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Cameroon CAP Vocational Trades study materials
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Cameroon CAP Vocational Trades practice questions

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Question 1Trade-Specific Technical Knowledge and Theory

In electrical installation work, what is the primary function of a miniature circuit breaker (MCB) in a final distribution board?

  1. To measure the energy consumed by the installation
  2. To step down the supply voltage to a safer level
  3. To improve the power factor of inductive loads
  4. To automatically open the circuit on overload or short circuit Correct answer.

Explanation

An MCB is a protective device that trips automatically when current exceeds its rating because of overload or a short circuit. It isolates the faulty circuit before conductors overheat, and can be manually reset after the fault is cleared. It does not transform voltage, meter energy, or correct power factor.

Question 2Trade-Specific Technical Knowledge and Theory

A mason is preparing a mortar mix and wants a 1:4 cement-to-sand ratio by volume. If 3 head-pans of cement are used, how many head-pans of sand are required?

  1. 4
  2. 12 Correct answer.
  3. 3
  4. 7

Explanation

A 1:4 ratio means four parts of sand for every one part of cement. Multiplying 3 pans of cement by 4 gives 12 pans of sand. Keeping the ratio constant ensures the mortar reaches its designed strength.

Question 3Trade-Specific Technical Knowledge and Theory

In carpentry, which tool is specifically designed for cutting accurate dovetail joints by hand?

  1. Dovetail saw Correct answer.
  2. Tenon saw
  3. Coping saw
  4. Rip saw

Explanation

A dovetail saw has a fine, stiff blade with a thin kerf and small teeth, making it suited to precise joinery cuts. Rip saws cut along the grain, coping saws cut curves, and tenon saws are larger backsaws used for wider tenons. The fine teeth of the dovetail saw give the control needed for accurate pins and tails.

Question 4Trade-Specific Technical Knowledge and Theory

In metalwork, what is the main purpose of annealing a piece of work-hardened steel?

  1. To soften it by controlled heating and slow cooling Correct answer.
  2. To harden its surface by rapid quenching
  3. To increase its carbon content
  4. To give it a mirror-polished finish

Explanation

Annealing involves heating the steel to a suitable temperature and cooling it slowly, usually in a furnace or in air. This relieves internal stresses and softens the metal so it can be machined or formed more easily. Quenching would harden rather than soften, and annealing does not change carbon content or polish the surface.

Question 5Trade-Specific Technical Knowledge and Theory

In plumbing, what is the function of a trap fitted below a sanitary fitting?

  1. It filters solid waste before it reaches the drain
  2. It holds a water seal that prevents sewer gases from entering the building Correct answer.
  3. It increases the flow rate of waste water
  4. It regulates the water supply pressure

Explanation

A trap retains a small body of water that blocks the passage of foul air from the drainage system into the room. The depth of the seal must be sufficient to resist pressure fluctuations. Traps do not increase flow, filter solids, or regulate supply pressure.

Question 6Trade-Specific Technical Knowledge and Theory

A builder is laying a concrete slab and mixes 1 part cement, 2 parts sand, and 4 parts coarse aggregate. This mix is best described as which grade of concrete?

  1. No-fines concrete
  2. Rich 1:1:2 mix
  3. C20/25 nominal mix Correct answer.
  4. M10 lean mix

Explanation

A 1:2:4 cement-sand-aggregate mix is a standard nominal mix commonly associated with grade C20/25 concrete. It provides moderate strength suitable for general structural slabs and beams. Leaner mixes such as 1:4:8 are used for blinding, while 1:1:2 is much richer.

Question 7Trade-Specific Technical Knowledge and Theory

In an AC circuit, a resistor of 30 ohms is connected in series with an inductive reactance of 40 ohms. What is the impedance of the circuit?

  1. 10 ohms
  2. 50 ohms Correct answer.
  3. 70 ohms
  4. 1200 ohms

Explanation

Impedance in a series R-L circuit is found using Z equals the square root of R squared plus X_L squared. Here that is the square root of 900 plus 1600, which equals the square root of 2500, or 50 ohms. Resistance and reactance add vectorially, not arithmetically.

