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Maharashtra SSC Multi-Skill Assistant Technician Pre-Voc/NSQF study materials
Maharashtra SSC Multi-Skill Assistant Technician Pre-Voc/NSQF study resources

Maharashtra SSC Multi-Skill Assistant Technician Pre-Voc/NSQF practice questions

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Question 1Trade Theory - Mechanical and Electrical Fundamentals

A vernier caliper has a main scale with 1 mm divisions. Its vernier scale has 50 divisions that coincide with 49 main scale divisions. What is the least count of this caliper?

  1. 0.5 mm
  2. 0.02 mm Correct answer.
  3. 0.05 mm
  4. 0.1 mm

Explanation

Least count = 1 main scale division - 1 vernier scale division = 1 mm - (49/50) mm = 0.02 mm. With 50 vernier divisions spanning 49 mm, each vernier division is 0.98 mm, so the difference is 0.02 mm. This is the smallest reading the caliper can resolve.

Question 2Trade Theory - Mechanical and Electrical Fundamentals

A 12 V DC supply is connected across a 4 Ω resistor. What current flows through the resistor?

  1. 0.33 A
  2. 48 A
  3. 16 A
  4. 3 A Correct answer.

Explanation

Ohm's law gives I = V/R. Substituting V = 12 V and R = 4 Ω gives I = 12/4 = 3 A. The resistor therefore draws 3 A from the supply.

Question 3Trade Theory - Mechanical and Electrical Fundamentals

What is the main purpose of a fuse in an electrical circuit?

  1. To open the circuit when current is excessive Correct answer.
  2. To store electrical energy for use during a power failure
  3. To raise the supply voltage to the required level
  4. To convert alternating current into direct current

Explanation

A fuse is a sacrificial protective device: its element carries normal current but melts when the current exceeds its rating, opening the circuit. This prevents overheating of cables and damage to equipment downstream. It does not change voltage, rectify current or store energy.

Question 4Trade Theory - Mechanical and Electrical Fundamentals

The spindle of a micrometer moves 0.5 mm in one full turn of the thimble, and the thimble has 50 equal divisions. What is its least count?

  1. 0.01 mm Correct answer.
  2. 0.05 mm
  3. 0.02 mm
  4. 0.5 mm

Explanation

Least count = pitch ÷ number of thimble divisions = 0.5 mm ÷ 50 = 0.01 mm. One thimble division therefore represents 0.01 mm of spindle movement. This is the standard least count of a metric micrometer with 0.5 mm pitch.

Question 5Trade Theory - Mechanical and Electrical Fundamentals

A metric coarse thread M10 × 1.5 is to be tapped in a mild steel plate. Which drill size should be used for the tapping hole?

  1. 10.0 mm
  2. 11.5 mm
  3. 8.5 mm Correct answer.
  4. 6.5 mm

Explanation

For a metric thread, the tapping drill diameter is approximately the major diameter minus the pitch: 10 mm - 1.5 mm = 8.5 mm. This leaves a suitable thread depth for a strong thread without overloading the tap. A 10 mm hole would leave no thread at all.

Question 6Trade Theory - Mechanical and Electrical Fundamentals

How is the direction of rotation of a three-phase induction motor reversed?

  1. By interchanging any two supply phases Correct answer.
  2. By reducing the supply voltage
  3. By connecting a capacitor in series with one phase
  4. By increasing the number of stator poles

Explanation

The rotating magnetic field of a three-phase motor depends on the phase sequence of the supply. Swapping any two of the three phase connections reverses that sequence and therefore reverses the rotor direction. Voltage reduction and pole changing alter torque or speed but do not reverse rotation.

Question 7Trade Theory - Mechanical and Electrical Fundamentals

What is the main function of a thrust bearing in a machine assembly?

  1. To carry axial loads along the shaft Correct answer.
  2. To measure the end play of the shaft
  3. To increase the speed of the rotating shaft
  4. To support the shaft against loads acting at right angles to its axis

Explanation

A thrust bearing is designed to resist force acting parallel to the shaft axis, such as the weight of a vertical shaft or the axial thrust from a cutting operation. Loads acting at right angles to the axis are carried by journal or radial bearings. Bearings do not increase shaft speed or measure end play.

Question 8Trade Theory - Mechanical and Electrical Fundamentals

Before measuring the resistance of a component with a digital multimeter, the technician should:

  1. set the meter to the DC volts range and keep the circuit energized
  2. connect the meter in series with the supply
  3. short the test leads across the supply terminals
  4. isolate the component and make sure it is not energized Correct answer.

