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ITI Technician Mechatronics (AITT Theory) study materials
ITI Technician Mechatronics (AITT Theory) study resources

ITI Technician Mechatronics (AITT Theory) practice questions

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Question 1Trade Safety, Occupational Health and Environmental Practices

Before starting maintenance on a mechatronic assembly line, which practice best implements lockout/tagout (LOTO) for stored mechanical energy?

  1. Applying a personal lock and tag to the energy-isolating device and releasing residual pressure or spring tension before work Correct answer.
  2. Telling the operator to hold the emergency stop button pressed while you work inside the guard
  3. Attaching a warning tag to the control panel pushbutton without isolating the supply
  4. Asking the shift supervisor to switch off the main breaker at the panel and to keep watch

Explanation

LOTO requires isolating every energy source, applying a personal lock and tag, and then dissipating stored energy such as pneumatic pressure, hydraulic pressure, or compressed springs. Only the person who applied the lock removes it, which prevents unexpected re-energisation while hands are inside the machine.

Question 2Trade Safety, Occupational Health and Environmental Practices

In a pneumatic mechatronics trainer, what is the correct first action when a compressed-air hose develops a visible bulge near the coupling?

  1. Continue working and report the bulge at the end of the practical session
  2. Increase the regulator setting so the bulge expands evenly and the hose settles
  3. Wrap the bulge with self-adhesive tape and continue the exercise at reduced pressure
  4. Isolate the air supply, vent the line to zero pressure, and replace the hose before reuse Correct answer.

Explanation

A bulging hose has a weakened wall and can burst under pressure, releasing a high-velocity air jet or whipping the coupling. The safe response is to isolate and depressurise the circuit, then replace the damaged hose rather than repair it.

Question 3Trade Safety, Occupational Health and Environmental Practices

Which PPE item is essential when using an angle grinder to dress a welded frame in the fitting shop?

  1. Close-fitting impact-rated eye protection with a face shield Correct answer.
  2. Anti-static wrist strap
  3. Disposable dust mask only
  4. Cotton laboratory coat with open cuffs

Explanation

Grinding throws high-speed abrasive particles and fragments, so impact-rated eye protection combined with a face shield protects the eyes and face. A laboratory coat, a dust mask alone, or an anti-static strap does not resist abrasive projectiles.

Question 4Trade Safety, Occupational Health and Environmental Practices

A technician must drill a wall that may contain concealed electrical conduit. Which control best reduces the risk of electric shock before drilling begins?

  1. Use a cable detector to scan the wall and isolate the relevant circuit before drilling Correct answer.
  2. Wear rubber-soled shoes and proceed without further checks
  3. Drill slowly with a hammer-action bit so contact with the conduit is gentle
  4. Ask a colleague to stand by the distribution board ready to switch off

Explanation

Scanning with a suitable cable detector locates concealed services, and isolating the circuit removes the shock and arc risk if the drill still contacts conduit. Drilling technique and standby personnel do not prevent contact with a live conductor.

Question 5Trade Safety, Occupational Health and Environmental Practices

Under the hierarchy of controls used in occupational health and safety, which measure ranks highest for eliminating a hazard?

  1. Provision of personal protective equipment
  2. Elimination of the hazard at source Correct answer.
  3. Warning signage at the workstation
  4. Administrative control such as job rotation

Explanation

The hierarchy of controls places elimination first because removing the hazard at source protects everyone without relying on human behaviour. Administrative controls, signage, and PPE rank lower because they depend on compliance and only reduce exposure.

Question 6Trade Safety, Occupational Health and Environmental Practices

A technician is about to weld a bracket on a mechatronic frame in a bay containing flammable solvent drums. Which precaution is most appropriate?

  1. Weld only at low current so that fewer sparks are produced
  2. Open the bay doors and weld with a fire extinguisher placed nearby
  3. Wet the floor around the drums and proceed with welding
  4. Move the solvent to a designated flammable store and use fire-resistant blankets to contain sparks before welding Correct answer.

Explanation

Hot-work permits require flammable materials to be removed from the area, and fire-resistant blankets contain sparks and slag that could ignite residues. Keeping a extinguisher nearby is a secondary measure, not a substitute for removing the fuel.

Question 7Trade Safety, Occupational Health and Environmental Practices

Which action correctly follows the emergency procedure when a colleague receives an electric shock while still in contact with a live conductor?

