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MATSEC SEC Engineering Technology study materials
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MATSEC SEC Engineering Technology practice questions

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Question 1Health, Safety and Workshop Practice

A student is about to use a bench-mounted pedestal grinder to sharpen a chisel. Which item of personal protective equipment is required specifically to protect the eyes from flying abrasive particles?

  1. Disposable dust mask
  2. Ear defenders
  3. Safety goggles Correct answer.
  4. Leather welding gauntlets

Explanation

Impact-rated eye protection is essential because abrasive fragments leave the wheel at high speed and can strike the eye from any direction. Safety goggles seal against the face and are the preferred choice at a grinder, with a face shield worn over them for extra cover. Gloves must not be worn at rotating machinery because they can be caught and drag the hand into the wheel.

Question 2Health, Safety and Workshop Practice

Under the colour-coding system used on portable fire extinguishers in Malta, which colour identifies a carbon dioxide extinguisher?

  1. Red
  2. Cream
  3. Blue
  4. Black Correct answer.

Explanation

Portable extinguishers follow the European colour-code scheme, in which the body of the extinguisher is red and a coloured band names the extinguishing medium inside. Carbon dioxide units carry a black band, foam units a cream band, dry powder units a blue band and water units a red band. Knowing the code lets a user select the correct medium without having to read a label in an emergency.

Question 3Health, Safety and Workshop Practice

A blue circular pictogram is displayed at the entrance to a workshop area. What type of message does this sign shape and colour convey?

  1. A mandatory action or behaviour Correct answer.
  2. A warning of a specific hazard
  3. A prohibition that must be obeyed
  4. The location of emergency equipment

Explanation

Safety signs follow the shape and colour conventions of BS EN ISO 7010. A blue circle means a mandatory instruction, such as wearing eye protection or keeping a machine guard closed. Prohibition signs are red circles with a diagonal bar, warning signs are yellow triangles and safe-condition or escape signs are green rectangles.

Question 4Health, Safety and Workshop Practice

A student has just tightened the drill bit in the chuck of a pillar drill. Why must the chuck key be removed before the machine is switched on?

  1. To stop the chuck bearings from overheating during a long run
  2. To allow the drill table to be repositioned without obstruction
  3. To prevent damage to the key from hot metal swarf
  4. To stop the key being flung out of the spinning chuck Correct answer.

Explanation

If the key is left in the chuck it becomes an unsecured projectile as soon as the spindle turns, and it can strike the operator or a bystander at high speed. The drill must not be started until the key has been removed and the chuck guard is in position. This is why many pillar drills are fitted with a spring-loaded chuck key holder that returns the key automatically.

Question 5Health, Safety and Workshop Practice

Portable 230 V hand tools are used in a damp workshop area. What is the purpose of supplying them through a residual current device (RCD)?

  1. It limits the tool to a safe maximum running speed
  2. It prevents the tool from drawing excessive current under load
  3. It converts the supply to a lower, safer voltage
  4. It cuts the supply quickly when current leaks to earth Correct answer.

Explanation

An RCD continuously compares the current flowing in the live and neutral conductors. If some current leaks to earth, for example through a damaged tool body and a person, the imbalance trips the device within milliseconds, typically at a residual current of 30 mA. It does not change the voltage, control speed or act as overload protection.

Question 6Health, Safety and Workshop Practice

A technician must move a heavy steel vice from a bench down to a trolley at floor level. Which technique best reduces the risk of back injury?

  1. Keep the load close, bend the knees and lift smoothly Correct answer.
  2. Bend at the waist and lift the vice quickly to save strain
  3. Ask a colleague to lift the opposite end while you twist round
  4. Hold the vice at arm's length and twist towards the trolley

Explanation

Manual handling injuries are reduced by keeping the load close to the trunk, which shortens the lever arm acting on the lower back, and by using the strong leg muscles rather than the back. The lift should be smooth, and the feet should be repositioned instead of twisting the trunk while it is loaded. Twisting under load is a common cause of disc injury.