Explanation

Resistance must be measured with the component disconnected and the circuit dead, because any voltage present would drive current through the meter and corrupt the reading or damage it. The ohmmeter supplies its own small test current and is connected across the component, not in series with the supply.

Question 9Trade Theory - Mechanical and Electrical Fundamentals

A 10 mm diameter drill is to be used with a cutting speed of 30 m/min. Using N = 1000V/(πD), what spindle speed is required?

  1. 300 rpm
  2. 95 rpm
  3. 3000 rpm
  4. 955 rpm Correct answer.

Explanation

N = 1000V/(πD) = (1000 × 30)/(3.14 × 10) ≈ 955 rpm. The factor 1000 converts metres per minute into millimetres per minute so that the diameter in millimetres is consistent. The nearest practical machine speed is therefore about 955 rpm.

Question 10Trade Theory - Mechanical and Electrical Fundamentals

A transformer has 200 turns on its primary and 1000 turns on its secondary. If the primary is connected to a 230 V AC supply, what is the secondary voltage of the ideal transformer?

  1. 1150 V Correct answer.
  2. 230 V
  3. 46 V
  4. 2300 V

Explanation

For an ideal transformer, Vs/Vp = Ns/Np, so Vs = 230 × (1000/200) = 230 × 5 = 1150 V. The secondary has five times as many turns as the primary, so it is a step-up transformer with five times the voltage. Because an ideal transformer transfers the same power, the secondary current is correspondingly lower.

Question 11Trade Theory - Mechanical and Electrical Fundamentals

In the hole-basis system of limits and fits, the fundamental deviation of an H hole is such that the hole's

  1. lower deviation is zero, so the hole is never undersize Correct answer.
  2. upper deviation is zero, so the hole is never oversize
  3. both deviations are zero, so the hole equals basic size
  4. the tolerance is divided equally above and below the basic size

Explanation

In the hole-basis system, an H hole has its lower deviation at zero, so the hole tolerance zone lies above the basic size. The hole is therefore never smaller than the nominal diameter, and the shaft carries the clearance or interference deviation.

Question 12Trade Theory - Mechanical and Electrical Fundamentals

An SMD resistor is marked 4R7. What is its nominal resistance?

  1. 470 Ω
  2. 47 Ω
  3. 4.7 Ω Correct answer.
  4. 0.47 Ω

Explanation

The letter R marks the decimal point position, so 4R7 is read as 4.7 Ω. For example, R47 would mean 0.47 Ω, while 47R would mean 47 Ω.

Question 13Trade Theory - Mechanical and Electrical Fundamentals

Which instrument is used to measure the insulation resistance of a motor winding before commissioning?

  1. A tachometer
  2. A clamp meter
  3. A multimeter set to continuity
  4. A megger Correct answer.

Explanation

A megger applies a high test voltage and measures insulation resistance in megohms. It is used on de-energised windings to check insulation between conductors and earth before commissioning.

Question 14Trade Theory - Mechanical and Electrical Fundamentals

Two resistors of 6 Ω and 3 Ω are connected in series across a 12 V DC supply. What is the voltage across the 6 Ω resistor?

  1. 8 V Correct answer.
  2. 9 V
  3. 6 V
  4. 4 V

Explanation

The series resistance is 6 + 3 = 9 Ω, so the current is 12/9 = 1.33 A. The voltage across the 6 Ω resistor is then IR = 1.33 × 6 = 8 V.

Question 15Trade Theory - Mechanical and Electrical Fundamentals

A 20-tooth gear rotating at 600 rpm drives a 60-tooth gear. What is the speed of the driven gear?

  1. 300 rpm
  2. 1800 rpm
  3. 600 rpm
  4. 200 rpm Correct answer.

Explanation

The gear ratio is 60/20 = 3, so the driven gear turns at one-third of the driver speed. Therefore 600/3 = 200 rpm.

Question 16Trade Theory - Mechanical and Electrical Fundamentals

A taper has a taper ratio of 1:20 and a length of 100 mm. What is the difference between the large and small diameters?

  1. 4 mm
  2. 2 mm
  3. 5 mm Correct answer.
  4. 20 mm

Explanation

Taper ratio is the diameter difference divided by length, so (D − d)/L = 1/20. For L = 100 mm, D − d = 100/20 = 5 mm.

Question 17Trade Theory - Mechanical and Electrical Fundamentals

What is the main purpose of a star-delta starter for a three-phase squirrel-cage induction motor?