  1. Pull the casualty away immediately by the arm
  2. Throw water on the casualty to break the contact
  3. Start chest compressions while the casualty is still in contact with the conductor
  4. Isolate the supply at the distribution board before touching the casualty Correct answer.

Explanation

Touching a casualty still in contact with a live conductor can pass the current through the rescuer. The supply must be isolated first, or the casualty moved using an insulated object if isolation is impossible.

Question 8Trade Safety, Occupational Health and Environmental Practices

In a workshop, a small hydraulic leak sprays fluid onto a hot manifold and produces a fine mist. Why is this condition treated as a serious fire hazard?

  1. Hydraulic fluid evaporates completely before it can ignite
  2. Atomised hydraulic fluid can ignite on a hot surface and produce a sustained spray fire Correct answer.
  3. The mist cools the manifold and prevents ignition
  4. Hydraulic fluid is non-flammable and the mist only creates a slipping risk

Explanation

Hydraulic oil under pressure forms a fine mist when it leaks, and the mist ignites readily on hot surfaces, creating a jet or spray fire that is difficult to extinguish. Isolation and repair of the leak are required before continuing.

Question 9Trade Safety, Occupational Health and Environmental Practices

A technician must dispose of a used lithium-ion battery pack removed from a robot. Which disposal route is correct?

  1. Place it in a designated battery collection container for recycling Correct answer.
  2. Store it in a metal drawer with other scrap components
  3. Put it in the general workshop waste bin
  4. Cut the terminals off and discard the cells with electronic waste

Explanation

Lithium-ion packs are hazardous waste that must go to a designated collection point for recycling because damaged cells can short-circuit and ignite. General waste and mixed scrap storage create fire and environmental risks.

Question 10Trade Safety, Occupational Health and Environmental Practices

When should a workshop's emergency stop circuit be tested as part of routine mechatronics maintenance?

  1. Only when the machine is first installed
  2. Only after an accident has occurred
  3. At planned intervals recorded in the maintenance schedule, with the result documented Correct answer.
  4. Whenever an operator reports that a button feels loose

Explanation

Emergency stop circuits are safety-related functions, so their operation must be verified at defined intervals and the result recorded to demonstrate the control remains effective. Reactive testing after accidents or complaints leaves undetected failures.

Question 11Trade Safety, Occupational Health and Environmental Practices

Which practice correctly manages the risk of musculoskeletal injury when lifting a 20 kg servo motor from a pallet?

  1. Twist the torso while lifting to place the motor on the bench
  2. Bend at the waist and lift quickly to reduce the time under load
  3. Hold the motor at arm's length to keep it clear of the legs
  4. Use a mechanical hoist or two-person lift and keep the load close to the body Correct answer.

Explanation

Heavy or awkward loads should be handled with mechanical aids or a team lift, keeping the load close to the body to reduce spinal loading. Bending, twisting, and reaching increase the strain on the lower back.

Question 12Trade Safety, Occupational Health and Environmental Practices

A workshop uses a solvent degreaser in an open tray. Which combination of controls best limits inhalation exposure?

  1. Rely on general room ventilation and short exposure times
  2. Issue respirators to all staff and keep the tray uncovered
  3. Substitute with a less hazardous cleaner and use local exhaust ventilation at the tray Correct answer.
  4. Increase the room temperature so vapours disperse faster

Explanation

Substitution removes the hazard where possible, and local exhaust ventilation captures vapour at the source before it reaches the breathing zone. General ventilation and respirators are lower-order controls that depend on conditions and correct use.

Question 13Trade Safety, Occupational Health and Environmental Practices

During a risk assessment of a robotic cell, a technician identifies a task that requires reaching into the cell while the robot is powered. Which control best follows the hierarchy of controls?

  1. Redesign the fixture so the task can be done outside the robot's reach Correct answer.
  2. Add a warning sign at the cell entrance
  3. Require the technician to wear a high-visibility vest
  4. Shorten the task time to reduce exposure

Explanation

Redesigning the fixture eliminates the need to enter the hazard zone and is an engineering control high in the hierarchy. Signage, vests, and time reduction are administrative or PPE measures that leave the hazard in place.

Question 14Trade Safety, Occupational Health and Environmental Practices

A technician finds that a machine guard interlock has been bypassed with a jumper wire so production can continue. What is the correct response?