Question 8Trade-Specific Technical Knowledge and Theory

A welder notices porosity in a completed fillet weld. Which cause is most directly responsible?

  1. Excessive travel speed with a long arc length only
  2. Using a welding current that is too high
  3. Cooling the joint too slowly after welding
  4. Moisture or dirt on the electrode or workpiece Correct answer.

Explanation

Porosity is caused by gas trapped in the weld metal, commonly from moisture, oil, paint, or rust on the surfaces or electrode. Cleaning the joint and using properly stored electrodes prevents it. Current and travel speed affect penetration and bead shape more than porosity.

Question 9Trade-Specific Technical Knowledge and Theory

A tailor is cutting fabric for a garment and needs to account for seam allowance. What does seam allowance refer to?

  1. The fold at the hem of the garment
  2. The extra fabric beyond the stitching line, needed for the seam Correct answer.
  3. The space between two buttons
  4. The width of the fabric bolt

Explanation

Seam allowance is the margin of fabric left beyond the seam line so the pieces can be joined and finished. It is added to pattern pieces before cutting. It is not a hem fold, a fabric width, or a button spacing.

Question 10Trade-Specific Technical Knowledge and Theory

In an electrical installation, why is the earth continuity conductor sized and connected with particular care?

  1. It reduces the electricity bill by returning current
  2. It carries the normal load current during operation
  3. It provides the low-resistance path that lets protective devices operate during a fault Correct answer.
  4. It balances the voltage between phases

Explanation

The earth continuity conductor ensures that a fault current flows in sufficient magnitude to trip the protective device quickly. A poor earth path leaves exposed metalwork live and dangerous. It does not carry normal load current or balance phase voltages.

Question 11Trade-Specific Technical Knowledge and Theory

A motor vehicle technician finds that a battery is flat after standing overnight. Which test most directly identifies an excessive current drain with the ignition off?

  1. Measuring current flow between the battery negative terminal and the earth cable Correct answer.
  2. Checking the specific gravity of the electrolyte
  3. Testing the compression of the engine
  4. Measuring the charging voltage at the alternator

Explanation

A parasitic drain is found by measuring the current flowing in the earth circuit with all loads switched off. An abnormally high reading indicates a circuit drawing current when it should not. Specific gravity, charging voltage, and compression test other functions.

Question 12Trade-Specific Technical Knowledge and Theory

In bricklaying, what is the main purpose of a bond such as English bond in a wall?

  1. To speed up the setting of the mortar
  2. To distribute load and prevent continuous vertical joints Correct answer.
  3. To reduce the amount of mortar required
  4. To improve the water resistance of the bricks

Explanation

A bond arranges bricks so that vertical joints in successive courses do not align, spreading loads and giving the wall strength. English bond alternates header and stretcher courses for this purpose. Bonds do not control mortar setting or brick water resistance.

Question 13Trade-Specific Technical Knowledge and Theory

A plumber is installing a soil pipe and must maintain a fall to ensure self-cleansing flow. What does the recommended gradient primarily ensure?

  1. Water pressure in the building increases
  2. The pipe can be made from any material
  3. Waste travels at a velocity that carries solids along the pipe Correct answer.
  4. The pipe never needs cleaning

Explanation

The gradient is set so that waste flows fast enough to carry solids but not so fast that water outruns them. This self-cleansing velocity keeps the drain clear. Gradient does not eliminate maintenance, raise pressure, or dictate material choice.

Question 14Trade-Specific Technical Knowledge and Theory

In a three-phase system, what is the phase relationship between the three supply voltages?

  1. Each phase is displaced by 120 electrical degrees from the others Correct answer.
  2. Each phase is displaced by 90 electrical degrees
  3. All three phases are in phase with each other
  4. Each phase is displaced by 180 electrical degrees

Explanation

A balanced three-phase supply has three voltages of equal magnitude displaced by one-third of a cycle, which is 120 electrical degrees. This spacing gives constant total power and enables rotating fields in motors. Ninety or 180 degrees would not produce a balanced three-phase set.

Question 15Trade-Specific Technical Knowledge and Theory

A carpenter needs to check whether a long timber is straight along its length. Which tool is most appropriate?

