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UPMSP Vocational Domestic Electrical Appliances & Repair study materials
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UPMSP Vocational Domestic Electrical Appliances & Repair practice questions

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Question 1Electrical Fundamentals and Safety

A domestic mixer grinder rated 750 W is run for 2 hours. What is the energy consumed in kWh?

  1. 1.5 kWh Correct answer.
  2. 7.5 kWh
  3. 0.375 kWh
  4. 3.0 kWh

Explanation

Energy in kWh equals power in kilowatts multiplied by time in hours. Here 750 W is 0.75 kW, and 0.75 × 2 = 1.5 kWh. This is the figure a technician reports when estimating running cost.

Question 2Electrical Fundamentals and Safety

In a typical Indian domestic wiring installation, what is the standard nominal single-phase supply voltage between phase and neutral?

  1. 230 V Correct answer.
  2. 415 V
  3. 24 V
  4. 110 V

Explanation

Indian domestic single-phase supply is standardized at 230 V between phase and neutral. The 415 V figure refers to the line-to-line voltage of a three-phase supply. Appliances are rated for the 230 V nominal value.

Question 3Electrical Fundamentals and Safety

Which safety device is designed to disconnect the supply when current leaks to earth through a faulty appliance body?

  1. Miniature circuit breaker
  2. Metal oxide varistor
  3. Fuse
  4. Earth leakage circuit breaker Correct answer.

Explanation

An earth leakage circuit breaker (also called an RCCB or ELCB) senses imbalance between live and neutral currents and trips on earth leakage. This protects people from electric shock from faulty appliance bodies. An MCB or fuse responds only to overload and short-circuit current.

Question 4Electrical Fundamentals and Safety

What is the primary purpose of earthing the metal body of a domestic appliance such as a washing machine?

  1. To reduce the electricity bill
  2. To increase the heating efficiency of the element
  3. To provide a low-resistance path so fault current trips the protective device Correct answer.
  4. To convert AC supply into DC for the motor

Explanation

Earthing connects the exposed metal body to a low-resistance path back to the supply. If a live conductor touches the body, fault current flows and quickly operates the fuse or breaker. This keeps the body potential near earth and limits shock risk.

Question 5Electrical Fundamentals and Safety

A heating element draws 5 A from a 230 V supply. What is its resistance?

  1. 0.0217 Ω
  2. 1150 Ω
  3. 230 Ω
  4. 46 Ω Correct answer.

Explanation

Ohm's law gives resistance as voltage divided by current. Dividing 230 V by 5 A gives 46 Ω. The same result follows from R = V²/P with P = 1150 W.

Question 6Electrical Fundamentals and Safety

Which conductor colour conventionally identifies the protective earth wire in Indian domestic flexible cords?

  1. Black
  2. Blue
  3. Red
  4. Green with yellow stripe Correct answer.

Explanation

The green-with-yellow-stripe conductor is reserved internationally for protective earthing. In Indian three-core flexible cords, red is phase, black is neutral, and green-yellow is earth. A technician must never use the earth conductor for any other purpose.

Question 7Electrical Fundamentals and Safety

Which effect of electric current is used in a domestic electric iron to produce heat?

  1. Photoelectric effect
  2. Chemical effect
  3. Magnetic effect
  4. Heating effect Correct answer.

Explanation

When current passes through the high-resistance nichrome element, electrical energy converts into heat. This is the heating effect of current, described by I²R losses. The iron, heater, and geyser all rely on it.

Question 8Electrical Fundamentals and Safety

A 230 V appliance has a rated current of 10 A. Which MCB rating is the most appropriate choice for its dedicated circuit?

  1. 16 A
  2. 10 A Correct answer.
  3. 6 A
  4. 32 A

Explanation

An MCB must carry the rated load current without nuisance tripping, so a 10 A device suits a 10 A load on a dedicated circuit. A lower rating would trip during normal operation. A much higher rating would fail to protect the appliance cable.

