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JEECUP (UP Polytechnic) study materials
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JEECUP (UP Polytechnic) practice questions

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Question 1Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In the JEECUP counselling process for government polytechnic colleges of Uttar Pradesh, admission to diploma seats is finally confirmed only after which step?

  1. Submitting the online application form
  2. Filling the choice-locking option once
  3. Downloading the admit card for the entrance test
  4. Paying the seat acceptance fee and reporting for document verification Correct answer.

Explanation

JEECUP allotment is provisional until the candidate pays the prescribed seat acceptance fee and completes physical reporting with original documents at the allotted institute. Choice filling and application submission only make a candidate eligible for allotment.

Question 2Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A diploma student in a UP polytechnic measures the diameter of a wire with a vernier calliper whose least count is 0.02 mm. The main scale reads 12 mm and the 7th vernier division coincides with a main scale line. What is the diameter?

  1. 12.35 mm
  2. 12.14 mm Correct answer.
  3. 12.07 mm
  4. 12.70 mm

Explanation

Vernier reading = main scale reading + (vernier division coinciding × least count). Here 12 mm + (7 × 0.02 mm) = 12 mm + 0.14 mm = 12.14 mm.

Question 3Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which law of thermodynamics is used to define the concept of entropy and states that entropy of an isolated system never decreases?

  1. Second law Correct answer.
  2. First law
  3. Third law
  4. Zeroth law

Explanation

The second law introduces entropy and states that the entropy of an isolated system always increases or remains constant for reversible processes. The zeroth law defines thermal equilibrium and temperature, while the first law is energy conservation.

Question 4Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a DC shunt motor running at no load, the field winding is accidentally disconnected. What is the most likely consequence?

  1. The motor speed rises dangerously because flux collapses Correct answer.
  2. The motor runs at half its rated speed steadily
  3. The motor reverses its direction of rotation smoothly
  4. The motor stops immediately without any damage

Explanation

With the field circuit open, only a small residual flux remains, so the back EMF falls and armature current rises sharply, driving speed to a dangerously high value. This is why field failure protection is essential in DC shunt motors.

Question 5Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

The SI unit of the coefficient of thermal conductivity of a material used in a polytechnic heat transfer experiment is:

  1. W m⁻² K⁻¹
  2. W m⁻¹ K⁻¹ Correct answer.
  3. J kg⁻¹ K⁻¹
  4. N m⁻¹ K⁻¹

Explanation

Fourier's law gives Q/t = kA(dT/dx), so k = (W × m)/(m² × K) = W m⁻¹ K⁻¹. This unit describes heat flow per unit length per unit temperature difference.

Question 6Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a simply supported beam of span 4 m carrying a central point load of 20 kN, what is the maximum bending moment?

  1. 20 kN·m Correct answer.
  2. 10 kN·m
  3. 40 kN·m
  4. 80 kN·m

Explanation

For a simply supported beam with a central point load W and span L, the maximum bending moment is WL/4 = (20 × 4)/4 = 20 kN·m at mid-span. Each reaction is W/2 = 10 kN.

Question 7Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which type of cement is most suitable for mass concrete work such as dams, where low heat of hydration is required?

  1. Low heat Portland cement Correct answer.
  2. Rapid hardening Portland cement
  3. Sulphate resisting cement
  4. White Portland cement

Explanation

Low heat Portland cement contains a lower proportion of tricalcium aluminate and tricalcium silicate, which reduces the heat liberated during setting. This limits thermal cracking in large concrete masses such as dams.

Question 8Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A four-stroke diesel engine has a compression ratio of 16 and a cut-off ratio of 2. If the air-standard efficiency formula is used, which factor most directly increases its efficiency?

  1. Reducing the compression ratio and raising the load
  2. Raising the compression ratio while keeping the cut-off ratio low Correct answer.
  3. Adding more fuel per cycle at the same compression ratio
  4. Increasing the cut-off ratio at constant compression ratio

Explanation

Diesel cycle efficiency rises with compression ratio and falls as the cut-off ratio increases. Keeping the fuel cut-off short while raising compression therefore improves the air-standard efficiency.

Question 9Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In an alternating current circuit, a pure capacitor is connected across a sinusoidal supply. The current in the circuit:

  1. Lags the applied voltage by 90 degrees
  2. Is exactly in phase with the voltage
  3. Leads the voltage by 45 degrees
  4. Leads the applied voltage by 90 degrees Correct answer.

Explanation

In a purely capacitive circuit the current reaches its maximum a quarter cycle before the voltage, so it leads the voltage by 90°. The opposition offered is the capacitive reactance 1/(2πfC).