Question 7Health, Safety and Workshop Practice

Before clearing a jammed workpiece from inside a band saw, a technician switches the machine off at the isolator. Why is a lock and tag then fitted to the isolator?

  1. To warn operators that the blade is at the end of its working life
  2. To record which technician is responsible for the machine's output
  3. To stop anyone restoring power while the technician is at risk Correct answer.
  4. To show that the machine has been serviced within its schedule

Explanation

A lock and a personal tag show that the machine has been deliberately isolated and that someone is working inside a danger zone. Each person working on the machine fits their own lock, and power cannot be restored until every lock has been removed by the person who fitted it. This prevents an unexpected start-up, which is a recognised cause of serious injury.

Question 8Health, Safety and Workshop Practice

A technician is arc welding in a bay next to other students. Besides the welder's own helmet, why should a welding screen be placed around the work?

  1. To reduce the noise level produced by the welding arc
  2. To stop sparks from setting light to the workshop floor
  3. To shield nearby people from harmful ultraviolet radiation Correct answer.
  4. To keep the welding fumes from reaching the extractor hood

Explanation

The electric arc emits intense ultraviolet and infrared radiation that can burn an unprotected eye, causing the painful condition known as arc eye or photokeratitis. A welding screen with filtered panels blocks this radiation so that people working nearby are not exposed. Fume extraction and fire precautions are separate controls and are not provided by the screen.

Question 9Health, Safety and Workshop Practice

A bench grinder is to be fitted with a new abrasive wheel marked 32 m/s. The machine spindle would run the wheel at a peripheral speed of 40 m/s. Why must this wheel not be used on that machine?

  1. It will not fit the guard supplied with the machine
  2. It will produce a coarser surface finish than intended
  3. It may burst because it is run above its rated speed Correct answer.
  4. It will glaze over more quickly at the higher speed

Explanation

The speed marked on an abrasive wheel is the maximum peripheral speed at which it may be run, and exceeding it raises the centrifugal stress beyond what the wheel was designed to withstand. A wheel run overspeed may burst and throw fragments through the guard and into the workshop. The wheel must be matched to the machine, ring-tested before mounting and never run faster than its marked limit.

Question 10Health, Safety and Workshop Practice

A risk assessment finds that operators are exposed to fine dust when hand-sanding wooden components. Which control should be considered first, in accordance with the hierarchy of control?

  1. Display a warning sign at the workshop entrance
  2. Rotate operators between tasks so exposure is shared equally
  3. Replace hand sanding with a dust-extracted machine process Correct answer.
  4. Issue close-fitting respirators to each operator

Explanation

The hierarchy of control places elimination of the hazard first, followed by substitution, engineering controls, administrative controls and finally personal protective equipment. Replacing a dusty hand operation with a dust-extracted machine process removes much of the exposure at source. Respirators, signs and rotation all depend on human behaviour and should only supplement the higher-level controls.

Question 11Health, Safety and Workshop Practice

A 230 V to 110 V portable tool transformer used on a construction site has its 110 V secondary centre-tapped to earth. What is the main safety benefit of this arrangement?

  1. It increases the current available so that tools run more powerfully
  2. It allows the tool to be used safely in wet conditions without an RCD
  3. It limits the maximum voltage to earth to about 55 V Correct answer.
  4. It removes the need for any inspection of the tool and its lead

Explanation

The secondary winding is centre-tapped to earth so the highest voltage to earth from either line is about 55 V, half the 110 V line-to-line value. This reduces the severity of a shock if a live conductor is touched, but the tool and lead still need inspection and an RCD is normally required.

Question 12Health, Safety and Workshop Practice

In the fire classification system used for selecting extinguishers, which class covers flammable liquids such as paint thinners and paraffin?