Question 9Electrical Fundamentals and Safety

Two resistors of 100 Ω and 150 Ω are connected in series across 230 V. What is the current through the circuit?

  1. 2.30 A
  2. 0.92 A Correct answer.
  3. 1.53 A
  4. 3.83 A

Explanation

In series, resistances add to give 250 Ω. Dividing 230 V by 250 Ω gives 0.92 A. The same current flows through both resistors in a series circuit.

Question 10Electrical Fundamentals and Safety

Why is a fuse wire made of a material with a low melting point and suitable resistivity?

  1. So it melts and opens the circuit when current exceeds the rated value Correct answer.
  2. So it can carry higher current than the circuit needs
  3. So it can convert excess current into useful heat for the appliance
  4. So it can store charge during normal operation

Explanation

A fuse is a sacrificial weak link: excess current heats it beyond its melting point and it opens the circuit. Low melting point ensures it operates before cables are damaged. Its rated current is chosen below the cable capacity.

Question 11Electrical Fundamentals and Safety

What is the main function of a thermostat in a domestic electric iron?

  1. To convert AC into DC for the indicator lamp
  2. To step down the supply voltage to the element
  3. To measure the current drawn by the element
  4. To open and close the element circuit to hold a set temperature Correct answer.

Explanation

A bimetallic thermostat senses soleplate temperature and cycles the element on and off. This maintains the temperature selected by the user's dial. It does not regulate voltage or measure current.

Question 12Electrical Fundamentals and Safety

A technician touches a live conductor while standing on a dry insulating mat. Which factor most strongly limits the resulting shock current?

  1. The wattage rating of the appliance
  2. The frequency of the supply
  3. The colour of the conductor insulation
  4. The body resistance plus the mat resistance in series Correct answer.

Explanation

Shock current is set by supply voltage divided by total circuit resistance. Body resistance and the insulating mat add in series, so the mat greatly reduces current. This is why dry insulating footwear and mats improve safety.

Question 13Electrical Fundamentals and Safety

In a domestic installation, why are sockets in wet areas such as bathrooms and kitchens protected by a 30 mA RCCB rather than only by an MCB?

  1. Because 30 mA is the normal load current of kitchen appliances
  2. Because RCCBs improve the power factor of appliances
  3. Because a 30 mA trip limits shock energy to a level usually survivable Correct answer.
  4. Because MCBs cannot protect against short circuits

Explanation

A 30 mA residual current device trips fast enough to limit the duration and energy of a shock. An MCB protects cables against overload but does not sense small earth leakage. Wet areas raise shock risk, so sensitive residual protection is required.

Question 14Electrical Fundamentals and Safety

What happens to the total resistance of a circuit when an additional appliance is switched on in parallel across the same domestic supply?

  1. It decreases Correct answer.
  2. It stays exactly the same
  3. It increases
  4. It becomes zero

Explanation

Parallel connection adds another current path, so the equivalent resistance falls. The supply then delivers more total current. This is why switching on many appliances increases the load current drawn from the mains.

Question 15Electrical Fundamentals and Safety

Which instrument is used to measure the insulation resistance of a domestic wiring circuit before energizing it?

  1. Wattmeter
  2. Megger Correct answer.
  3. Multimeter on the voltage range
  4. Clamp meter

Explanation

A megger applies a high test voltage and measures very high resistance values. It verifies that insulation between conductors and earth is sound. Clamp meters and wattmeters measure current or power, not insulation quality.

Question 16Electrical Fundamentals and Safety

A 1500 W geyser operates at 230 V. What current does it draw, and which standard fuse rating best protects it?

  1. About 3.3 A, protected by a 5 A fuse
  2. About 6.5 A, protected by a 10 A fuse Correct answer.
  3. About 15 A, protected by a 20 A fuse
  4. About 0.15 A, protected by a 1 A fuse

Explanation

Current equals power divided by voltage, so 1500 divided by 230 gives about 6.5 A. A 10 A fuse carries this load comfortably while still protecting the circuit. The rating must exceed the load current but stay within cable capacity.