Question 10Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A transformer used in a polytechnic laboratory has 400 turns on the primary and 100 turns on the secondary. If the primary is supplied at 220 V, what is the secondary voltage on no load?

  1. 220 V
  2. 55 V Correct answer.
  3. 880 V
  4. 110 V

Explanation

For an ideal transformer, V2/V1 = N2/N1, so V2 = 220 × (100/400) = 55 V. This is a step-down transformer with a turns ratio of 4:1.

Question 11Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

The binary number 1101₂ converted to decimal is:

  1. 13 Correct answer.
  2. 11
  3. 9
  4. 15

Explanation

Expanding place values: 1×8 + 1×4 + 0×2 + 1×1 = 8 + 4 + 1 = 13. Each position doubles in weight from right to left.

Question 12Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A logic gate gives a HIGH output only when both of its inputs are different. Which gate is it?

  1. NOR
  2. Exclusive-OR Correct answer.
  3. NAND
  4. AND

Explanation

The XOR gate output is 1 when exactly one input is 1, that is, when the inputs differ. Its Boolean expression is A·B̄ + Ā·B.

Question 13Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In an 8085 microprocessor, which register pair is used to hold the memory address during instruction fetch?

  1. Accumulator
  2. Instruction register
  3. Program counter Correct answer.
  4. Stack pointer

Explanation

The program counter holds the address of the next instruction byte to be fetched, and it is automatically incremented after each fetch. The fetched opcode itself goes into the instruction register.

Question 14Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A lap winding is preferred for a DC machine that must deliver:

  1. High current at low voltage Correct answer.
  2. Low current at high voltage
  3. High voltage with small conductor size
  4. Constant voltage irrespective of load

Explanation

Lap winding provides as many parallel paths as poles, so it carries a large current at relatively low voltage. Wave winding, with only two parallel paths, suits high-voltage low-current machines.

Question 15Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

The process of removing excess material from a workpiece using a rotating multi-point cutter is known as:

  1. Broaching
  2. Turning
  3. Drilling
  4. Milling Correct answer.

Explanation

Milling uses a rotating cutter with multiple teeth, and the work is fed against it to produce flat or profiled surfaces. Turning uses a single-point tool on a lathe with the work rotating.

Question 16Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a lathe, the component that transmits motion from the feed rod to the carriage for automatic longitudinal feed is the:

  1. Headstock
  2. Apron mechanism Correct answer.
  3. Lead screw
  4. Tailstock

Explanation

The apron is mounted on the carriage and contains the handwheel, gears and clutch that engage the feed rod or lead screw to move the carriage. The lead screw itself is used mainly for thread cutting.

Question 17Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which heat treatment process involves heating steel above its critical temperature, holding, and then cooling in still air?

  1. Normalising Correct answer.
  2. Tempering
  3. Quenching
  4. Annealing

Explanation

Normalising refines grain structure and relieves internal stresses by cooling in still air, giving a harder and stronger structure than annealing. Quenching uses a liquid medium for much faster cooling.

Question 18Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A simply supported rectangular beam of width 100 mm and depth 200 mm carries a bending moment of 6 kN·m. What is the maximum bending stress?

  1. 9 N/mm² Correct answer.
  2. 36 N/mm²
  3. 18 N/mm²
  4. 4.5 N/mm²

Explanation

Section modulus Z = bd²/6 = (100 × 200²)/6 = 666 667 mm³. Bending stress = M/Z = (6 × 10⁶)/666 667 ≈ 9 N/mm².

Question 19Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

The main purpose of providing a slump test on fresh concrete at a polytechnic site laboratory is to measure:

  1. Workability or consistency Correct answer.
  2. Durability against frost
  3. Compressive strength
  4. Setting time of cement

Explanation

The slump test indicates the consistency and workability of a fresh concrete mix by measuring the vertical settlement of a moulded cone. Strength and durability are assessed by other tests on hardened concrete.

Question 20Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In surveying, the horizontal angle measured clockwise from the magnetic north to a survey line is called the:

  1. Deflection angle
  2. Dip of the needle
  3. Reduced bearing
  4. Whole circle bearing Correct answer.

Explanation

Whole circle bearing is measured clockwise from magnetic north and ranges from 0° to 360°. Reduced bearing is the acute angle measured from the nearer end of the north-south line.

Question 21Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A pump lifts water through a height of 10 m at a discharge of 0.02 m³/s. Taking g = 10 m/s² and density 1000 kg/m³, the minimum power required is:

  1. 200 kW
  2. 20 kW
  3. 0.2 kW
  4. 2 kW Correct answer.