  1. Class D
  2. Class A
  3. Class B Correct answer.
  4. Class C

Explanation

Class B fires involve flammable liquids such as paint thinners, paraffin and solvents. Class A covers solid combustibles, Class C flammable gases and Class D combustible metals, so water must not be used on a Class B fire because it can spread the burning liquid.

Question 13Health, Safety and Workshop Practice

A technician picks up a file that has no handle fitted and is holding the bare tang. Why is this unsafe?

  1. The file cuts more slowly without a handle
  2. The sharp tang can puncture the hand Correct answer.
  3. The tang corrodes faster in a damp workshop
  4. The file loses hardness when held by the tang

Explanation

A file should be fitted with a handle that covers the tang; a bare tang is a sharp spike that can be driven into the wrist or palm if the file slips or the workpiece moves. The handle also gives a safer, more controlled grip.

Question 14Health, Safety and Workshop Practice

A 4 m extension ladder is being set up to reach a roof edge. At what angle to the horizontal should it be placed?

  1. At about 75° to the horizontal Correct answer.
  2. At about 45° to the horizontal
  3. At about 60° to the horizontal
  4. At about 85° to the horizontal

Explanation

The recommended setting is about 75° to the horizontal, often described as the 1 in 4 rule: for every four units up, the foot is one unit out. A ladder set too steeply can tip backwards, while one set too shallowly can slide out at the foot.

Question 15Health, Safety and Workshop Practice

Why must oxygen regulator and cylinder fittings never be lubricated with oil or grease?

  1. Oil attracts abrasive dust into the regulator
  2. Oil can ignite violently in the presence of oxygen Correct answer.
  3. Oil freezes the regulator at high flow
  4. Oil softens the rubber diaphragm

Explanation

Oxygen under pressure greatly lowers the ignition temperature of oil and grease, and a contaminated regulator can ignite or even explode when the cylinder valve is opened. Fittings must therefore be kept clean and free of oil, and only oxygen-compatible lubricants may be used.

Question 16Health, Safety and Workshop Practice

A machine in the workshop produces a high noise level throughout the day. According to the hierarchy of control, which action should be considered first?

  1. Rotate staff so that exposure is shared
  2. Enclose the machine to reduce noise at source Correct answer.
  3. Display a warning sign at the workshop entrance
  4. Issue ear defenders and rely on them

Explanation

The hierarchy of control requires risks to be reduced at source before relying on personal protection. Enclosing the machine or fitting silencers reduces the noise reaching everyone in the area, whereas ear defenders protect only the wearer and depend on correct fit.

Question 17Health, Safety and Workshop Practice

A milling machine is fitted with an interlocked guard over the rotating cutter. Why does the interlock stop the spindle when the guard is opened?

  1. It stops the machine from overheating
  2. It prevents the cutter from cutting oversize parts
  3. It stops the spindle before hands can reach the cutter Correct answer.
  4. It reduces the noise produced by the cutter

Explanation

An interlocked guard is linked to the machine control so that opening it stops the spindle, usually with a short braking time. The guard must prevent access until the cutter has stopped, because a rotating cutter can cause severe injury even after the power is switched off.

Question 18Health, Safety and Workshop Practice

Why is local exhaust ventilation preferred to a general workshop fan for controlling welding fume?

  1. It filters the shielding gas before it reaches the torch
  2. It removes the need for the welder to wear a helmet
  3. It captures fume at source before it is inhaled Correct answer.
  4. It lowers the current needed to strike the welding arc

Explanation

Local exhaust ventilation captures welding fume close to the arc, before it rises into the welder's breathing zone and mixes with the general workshop air. A general fan or open door dilutes fume but does not remove it at source, and a welding helmet protects the face and eyes rather than the lungs.

Question 19Health, Safety and Workshop Practice

Why is a flashback arrestor fitted to the hose at the regulator outlet on oxy-acetylene equipment?