Question 17Electrical Fundamentals and Safety

A technician finds a two-pin plug appliance with a metal body and no earth connection. What is the correct safety recommendation?

  1. Use it only on a wooden floor
  2. Increase the fuse rating to prevent blowing
  3. Replace the cord with a three-core earthed plug and ensure the body is earthed Correct answer.
  4. Wrap the body in insulating tape and continue use

Explanation

Class I metal-bodied appliances depend on a reliable protective earth connection. A two-core cord leaves the body unearthed, so a fault could make it live. The correct remedy is a proper three-core cord with the earth conductor securely bonded to the body.

Question 18Electrical Fundamentals and Safety

In a domestic single-phase circuit, the neutral conductor is normally connected to earth at the supply transformer. What is the practical consequence for a person touching a neutral wire while the load is connected?

  1. No current can ever flow through the person from neutral
  2. The neutral may be near earth potential but can rise if the neutral path is broken or loaded Correct answer.
  3. The neutral is always at exactly 230 V above earth
  4. The neutral carries the highest voltage in the installation

Explanation

Neutral is bonded to earth at the source, so its potential is near zero under normal conditions. However, a broken or high-resistance neutral lets its potential rise towards the phase voltage. Neutral must therefore never be treated as guaranteed safe.

Question 19Electrical Fundamentals and Safety

A table fan motor sparks continuously at the commutator and runs hot. Which is the most likely cause?

  1. The fan being placed on a level surface
  2. The supply voltage being exactly 230 V
  3. Worn carbon brushes or a dirty commutator Correct answer.
  4. A correctly functioning capacitor

Explanation

Continuous sparking at the commutator usually indicates worn brushes, weak brush spring tension, or a dirty or eccentric commutator. These increase arcing and heating. Cleaning or replacing brushes and resurfacing the commutator is the standard remedy.

Question 20Electrical Fundamentals and Safety

Why must the supply be isolated and the capacitor discharged before opening a microwave oven for repair?

  1. Because the high-voltage capacitor can store a lethal charge after disconnection Correct answer.
  2. Because the door interlock is mechanical and needs no isolation
  3. Because the cooling fan keeps running on stored mechanical energy
  4. Because the magnetron is powered by a low-voltage battery

Explanation

The high-voltage capacitor in a microwave can retain a dangerous charge even after the mains is switched off. It must be discharged through a suitable resistor before any work. This stored energy is a recognized lethal hazard in microwave servicing.

Question 21Electrical Fundamentals and Safety

A domestic circuit protected by a 16 A MCB has a total connected load that draws 20 A. What is the expected result and the correct technical interpretation?

  1. The MCB will convert the excess current into useful voltage
  2. The load will draw less current automatically to match the MCB
  3. The MCB will trip after a time delay because the load exceeds its rating Correct answer.
  4. The MCB will never trip because MCBs ignore overload

Explanation

An MCB carries its rated current continuously but trips on sustained overload according to its time-current characteristic. A 20 A load on a 16 A device is a sustained overload, so it trips after a delay. The correct response is to reduce the load or use a properly sized dedicated circuit.

Question 22Electrical Fundamentals and Safety

A 230 V, 1000 W heater and a 230 V, 1000 W motor are both operated for one hour. Which statement about energy consumption and current is correct?

  1. The heater draws more current because resistive loads always draw more
  2. Both consume 1 kWh, but the motor draws a higher current because of its lower power factor Correct answer.
  3. The motor consumes more energy because motors are less efficient
  4. Both consume 1 kWh and draw exactly the same current at all times

Explanation

Energy in kWh depends on real power and time, so both use 1 kWh in one hour. The motor draws a higher RMS current for the same real power because its power factor is below unity. The heater is essentially resistive with a power factor near one.

Question 23Electrical Fundamentals and Safety

In a three-pin domestic socket outlet, which pin is longer and thicker, and why?

