UPMSP Vocational Domestic Electrical Appliances & Repair flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's law

Voltage equals current multiplied by resistance (V = I × R). It is used to calculate expected current, voltage drop, and element resistance in domestic appliance circuits.

RCCB 30 mA

A residual current device that trips when leakage to earth exceeds 30 mA within about 30 ms. It protects people from electric shock in wet areas like bathrooms and kitchens.

Earth resistance limit

Domestic earthing should measure below 5 ohms to the earth pit. Higher values mean poor earthing, so the pit needs watering, salt, or charcoal treatment.

Megger insulation test

A 500 V DC test between a winding and the metal body. A healthy domestic appliance reads above 1 megohm; a lower reading means moisture or insulation failure.

Clamp meter use

It measures AC current by surrounding one conductor only. Clamping both live and neutral together gives near zero because their magnetic fields cancel each other.

Continuity test

A multimeter buzzer or ohms check that confirms a closed path. A good fuse or switch reads near zero ohms, while an open circuit shows overload on the display.

IEC wiring colours

Brown is live, blue is neutral, and green-yellow is earth. The older Indian code used red for live, black for neutral, and green for earth.

Switch in live conductor

A switch must break the live wire, never the neutral. Switching the neutral leaves the appliance live even when it appears switched off, creating a shock hazard.

Two-way switch strappers

Two wires connect the L1 and L2 terminals of two SPDT switches. The live feeds the first common and the lamp connects to the second common terminal.

Element resistance formula

Resistance equals supply voltage squared divided by wattage (R = V squared divided by P). A 1000 W, 230 V element measures about 53 ohms when healthy.

Geyser element leakage

A geyser that trips the MCB often has a leaking element. A megger reading below 1 megohm from element to body confirms the element must be replaced.

Induction cooktop principle

Eddy currents induced in a ferromagnetic pan base produce heat. Glass, aluminium, and copper pans do not heat because they are not ferromagnetic and have low resistance.

Universal motor brushes

Mixer-grinder motors use carbon brushes on a commutator. Worn brushes below about 5 mm cause sparking, weak torque, and intermittent running and must be replaced.

Fan capacitor fault

A ceiling fan that hums but does not turn usually has a failed run capacitor. Replace it with the same microfarad and voltage rating to restore starting torque.

Washing machine drain fault

If the machine does not drain, check the drain filter, drain hose, and pump. A blocked filter or failed pump is the most common cause of this complaint.

Submersible pump megger test

Before installation, test winding insulation to body at 500 V DC. A reading below 1 megohm means water has entered the winding and the pump must be dried.

Refrigeration cycle order

Compressor, condenser, expansion device, then evaporator. Cooling occurs in the evaporator where low-pressure refrigerant absorbs heat from the cabinet or room.

Superheat definition

Evaporator outlet temperature minus the refrigerant saturation temperature at that pressure. Normal superheat is 5 to 8 K; higher values suggest undercharge.

R-600a safety

Isobutane refrigerant used in many domestic refrigerators is flammable. Ventilate the area, avoid sparks and open flames, and use spark-free vacuum equipment during service.

AC capacity in tons

One ton of cooling equals about 3.5 kilowatts of heat removal. Room size, insulation, and sun exposure determine the correct capacity for a split air conditioner.

Triac regulator fault

A shorted triac gives full power all the time in a fan regulator or dimmer. An open triac or faulty diac gives no output at all, so test both components.

NTC thermistor

A temperature sensor whose resistance falls as temperature rises. An open or wrong-value thermistor gives false temperature readings and error codes in inverter appliances.

SMPS fuse check

When the fuse in a switch-mode supply is blown, check the bridge rectifier and switching MOSFET for shorts before fitting a new fuse, or it will blow again.

IPM module fault

The intelligent power module drives the inverter compressor. An IPM error code usually means a shorted compressor winding or a failed module and heat sink compound.

Diagnosis sequence

Gather the complaint, check supply and plug, check fuse or MCB, then isolate the appliance and test components with a multimeter before opening any covers.

Fuse replacement rule

After replacing a blown fuse, find the cause. A fuse that blows again immediately indicates a short circuit downstream that must be located and repaired.

Earth continuity test

Measure resistance from the plug earth pin to the appliance metal body. It should be below 0.1 ohm; a higher value means a loose or broken earth connection.

Job sheet record

A written record of customer details, appliance model and serial number, fault found, parts replaced, tests done, and charges. It supports warranty claims and disputes.

Service rate card

A published list of diagnosis and labour charges by job type. It prevents billing disputes and helps the customer understand the cost before work begins.

Repair warranty terms

A service shop typically offers one to three months warranty on labour and parts. Manufacturer warranty covers defects, not misuse or accidental damage.

Lock-out tag-out

Switch off the isolator, lock it, attach a warning tag, and verify the circuit is dead with a tester before touching any conductor during repair work.

Electrical fire extinguisher

Class B electrical fires need carbon dioxide or dry powder extinguishers. Never use water, and switch off the mains supply before attempting to fight the fire.