Explanation

Power = ρ g Q H = 1000 × 10 × 0.02 × 10 = 2000 W = 2 kW. This is the hydraulic power, and the shaft power would be larger by the pump efficiency.

Question 22Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which property of a lubricating oil is most important for reducing friction between sliding machine parts at high temperature?

  1. Flash point
  2. Cloud point
  3. Viscosity index Correct answer.
  4. Specific gravity

Explanation

Viscosity index expresses how little the viscosity changes with temperature; a high index keeps the oil film effective when parts become hot. Flash point and cloud point relate to safety and low-temperature behaviour, not friction control directly.

Question 23Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

The efficiency of a Carnot engine working between 500 K and 300 K is:

  1. 80%
  2. 60%
  3. 40% Correct answer.
  4. 20%

Explanation

Carnot efficiency = 1 − T2/T1 = 1 − 300/500 = 0.4, that is, 40%. The efficiency depends only on the absolute temperatures of the source and sink.

Question 24Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a three-phase induction motor, the synchronous speed of the rotating magnetic field with 4 poles on a 50 Hz supply is:

  1. 1000 rpm
  2. 750 rpm
  3. 1500 rpm Correct answer.
  4. 3000 rpm

Explanation

Synchronous speed Ns = 120f/P = (120 × 50)/4 = 1500 rpm. The rotor runs slightly slower than this value, and the difference is the slip.

Question 25Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a CAD drawing prepared by a diploma student, a line type that uses long and short dashes alternately is conventionally used to show:

  1. Cutting plane lines
  2. Visible outlines
  3. Centre lines
  4. Hidden edges Correct answer.

Explanation

As per standard drafting practice, hidden edges are drawn with medium-weight short dashes, usually evenly spaced. Centre lines use alternate long and short dashes, which is a distinct pattern.

Question 26Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In the JEECUP counselling process for UP polytechnic admission, what is the purpose of the seat allotment round followed by document verification at a facilitation centre?

  1. To confirm the candidate's eligibility and category claims before the allotted seat is frozen Correct answer.
  2. To allow colleges to interview candidates and select only the highest scorers
  3. To let candidates change their branch after paying the full first-year fee
  4. To replace the entrance examination score with a fresh college-level test

Explanation

JEECUP counselling allots seats based on rank, choices filled and category, and the candidate must then report for document verification so that eligibility and reservation claims are checked before the seat is confirmed. The entrance score itself is never replaced at this stage.

Question 27Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A diploma student in a UP polytechnic workshop measures a steel rod with a vernier caliper whose main scale reads 24 mm and whose 6th vernier division coincides with a main scale division. If the least count is 0.02 mm, what is the measured diameter?

  1. 24.06 mm
  2. 25.20 mm
  3. 24.12 mm Correct answer.
  4. 24.60 mm

Explanation

The vernier reading equals the number of the coinciding division multiplied by the least count, so 6 × 0.02 mm = 0.12 mm. Adding this to the main scale reading of 24 mm gives 24.12 mm.

Question 28Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which engineering material is most commonly specified for the body of a lathe bed because it absorbs vibration and retains dimensional stability?

  1. Cast iron Correct answer.
  2. Mild steel sheet
  3. Aluminium alloy
  4. High-carbon tool steel

Explanation

Cast iron has high damping capacity, good machinability and rigidity, which is why lathe beds and machine frames are usually cast from it. Sheet steel and aluminium lack the mass and vibration damping needed for a machine tool base.

Question 29Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a first-angle projection drawing prepared for a polytechnic workshop assignment, where is the top view placed relative to the front view?

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

Explanation

In first-angle projection the object is imagined between the observer and the plane, so the view obtained from above is projected below the front view. This is the standard practice followed in Indian drawing offices.

Question 30Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A polytechnic trainee connects three resistors of 6 Ω each in parallel across a 12 V supply. What is the total current drawn from the supply?

  1. 0.67 A
  2. 18 A
  3. 6 A Correct answer.
  4. 2 A

Explanation

Three equal 6 Ω resistors in parallel give an equivalent resistance of 6/3 = 2 Ω. The current is then V/R = 12/2 = 6 A.

Question 31Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which fuel property is measured by the octane number of petrol used in spark-ignition engines?

  1. Viscosity of the fuel
  2. Calorific value of the fuel
  3. Resistance to knocking or auto-ignition Correct answer.
  4. Flash point of the fuel

Explanation

Octane number expresses a petrol's ability to resist detonation, with iso-octane rated 100 and normal heptane rated 0. A higher octane number means the fuel can withstand higher compression without knocking.