  1. The earth pin, so it makes contact first and breaks last Correct answer.
  2. The phase pin, to carry the full load current
  3. The neutral pin, to reduce voltage drop
  4. The earth pin, to increase the supply voltage

Explanation

The earth pin is made longer and thicker so that earthing is established before phase and neutral make contact. On withdrawal, earth is the last to break. This sequencing ensures the appliance body is earthed whenever it is energized.

Question 24Electrical Fundamentals and Safety

A technician measures 0 V between phase and neutral at a socket, but the MCB is ON and other circuits work. Which fault is most consistent with this reading?

  1. A short circuit between phase and neutral at the socket
  2. A leakage of 30 mA to earth at the socket
  3. An open circuit in the phase or neutral conductor feeding that socket Correct answer.
  4. An earth conductor with slightly high resistance

Explanation

Zero volts at the socket while the breaker is closed indicates the supply path to that point is broken. An open phase or neutral conductor interrupts the voltage. A short circuit would instead trip the breaker, and leakage would not normally remove the voltage.

Question 25Tools, Measuring Instruments and Workshop Practice

While servicing a domestic electric iron, a technician needs to open the terminal cover to check the cord connections. Which tool is most appropriate for loosening the small recessed screws on the cover?

  1. A flat-blade screwdriver matched to the slot width Correct answer.
  2. A cold chisel struck with a hammer
  3. A hacksaw blade used as a lever
  4. A pipe wrench applied to the screw head

Explanation

Small recessed cover screws are driven by a screwdriver whose blade width and thickness fit the slot, so the tip seats fully and torque is transferred without damaging the head. Impact or gripping tools deform the slot and can crack the plastic cover.

Question 26Tools, Measuring Instruments and Workshop Practice

Which instrument is used to measure the insulation resistance between the live and earth terminals of a domestic appliance before returning it to the customer?

  1. A clamp meter
  2. A wire stripper
  3. A soldering gun
  4. An insulation resistance tester (megohmmeter) Correct answer.

Explanation

An insulation resistance tester applies a high DC test voltage and reads the very high resistance of the insulation, which is the standard check for leakage paths to earth. Clamp meters read load current, while the other items are workshop tools, not measuring instruments.

Question 27Tools, Measuring Instruments and Workshop Practice

A technician must cut a rectangular opening in the plastic back panel of a room heater to fit a new switch. Which sequence of workshop operations is most suitable?

  1. Mark the outline, drill corner holes, cut between them with a fine saw, then file the edges Correct answer.
  2. Punch the opening with a centre punch and hammer only
  3. Heat the panel with a blowlamp until it melts through, then press the switch in
  4. Mark the outline and shear it with tin snips in one straight cut

Explanation

Marking first, drilling corner relief holes, sawing between them and finishing with a file gives a clean, accurately sized opening without cracking the plastic. Shearing, melting or punching would distort or fracture the panel and ruin the switch fit.

Question 28Tools, Measuring Instruments and Workshop Practice

A multimeter set to the 200 V AC range displays a steady reading when its probes are placed across the element terminals of a switched-on electric kettle. What does this reading indicate about the element circuit?

  1. The element is short-circuited to earth
  2. The element is open-circuited and must be replaced
  3. Supply voltage is present at the element terminals, so the fault lies elsewhere in the circuit Correct answer.
  4. The multimeter is out of calibration

Explanation

A voltage reading across the element terminals proves the supply reaches the element, so any failure to heat must be traced to the element itself or downstream connections rather than to the supply wiring. An open element would still show supply voltage at its terminals, so resistance testing is needed to confirm element condition.

Question 29Tools, Measuring Instruments and Workshop Practice

What is the primary purpose of fitting a fuse in the live conductor of a domestic appliance circuit?

  1. To melt and open the circuit when current exceeds its rating Correct answer.
  2. To convert alternating current into direct current
  3. To improve the power factor of the appliance
  4. To reduce the supply voltage to the appliance

Explanation

A fuse is a deliberate weak link: excess current heats its element until it melts, breaking the circuit before conductors or windings are damaged. It does not regulate voltage, correct power factor or rectify current.