  1. It stops a flame front travelling back into the cylinder Correct answer.
  2. It prevents the hose from being over-pressurised
  3. It regulates the gas pressure to a steady value
  4. It filters soot out of the acetylene supply

Explanation

A flashback arrestor contains a flame barrier and a check valve that stop a flame front or reverse gas flow from travelling back down the hose into the cylinder. Without it, a flashback can reach the acetylene cylinder and cause a serious explosion.

Question 20Health, Safety and Workshop Practice

A tight-fitting respirator is being issued for use against wood dust. Why must the wearer have a fit test rather than simply trying the mask on?

  1. It measures the oxygen level inside the mask
  2. It checks that the filter canister is within its expiry date
  3. It checks that the mask seals to the wearer's face without leakage Correct answer.
  4. It confirms the mask is resistant to solvent splashes

Explanation

A tight-fitting respirator depends on a continuous seal between the mask and the wearer's skin. A fit test checks that seal for that individual; a poor seal lets contaminated air leak in even when the correct filter is fitted.

Question 21Engineering Materials and Their Properties

Which mechanical property is defined as a material's resistance to localised plastic deformation, such as indentation or scratching?

  1. Elastic limit
  2. Ductility
  3. Toughness
  4. Hardness Correct answer.

Explanation

Hardness describes how well a surface resists localised plastic deformation, including indentation and scratching. Toughness is the energy absorbed before fracture, while the elastic limit marks the onset of permanent deformation. Ductility measures how much a material can be stretched plastically before it breaks.

Question 22Engineering Materials and Their Properties

Mild steel is a low-carbon steel widely used for structural sections. Its carbon content lies in which approximate range?

  1. 0.05% to 0.25% carbon Correct answer.
  2. 0.60% to 0.90% carbon
  3. 1.00% to 1.50% carbon
  4. 2.00% to 4.00% carbon

Explanation

Mild steel contains roughly 0.05% to 0.25% carbon, which gives it good ductility and weldability at moderate strength. Steels with about 0.6% to 0.9% carbon are high-carbon steels, and cast irons generally exceed 2% carbon.

Question 23Engineering Materials and Their Properties

Which of these polymers is a thermosetting material that cures permanently and cannot be remelted?

  1. Nylon 6,6
  2. Polypropylene
  3. Polyethylene
  4. Epoxy resin Correct answer.

Explanation

Epoxy resin cures by cross-linking its polymer chains into a rigid three-dimensional network, so it cannot be softened and remelted repeatedly. Polyethylene, polypropylene and nylon are thermoplastics, which soften on heating and can be reshaped.

Question 24Engineering Materials and Their Properties

A tensile test uses a specimen with a 50 mm gauge length. Under load, the gauge length increases by 0.25 mm. What is the engineering strain?

  1. 0.0025
  2. 0.05
  3. 0.5
  4. 0.005 Correct answer.

Explanation

Engineering strain is the change in length divided by the original gauge length, so 0.25 mm divided by 50 mm gives 0.005. This is equivalent to 0.5% strain. The result is dimensionless because both lengths are measured in the same units.

Question 25Engineering Materials and Their Properties

A copper alloy fitting contains approximately 65% copper and 35% zinc. This alloy is best classified as:

  1. Bronze
  2. Brass Correct answer.
  3. Duralumin
  4. Soft solder

Explanation

Brass is the copper-zinc alloy family, and a composition near 65% copper with 35% zinc is a common alpha-beta brass. Bronze is primarily a copper-tin alloy, while duralumin is an aluminium-copper alloy and solder is usually a tin-lead or tin-based alloy.

Question 26Engineering Materials and Their Properties

After a plain carbon steel component has been quenched from the austenitising temperature, it is usually tempered. What is the main purpose of tempering?

  1. To produce a fully annealed, coarse-grained structure
  2. To reduce brittleness and relieve internal stresses while retaining useful hardness Correct answer.
  3. To raise the carbon content at the surface
  4. To form martensite and maximise hardness

Explanation

Quenching transforms austenite into hard, brittle martensite and leaves high internal stresses. Tempering reheats the steel to a lower temperature, allowing some carbon to precipitate and relieving stress so that toughness improves while useful hardness is retained.