  1. A marking gauge
  2. A mortise gauge
  3. A try square
  4. A straightedge or winding sticks Correct answer.

Explanation

A straightedge reveals bow or winding along the length, and winding sticks show twist when sighted along the timber. Squares check right angles, and gauges mark lines parallel to an edge. Straightness along the length is best assessed with a straightedge.

Question 16Trade-Specific Technical Knowledge and Theory

In electrical theory, what happens to the total resistance when two resistors are connected in parallel?

  1. It equals the sum of the two resistances
  2. It becomes less than the smallest individual resistance Correct answer.
  3. It remains equal to one of the resistances
  4. It becomes greater than the largest resistance

Explanation

In parallel, the reciprocal of the total resistance equals the sum of the reciprocals of the individual resistances. This makes the total smaller than the smallest resistor because the current has more paths. Series connection, by contrast, simply adds the resistances.

Question 17Trade-Specific Technical Knowledge and Theory

A mason needs to check that a corner is a true right angle when setting out a building. Which method is correct?

  1. Measuring only one side twice
  2. Using a spirit level alone on the wall face
  3. Using the 3-4-5 method to form a right triangle Correct answer.
  4. Comparing two diagonals of a square

Explanation

The 3-4-5 method applies Pythagoras to create a right angle: a triangle with sides in the ratio 3:4:5 has a right angle opposite the 5 side. A spirit level checks verticality, not plan squareness. Comparing diagonals works for rectangles but requires equal opposite sides first.

Question 18Trade-Specific Technical Knowledge and Theory

In plumbing, which material is commonly chosen for hot water distribution because it resists heat and corrosion?

  1. Unplasticised PVC
  2. Cast iron
  3. Copper Correct answer.
  4. Galvanised mild steel

Explanation

Copper withstands high temperatures and resists corrosion, making it suitable for hot water pipes. UPVC softens at elevated temperatures and is used for cold water and drainage. Galvanised steel and cast iron are more typical for cold supply and drainage respectively.

Question 19Trade-Specific Technical Knowledge and Theory

A welder is joining two thin sheets of metal and wants to avoid burning through. Which adjustment is most appropriate?

  1. Reduce the current and use a shorter arc Correct answer.
  2. Use a larger electrode at higher current
  3. Increase the current and lengthen the arc
  4. Increase travel speed while raising current

Explanation

Thin sheet metal is easily burnt through if heat input is too high, so current should be reduced and the arc kept short for control. A larger electrode or higher current adds heat and worsens burn-through. Adjusting current downward is the primary control.

Question 20Trade-Specific Technical Knowledge and Theory

In garment making, what does the term grain line on a pattern piece indicate?

  1. The direction of the warp threads in the fabric Correct answer.
  2. The position of the buttons
  3. The location of the hem
  4. The seam allowance width

Explanation

The grain line shows how the pattern piece must be aligned with the warp of the fabric, usually parallel to the selvedge. Correct alignment prevents the finished garment from twisting or hanging poorly. It does not mark buttons, seam allowances, or hems.

Question 21Trade-Specific Technical Knowledge and Theory

A technician measures the voltage across a resistor as 12 V and the current through it as 0.5 A. What is the resistance?

  1. 0.04 ohms
  2. 6 ohms
  3. 12.5 ohms
  4. 24 ohms Correct answer.

Explanation

Ohm's law states that resistance equals voltage divided by current. Dividing 12 V by 0.5 A gives 24 ohms. Multiplying or adding the values would not follow the relationship.

Question 22Trade-Specific Technical Knowledge and Theory

In metalwork, what is the purpose of using a centre punch before drilling a hole?

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

Explanation

A centre punch mark gives the drill bit a starting point so it does not slip on the smooth surface. It is made with a hammer after marking the position. It does not enlarge, harden, or deburr the hole.

Question 23Trade-Specific Technical Knowledge and Theory

A building team is casting a reinforced concrete beam and must position the steel reinforcement correctly. Why is the concrete cover over the reinforcement specified?