Question 30Tools, Measuring Instruments and Workshop Practice

A technician is about to test a suspected faulty mixer grinder. Which workshop safety practice should be followed before opening the appliance?

  1. Isolate the appliance from the supply and verify isolation at the plug Correct answer.
  2. Test the circuit with wet hands to detect leakage
  3. Leave the plug in the socket and work with insulated pliers only
  4. Hold the appliance steady by gripping the rotating blade

Explanation

Safe repair begins with disconnecting the appliance and confirming that no voltage remains at the plug or terminals. Working live, gripping blades, or using moisture as a test medium all create shock or injury hazards.

Question 31Tools, Measuring Instruments and Workshop Practice

A 1000 W domestic appliance is connected to a 230 V supply. What current does it draw, and which fuse rating is the closest suitable choice?

  1. About 0.43 A, so a 0.5 A fuse
  2. About 2.3 A, so a 3 A fuse
  3. About 10 A, so a 10 A fuse
  4. About 4.3 A, so a 5 A fuse Correct answer.

Explanation

Current equals power divided by voltage, so 1000 W divided by 230 V gives approximately 4.3 A. A 5 A fuse is the nearest standard rating above this current, giving protection without nuisance blowing.

Question 32Tools, Measuring Instruments and Workshop Practice

Why is a soldering iron tip cleaned and re-tinned before making a joint on an appliance terminal?

  1. To remove oxide and ensure rapid, reliable heat transfer to the joint Correct answer.
  2. To increase the melting point of the solder
  3. To insulate the tip from the mains supply
  4. To reduce the wattage drawn by the soldering iron

Explanation

Oxide on the tip acts as a thermal barrier, so cleaning and coating with fresh solder restores a bright, wetted surface that transfers heat quickly. This produces a sound joint instead of a cold, high-resistance one.

Question 33Tools, Measuring Instruments and Workshop Practice

A technician checks the heating element of a 230 V electric iron with an ohmmeter and reads continuity of about 50 ohms, while the element is visibly intact. What can be concluded?

  1. The element is definitely short-circuited
  2. The element must be replaced because continuity indicates failure
  3. The element has a plausible resistance for its power rating and is not open Correct answer.
  4. The ohmmeter is reading the thermostat, not the element

Explanation

A 50 ohm element on 230 V would draw about 4.6 A, giving roughly 1 kW, which is a normal iron rating, so continuity with a finite resistance indicates an intact element. A short would read near zero ohms and an open element would read infinity.

Question 34Tools, Measuring Instruments and Workshop Practice

Which measuring instrument is most suitable for checking the resistance of a thermostat contact that should be closed at room temperature?

  1. A clamp meter set to the 100 A range
  2. A soldering iron with a temperature dial
  3. A digital multimeter set to the lowest resistance range Correct answer.
  4. A megger set to 1000 V for a long-duration test

Explanation

A closed contact should read near zero ohms, so the low resistance range of a multimeter is the correct instrument and setting. A clamp meter measures current and a megger is for insulation, not contact continuity.

Question 35Tools, Measuring Instruments and Workshop Practice

A technician needs to strip the insulation from a 3-core flexible cord without nicking the copper strands. Which practice gives the best result?

  1. Twist the wire sharply until the insulation splits
  2. Burn the insulation with a lighter and wipe it off
  3. Use a hacksaw to cut through the insulation around the circumference
  4. Use a wire stripper set to the conductor size and pull gently along the wire axis Correct answer.

Explanation

A correctly sized wire stripper grips the insulation and pulls it away cleanly without cutting into the copper, preserving the current-carrying capacity of the strands. Cutting, burning or twisting damages strands or leaves a ragged end.

Question 36Tools, Measuring Instruments and Workshop Practice

Why should a continuity test on a cord be made with the appliance disconnected from the mains and the switch in the on position?