  1. Stop the machine, remove the bypass, and report the defect so the interlock is restored and verified Correct answer.
  2. Ask the operator to be extra careful while the bypass remains
  3. Leave the bypass in place but add a warning label near the interlock
  4. Continue production and record the bypass in the shift log

Explanation

A bypassed interlock defeats a safety function and allows access to dangerous parts, so the machine must be stopped and the defect corrected and verified before production resumes. Recording or labelling the bypass does not restore the protective function.

Question 15Trade Safety, Occupational Health and Environmental Practices

Two technicians disagree about whether a confined space beneath a conveyor pit requires a permit before entry. Which reasoning correctly applies confined-space principles?

  1. A permit is required only if the technician smells solvent vapour before entering
  2. A permit is unnecessary if the entry lasts less than ten minutes
  3. A permit is required because the pit is enclosed, has restricted entry, and may accumulate gas or reduce oxygen Correct answer.
  4. A permit is unnecessary because the pit is indoors and connected to the workshop floor

Explanation

A confined space is defined by enclosed construction, restricted entry or exit, and the potential for hazardous atmosphere or engulfment, which fits a conveyor pit. A permit with atmospheric testing and rescue arrangements is required before entry regardless of duration.

Question 16Trade Safety, Occupational Health and Environmental Practices

An investigation finds that a near miss occurred when a pallet fell from a stack beside a walkway. Which finding best reflects a systemic safety approach rather than blaming an individual?

  1. The nearest operator should be disciplined for not noticing the unstable stack
  2. The stacking height standard and walkway segregation were inadequate, so both are revised and communicated Correct answer.
  3. The walkway should be closed permanently to avoid any future incident
  4. The pallet supplier should be changed without reviewing storage practice

Explanation

A systemic approach examines the conditions that allowed the near miss, such as storage standards and separation of pedestrians from loads, and corrects them. Blaming individuals or applying a single narrow fix leaves the underlying causes in place.

Question 17Engineering Drawing, Fits, Tolerances and Metrology

In the ISO system of limits and fits, a hole is designated H7. What does the capital letter H specify about this hole?

  1. The tolerance grade, which fixes the total width of the tolerance zone
  2. The fundamental deviation of the hole, with its lower limit on the basic size Correct answer.
  3. The surface roughness value to be achieved by the boring operation
  4. The type of fit obtained when assembled with an h-shaft

Explanation

In ISO 286, the capital letter gives the fundamental deviation of a hole and the number gives the tolerance grade. For a hole designated H, the fundamental deviation is zero, so the lower limit coincides with the basic size and the tolerance zone lies wholly above it. The number 7 alone fixes the width of the zone, not the letter.

Question 18Engineering Drawing, Fits, Tolerances and Metrology

A drawing shows a dimension as 40 ±0.05. Which statement correctly describes the permitted size range?

  1. The part must measure exactly 40.00 in every case
  2. The part may measure from 40.05 to 40.10
  3. The tolerance is 0.10 on each side of 40.00
  4. The part may measure anywhere from 39.95 to 40.05 Correct answer.

Explanation

The ± symbol means the tolerance is applied in both directions from the nominal size. Adding and subtracting 0.05 from 40 gives an upper limit of 40.05 and a lower limit of 39.95, a total tolerance of 0.10. Any size within this range is acceptable.

Question 19Engineering Drawing, Fits, Tolerances and Metrology

On an engineering drawing, which symbol denotes a diameter dimension?

  1. Ø Correct answer.
  2. □
  3. R
  4. ⌓

Explanation

The symbol Ø placed before a numerical value indicates a diameter, meaning the dimension applies across the full circular feature through its centre. R denotes a radius, □ denotes a square section, and the arc symbol denotes a radius dimensioned from a centre that is not the true centre of the arc.

Question 20Engineering Drawing, Fits, Tolerances and Metrology

A vernier calliper has a main scale with 1 mm divisions and a vernier scale of 50 divisions spanning 49 mm. What is the least count of the instrument?

  1. 0.05 mm
  2. 0.10 mm
  3. 0.01 mm
  4. 0.02 mm Correct answer.

Explanation

The least count equals the main scale division divided by the number of vernier divisions. Here one main division of 1 mm divided by 50 vernier divisions gives 0.02 mm. The vernier's 49 mm span confirms that each vernier division is 0.98 mm, a difference of 0.02 mm from a main division.