Question 27Engineering Materials and Their Properties

In a fibre-reinforced composite, which phase carries the majority of the applied tensile load and provides stiffness?

  1. The reinforcing fibres Correct answer.
  2. The coupling agent
  3. The polymer matrix
  4. The colour pigment

Explanation

The reinforcing fibres are usually much stiffer and stronger than the matrix, so they carry most of the tensile load when the composite is stressed along the fibre direction. The matrix binds the fibres together, transfers load between them and protects their surfaces.

Question 28Engineering Materials and Their Properties

A buried steel pipeline is connected to blocks of magnesium to slow corrosion. The magnesium protects the steel because it:

  1. is more reactive than iron and acts as a sacrificial anode Correct answer.
  2. is cathodic to steel and prevents electrons reaching the steel
  3. has a lower melting point than steel and forms a protective oxide
  4. reacts with soil to neutralise acids around the pipe

Explanation

Magnesium is higher than iron in the reactivity series, so it becomes the anode and corrodes preferentially while the steel becomes the cathode. This is cathodic protection by a sacrificial anode. The magnesium blocks are consumed over time and must be replaced.

Question 29Engineering Materials and Their Properties

A low-carbon steel sheet is to be shaped by deep drawing into a car body panel. Which combination of properties is most suitable?

  1. Low yield strength, high ductility and a high strain-hardening exponent Correct answer.
  2. High yield strength, high hardness and low elongation at fracture
  3. High yield strength, high elastic modulus and a low strain-hardening exponent
  4. Low elastic modulus, high hardness and a high proof stress

Explanation

Deep drawing requires the sheet to flow plastically without tearing, so a low yield strength reduces the forming force and high ductility allows large stretching. A high strain-hardening exponent delays localised thinning and necking, which improves drawability. Hard, high-yield-strength sheets are more likely to crack or spring back during forming.

Question 30Engineering Materials and Their Properties

A unidirectional glass-fibre composite contains 60% glass fibres by volume (E = 70 GPa) and 40% epoxy resin (E = 3 GPa). Using the rule of mixtures for loading parallel to the fibres, estimate the longitudinal modulus.

  1. 3 GPa
  2. 43 GPa Correct answer.
  3. 73 GPa
  4. 37 GPa

Explanation

For loading parallel to continuous fibres, the rule of mixtures gives E = VfEf + VmEm. Substituting the values gives 0.60 × 70 GPa + 0.40 × 3 GPa = 42 + 1.2 = 43.2 GPa, which rounds to 43 GPa. The result lies between the fibre and matrix moduli and is dominated by the stiffer fibres.

Question 31Engineering Materials and Their Properties

Pure iron has a body-centred cubic crystal structure at room temperature. When heated above 912 °C it transforms to austenite. Which crystal structure does austenite have?

  1. Hexagonal close-packed
  2. Simple cubic
  3. Face-centred cubic Correct answer.
  4. Body-centred tetragonal

Explanation

Austenite, the high-temperature phase of iron, has a face-centred cubic lattice. This more closely packed structure can dissolve considerably more carbon than body-centred cubic ferrite.

Question 32Engineering Materials and Their Properties

Stainless steel resists corrosion in moist outdoor environments mainly because:

  1. it contains no iron, so the rusting reaction cannot take place
  2. its nickel content makes it cathodic to every other metal present
  3. a thin, self-healing chromium-rich oxide film forms on its surface Correct answer.
  4. its carbon content is deliberately higher than that of mild steel

Explanation

Stainless steels contain at least about 10.5% chromium, which reacts with oxygen to form a very thin, adherent oxide layer. If the layer is scratched it re-forms, protecting the metal beneath.