  1. So the test current flows through the cord path without mains interference, and the switch does not falsely open the circuit Correct answer.
  2. So the multimeter battery is charged by the mains
  3. So the fuse blows if the cord is faulty
  4. So the appliance draws current during the test

Explanation

Continuity testing uses the meter's own small test current, so the mains must be off for safety and to avoid false readings. With the switch on, the full cord path is included and a broken conductor shows as an open circuit.

Question 37Tools, Measuring Instruments and Workshop Practice

A technician finds that a table fan runs but gives a mild tingling shock when touched. Which test should be carried out first to confirm the fault?

  1. Insulation resistance test between the live parts and the metal body Correct answer.
  2. Continuity test across the fan switch
  3. Check of the fan blade balance
  4. Measurement of the fan motor current with a clamp meter

Explanation

A tingling sensation on a metal body points to leakage from live parts to the frame, so insulation resistance between live conductors and the body is the direct test. Switch continuity, current measurement and blade balance do not reveal leakage paths.

Question 38Tools, Measuring Instruments and Workshop Practice

Which property of a workshop file determines the finish it produces on a metal bracket?

  1. The length of the file tang only
  2. The grade of cut, from coarse to smooth Correct answer.
  3. The colour of the handle
  4. The material of the workbench

Explanation

File teeth are cut in grades such as bastard, second cut and smooth, and the grade sets how much metal is removed and how fine the surface becomes. Handle colour, tang length and bench material do not control the finish.

Question 39Tools, Measuring Instruments and Workshop Practice

A technician is measuring the current drawn by a domestic refrigerator while it is running normally. Which instrument and connection is correct?

  1. An ohmmeter connected across the mains plug pins
  2. A multimeter in series with the circuit on the voltage range
  3. A megger connected across the compressor terminals
  4. A clamp meter placed around one supply conductor Correct answer.

Explanation

A clamp meter surrounds one conductor and reads the current by induction without breaking the circuit, which is ideal for a running appliance. A voltage-range meter in series would short the supply, and the other instruments do not measure load current.

Question 40Tools, Measuring Instruments and Workshop Practice

A technician is tracing a fault in a domestic appliance and finds that the fuse has blown but the replacement fuse also blows immediately. What is the most likely cause?

  1. A worn carbon brush in a motor
  2. An open circuit in the appliance switch
  3. A short circuit in the appliance wiring or element Correct answer.
  4. A loose earth connection only

Explanation

A fuse that blows again immediately indicates excessive current, typically from a short circuit between live and neutral or live and earth. An open circuit would stop current entirely, and a loose earth or worn brush would not normally blow the fuse repeatedly.

Question 41Tools, Measuring Instruments and Workshop Practice

Which precaution is essential when using an insulation resistance tester on a domestic appliance that contains electronic control circuitry?

  1. Test while the appliance is connected to the mains
  2. Apply the full test voltage directly to the module terminals
  3. Use the tester only on the lowest resistance range
  4. Disconnect or isolate the electronic module before applying the test voltage Correct answer.

Explanation

Insulation testers apply a high DC voltage that can damage sensitive electronic components, so modules should be disconnected or bypassed during the test. Testing live is dangerous, and the tester's resistance range is not the issue.

Question 42Tools, Measuring Instruments and Workshop Practice

Why is a centre punch used before drilling a hole in a metal bracket for an appliance mounting screw?

  1. To enlarge the hole to the final size
  2. To harden the metal around the hole
  3. To create a small indentation that stops the drill from wandering Correct answer.
  4. To remove burrs after drilling

Explanation

A centre punch mark gives the drill point a seat so it starts at the marked position instead of skidding across the surface. It does not size the hole, harden the metal or deburr the finished edge.

Question 43Tools, Measuring Instruments and Workshop Practice

A technician measures the resistance of a 230 V, 2000 W heating element and obtains 26.5 ohms. What does this confirm about the element?

  1. The element is short-circuited to the casing
  2. The element is open-circuited and must be replaced
  3. The element is rated for a much lower voltage
  4. The resistance is consistent with the rated power, so the element is sound Correct answer.