Question 21Engineering Drawing, Fits, Tolerances and Metrology

A shaft and hole form a clearance fit. Which relationship between their limits must hold?

  1. The minimum shaft size is larger than the maximum hole size
  2. The tolerance zones of shaft and hole overlap by half their width
  3. The maximum shaft size equals the minimum hole size
  4. The maximum shaft size is smaller than the minimum hole size Correct answer.

Explanation

A clearance fit guarantees that the shaft always enters the hole with play. This requires the largest permitted shaft to be smaller than the smallest permitted hole, so even the worst-case assembly has positive clearance. Any overlap of the zones would allow interference.

Question 22Engineering Drawing, Fits, Tolerances and Metrology

A drawing specifies a geometric tolerance of position for a hole with a maximum material condition modifier. What does the modifier permit?

  1. A reduction in the tolerance as the hole grows larger
  2. A bonus tolerance equal to the departure of the hole from its maximum material size Correct answer.
  3. A relaxation of the tolerance only when the hole is at its smallest permitted size
  4. An increase in the basic size of the hole to ease assembly

Explanation

The maximum material condition modifier allows the geometric tolerance to grow as the feature departs from its maximum material size toward least material size. For a hole, maximum material size is the smallest permitted diameter, so boring the hole larger releases extra positional tolerance equal to that departure. This is called bonus tolerance.

Question 23Engineering Drawing, Fits, Tolerances and Metrology

A surface is specified with a roughness value Ra of 1.6 µm. What does Ra represent?

  1. The maximum peak-to-valley height within a single sampling length
  2. The arithmetic mean deviation of the assessed profile from its mean line Correct answer.
  3. The ten-point height of irregularities averaged over five lengths
  4. The total waviness of the surface over the whole component

Explanation

Ra is the arithmetical mean deviation of the roughness profile from its mean line over the sampling length. It is the most commonly specified roughness parameter because it averages the profile and is relatively stable. Peak-to-valley and ten-point height are different parameters (Rz), and waviness is a longer-wavelength characteristic.

Question 24Engineering Drawing, Fits, Tolerances and Metrology

A rectangular component is drawn to a scale of 1:5 and measures 36 mm on the drawing. What is its actual length?

  1. 7.2 mm
  2. 180 mm Correct answer.
  3. 72 mm
  4. 41 mm

Explanation

A scale of 1:5 means one unit on the drawing represents five units on the object. Multiplying the drawn length of 36 mm by the scale factor 5 gives an actual length of 180 mm. Dividing instead of multiplying is the common error.

Question 25Engineering Drawing, Fits, Tolerances and Metrology

In first-angle projection, where is the view from the left of the object placed on the drawing sheet?

  1. On the right side of the front view Correct answer.
  2. Below the front view
  3. On the left side of the front view
  4. Above the front view

Explanation

First-angle projection places each view on the far side of the object from the observer, as if the object were pushed onto the plane behind it. The left-hand view therefore appears on the right of the front view. Third-angle projection places it on the left instead.

Question 26Engineering Drawing, Fits, Tolerances and Metrology

A hole is dimensioned 25.000/25.021 mm and its mating shaft 24.980/24.993 mm. Which type of fit results?

  1. Interference fit with maximum interference 0.041 mm
  2. Clearance fit with minimum clearance 0.020 mm
  3. Clearance fit with minimum clearance 0.007 mm Correct answer.
  4. Transition fit with possible clearance or interference

Explanation

The smallest hole is 25.000 mm and the largest shaft is 24.993 mm, so even the tightest assembly leaves 0.007 mm of clearance. Since the shaft is always smaller than the hole, the fit is clearance throughout. The maximum clearance is 25.021 minus 24.980, equal to 0.041 mm.

Question 27Engineering Drawing, Fits, Tolerances and Metrology

Which instrument is most appropriate for measuring the depth of a blind bore to an accuracy of 0.02 mm?

  1. A depth micrometer Correct answer.
  2. An outside micrometer
  3. A steel rule
  4. A dial test indicator

Explanation

A depth micrometer uses a calibrated spindle with a hardened base and reads directly to 0.01 mm, so it suits a 0.02 mm bore depth requirement. A steel rule is far too coarse, an outside micrometer measures external sizes, and a dial test indicator is used for comparative measurement of runout or alignment.