Question 33Engineering Materials and Their Properties

For a thermoplastic, the glass transition temperature Tg marks the point at which:

  1. the polymer melts to a low-viscosity liquid that can be poured
  2. cross-links form permanently between the polymer chains
  3. the polymer changes from a hard, glassy state to a softer, rubbery state Correct answer.
  4. the polymer begins to decompose and give off smoke

Explanation

Below Tg the amorphous chain segments are frozen and the plastic is glassy and often brittle; above Tg they can move, so the material becomes softer and more rubbery. Melting of crystalline regions occurs at a higher temperature and is a different transition.

Question 34Engineering Materials and Their Properties

A rotating steel shaft has been in service for several years. It breaks suddenly at a stress well below the yield strength of the steel, and the fracture surface shows smooth concentric beach marks. Which failure mechanism is indicated?

  1. Hydrogen embrittlement
  2. Ductile overload failure
  3. Fatigue failure Correct answer.
  4. Creep failure

Explanation

Repeated cyclic loading, even at stresses below yield, can initiate and grow a crack until the remaining section fractures. Beach marks and a smooth crack-growth region are characteristic of fatigue, with a rougher final fast-fracture zone.

Question 35Engineering Materials and Their Properties

A thermostat uses a bimetallic strip made by bonding brass to Invar. When the strip is warmed, it bends because:

  1. the two metals have different electrical resistivities, which produces a bending moment
  2. Invar expands more than brass, so the strip bends towards the brass
  3. both metals expand equally but have different melting points
  4. brass has a higher coefficient of thermal expansion than Invar, so it expands more Correct answer.

Explanation

Brass has a coefficient of linear expansion of roughly 19 × 10⁻⁶ per °C, while Invar is an iron-nickel alloy designed to have a very low coefficient of about 1 × 10⁻⁶ per °C. Because the two are bonded, the brass expands more and the strip curves towards the Invar side.

Question 36Engineering Materials and Their Properties

In a glass-fibre-reinforced polyester composite, what is the main function of the polyester matrix?

  1. To increase the electrical conductivity of the finished laminate
  2. To carry the majority of the tensile load and provide stiffness
  3. To reduce the density of the composite below that of the fibres
  4. To bind the fibres together and transfer stress between them Correct answer.

Explanation

The matrix holds the fibres in position, protects them from damage and the environment, and transfers load to the fibres through shear at the interface. The fibres, not the matrix, provide most of the stiffness and strength along their direction.

Question 37Engineering Materials and Their Properties

Which set of properties is typical of a technical ceramic such as alumina?

  1. Low compressive strength but very high tensile ductility
  2. High hardness, high compressive strength and low toughness Correct answer.
  3. High electrical conductivity and high thermal expansion
  4. High ductility, low hardness and a low melting point

Explanation

Alumina has strong ionic and covalent bonds, giving high hardness, a high melting point and good compressive strength. Its lack of slip systems makes it brittle, so it has low fracture toughness and poor resistance to thermal shock.

Question 38Engineering Materials and Their Properties

A low-carbon steel gear is required to have a hard, wear-resistant surface while its core remains tough. Which treatment is most suitable?

  1. Annealing the whole component
  2. Stress relieving the whole component
  3. Normalising the whole component
  4. Carburising the surface and then hardening it Correct answer.

Explanation

Carburising diffuses carbon into the surface of a low-carbon steel, so that after quenching the surface becomes high-carbon martensite while the core stays low-carbon and tough. Normalising, annealing and stress relieving treat the whole section and do not produce a hard case.

Question 39Engineering Materials and Their Properties

A material has a high yield strength but a low fracture toughness. What does this combination mean in service?

  1. It cannot support a static load without yielding immediately
  2. It has high resistance to indentation and therefore cannot crack
  3. It resists plastic deformation well but a crack can propagate with little energy absorption Correct answer.
  4. It will deform a great deal before breaking, giving plenty of warning

Explanation

Yield strength measures resistance to the onset of plastic deformation, whereas fracture toughness measures resistance to crack growth. A strong but brittle material can fail suddenly once a crack is present, with little plastic deformation or energy absorbed.