  1. To control running speed continuously
  2. To reverse rotation at every start
  3. To increase starting torque above direct-on-line value
  4. To limit starting current by reducing voltage Correct answer.

Explanation

A star-delta starter first connects the motor windings in star, so each winding receives only 1/√3 of the line voltage. This reduces the starting current to about one-third of the direct-on-line value, though starting torque is also reduced.

Question 18Trade Theory - Mechanical and Electrical Fundamentals

In a single-phase capacitor-start induction motor, what is the function of the capacitor in the auxiliary winding circuit?

  1. It supplies direct current to the rotor
  2. It splits phase to produce a rotating field Correct answer.
  3. It regulates the shaft speed to a fixed value
  4. It increases the resistance of the main winding

Explanation

The capacitor makes the auxiliary winding current lead the main winding current, producing a phase split. This creates a rotating magnetic field so the single-phase motor can develop starting torque.

Question 19Trade Theory - Mechanical and Electrical Fundamentals

Two capacitors of 6 µF and 3 µF are connected in series across a 12 V DC supply. What charge is stored on each capacitor?

  1. 24 µC Correct answer.
  2. 72 µC
  3. 48 µC
  4. 36 µC

Explanation

For series capacitors, 1/C = 1/6 + 1/3, giving C = 2 µF. The charge is Q = CV = 2 µF × 12 V = 24 µC, and the same charge is stored on each series capacitor.

Question 20Trade Theory - Mechanical and Electrical Fundamentals

A shaft transmits 5 kW at 1000 rpm. Using T = 9550 P/N with P in kW and N in rpm, what torque is transmitted?

  1. 9550 N·m
  2. 477.5 N·m
  3. 47.75 N·m Correct answer.
  4. 4.775 N·m

Explanation

Using T = 9550 P/N with P in kW, T = 9550 × 5/1000 = 47.75 N·m. The constant 9550 comes from converting power in kW and speed in rpm into torque in N·m.

Question 21Trade Theory - Mechanical and Electrical Fundamentals

Which type of coupling is used to connect two shafts that have a slight parallel misalignment?

  1. Oldham coupling Correct answer.
  2. Universal joint
  3. Sleeve coupling
  4. Rigid flange coupling

Explanation

An Oldham coupling uses a central disc with tongues that slide in slots on the two shaft hubs, so it can transmit torque while allowing parallel offset. Rigid flange and sleeve couplings require the shafts to be aligned closely, and a universal joint is mainly used for angular misalignment.

Question 22Trade Theory - Mechanical and Electrical Fundamentals

A hole is specified with limits 25.000 mm and 25.021 mm. The mating shaft has limits 24.980 mm and 24.993 mm. Which type of fit is obtained?

  1. Clearance fit, with shaft always smaller Correct answer.
  2. Shrink fit, using cooled shaft for assembly
  3. Interference fit, with shaft larger than hole
  4. Transition fit, with limits partly overlapping

Explanation

The largest permitted shaft is 24.993 mm, which is smaller than the smallest permitted hole of 25.000 mm, so clearance always exists. This makes the fit a clearance fit. Interference needs the shaft larger than the hole, and a transition fit needs overlapping tolerance zones.

Question 23Trade Theory - Mechanical and Electrical Fundamentals

In a metric screw thread, the pitch is defined as the

  1. total length of the threaded portion
  2. angle between the thread flanks
  3. diameter at the bottom of the thread groove
  4. axial distance between adjacent thread points Correct answer.

Explanation

Pitch is the axial distance from a point on one thread to the corresponding point on the next adjacent thread. It is a measure of thread spacing along the axis, not the thread angle, threaded length, or root diameter.

Question 24Trade Theory - Mechanical and Electrical Fundamentals

A belt drive has a driver pulley of 100 mm diameter running at 1440 rpm and a driven pulley of 250 mm diameter. Neglecting slip, what is the speed of the driven pulley?

  1. 576 rpm Correct answer.
  2. 720 rpm
  3. 360 rpm
  4. 900 rpm

Explanation

For a belt drive without slip, the pulley speeds are inversely proportional to their diameters: N1D1 = N2D2. Therefore N2 = 1440 × 100 / 250 = 576 rpm.

Question 25Trade Theory - Mechanical and Electrical Fundamentals

Three resistors of 4 Ω, 6 Ω, and 12 Ω are connected in parallel across a DC supply. What is the equivalent resistance of the combination?