  1. To increase the amount of steel needed
  2. To reduce the weight of the beam
  3. To make the formwork easier to remove
  4. To protect the steel from corrosion and provide fire resistance Correct answer.

Explanation

Cover is the depth of concrete between the steel and the outer surface. Adequate cover protects the reinforcement from moisture and fire, and ensures bond between steel and concrete. It does not reduce weight or increase steel demand.

Question 24Trade-Specific Technical Knowledge and Theory

In an electrical installation, a residual current device (RCD) with a 30 mA rating is installed. What does the 30 mA value represent?

  1. The earth loop impedance it requires
  2. The rated residual operating current at which it trips Correct answer.
  3. The maximum load current it can carry continuously
  4. The supply voltage it can withstand

Explanation

The 30 mA figure is the rated residual operating current, meaning the device trips when the imbalance between live and neutral reaches about that value. It provides additional protection against electric shock. It is not a load rating, voltage rating, or impedance value.

Question 25Trade-Specific Technical Knowledge and Theory

A refrigeration technician observes that a domestic refrigerator runs continuously but does not cool adequately. Which fault best explains this?

  1. A faulty door light switch
  2. A loss of refrigerant through a leak Correct answer.
  3. A blocked condensate drain
  4. A worn door gasket only

Explanation

Insufficient refrigerant from a leak reduces the cooling effect, so the compressor runs continuously without reaching the set temperature. A light switch or condensate drain does not affect cooling capacity, and a worn gasket alone would not fully explain continuous running without cooling.

Question 26Trade-Specific Technical Knowledge and Theory

A carpenter is selecting a saw to cut a curved profile in a thin piece of timber. Which saw is most appropriate for this task?

  1. Coping saw Correct answer.
  2. Crosscut saw
  3. Tenon saw
  4. Rip saw

Explanation

A coping saw has a thin, narrow blade held under tension in a U-shaped frame, allowing it to turn and follow curved lines in thin timber or sheet material. Rip saws, crosscut saws, and tenon saws have stiff, wide blades intended for straight cuts along or across the grain. Therefore, the coping saw is the correct tool for cutting a curved profile.

Question 27Trade-Specific Technical Knowledge and Theory

In a masonry wall, what is the function of a damp-proof course (DPC)?

  1. To bond the facing bricks to the backing bricks
  2. To prevent moisture rising through the wall by capillary action Correct answer.
  3. To provide a decorative band at floor level
  4. To allow water to drain out of the wall cavity

Explanation

A damp-proof course is a continuous impermeable layer installed near the base of a wall to block the upward movement of groundwater by capillary action. It protects the interior from rising damp and must be lapped correctly with the damp-proof membrane. Without a DPC, moisture can rise into the wall and cause decay and unhealthy conditions.

Question 28Trade-Specific Technical Knowledge and Theory

A plumber is joining two lengths of copper pipe and needs a permanent, leak-free joint. Which method is most suitable?

  1. Using a compression fitting without tightening
  2. Soldering with a lead-free solder and flux Correct answer.
  3. Wrapping with PTFE tape and pushing together
  4. Securing with a hose clamp and rubber sleeve

Explanation

Soldering copper pipe creates a metallurgical bond when the filler metal flows into the joint clearance under capillary action. The surfaces must be cleaned and fluxed, and lead-free solder is used for potable water systems. This produces a permanent, leak-free joint that is standard in plumbing.

Question 29Trade-Specific Technical Knowledge and Theory

In electrical installations, what is the primary purpose of a fuse or circuit breaker?

  1. To reduce the voltage supplied to appliances
  2. To convert alternating current to direct current
  3. To improve the power factor of the installation
  4. To interrupt the circuit when current exceeds a safe value Correct answer.

Explanation

A fuse or circuit breaker is a protective device that opens the circuit when the current exceeds its rated value, preventing overheating and fire. It does not regulate voltage, correct power factor, or rectify current. Correct selection and coordination of these devices are essential for installation safety.

Question 30Trade-Specific Technical Knowledge and Theory

A welder is preparing to strike an arc with a manual metal arc (MMA) electrode. What is the correct action to initiate the arc?