Question 28Engineering Drawing, Fits, Tolerances and Metrology

What is the primary purpose of a limit gauge such as a go/no-go plug gauge?

  1. To measure the exact diameter of the hole to 0.001 mm
  2. To check the surface roughness of the bore
  3. To verify quickly whether a hole lies within its specified limits Correct answer.
  4. To determine the roundness error of the hole

Explanation

A go/no-go plug gauge has two members: the go end must enter the hole and the no-go end must not. This confirms that the feature lies within its limits without giving a numerical size, which makes it fast for production inspection. It does not measure exact size, roughness, or form.

Question 29Engineering Drawing, Fits, Tolerances and Metrology

A drawing carries the datum symbol for surface A and a perpendicularity tolerance of 0.05 mm referencing that datum on a face. What is being controlled?

  1. The surface roughness of the face must not exceed 0.05 mm
  2. The face must be flat within 0.05 mm regardless of datum A
  3. The distance between the face and datum A must be 0.05 mm
  4. The face must lie between two parallel planes 0.05 mm apart that are perpendicular to datum A Correct answer.

Explanation

A perpendicularity tolerance controls orientation relative to a datum. The tolerance zone is two parallel planes, separated by the stated 0.05 mm, oriented exactly perpendicular to datum A, and the toleranced face must lie within them. It does not control flatness alone, a linear distance, or roughness.

Question 30Engineering Drawing, Fits, Tolerances and Metrology

When reading a metric outside micrometer, the thimble shows 37 divisions beyond the last main scale mark of 8 mm. If the thimble has 50 divisions and the pitch is 0.5 mm, what is the reading?

  1. 8.740 mm
  2. 8.370 mm Correct answer.
  3. 8.037 mm
  4. 8.185 mm

Explanation

Each thimble division represents the pitch divided by the number of thimble divisions, here 0.5 mm divided by 50, which is 0.01 mm. Thirty-seven divisions therefore add 0.37 mm to the 8 mm main scale reading. The total is 8.370 mm.

Question 31Engineering Drawing, Fits, Tolerances and Metrology

A hole and shaft are specified as 30 H7/g6. What does this designation tell the technician?

  1. A clearance fit with the hole zone below the basic size
  2. An interference fit with a basic shaft and a hole above the basic size
  3. A clearance fit with a basic hole and a shaft whose tolerance zone lies below the basic size Correct answer.
  4. A transition fit where hole and shaft zones overlap

Explanation

In the ISO system, H is a basic hole whose lower limit equals the basic size, and g is a shaft whose upper limit lies below the basic size. Combining H with g therefore always produces clearance. The numbers 7 and 6 give the respective tolerance grades.

Question 32Engineering Drawing, Fits, Tolerances and Metrology

A straightness tolerance is applied to the axis of a cylindrical shaft. What does the tolerance zone represent?

  1. A cylinder within which the derived median line of the shaft must lie Correct answer.
  2. Two concentric circles on the end faces
  3. Two parallel planes within which the surface elements must lie
  4. A sphere enclosing the whole shaft

Explanation

When straightness is applied to a size dimension of a cylindrical feature, the tolerance zone is a cylinder of the stated diameter. The derived median line of the actual shaft must lie within this cylinder along its full length. Two parallel planes would apply to a surface line element, not to an axis.

Question 33Engineering Drawing, Fits, Tolerances and Metrology

Which statement correctly describes the difference between accuracy and precision of a measuring instrument?

  1. Accuracy and precision both refer only to the resolution of the display
  2. Precision is closeness to the true value, while accuracy is repeatability of readings
  3. Accuracy is closeness to the true value, while precision is the closeness of repeated readings to one another Correct answer.
  4. Accuracy is the smallest scale division, while precision is the calibration certificate value

Explanation

Accuracy describes how close a measurement is to the true value, whereas precision describes how closely repeated measurements agree with each other. An instrument can be precise but inaccurate if it has a systematic bias. Resolution is a separate concept describing the smallest readable increment.

Question 34Engineering Drawing, Fits, Tolerances and Metrology

A component is to be checked for circularity. Which measurement approach directly assesses this form error?

  1. Checking the length of the part with a vernier height gauge
  2. Assessing the surface with a roughness comparator plate
  3. Measuring the diameter at two positions with a micrometer
  4. Comparing radial variation of the profile about a fixed axis using a rotating precision spindle Correct answer.

