor is rated in microfarads (µF) and voltage. A wrong or weak capacitor causes slow starting or no rotation; replace with the same rating.
- Heating elements are usually nichrome. A thermostat cycles the element to hold temperature; bypassing it removes safety control.
- Metal-bodied appliances must be earthed. Geysers and air-conditioners should have dedicated circuits with an MCB and a 30 mA RCCB.
- Plug-top fuses must match the appliance current, not the socket rating.
- Common faults include loose terminals, burnt plugs, open heating elements, faulty capacitors, and blocked ventilation.
Worked example
A 2,000 W geyser on 230 V draws I = 2,000 ÷ 230 = 8.7 A. A 16 A dedicated circuit with 2.5 mm² copper, a 16 A MCB and a 30 mA RCCB is suitable. The metal tank and body are earthed. A 6 A plug-top fuse would nuisance-blow, so the correct 16 A plug and fuse are used.
Traps that cost marks
Fitting a capacitor of a different µF value; using an extension board for a heater; bypassing a thermostat; and operating a metal appliance without an earth connection.