JKSSB Refrigerator Mechanic 2025 Solved Question Paper

Question 1

Which of the following is NOT a basic refrigeration cycle?

Accepted Answer

Option D: Electrical compression. Vapour compression, vapour absorption, thermo-acoustic, and gas-cycle refrigeration are established thermodynamic cycles; 'Electrical compression' is not a thermodynamic refrigeration cycle.

Question 2

Identify the ongoing operation in the given diagram showing a hand tap inserted into a drilled hole with a tap wrench.

Accepted Answer

Option C: Tapping. Tapping is the mechanical machining operation of cutting internal screw threads in a pre-drilled hole using a tap and tap wrench.

Question 3

In sheet metal work, the angle of the V-notch is typically represented as X. What is the value of X?

Accepted Answer

Option A: 90°. In sheet metal pattern development, a standard $90^\circ$ V-notch is cut at the corners to allow clean right-angle bending without overlapping edges.

Question 4

For air with a relative humidity of 80%

Accepted Answer

Option B: The dew point temperature is less than wet bulb temperature. For any unsaturated moist air ($RH < 100\%$), the psychrometric temperature hierarchy is strictly: $	ext{Dew Point Temperature (DPT)} < 	ext{Wet Bulb Temperature (WBT)} < 	ext{Dry Bulb Temperature (DBT)}$.

Question 5

Arrange the following AC repair tools in order of price (lowest to highest).
1. Refrigerant Gauge Set
2. Digital Thermometer
3. Vacuum Pump
4. Refrigerant Recovery Machine
5. Manifold Gauge Set
Which of the above is/are correct?

Accepted Answer

Option B: 2, 5, 1, 3, 4. Tool price progression (lowest to highest): Digital Thermometer (2) -> Gauge Sets (5/1) -> Rotary Vane Vacuum Pump (3) -> Commercial Refrigerant Recovery Machine (4).

Question 6

During the chemical dehumidification process of air

Accepted Answer

Option B: Dry bulb temperature increases and specific humidity decreases. In chemical/adsorption dehumidification (using silica gel or activated alumina), moisture is adsorbed (latent heat released), causing specific humidity to decrease while dry bulb temperature (DBT) increases.

Question 7

What is the method of varying inductance in a coil?

Accepted Answer

Option A: Adjusting the core. Inductance $L = \frac{\mu N^2 A}{l}$ is varied physically by adjusting the position or magnetic permeability of the ferromagnetic core inside the coil.

Question 8

Match the List-I with the List-II and select the correct one.
List-I:
i. Saturated liquid
ii. Superheated vapour
iii. High pressure
iv. Dry saturated vapour

List-II:
1. Before entering the compressor
2. Before passing the condenser
3. Before entering the expansion valve
4. After passing through condenser

Which of the above is/are correct?

Accepted Answer

Option B: i-4, ii-2, iii-3, iv-1. In a standard VCR cycle: Saturated liquid = exiting condenser (i-4); Superheated vapour = discharge before condenser (ii-2); High pressure = high side before expansion valve (iii-3); Dry saturated vapour = exiting evaporator before compressor (iv-1).

Question 9

Which process is being performed with a capacitor using a resistor placed across its terminals?

Accepted Answer

Option D: Discharging. Connecting a high-wattage bleed resistor across the terminals of a charged capacitor safely bleeds off stored electric charge (discharging) to prevent electrical shock.

Question 10

When two resistors, $R_1$ and $R_2$, are connected in series, what is their combined resistance?

Accepted Answer

Option B: $(R_1 + R_2)$ ohms. In a series circuit, total equivalent resistance is the arithmetic sum of individual resistances: $R_{eq} = R_1 + R_2$.

Question 11

The item consists of two statements; one labeled as Assertion (A) and other as Reason.
Assertion (A): Hydrogen is chosen in Electrolux refrigerator
Reason (R): It is non-corrosive and insoluble
Select the answers to these items using the code given below:

Accepted Answer

Option A: Both A and R are true and R is the correct explanation of A. In the 3-fluid Electrolux (Platen-Munters) absorption refrigerator, hydrogen is introduced into the evaporator to lower the partial pressure of ammonia (inducing evaporation at low temperature) because hydrogen is lightweight, chemically inert, non-corrosive, and insoluble in water.