  1. Tap or scratch the electrode lightly on the workpiece and lift it slightly Correct answer.
  2. Hold the electrode several centimetres above the workpiece before switching on
  3. Press the electrode firmly into the workpiece and hold it there
  4. Touch the electrode to the workpiece and immediately switch off the current

Explanation

To strike an arc in MMA welding, the electrode is lightly tapped or scratched on the workpiece to make contact and then lifted a short distance to establish the arc gap. Holding contact or keeping too large a gap prevents a stable arc. The technique protects the electrode coating and starts the weld cleanly.

Question 31Trade-Specific Technical Knowledge and Theory

In garment construction, what is the purpose of clipping the seam allowance on a curved seam?

  1. To allow the seam to lie flat when turned Correct answer.
  2. To prevent the fabric from fraying
  3. To strengthen the seam against tearing
  4. To mark the position of the grain line

Explanation

Clipping involves cutting small snips into the seam allowance of a convex curve so that the fabric can spread and the seam lies flat when turned to the right side. Without clipping, the seam allowance bunches and distorts the curve. It is a shaping technique, not a strengthening or finishing one.

Question 32Trade-Specific Technical Knowledge and Theory

A motor vehicle technician is checking a lead-acid battery. Which test indicates the battery's state of charge most directly?

  1. Measuring the specific gravity of the electrolyte Correct answer.
  2. Inspecting the battery casing for cracks
  3. Checking the battery terminal tightness
  4. Measuring the alternator belt tension

Explanation

The specific gravity of the electrolyte in a lead-acid battery changes with the state of charge, so a hydrometer reading gives a direct indication of charge level. Belt tension, terminal tightness, and casing condition are important checks but do not measure state of charge. Therefore, the hydrometer test is the most direct.

Question 33Trade-Specific Technical Knowledge and Theory

In a refrigeration system, what is the function of the expansion valve?

  1. To store excess refrigerant during low load
  2. To increase refrigerant pressure before the condenser
  3. To reduce refrigerant pressure and temperature before the evaporator Correct answer.
  4. To remove moisture from the refrigerant

Explanation

The expansion valve throttles the refrigerant from high pressure to low pressure, causing its temperature to drop before it enters the evaporator. This pressure reduction allows the refrigerant to absorb heat from the refrigerated space. It is a key component in the vapour-compression cycle.

Question 34Trade-Specific Technical Knowledge and Theory

In a DC circuit, a resistor of 10 ohms carries a current of 2 A. What is the voltage across the resistor?

  1. 12 V
  2. 0.2 V
  3. 5 V
  4. 20 V Correct answer.

Explanation

Ohm's law states that voltage equals current multiplied by resistance (V = I × R). Substituting the values gives V = 2 A × 10 Ω = 20 V. The other values result from incorrect operations such as division or addition.

Question 35Trade-Specific Technical Knowledge and Theory

A mason is laying bricks and needs to check that each course is horizontal. Which tool is most appropriate?

  1. Plumb rule
  2. Trowel
  3. Chalk line
  4. Spirit level Correct answer.

Explanation

A spirit level contains a bubble in a curved vial that indicates when a surface is truly horizontal or vertical. It is the standard tool for checking the level of brick courses. A plumb rule checks verticality, while a trowel and chalk line serve other purposes.

Question 36Trade-Specific Technical Knowledge and Theory

A metalworker is drilling a hole in a steel plate and the drill bit keeps wandering from the marked centre. What is the most appropriate action to prevent this?

  1. Apply cutting fluid only after the hole is started
  2. Use a centre punch to make a starting indentation Correct answer.
  3. Use a larger drill bit for the initial hole
  4. Increase the drilling speed and apply more pressure

Explanation

A centre punch creates a small indentation at the marked centre, which guides the drill point and prevents it from wandering. Increasing speed or pressure without a starting point can worsen the problem. Using a larger bit initially would not provide the needed accuracy.

Question 37Trade-Specific Technical Knowledge and Theory

In brickwork, why is a half-brick wall often considered unsuitable for load-bearing external walls?