  1. 6 Ω
  2. 2 Ω Correct answer.
  3. 4 Ω
  4. 22 Ω

Explanation

For parallel resistors, 1/R = 1/4 + 1/6 + 1/12 = 3/12 + 2/12 + 1/12 = 6/12, so R = 2 Ω. The equivalent parallel resistance is always less than the smallest branch resistance.

Question 26Trade Theory - Mechanical and Electrical Fundamentals

A single-phase AC load draws 5 A from a 230 V supply at a power factor of 0.8. What is the active power consumed by the load?

  1. 184 W
  2. 1437 W
  3. 1150 W
  4. 920 W Correct answer.

Explanation

Active power in a single-phase AC circuit is P = V × I × cos φ. Substituting the values gives P = 230 × 5 × 0.8 = 920 W.

Question 27Trade Theory - Mechanical and Electrical Fundamentals

Which protective device is connected in the supply circuit of a three-phase induction motor to trip the motor on sustained overcurrent caused by overload?

  1. Earth-leakage circuit breaker
  2. Thermal overload relay Correct answer.
  3. Ammeter with a selector switch
  4. Metal-oxide varistor

Explanation

A thermal overload relay senses the current in the motor supply lines and trips after a sustained overload, protecting the winding from overheating. An earth-leakage circuit breaker responds to earth faults, a varistor limits voltage surges, and an ammeter only indicates current.

Question 28Trade Theory - Mechanical and Electrical Fundamentals

A three-phase, 50 Hz induction motor has 4 poles and runs with a full-load slip of 4%. What is the rotor speed at full load?

  1. 1500 rpm
  2. 1560 rpm
  3. 1350 rpm
  4. 1440 rpm Correct answer.

Explanation

Synchronous speed is Ns = 120f/P = 120 × 50 / 4 = 1500 rpm. Rotor speed is N = Ns(1 − s) = 1500 × 0.96 = 1440 rpm at 4% slip.

Question 29Trade Theory - Mechanical and Electrical Fundamentals

A compound gear train has gear A with 20 teeth driving gear B with 40 teeth. Gear B is fixed on the same shaft as gear C with 15 teeth, which drives gear D with 45 teeth. If gear A rotates at 900 rpm, what is the speed of gear D?

  1. 600 rpm
  2. 150 rpm Correct answer.
  3. 300 rpm
  4. 450 rpm

Explanation

The overall speed ratio is (teeth on A / teeth on B) × (teeth on C / teeth on D) = (20/40) × (15/45) = 1/6. Therefore gear D rotates at 900 / 6 = 150 rpm.

Question 30Trade Theory - Mechanical and Electrical Fundamentals

What is the main purpose of connecting the metal enclosure of an electrical appliance to earth?

  1. To reduce the active power consumed by the appliance
  2. To provide a return path for the normal operating current
  3. To increase the operating voltage of the appliance
  4. To protect the user from shock if the live conductor touches the enclosure Correct answer.

Explanation

Earthing provides a low-resistance path so that a fault current trips the protective device and the metal enclosure stays near earth potential. This protects the user from electric shock if insulation fails and the live conductor touches the enclosure.

Question 31Trade Theory - Mechanical and Electrical Fundamentals

A carbon resistor carries the colour bands yellow, violet, red and gold in that order. What is its nominal resistance and tolerance?

  1. 470 Ω with a tolerance of ±5%
  2. 4.7 kΩ with a tolerance of ±10%
  3. 47 kΩ with a tolerance of ±5%
  4. 4.7 kΩ with a tolerance of ±5% Correct answer.

Explanation

Yellow stands for the digit 4 and violet for 7, giving the significant figures 47. The red band is a multiplier of ×100, so the value is 4700 Ω, that is 4.7 kΩ. The fourth band is gold, which specifies a tolerance of ±5%.

Question 32Trade Theory - Mechanical and Electrical Fundamentals

Which nut has slots cut across its top face so that a split pin can pass through the slot and the drilled shank of the bolt?

  1. Castle nut Correct answer.
  2. Jam nut
  3. Dome nut
  4. Wing nut

Explanation

A castle (castellated) nut carries slots machined across its upper face; once tightened, a split pin is passed through the slot and the cross-hole in the bolt, giving positive locking that cannot loosen under vibration.

Question 33Trade Theory - Mechanical and Electrical Fundamentals

What is the electrolyte used in a lead-acid storage battery?