Question 12

Match the tool with its purpose in AC repair and select the correct answer for given below.
Tool:
1. Core Tool
2. Vacuum Pump
3. O-Ring Tool
4. Tube Bender
5. Pressure Gauge

Purpose:
i. Used for adding refrigerant to the system.
ii. Creates a vacuum to remove air and moisture from the AC system.
iii. Used to remove or install O-rings in AC system components.
iv. Helps in bending tubing to fit the AC system layout.
v. Measures the pressure in the AC system to diagnose problems.

Choose the correct option:

Accepted Answer

Option B: 1-iii, 2-ii, 3-i, 4-iv, 5-v. 1-iii (Core/O-ring servicing), 2-ii (Vacuum pump evacuates moisture), 3-i/iii (O-ring tool), 4-iv (Tube bender curves copper tubing), 5-v (Pressure gauge measures system pressure).

Question 13

Which refrigerant is considered ozone-friendly?

Accepted Answer

Option B: R-134a. R-134a (Tetrafluoroethane) is an HFC containing zero chlorine atoms, giving it an Ozone Depletion Potential (ODP) of 0.

Question 14

In gas welding, the maximum flame temperature occurs

Accepted Answer

Option B: At the inner cone. In an oxy-acetylene neutral flame, the highest combustion temperature (approximately $3100^\circ	ext{C}$ to $3300^\circ	ext{C}$) is concentrated at the tip of the inner luminous cone.

Question 15

Match the new air conditioning technologies with their descriptions.
AC Technology:
i. Inverter Technology
ii. Smart AC
iii. Variable Refrigerant Flow
iv. Portable AC

Feature:
1. Reduces energy consumption by adjusting compressor speed.
2. Allows remote control via smartphones, voice assistants, and AI.
3. Distributes refrigerant to multiple indoor units, maintaining efficiency.
4. Compact and mobile unit for cooling smaller spaces.

Which of the above is/are correct?

Accepted Answer

Option A: i-1, ii-2, iii-3, iv-4. Inverter -> Variable compressor speed (i-1), Smart AC -> IoT/Smartphone control (ii-2), VRF -> Multi-split zoned refrigerant distribution (iii-3), Portable AC -> Mobile compact cooling (iv-4).

Question 16

Which of the following statements are true regarding industrial safety and fire fighting in occupational health?
1. Industrial safety focuses on the prevention of injuries and accidents in the workplace.
2. Fire fighting techniques are primarily concerned with preventing damage to machinery.
3. Occupational health safety includes physical, chemical, and biological hazards at the work-place.
4. Fire safety measures in an industrial setting do not require employee training.

Which of the above statements is/are true?

Accepted Answer

Option A: 1 and 3 only. Statements 1 and 3 are correct. Fire safety prioritizes preservation of human life over machinery, and employee training is mandatory.

Question 17

Water at 42°C is sprayed into a stream of air at atmospheric pressure, dry bulb temperature of 40°C and a wet bulb temperature of 20°C. The air leaving the spray humidifier is not saturated. Which of the following statements is true?

Accepted Answer

Option B: Air gets heated and humidified. Because the spray water temperature ($42^\circ	ext{C}$) exceeds the air dry bulb temperature ($40^\circ	ext{C}$), sensible heat transfers from water to air (heating) while water evaporates into the air stream (humidification).

Question 18

What is used to provide thermal insulation in refrigeration systems?

Accepted Answer

Option C: Polystyrene. Expanded/Extruded Polystyrene (EPS/XPS) and Polyurethane Foam (PUF) are closed-cell thermal insulators widely used in domestic refrigerator cabinets and cold rooms.

Question 19

Which is the correct combination for psychrometric process?
List-I:
i. Activated alumina
ii. Water injection
iii. Steam injection
iv. Hygroscopic

List-II:
1. Heating and humidification
2. Heating and dehumidification
3. Cooling and dehumidification
4. Cooling and humidification

Choose the correct Answer:

Accepted Answer

Option B: i-2, ii-4, iii-1, iv-3. Activated alumina -> Chemical dehumidification / Heating & dehumidification (i-2); Water injection -> Evaporative cooling & humidification (ii-4); Steam injection -> Heating & humidification (iii-1).