  1. Its thickness provides insufficient resistance to lateral loads and weather penetration Correct answer.
  2. It is more expensive to construct than a cavity wall
  3. It requires more mortar than a one-brick wall
  4. It cannot be built with a damp-proof course

Explanation

A half-brick wall is only 102.5 mm thick and lacks the mass and stiffness to resist lateral loads such as wind, and it provides less weather resistance. Building regulations typically require a thicker or cavity wall for external load-bearing use. The other options are not the primary structural reasons.

Question 38Trade-Specific Technical Knowledge and Theory

A plumber is installing a discharge pipe from a washbasin. Which factor most directly determines the minimum diameter of the trap and pipe?

  1. The colour of the fixture
  2. The water pressure in the supply main
  3. The flow rate and solid waste load from the fixture Correct answer.
  4. The height of the building

Explanation

The diameter of a discharge pipe and trap must be sized to carry the expected flow and any solids without blockage. Fixture units and drainage regulations specify minimum sizes based on the type of fixture. Colour, building height, and supply pressure do not determine the drain size.

Question 39Trade-Specific Technical Knowledge and Theory

In an electrical circuit, a 12 V supply is connected to two resistors of 6 Ω and 3 Ω in series. What is the current in the circuit?

  1. 0.75 A
  2. 2 A
  3. 1.33 A Correct answer.
  4. 4 A

Explanation

In a series circuit, the total resistance is the sum of the individual resistances: 6 Ω + 3 Ω = 9 Ω. Using Ohm's law, current equals voltage divided by resistance: 12 V ÷ 9 Ω = 1.33 A. The other values come from incorrect resistance calculations.

Question 40Trade-Specific Technical Knowledge and Theory

A tailor is working with a fabric that has a directional nap. What does this mean for pattern layout?

  1. The pattern pieces must be placed at 45 degrees to the selvedge
  2. Pattern pieces can be laid in any direction to save fabric
  3. The fabric must be cut on the bias
  4. All pattern pieces must be laid in the same direction along the fabric Correct answer.

Explanation

A directional nap means the fabric surface has a different appearance when viewed from different directions, so all pattern pieces must be laid with the nap running the same way. Otherwise, adjacent panels will appear to be different shades. This is a key layout rule for fabrics such as velvet or corduroy.

Question 41Trade-Specific Technical Knowledge and Theory

A welder is using the metal inert gas (MIG) welding process. What is the primary role of the shielding gas?

  1. To increase the deposition rate of the filler wire
  2. To provide the electrical path for the arc
  3. To protect the molten weld pool from atmospheric contamination Correct answer.
  4. To cool the weld quickly to increase hardness

Explanation

In MIG welding, the shielding gas flows around the arc and weld pool to exclude oxygen, nitrogen, and moisture from the atmosphere, preventing porosity and embrittlement. It does not carry the current or intentionally cool the weld. Correct gas selection is critical for weld quality.

Question 42Trade-Specific Technical Knowledge and Theory

In a motor vehicle engine, what is the purpose of the thermostat in the cooling system?

  1. To increase the boiling point of the coolant
  2. To regulate engine temperature by controlling coolant flow Correct answer.
  3. To measure the coolant temperature for the gauge
  4. To circulate coolant through the radiator

Explanation

The thermostat is a valve that opens and closes in response to coolant temperature, regulating flow to the radiator and keeping the engine within its optimal operating range. It does not pump coolant, measure temperature for the gauge, or change the boiling point. Proper thermostat operation is essential for efficiency and emissions.

Question 43Trade-Specific Technical Knowledge and Theory

A carpenter is constructing a timber stud partition wall and needs to provide an opening for a door. Which method is structurally appropriate for the header above the door?

  1. Simply leave out the studs above the door
  2. Replace the studs with a thinner horizontal timber
  3. Install a lintel or header beam to carry the loads above the opening Correct answer.
  4. Use a single horizontal nogging without additional support

Explanation

A header or lintel is required above a door opening to transfer the loads from above to the adjacent studs or wall. Simply omitting studs or using inadequate horizontal members can lead to sagging and structural failure. Proper framing around openings is essential for wall integrity.