Question 40Engineering Materials and Their Properties

Increasing the degree of crystallinity in a thermoplastic generally has which effect on its properties?

  1. It makes the polymer thermosetting and non-recyclable
  2. It lowers stiffness and raises impact toughness
  3. It raises stiffness and strength but lowers optical clarity Correct answer.
  4. It removes the glass transition temperature entirely

Explanation

Crystalline regions pack the polymer chains closely, increasing density, stiffness, strength and resistance to solvents, but they scatter light so the polymer becomes less transparent. They do not cross-link the chains, so the material remains a thermoplastic.

Question 41Engineering Materials and Their Properties

In a solid metal, the high electrical conductivity is best explained by which statement?

  1. Positive metal ions migrate through the solid and carry the current
  2. Valence electrons are delocalised and free to move through the lattice Correct answer.
  3. Electrons are transferred permanently between neighbouring atoms
  4. Shared electron pairs are locked in fixed directions between atoms

Explanation

Metals are held together by metallic bonding, in which the outer (valence) electrons are not localised on individual atoms but form a 'sea' of delocalised electrons around the cations. When a potential difference is applied across the metal, these mobile electrons drift through the lattice and carry the current. The same delocalised electrons also explain why metals are good thermal conductors and why they are opaque and reflective.

Question 42Engineering Materials and Their Properties

A copper rod is cold drawn through a die to produce a wire of smaller diameter. Which change occurs in the copper as a result of this cold working?

  1. Dislocation density decreases, so the wire becomes softer and more ductile
  2. Grains grow larger, so the yield strength rises and toughness falls
  3. The lattice changes from face-centred cubic to body-centred cubic
  4. Dislocation density increases, raising strength and lowering ductility Correct answer.

Explanation

Cold working plastically deforms the grains and multiplies dislocations inside them. These dislocations obstruct one another's movement, so further slip becomes harder: the yield strength and hardness increase while elongation to fracture decreases. The same reason explains why the wire must be annealed between drawing passes to restore ductility.

Question 43Engineering Materials and Their Properties

Unplasticised PVC is rigid enough for soil and drain pipes, whereas cable insulation needs a much more flexible grade of PVC. Which additive is used to make the flexible compound?

  1. A heat stabiliser
  2. A filler such as calcium carbonate
  3. A lubricant
  4. A plasticiser Correct answer.

Explanation

Plasticisers are low-volatility liquids or small molecules that penetrate between the polymer chains and weaken the secondary forces holding them together. This lowers the glass transition temperature and increases free volume, so the chains can slide past one another and the compound behaves flexibly at room temperature. Rigid and flexible PVC grades therefore differ mainly in how much plasticiser is compounded in.

Question 44Engineering Materials and Their Properties

A steel deck structure will be exposed to service temperatures as low as -20 °C. Charpy impact tests on candidate steels show a sharp drop in absorbed energy as temperature falls. Which selection decision is technically sound?

  1. Choose a steel whose impact transition temperature lies below the lowest service temperature Correct answer.
  2. Choose the steel with the highest room-temperature tensile strength, since stronger steels resist brittle fracture better
  3. Choose the hardest steel available, because hardness indicates resistance to sudden loading
  4. Choose a steel with a coarse grain size, since coarse grains absorb more impact energy

Explanation

Body-centred cubic steels show a ductile-to-brittle transition: absorbed impact energy falls steeply as temperature drops, and below the transition temperature fracture occurs by fast cleavage with little plastic deformation. A structure loaded at -20 °C therefore needs a steel whose transition temperature is comfortably below the lowest service temperature, usually achieved with fine grain size, low sulphur and phosphorus, and normalising or quenching and tempering.

Question 45Hand Tools, Portable Power Tools and Measuring Instruments

A carpenter needs to confirm that a corner of a timber frame is exactly 90° before fixing the joint. Which hand tool is designed specifically for checking squareness?