Question 20

Consider the following statements about spray humidification process.
1. Dry bulb temperature is increased
2. Total heat process remains same
Choose the correct statement is

Accepted Answer

Option B: 2 only. In adiabatic spray humidification (recirculated water at WBT), sensible heat is converted into latent heat; hence Dry Bulb Temperature decreases while total enthalpy (heat content) remains approximately constant ($h = 	ext{constant}$).

Question 21

What role does the accumulator play in a refrigerator system?

Accepted Answer

Option D: Prevents liquid flood back to compressor. A suction line accumulator traps unevaporated liquid refrigerant exiting the evaporator, ensuring that only dry gas enters the compressor suction port, preventing liquid slugging.

Question 22

What could cause a reduction in the suction pressure of a refrigeration system?

Accepted Answer

Option A: Chocked air filter. A choked air filter restricts airflow over the evaporator coil, reducing heat absorption and causing lower evaporating temperature and reduced suction pressure.

Question 23

Match List-I (Process) with List-II (Type) for air refrigeration cycle and select the correct answer using the codes given below the lists:
List -I:
i. Compression
ii. Heat rejection
iii. Expansion
iv. Heat absorption

List-II:
1. Isobaric
2. Isothermal
3. Isentropic
4. Isenthalpic

Which of the above is/are correct?

Accepted Answer

Option B: i-3, ii-1, iii-3, iv-1. In the standard Bell-Coleman / Reversed Brayton air cycle: Compression = Isentropic ($s=	ext{const}$, i-3); Heat rejection = Isobaric ($P=	ext{const}$, ii-1); Expansion = Isentropic ($s=	ext{const}$, iii-3); Heat absorption = Isobaric ($P=	ext{const}$, iv-1).

Question 24

Arrange the following AC systems in ascending order of cooling capacity (BTU/h).
1. Portable Air Conditioner
2. Window Air Conditioner
3. Split Air Conditioner
4. Central Air Conditioning System
Which of the above is/are correct?

Accepted Answer

Option A: 1, 2, 3, 4. Ascending cooling capacity: Portable AC (8,000–14,000 BTU/h, 1) -> Window AC (9,000–24,000 BTU/h, 2) -> Split AC (12,000–36,000 BTU/h, 3) -> Central AC (60,000 to >500,000 BTU/h, 4).

Question 25

Which defective component leads to the formation of frost in a water cooler?

Accepted Answer

Option B: Thermostat. A stuck or defective thermostat fails to open contacts when water reaches the setpoint, causing continuous compressor running and freezing/frosting of the water coil.

Question 26

Consider the following statements
1. First law of thermodynamics states that energy is conserved
2. The second law of thermodynamics state that though energy is conserved its quality improves.
3. The second law of thermodynamics states that though energy is conserved its quality degrades.
4. First law of thermodynamics can tell about the feasibility of the process
Which of the above is/are correct?

Accepted Answer

Option C: 1 and 3. Statements 1 and 3 are correct. The First Law states conservation of energy; the Second Law states that in any spontaneous real process, entropy increases and energy quality degrades (exergy destruction).

Question 27

What state is the refrigerant in when it exits the dry expansion evaporator?

Accepted Answer

Option B: Only vapour. In a dry expansion (DX) evaporator, all liquid refrigerant is completely vaporized and slightly superheated ($5^\circ	ext{C}-8^\circ	ext{C}$) before exiting as 100% superheated vapour.

Question 28

Match the type of thermometer and their properties.
Thermometer:
i. Constant volume thermometer
ii. Constant pressure thermometer
iii. Electric resistance thermometer
iv. Thermocouple

Thermometric property:
1. Volume
2. Pressure
3. EMF
4. Resistance

Which is the above are correct?

Accepted Answer

Option A: i-2, ii-1, iii-4, iv-3. Constant volume -> Pressure ($P$, i-2); Constant pressure -> Volume ($V$, ii-1); Resistance thermometer -> Resistance ($R$, iii-4); Thermocouple -> Seebeck electromotive force ($EMF$, iv-3).