Explanation

Circularity is a form tolerance describing how close a cross-section is to a true circle, independent of the centre position. It is assessed by rotating the part on a precision spindle and recording radial variation about that axis. Two-point diameter checks can miss lobing and do not measure form directly.

Question 35Engineering Drawing, Fits, Tolerances and Metrology

A drawing uses a section view with hatching. What does the spacing and direction of the hatch lines conventionally indicate?

  1. The surface finish required on the cut face
  2. The tolerance grade of the sectioned feature
  3. The cut material of a single part, with adjacent parts hatched at different angles Correct answer.
  4. The direction of assembly of the component

Explanation

Hatching marks the solid material intersected by the cutting plane. Adjacent parts in an assembly are hatched at different angles or spacings so their boundaries remain distinguishable. Hatching carries no information about finish, assembly direction, or tolerance.

Question 36Engineering Drawing, Fits, Tolerances and Metrology

A shaft measures 24.97 mm against a specified limit of 25.00 mm minimum. Which conclusion is correct?

  1. The shaft is undersized and falls outside the lower limit, so it is rejected Correct answer.
  2. The shaft is acceptable because it is within 0.05 mm of nominal
  3. The shaft is acceptable if the surface finish is good
  4. The shaft is oversized and must be reworked

Explanation

The specified minimum size is 25.00 mm, and the measured 24.97 mm lies below it, so the part violates the lower limit and must be rejected or dispositioned. Being within an arbitrary distance of nominal is not a valid acceptance rule. Surface finish cannot compensate for a size outside its limits.

Question 37Basic Electrical and Electronic Fundamentals

In a mechatronics control panel, a resistor is marked with the colour bands brown, black, red and gold. What is its nominal resistance and tolerance?

  1. 100 Ω ±5%
  2. 1 kΩ ±5% Correct answer.
  3. 1 kΩ ±10%
  4. 10 kΩ ±5%

Explanation

The four-band code reads digit, digit, multiplier, tolerance: brown = 1, black = 0, red = ×100, giving 10 × 100 = 1000 Ω, and gold = ±5%. A 1 kΩ resistor with a gold band is therefore the correct reading of this marking.

Question 38Basic Electrical and Electronic Fundamentals

A coil draws 0.5 A when connected across a 24 V DC supply. What is the resistance of the coil?

  1. 0.02 Ω
  2. 48 Ω Correct answer.
  3. 12 Ω
  4. 24 Ω

Explanation

Ohm's law states R = U / I, so 24 V divided by 0.5 A gives 48 Ω. The result is confirmed by U = I × R = 0.5 × 48 = 24 V.

Question 39Basic Electrical and Electronic Fundamentals

Which statement correctly describes the behaviour of a capacitor in a DC circuit?

  1. It converts direct current into alternating current.
  2. It stores energy in a magnetic field around its plates.
  3. It passes steady direct current with a fixed voltage drop.
  4. It blocks steady direct current once it is fully charged. Correct answer.

Explanation

A capacitor stores energy in an electric field between its plates and, once charged to the supply voltage, no further conventional current flows through the dielectric. It therefore blocks steady DC while allowing changing voltages and AC to pass.

Question 40Basic Electrical and Electronic Fundamentals

A diode is connected in series with a lamp and a DC supply in the forward-biased direction. What happens when the supply polarity is reversed?

  1. The lamp stays the same because a diode conducts in both directions.
  2. The lamp glows brighter because the diode conducts better.
  3. The lamp goes out because the diode blocks the reverse current. Correct answer.
  4. The lamp flickers because the diode oscillates.

Explanation

A silicon diode conducts only when its anode is positive with respect to its cathode. With reversed polarity the diode is reverse-biased and blocks current, so the lamp extinguishes.

Question 41Basic Electrical and Electronic Fundamentals

Which instrument connection is correct for measuring the current through a motor and the voltage across it?

  1. Both instruments connected in parallel with the motor
  2. Ammeter in series with the motor, voltmeter in parallel with it Correct answer.
  3. Both instruments connected in series with the motor
  4. Ammeter in parallel with the motor, voltmeter in series with it

Explanation

An ammeter must carry the current being measured, so it is connected in series, and it has a very low internal resistance. A voltmeter is connected in parallel across the component so that it senses the voltage while drawing almost no current.