  1. Dilute sulphuric acid Correct answer.
  2. Potassium hydroxide solution
  3. Concentrated nitric acid
  4. Sodium chloride solution

Explanation

A lead-acid cell uses dilute sulphuric acid as the electrolyte, with lead peroxide as the positive plate and sponge lead as the negative plate. During discharge the acid is consumed and the specific gravity of the electrolyte falls, which is how the state of charge is checked.

Question 34Trade Theory - Mechanical and Electrical Fundamentals

A vernier caliper has its main scale graduated in divisions of 0.5 mm, and 25 vernier divisions coincide with 24 main scale divisions. What is the least count of the caliper?

  1. 0.01 mm
  2. 0.02 mm Correct answer.
  3. 0.50 mm
  4. 0.05 mm

Explanation

Least count equals one main scale division minus one vernier scale division. Here 24 main scale divisions measure 12 mm, so one vernier division is 12 ÷ 25 = 0.48 mm, and the least count is 0.50 − 0.48 = 0.02 mm.

Question 35Trade Theory - Mechanical and Electrical Fundamentals

A single-phase transformer has 400 turns on its primary winding and 100 turns on its secondary winding. When the primary is connected to a 400 V, 50 Hz supply, what is the open-circuit secondary voltage?

  1. 100 V Correct answer.
  2. 25 V
  3. 1600 V
  4. 400 V

Explanation

For an ideal transformer the voltage ratio equals the turns ratio, so V2 = V1 × (N2/N1) = 400 × (100/400) = 100 V. The frequency stays at 50 Hz on both sides; only the voltage and current change.

Question 36Trade Theory - Mechanical and Electrical Fundamentals

In the rolling bearing designation 6205, the last two digits 05 indicate a bore diameter of

  1. 25 mm Correct answer.
  2. 5 mm
  3. 10 mm
  4. 50 mm

Explanation

For bore numbers 04 and above, the bore diameter in millimetres is the last two digits multiplied by 5; hence 05 gives 5 × 5 = 25 mm. In the same designation, 6 identifies a single-row deep groove ball bearing and 2 the light series.

Question 37Trade Theory - Mechanical and Electrical Fundamentals

A balanced three-phase load of 10 kW operates from a 415 V three-phase supply at a power factor of 0.8. What is the line current drawn by the load?

  1. 30.1 A
  2. 11.1 A
  3. 6.9 A
  4. 17.4 A Correct answer.

Explanation

For a balanced three-phase load, P = √3 × VL × IL × cos φ, so IL = P ÷ (√3 × VL × cos φ). Substituting gives IL = 10 000 ÷ (1.732 × 415 × 0.8) = 17.4 A.

Question 38Trade Theory - Mechanical and Electrical Fundamentals

A 20 mm diameter hole is to be drilled in mild steel at a cutting speed of 25 m/min. What spindle speed should be set on the drilling machine?

  1. 160 rpm
  2. 200 rpm
  3. 400 rpm Correct answer.
  4. 800 rpm

Explanation

Spindle speed is found from N = 1000V ÷ (πD), with V in m/min and D in mm. Thus N = 1000 × 25 ÷ (π × 20) = 398 rpm, which is set as 400 rpm on the machine.

Question 39Trade Theory - Mechanical and Electrical Fundamentals

Two identical 100 W, 230 V filament lamps are connected in series across a 230 V DC supply. What is the total power consumed by the pair?

  1. 25 W
  2. 200 W
  3. 100 W
  4. 50 W Correct answer.

Explanation

Each lamp has a resistance of V²/P = 230² ÷ 100 = 529 Ω, so the series pair presents 1058 Ω to the supply. Total power is then 230² ÷ 1058 = 50 W, because the doubled resistance at the same voltage halves the current and each lamp now receives only 25 W.

Question 40Trade Theory - Mechanical and Electrical Fundamentals

A mild steel rod of 20 mm diameter and 1 m length carries an axial tensile load of 20 kN. Taking E = 200 GPa, what is the elongation of the rod?

  1. 0.159 mm
  2. 0.032 mm
  3. 0.318 mm Correct answer.
  4. 3.18 mm

Explanation

The cross-sectional area is (π/4) × 20² = 314 mm², so the stress is 20 000 ÷ 314 = 63.7 N/mm². Using δ = σL ÷ E = 63.7 × 1000 ÷ 200 000 gives 0.318 mm, which can also be obtained directly from δ = FL ÷ (AE).