Question 44Trade-Specific Technical Knowledge and Theory

In plumbing, why is a trap required beneath a sanitary fixture?

  1. To filter solid waste from the discharge
  2. To reduce noise from the drainage system
  3. To retain a water seal that prevents sewer gases from entering the building Correct answer.
  4. To increase the flow rate of the discharge

Explanation

A trap holds a small amount of water that forms a seal, blocking sewer gases and odours from entering the building through the fixture. It does not increase flow, filter waste, or primarily reduce noise. The water seal must be maintained by proper venting to prevent siphonage.

Question 45Trade-Specific Technical Knowledge and Theory

A metalworker is using a lathe to turn a mild steel bar. Which parameter most directly affects the surface finish and tool life?

  1. Type of chuck used
  2. Length of the bar
  3. Colour of the workpiece
  4. Cutting speed Correct answer.

Explanation

Cutting speed, along with feed and depth of cut, directly influences the heat generated, surface finish, and tool wear. Too high a speed can cause rapid tool wear, while too low a speed may produce a poor finish. Other factors such as bar length or chuck type are less directly related to finish and tool life.

Question 46Trade-Specific Technical Knowledge and Theory

In electrical installation, what is the purpose of bonding metal parts such as water pipes and structural steel to the main earthing terminal?

  1. To reduce the current-carrying capacity of the installation
  2. To increase the resistance of the earthing system
  3. To ensure all metalwork is at the same potential and prevent dangerous touch voltages Correct answer.
  4. To provide a return path for the supply current

Explanation

Main protective bonding connects extraneous conductive parts to the earthing system so that they remain at substantially the same potential, reducing the risk of electric shock. It does not carry normal supply current or increase resistance. Proper bonding is a fundamental safety requirement.

Question 47Trade-Specific Technical Knowledge and Theory

A tailor is choosing a needle for sewing a lightweight silk fabric. Which needle type is most appropriate?

  1. Twin needle
  2. Fine sharp needle Correct answer.
  3. Leather needle
  4. Heavy denim needle

Explanation

Lightweight fabrics like silk require a fine, sharp needle to prevent visible holes and fabric damage. Heavy denim or leather needles are too thick and would leave large punctures. A twin needle is used for decorative stitching, not necessarily for lightweight fabric.

Question 48Trade-Specific Technical Knowledge and Theory

A mason is mixing mortar and needs to improve its workability without adding more water. Which material is commonly used as a plasticiser?

  1. Lime Correct answer.
  2. Coarse aggregate
  3. Portland cement
  4. Sand

Explanation

Lime is added to cement mortar to improve workability and water retention, acting as a plasticiser. Cement is the binder, sand is the fine aggregate, and coarse aggregate is not used in mortar. Adding lime can also increase flexibility and reduce cracking.

Question 49Trade-Specific Technical Knowledge and Theory

A refrigeration technician finds that a domestic refrigerator's compressor is running continuously and the evaporator is frosted unevenly. Which fault is most likely?

  1. A faulty thermostat that keeps the compressor off
  2. A partial blockage in the capillary tube or expansion device Correct answer.
  3. Excessive refrigerant charge causing high suction pressure
  4. A broken door seal allowing warm air into the cabinet

Explanation

A partial blockage in the capillary tube or expansion device reduces refrigerant flow, causing low suction pressure and uneven frosting on the evaporator. The compressor runs continuously because it cannot reach the set temperature. A faulty thermostat that keeps the compressor off would stop cooling entirely, and a broken door seal would cause sweating but not typically uneven frost.

Question 50Trade-Specific Technical Knowledge and Theory

In a three-phase induction motor, why does the rotor rotate?

  1. The stator winding creates a static magnetic field that pulls the rotor
  2. The rotor carries permanent magnets that align with the stator field
  3. The rotor is connected directly to the supply phases
  4. The rotating magnetic field induces currents in the rotor that interact with the field to produce torque Correct answer.

Explanation

The three-phase stator winding produces a rotating magnetic field. This field induces currents in the rotor conductors, which in turn create a magnetic field that interacts with the stator field to produce torque. The rotor is not directly connected to the supply, and a static field would not cause continuous rotation.