Question 29

The statements concern psychometric chart.
1. Constant relative humidity lines are uphill straight lines to the right
2. Constant wet bulb temperature lines are downhill straight lines to the right
3. Constant specific volume lines are downhill straight lines to the right
4. Constant enthalpy lines are coincident with constant dry bulb temperature lines
Which of the statements are correct?

Accepted Answer

Option A: 2 and 3. On a standard psychrometric chart: Constant relative humidity lines are curved lines; Constant WBT lines and constant specific volume lines slope downwards to the right (downhill straight lines).

Question 30

What is the primary characteristic of an air-cooled condenser used in commercial refrigeration systems?

Accepted Answer

Option B: It relies on air circulation to dissipate heat. Air-cooled condensers rely entirely on forced or natural air circulation driven by fans across finned tubes to reject latent heat of condensation directly to ambient air.

Question 31

Match the components in Column A (Electronic component) with column B (descriptions).
Column-A:
i. Rectifier
ii. Transistor
iii. Thermistor
iv. Transducer

Column-B:
1. Converts electrical energy into another form of energy or vice versa (e.g., sound, pressure).
2. Regulates current flow and can amplify electrical signals.
3. Converts AC into DC in power supply circuits.
4. Changes resistance significantly with changes in temperature.

Which is the above are correct?

Accepted Answer

Option D: i-3, ii-2, iii-1, iv-4. Rectifier -> AC to DC (i-3), Transistor -> Signal amplifier/switch (ii-2), Transducer -> Energy conversion (iv-1), Thermistor -> Temperature-dependent resistor (iii-4). Option D maps i-3, ii-2, iii-4, iv-1.

Question 32

Which of the following statements about AC Induction Motors are correct?
1. A single-phase AC motor is designed to run on both split-phase and capacitor start systems.
2. A squirrel cage motor is typically used for high-speed operations.
3. Slip ring motors are preferred for low torque applications.
4. Shaded-pole motors are used for high-power applications.
Which of the statements are correct?

Accepted Answer

Option A: 1 and 2 only. Statements 1 and 2 are correct. Shaded pole motors are low-power/low-efficiency, and slip ring motors are used for high starting torque applications.

Question 33

The heat removal rate from a refrigerated space and the power input to the compressor are 7.2 kW and 1.8 kW, respectively. The coefficient of performance (COP) of the refrigerator is

Accepted Answer

Option A: 4. Calculation: $	ext{COP} = \frac{	ext{Refrigeration Effect (Heat Removal Rate)}}{	ext{Work Input}} = \frac{7.2	ext{ kW}}{1.8	ext{ kW}} = 4.0$.

Question 34

A measure of feeling warmth or coolness by the human body in response to the air temperature, moisture content and air motion is called

Accepted Answer

Option B: Effective temperature. Effective Temperature (ET) is an empirical sensory index combining dry bulb temperature, relative humidity, and air velocity to evaluate human thermal comfort sensations.

Question 35

Which is the correct combination for given below?
Device:
i. Domestic Refrigerator
ii. Commercial Refrigerator
iii. Refrigerant
iv. Evaporator
v. Compressor

Use:
1. Used for cooling in homes, typically compact and energy efficient.
2. Circulates refrigerant by compressing it to a high-pressure, high-temperature state.
3. Larger systems used in stores or restaurants for preserving large quantities of food.
4. The medium that absorbs heat from the system and releases it outside.
5. The component where the refrigerant absorbs heat, causing cooling inside the system.

Choose the correct option:

Accepted Answer

Option C: i-1, ii-3, iii-4, iv-5, v-2. Domestic fridge -> Home cooling (i-1), Commercial fridge -> Large food preservation (ii-3), Refrigerant -> Heat transport fluid (iii-4), Evaporator -> Heat absorption (iv-5), Compressor -> Compression & circulation (v-2).

Question 36

Which of the following is commonly used in the descaling procedure of cooling towers?

Accepted Answer

Option A: Hydrochloric acid. Inhibited Hydrochloric acid ($HCl$) or sulfamic acid solutions are routinely used to dissolve calcium carbonate and mineral scale deposits in cooling tower heat exchangers.