Question 32Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a computer used in a polytechnic CAD laboratory, which storage device is non-volatile and retains data when power is switched off?

  1. Hard disk drive Correct answer.
  2. CPU register
  3. Dynamic RAM
  4. Cache memory

Explanation

A hard disk stores data magnetically and keeps it after power is removed, so it is non-volatile. RAM, registers and cache are semiconductor memories that lose their contents when power is cut.

Question 33Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A surveyor in a UP polytechnic field exercise measures a line as 250 m using a 30 m chain that is actually 30.05 m long. What is the correct length of the line?

  1. 249.95 m
  2. 250.05 m
  3. 250.42 m Correct answer.
  4. 249.58 m

Explanation

The true length equals the measured length multiplied by the actual chain length divided by the nominal chain length, that is 250 × 30.05/30 = 250.42 m. Because the chain is longer than nominal, the measured distance understates the true distance.

Question 34Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A mild steel specimen tested in a polytechnic materials laboratory shows a stress-strain curve with a clear yield point. What does the yield stress represent?

  1. The stress remaining after the load is removed
  2. The stress at which appreciable plastic deformation begins Correct answer.
  3. The maximum stress the specimen can withstand before fracture
  4. The stress at which the specimen regains its original length

Explanation

Yielding marks the transition from elastic to plastic behaviour, and beyond it the material deforms permanently with little increase in load. The ultimate tensile strength, which is higher, is the maximum stress reached before fracture.

Question 35Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A simply supported beam of span 6 m carries a uniformly distributed load of 10 kN/m over its entire length. What is the maximum shear force in the beam?

  1. 60 kN
  2. 10 kN
  3. 15 kN
  4. 30 kN Correct answer.

Explanation

The total load is 10 kN/m × 6 m = 60 kN, shared equally by the two supports, so each reaction is 30 kN. The shear force is maximum at the supports and equals the reaction, 30 kN.

Question 36Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a belt drive used on a workshop machine, the driving pulley of 200 mm diameter runs at 600 rpm. What is the speed of a driven pulley of 400 mm diameter, assuming no slip?

  1. 1200 rpm
  2. 150 rpm
  3. 600 rpm
  4. 300 rpm Correct answer.

Explanation

For a belt drive without slip, N₁D₁ = N₂D₂, so N₂ = 600 × 200/400 = 300 rpm. The larger driven pulley therefore rotates more slowly.

Question 37Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which thermodynamic cycle is used as the ideal reference cycle for a reciprocating petrol engine?

  1. Rankine cycle
  2. Otto cycle Correct answer.
  3. Bell-Coleman cycle
  4. Diesel cycle

Explanation

The Otto cycle models heat addition at constant volume, which approximates combustion in a spark-ignition petrol engine. The Diesel cycle uses constant-pressure heat addition and suits compression-ignition engines.

Question 38Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A single-phase transformer in a polytechnic electrical laboratory has a turns ratio of 10:1 and is supplied at 230 V on the primary. What is the secondary voltage on open circuit?

  1. 23 V Correct answer.
  2. 230 V
  3. 2.3 V
  4. 2300 V

Explanation

The voltage ratio equals the turns ratio, so V₂ = V₁ × N₂/N₁ = 230 × 1/10 = 23 V. A step-down turns ratio therefore gives a step-down voltage.

Question 39Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

Which type of DC motor is preferred for a domestic mixer grinder because it maintains speed under varying load without a separate starter?

  1. Shunt motor
  2. Universal motor Correct answer.
  3. Series DC motor
  4. Permanent magnet stepper motor

Explanation

A universal motor runs on either AC or DC and gives high speed and good torque for its size, which suits appliances such as mixers. Shunt and series DC motors require a DC supply and a starter for larger ratings.

Question 40Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a polytechnic electronics laboratory, a silicon diode is forward biased. What is the typical barrier potential that must be overcome before appreciable conduction starts?

  1. 1.5 V
  2. 5.0 V
  3. 0.7 V Correct answer.
  4. 0.3 V

Explanation

A forward-biased silicon junction starts conducting appreciably at about 0.7 V, while a germanium diode conducts at about 0.3 V. This knee voltage appears as a nearly constant drop across the diode.

Question 41Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A four-bit binary counter used in a polytechnic digital electronics practical is clocked continuously. How many distinct output states does it pass through before repeating?

  1. 8
  2. 4
  3. 32
  4. 16 Correct answer.

Explanation

A four-bit counter has 2⁴ = 16 possible combinations, from 0000 to 1111, before it returns to its starting state. The number of flip-flops determines the modulus of the counter.