Explanation

For a 2000 W element at 230 V, the expected resistance is voltage squared divided by power, about 26.5 ohms, so the measured value matches the rating. This confirms the element is neither open nor shorted.

Question 44Tools, Measuring Instruments and Workshop Practice

Which tool is designed for holding and bending small component leads while soldering on an appliance circuit board?

  1. A cold chisel
  2. A pipe wrench
  3. A ball-peen hammer
  4. Long-nosed pliers Correct answer.

Explanation

Long-nosed pliers have slim jaws that reach into confined spaces to grip and bend component leads without disturbing nearby joints. The other tools are for striking, cutting or gripping pipes and are unsuitable for fine electronic work.

Question 45Wiring, Cabling and Accessories

In a domestic single-phase installation, which conductor colour identifies the protective earth (PE) conductor in a flexible three-core cable to IS 694 / IS 732 convention?

  1. Red
  2. Green with a yellow stripe Correct answer.
  3. Black
  4. Brown

Explanation

Indian wiring practice reserves green-yellow for the protective conductor so that it can never be mistaken for a live or neutral core. This colour is mandatory for earth continuity throughout domestic circuits, including appliance casings and socket earth pins.

Question 46Wiring, Cabling and Accessories

What is the standard nominal supply voltage and frequency for a domestic single-phase connection in Uttar Pradesh?

  1. 110 V, 60 Hz
  2. 240 V, 60 Hz
  3. 415 V, 50 Hz
  4. 230 V, 50 Hz Correct answer.

Explanation

The Indian national supply standard for domestic single-phase consumers is 230 V at 50 Hz, with a permitted variation band. Three-phase domestic or small commercial connections use 415 V at 50 Hz between phases.

Question 47Wiring, Cabling and Accessories

Which wiring system is most commonly specified for concealed domestic wiring in modern Indian houses?

  1. TRS cable clipped directly to plaster
  2. Steel conduit laid on the surface
  3. Wooden batten with porcelain cleats
  4. PVC conduit concealed in wall chases Correct answer.

Explanation

Concealed PVC conduit protects the insulated conductors from mechanical damage and moisture while allowing later cable replacement by drawing through. It also keeps the wiring out of sight, which is why it dominates modern domestic construction.

Question 48Wiring, Cabling and Accessories

A 6 A three-pin domestic socket outlet has its earth pin made thicker and longer than the other two pins. What purpose does this serve?

  1. It prevents the plug from being inserted upside down
  2. It locks the plug mechanically into the socket
  3. It carries the full load current of the appliance
  4. It ensures the earth connection is made first and broken last Correct answer.

Explanation

The longer earth pin enters the socket first, so the appliance is earthed before live and neutral make contact, and it is the last to disconnect. This sequencing protects the user if a fault exists in the appliance.

Question 49Wiring, Cabling and Accessories

Which accessory is installed at the entry point of a domestic installation to disconnect all phases and neutral simultaneously?

  1. Socket outlet
  2. Main switch (ICDP or MCB type) Correct answer.
  3. Ceiling rose
  4. One-way light switch

Explanation

The main switch is the isolator for the whole installation and must break all poles including neutral so that the consumer's wiring can be made dead for maintenance. Light switches and sockets are final-circuit accessories and cannot isolate the supply.

Question 50Wiring, Cabling and Accessories

Why is a fuse or MCB rated at 6 A used on a domestic lighting sub-circuit rather than a 16 A device?

  1. The protective device must not exceed the current-carrying capacity of the smallest conductor in the circuit Correct answer.
  2. Larger devices are not permitted in single-phase installations
  3. Lighting circuits always draw more than 16 A
  4. A 16 A device would reduce the supply voltage

Explanation

Circuit protection is selected so that the device rating does not exceed the cable's current-carrying capacity, protecting the insulation from overheating. Lighting sub-circuits use 1.0 or 1.5 sq mm conductors whose capacity is well below 16 A.