Question 37

Which of the following method (s) is/are adopted in the design of air duct system?
1. Velocity reduction method
2. Equal friction method
3. Static regain method
Select the correct answer using the codes given below:

Accepted Answer

Option D: 1, 2 and 3. The three standard engineering methods for sizing HVAC ductwork systems are: Velocity Reduction, Equal Friction, and Static Regain.

Question 38

Match the components with their commonly used materials.
Component:
i. Condenser
ii. Fin
iii. Valve
iv. Body

Material of construction:
1. Copper or aluminium for efficient heat transfer and durability.
2. Aluminium for lightweight and excellent thermal conductivity.
3. Brass or stainless steel for strength and corrosion resistance in controlling refrigerant flow.
4. Steel or aluminium for structural support and durability.

Choose the correct option:

Accepted Answer

Option D: i-1, ii-2, iii-3, iv-4. Condenser tubes -> Copper/Aluminium (i-1), Fins -> Aluminium sheets (ii-2), Valves -> Brass/Stainless steel (iii-3), Body casing -> Galvanized Steel/Aluminium (iv-4).

Question 39

What could be the reason for a compressor continuing to run after its body has overheated?

Accepted Answer

Option C: Failure of OLP. The Overload Protector (OLP) is a bimetallic safety device designed to cut power when compressor motor current or temperature exceeds limits; if OLP fails closed, overheating persists.

Question 40

Why is a starting capacitor used in the electrical circuit of a deep freezer?

Accepted Answer

Option B: Increase staring torque. A start capacitor creates an auxiliary phase displacement approaching $90^\circ$ to provide high initial starting torque for compressor startup against differential head pressure.

Question 41

Identify the correct pairings of transformer types and their applications.
1. Auto transformer - Used for voltage regulation in large power systems.
2. Current transformer - Used for measuring current in high voltage circuits.
3. Potential transformer - Used in AC transmission to step up voltage.
4. Three-phase inverter - Used in electrical systems to convert AC to DC.
Which of the above is/are correct?

Accepted Answer

Option A: 1 and 2 only. Statements 1 and 2 are correct. Potential transformers are instrument transformers stepping down high voltage for metering; inverters convert DC to AC.

Question 42

Match List-I (Refrigerant) with List-II (miscibility with oil) and select the correct answer using the codes given below the lists:
List -I:
i. R-11
ii. CO2
iii. R-22

List-II:
1. Partial miscibility
2. Good miscibility
3. No miscibility

Which of the above is/are correct?

Accepted Answer

Option A: i-2, ii-3, iii-1. Refrigerant oil miscibility: R-11 / R-12 (CFCs) = Fully miscible with mineral oil (2); $CO_2$ = Non-miscible with standard mineral oil (3); R-22 (HCFC) = Partially miscible (1).

Question 43

The phenomenon that enables cooling towers to cool water to a temperature below the dry bulb temperature of air is termed as

Accepted Answer

Option B: Adiabatic evaporative cooling. Cooling towers operate via adiabatic evaporative cooling, where a small portion ($1-2\%$) of the circulating water evaporates, extracting latent heat and cooling water down towards the ambient Wet Bulb Temperature.

Question 44

Which of the following factors are to be considered while selecting a microcontroller?
1. Memory requirements
2. Processing speed required
3. Number of input/output pins
Which of the above statements are correct?

Accepted Answer

Option D: 1, 2 and 3. Microcontroller selection for intelligent HVAC control boards requires evaluating flash/RAM memory, clock speed/MIPS, I/O pin count, timers, and ADC channels.

Question 45

What function does the damper serve in a frost-free refrigerator?

Accepted Answer

Option B: Adjusting the air flow. An air damper (manual or motorized thermostat-controlled baffle) modulates the volume of chilled air circulating from the freezer compartment into the fresh food refrigerator compartment.

Question 46

In an inverter refrigerator, what role does the pulse-width modulation (PWM) control technique play?

Accepted Answer

Option C: As speed control. PWM inverters vary the voltage and frequency supplied to the BLDC compressor motor to achieve stepless variable speed control based on thermal cooling demand.