Question 41Workshop Calculation and Science

A workshop drawing specifies a plate thickness of 3/4 inch. Using 1 inch = 25.4 mm, what is the thickness in millimetres?

  1. 12.70 mm
  2. 25.40 mm
  3. 9.52 mm
  4. 19.05 mm Correct answer.

Explanation

Convert the fractional inch to millimetres by multiplying 3/4 by 25.4. The calculation is (3 × 25.4) ÷ 4 = 76.2 ÷ 4 = 19.05 mm.

Question 42Workshop Calculation and Science

A trainee purchases raw material worth ₹480. If 18% GST is added, what is the total payable amount?

  1. ₹518.40
  2. ₹498.00
  3. ₹576.00
  4. ₹566.40 Correct answer.

Explanation

GST is 18% of ₹480, which is 0.18 × 480 = ₹86.40. Adding this tax to the material cost gives ₹480 + ₹86.40 = ₹566.40.

Question 43Workshop Calculation and Science

Which SI unit is used to express pressure in workshop calculations?

  1. Joule (J)
  2. Newton (N)
  3. Pascal (Pa) Correct answer.
  4. Watt (W)

Explanation

Pressure is defined as force per unit area, and its SI unit is the pascal (Pa), equal to one newton per square metre.

Question 44Workshop Calculation and Science

A solid steel rod of diameter 50 mm and length 80 mm is to be turned. Taking π = 3.1416, what is its volume in cm³?

  1. 157.08 cm³ Correct answer.
  2. 62.83 cm³
  3. 314.16 cm³
  4. 39.27 cm³

Explanation

The radius is half the diameter, 25 mm, and the volume is πr²h. Substituting gives 3.1416 × 25² × 80 = 157,080 mm³, which is 157.08 cm³.

Question 45Workshop Calculation and Science

A drill of 50 mm diameter is to be used at a cutting speed of 30 m/min. Using N = 1000V/(πD), what spindle speed is required?

  1. 239 rpm
  2. 382 rpm
  3. 95 rpm
  4. 191 rpm Correct answer.

Explanation

Use N = 1000V/(πD) with V = 30 m/min and D = 50 mm. N = (1000 × 30) ÷ (3.1416 × 50) ≈ 191 rpm.

Question 46Workshop Calculation and Science

An alloy contains copper and zinc in the ratio 3:2 by mass. In a 15 kg batch, what mass of copper is present?

  1. 6 kg
  2. 10 kg
  3. 5 kg
  4. 9 kg Correct answer.

Explanation

The ratio 3:2 has 3 + 2 = 5 equal parts. One part is 15 ÷ 5 = 3 kg, so copper is 3 × 3 = 9 kg.

Question 47Workshop Calculation and Science

A sine bar with 100 mm between roller centres is set using a slip gauge height of 25 mm. What is the angle of the sine bar?

  1. 7.24°
  2. 14.04°
  3. 25.00°
  4. 14.48° Correct answer.

Explanation

For a sine bar, sin θ = slip gauge height ÷ roller centre distance. Here sin θ = 25 ÷ 100 = 0.25, so θ = sin⁻¹(0.25) ≈ 14.48°.

Question 48Workshop Calculation and Science

A 12 V DC supply is connected across a 6 Ω resistor. What current flows through the circuit?

  1. 18 A
  2. 0.5 A
  3. 72 A
  4. 2 A Correct answer.

Explanation

Ohm's law gives I = V ÷ R. Substituting V = 12 V and R = 6 Ω gives I = 12 ÷ 6 = 2 A.

Question 49Workshop Calculation and Science

A taper has a large diameter of 50 mm, a small diameter of 42 mm and a length of 60 mm. What is the included taper angle, to the nearest 0.1°?

  1. 7.6° Correct answer.
  2. 3.8°
  3. 4.8°
  4. 15.2°

Explanation

The half-angle satisfies tan(α/2) = (D − d) ÷ (2L) = 8 ÷ 120 = 0.06667. Thus α/2 ≈ 3.81°, and the included angle α ≈ 7.6°.

Question 50Workshop Calculation and Science

A 2 kW immersion heater is used to raise the temperature of 5 kg of water by 20 K. Taking the specific heat capacity of water as 4.18 kJ/kg·K and ignoring losses, how long will it take?

  1. 209 s Correct answer.
  2. 52 s
  3. 418 s
  4. 105 s

Explanation

Heat required is Q = mcΔT = 5 × 4.18 × 20 = 418 kJ. At 2 kW (2 kJ/s), time = 418 ÷ 2 = 209 s.