Question 42Basic Electrical and Electronic Fundamentals

Which material is the most suitable conductor for the current-carrying cores of a flexible machine-tool cable?

  1. Silicon carbide
  2. Annealed copper Correct answer.
  3. Bakelite
  4. Hard-drawn steel

Explanation

Annealed copper combines very low resistivity with the ductility needed for repeated flexing, which is why it is used for flexible cable cores. Steel has much higher resistivity, and the other two materials are not electrical conductors of practical use for this purpose.

Question 43Basic Electrical and Electronic Fundamentals

Two resistors of 120 Ω and 60 Ω are connected in parallel. What is the equivalent resistance of the combination?

  1. 20 Ω
  2. 180 Ω
  3. 40 Ω Correct answer.
  4. 90 Ω

Explanation

For two resistors in parallel, R = (R1 × R2)/(R1 + R2) = (120 × 60)/(180) = 40 Ω. The result is also sensible because the equivalent of parallel resistors is always smaller than the smallest branch value.

Question 44Basic Electrical and Electronic Fundamentals

A 12 V battery supplies a circuit whose total resistance is 4 Ω. What power is dissipated in the circuit?

  1. 3 W
  2. 0.33 W
  3. 48 W
  4. 36 W Correct answer.

Explanation

Power can be found from P = U² / R = 12² / 4 = 144 / 4 = 36 W. The same value follows from I = 3 A and P = U × I = 12 × 3 = 36 W.

Question 45Basic Electrical and Electronic Fundamentals

An alternating supply has a peak voltage of 325 V. What is its RMS value?

  1. 230 V Correct answer.
  2. 325 V
  3. 163 V
  4. 460 V

Explanation

For a sine wave, U(rms) = U(peak)/√2 = 325/1.414 ≈ 230 V. The RMS value is the equivalent steady DC value that produces the same heating effect.

Question 46Basic Electrical and Electronic Fundamentals

In a purely inductive AC circuit, how does the current behave relative to the applied voltage?

  1. Current lags voltage by 90°. Correct answer.
  2. Current and voltage are exactly in phase.
  3. Current leads voltage by 90°.
  4. Current lags voltage by 45°.

Explanation

An inductor opposes changes in current, so in a purely inductive circuit the current reaches its peak a quarter cycle after the voltage. The phase angle is therefore 90° with current lagging voltage.

Question 47Basic Electrical and Electronic Fundamentals

A transformer has 400 turns on the primary and 100 turns on the secondary. If the primary is connected to 230 V AC, what is the secondary voltage?

  1. 57.5 kV
  2. 57.5 V Correct answer.
  3. 920 V
  4. 230 V

Explanation

The turns ratio equals the voltage ratio: U2 = U1 × (N2/N1) = 230 × (100/400) = 57.5 V. The step-down transformer reduces voltage in proportion to the turns.

Question 48Basic Electrical and Electronic Fundamentals

What is the primary function of a bridge rectifier in a DC power supply for a control circuit?

  1. To step down the mains voltage to a safe level
  2. To regulate the output voltage against load changes
  3. To smooth the ripple voltage to a steady level
  4. To convert alternating current into pulsating direct current Correct answer.

Explanation

A bridge rectifier uses four diodes to make the output unidirectional, converting AC into pulsating DC. Smoothing and regulation are performed by the filter capacitor and regulator stages that follow it.

Question 49Basic Electrical and Electronic Fundamentals

In a forward-biased silicon diode, what is the typical voltage drop across the junction?

  1. 0.3 V
  2. 5.0 V
  3. 0.7 V Correct answer.
  4. 1.4 V

Explanation

A conducting silicon pn junction has a barrier potential of about 0.7 V, which must be exceeded before significant forward current flows. Germanium diodes are lower at roughly 0.3 V, while 1.4 V is typical of two junctions in series.

Question 50Basic Electrical and Electronic Fundamentals

A transistor is used as a switch to energise a relay coil. Which condition places the transistor firmly in saturation?

  1. Base current is reduced to zero
  2. Base current is large enough to drive the collector current to its maximum Correct answer.
  3. Collector-emitter voltage is held at half the supply
  4. Base-emitter junction is reverse-biased

Explanation

In saturation the base is driven hard enough that the collector current is limited by the external load rather than the transistor, and the collector-emitter voltage falls to a small value. This minimises dissipation in the switching transistor.