  1. Try square Correct answer.
  2. Sliding bevel
  3. Marking gauge
  4. Mortise gauge

Explanation

A try square has a stock and blade fixed permanently at 90°, so it can be used to test and mark right angles but nothing else. Adjustable tools are set to whatever angle the user chooses and are not dedicated squareness references. Gauges score lines parallel to a prepared face and give no angular information at all.

Question 46Hand Tools, Portable Power Tools and Measuring Instruments

A technician must drill an 8 mm fixing hole into a solid concrete wall using a portable percussion drill. Which drill bit is suitable for this material?

  1. Auger bit
  2. Carbide-tipped masonry bit Correct answer.
  3. Forstner bit
  4. Brad-point wood bit

Explanation

Concrete is abrasive and brittle, so the bit needs a tungsten-carbide tip that survives impact and pulverises the material ahead of the flutes. Brad-point, Forstner and auger bits are wood-cutting designs whose sharp spurs or centre points would be destroyed by masonry. A carbide-tipped bit used in percussion mode is the normal combination.

Question 47Hand Tools, Portable Power Tools and Measuring Instruments

A plumber has to cut thin-walled copper tube to length with a hacksaw. Which blade specification gives the cleanest cut with least risk of torn teeth?

  1. A rip saw blade with 8 TPI
  2. An 18 TPI general-purpose blade
  3. A 32 TPI fine-pitch blade Correct answer.
  4. A 14 TPI coarse-pitch blade

Explanation

Thin tube wall engages only a few teeth at a time, so a coarse blade hooks the wall and strips teeth. A fine 32 TPI blade spreads the cut across many teeth and gives a smooth, controlled finish. Coarse pitches are reserved for thick solid sections and soft materials.

Question 48Hand Tools, Portable Power Tools and Measuring Instruments

A vernier caliper has a main scale in 1 mm divisions and a vernier scale of 50 divisions, giving a least count of 0.02 mm. The vernier zero sits just past the 37 mm mark and the sixth vernier division lines up exactly with a main-scale division. What is the reading?

  1. 37.12 mm Correct answer.
  2. 37.06 mm
  3. 37.30 mm
  4. 37.60 mm

Explanation

The reading equals the main-scale value plus the number of the aligned vernier division multiplied by the least count. Here that is 37 mm + (6 × 0.02 mm) = 37.12 mm. Miscounting the aligned line or misreading the scale interval produces the other figures.

Question 49Hand Tools, Portable Power Tools and Measuring Instruments

A metric micrometer has a 0.5 mm spindle pitch and a thimble with 50 divisions. The barrel exposes the 5.5 mm graduation and the thimble reads 28 divisions. What is the measured size?

  1. 5.56 mm
  2. 5.28 mm
  3. 6.00 mm
  4. 5.78 mm Correct answer.

Explanation

The barrel records whole and half millimetres, so 5.5 mm is already visible. Because 50 thimble divisions cover the 0.5 mm pitch, each division adds 0.01 mm, so 28 divisions add 0.28 mm. The total is therefore 5.78 mm.

Question 50Hand Tools, Portable Power Tools and Measuring Instruments

Before using a portable angle grinder to cut a steel bar, which precaution most reduces the risk of injury from a bursting disc?

  1. Soak the cutting disc in water before use so that it does not overheat.
  2. Remove the wheel guard so that the full disc is visible for better control of the cut.
  3. Wear loose-fitting gloves so that the wheel can be gripped if it kicks back.
  4. Check the disc speed rating against the no-load speed and keep the guard fitted. Correct answer.

Explanation

A bonded abrasive disc can shatter if it runs faster than its rated speed, so its maximum permissible speed must equal or exceed the grinder's no-load speed. The guard must remain fitted and be positioned to intercept fragments. Loose clothing and gloves near a spinning wheel create entanglement hazards rather than protection.