Question 42Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A polytechnic workshop uses a milling machine to produce a flat surface on a cast iron block. Which cutter is most suitable for face milling this surface?

  1. Slitting saw
  2. Face milling cutter Correct answer.
  3. Woodruff keyseat cutter
  4. Twist drill

Explanation

A face milling cutter has teeth on its periphery and face and is designed to machine flat surfaces perpendicular to the spindle axis. Slitting saws cut narrow slots and Woodruff cutters form keyseats.

Question 43Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a house wiring installation, which device protects the circuit by automatically breaking the supply when the current exceeds a set value?

  1. Miniature circuit breaker Correct answer.
  2. Ceiling rose
  3. Energy meter
  4. Two-way switch

Explanation

A miniature circuit breaker trips on overload or short circuit and can be reset once the fault is cleared. Switches, meters and ceiling roses do not perform overcurrent protection.

Question 44Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A polytechnic civil site stores cement bags on the ground floor of a building under construction. What is the recommended maximum stacking height to prevent bag hardening due to pressure?

  1. Five bags
  2. Twenty bags
  3. Ten bags Correct answer.
  4. Fifteen bags

Explanation

Cement bags are generally stacked no more than ten high to avoid the weight of the pile setting the lower bags. Stacks also need to be kept off the floor on wooden planks and away from moisture.

Question 45Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A polytechnic student calculates the volume of earthwork for a canal of trapezoidal section 4 m wide at the base, 1 m deep and side slopes 1:1. What is the cross-sectional area?

  1. 8 m²
  2. 4 m²
  3. 6 m²
  4. 5 m² Correct answer.

Explanation

For a trapezoid, area = bd + sd², where s is the side slope. Here 4 × 1 + 1 × 1² = 5 m². The side triangles contribute 1 m² in total.

Question 46Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a three-phase 400 V, 50 Hz induction motor with a full-load slip of 4 percent and 4 poles, what is the rotor speed?

  1. 1560 rpm
  2. 1440 rpm Correct answer.
  3. 1500 rpm
  4. 1380 rpm

Explanation

Synchronous speed is 120f/P = 120 × 50/4 = 1500 rpm, and rotor speed is Ns(1 − s) = 1500 × 0.96 = 1440 rpm. The rotor always runs slightly below synchronous speed in motoring mode.

Question 47Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A simply supported beam of rectangular section carries a load that produces a bending moment M. If the depth of the section is doubled while the width and moment remain unchanged, how does the maximum bending stress change?

  1. It becomes one-half of the original value
  2. It becomes one-fourth of the original value Correct answer.
  3. It remains unchanged
  4. It becomes double the original value

Explanation

Bending stress is σ = M/Z, and the section modulus of a rectangle is bd²/6, so it varies with the square of the depth. Doubling the depth quadruples Z and therefore reduces the stress to one-fourth.

Question 48Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

In a vapour compression refrigeration cycle, the effect of subcooling the liquid refrigerant before it enters the expansion valve is to:

  1. Eliminate the need for an expansion device
  2. Increase the refrigerating effect per unit mass of refrigerant Correct answer.
  3. Increase the condenser pressure above the critical pressure
  4. Reduce the compressor work to zero

Explanation

Subcooling lowers the enthalpy of the liquid entering the evaporator, so more heat can be absorbed per kilogram of refrigerant and the refrigerating effect increases. The expansion valve is still required and the compressor work is not eliminated.

Question 49Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A polytechnic automation project uses a PLC ladder program in which a normally open contact of a start push button is wired in parallel with a normally open contact of the output relay. What function does this parallel contact perform?

  1. Latching or holding the output after the push button is released Correct answer.
  2. Resetting the output whenever the input is pressed
  3. Delaying the output by a fixed time interval
  4. Interlocking two outputs so both cannot run together

Explanation

Placing a contact of the output relay in parallel with the start input creates a seal-in or latch, so the output stays energised after the momentary push button is released. The stop contact, wired in series, is what breaks the circuit.

Question 50Engineering and Technology diploma admission (government and private polytechnic colleges of Uttar Pradesh)

A 3-phase, 400 V star-connected load draws a line current of 10 A at a power factor of 0.8 lagging. What is the total active power drawn by the load?

  1. 6.93 kW
  2. 4.00 kW
  3. 5.54 kW Correct answer.
  4. 8.00 kW

Explanation

For a balanced three-phase load, P = √3 V_L I_L cos φ = 1.732 × 400 × 10 × 0.8, which gives about 5542 W or 5.54 kW. The √3 factor arises from the relationship between line and phase quantities in a star connection.