Question 47

Match the air conditioning problems with their respective solutions and select correct one.
Problem:
i. Insufficient cooling
ii. Water leakage from the indoor unit
iii. Unusual noises from the AC
iv. AC not turning on
v. Bad odour from the AC

Possible Solution:
1. Check and clean the air filters or ensures adequate refrigerant levels.
2. Inspect and clean the drainage system; ensure no blockages.
3. Verify electrical connections, the thermostat settings, and the power supply.
4. Clean the evaporator coil and the air filters; ensure there is no mold or debris build-up.
5. Inspect for loose components or damaged fan blades and tighten or repair as needed.

Choose the correct option:

Accepted Answer

Option D: i-1, ii-2, iii-5, iv-3, v-4. Insufficient cooling -> Clean filter/refrigerant (i-1), Water leakage -> Clean drain pipe (ii-2), Unusual noise -> Tighten loose fan parts (iii-5), Not turning on -> Electrical power check (iv-3), Bad odour -> Clean mold on evaporator coil (v-4).

Question 48

Arrange the cooling technologies in descending order of energy efficiency.
1. Air-source heat pump
2. Water-cooled chiller
3. Evaporative cooling system
4. Ground-source heat pump
Which of the above is/are correct?

Accepted Answer

Option C: 4 -> 2 -> 1 -> 3. Theoretical and seasonal COP hierarchy: Ground-Source Heat Pump (COP 4.5–6.0, 4) > High-efficiency Water-Cooled Chiller (COP 4.0–5.5, 2) > Air-Source Heat Pump (COP 3.0–4.0, 1) > Direct Evaporative Cooling (3).

Question 49

Match List-I (optimum design condition for comfort) with List-II (parameter value) and select the correct answer using the codes given below the lists:
List -I:
i. Effective temperature for Summer A/C
ii. Effective temperature for Winter A/C
iii. DBT for summer A/C

List-II:
1. 22 (°C)
2. 21.7 (°C)
3. 25 (°C)

Which of the above is/are correct?

Accepted Answer

Option A: i-2, ii-1, iii-3. ASHRAE standard comfort parameters: Summer Effective Temperature $\approx 21.7^\circ	ext{C}$ (i-2), Winter Effective Temperature $\approx 20^\circ	ext{C}-22^\circ	ext{C}$ (ii-1), Summer Design DBT $\approx 24^\circ	ext{C}-25^\circ	ext{C}$ (iii-3).

Question 50

Which of the following correctly describes thermal insulation types and their properties?
1. Fiberglass insulation is known for its high thermal conductivity and is primarily used for soundproofing.
2. Mineral wool insulation provides both thermal and fire resistance.
3. Aerogel insulation has one of the lowest thermal conductivities, making it ideal for extreme conditions.
4. Spray foam insulation is often used in industrial applications due to its low durability.
Which of the statement is/are correct?

Accepted Answer

Option B: 2 and 3 only. Statements 2 and 3 are correct. Fiberglass has low (not high) thermal conductivity, and spray foam insulation possesses high durability.

Question 51

Which type of refrigeration system is typically used in an ice plant?

Accepted Answer

Option B: Vapor compression refrigeration system. Commercial ice manufacturing plants utilize large-scale ammonia ($NH_3$ / R-717) Vapour Compression Refrigeration systems with brine tanks.

Question 52

What is the primary advantage of the Cassette Type Air Conditioning system?

Accepted Answer

Option B: It is ceiling-mounted, ensuring efficient and uniform cooling distribution in rooms.. Cassette indoor units mount flush into false ceilings, featuring 4-way or 360-degree motorized louvers that deliver uniform draft-free air distribution across large open spaces.

Question 53

Match List-I with List-II and select the correct answer using the codes given below the lists:
List -I:
i. Fans
ii. Blowers
iii. Air washer

List-II:
1. System that increases air pressure and forces air through ducts.
2. Device that regulates the flow of air and ensures proper ventilation
3. Equipment used to cool, humidify, and clean the air through water spraying.

Which of the above is/are correct?

Accepted Answer

Option A: i-2, ii-1, iii-3. Fans -> Low-pressure air circulation/ventilation (i-2); Blowers -> Higher-pressure centrifugal air propulsion through ductwork (ii-1); Air washer -> Chamber cooling, humidifying, and cleaning air via water spray (iii-3).

Question 54

Which property is considered ideal for POE lubricant in refrigeration systems?

Accepted Answer

Option B: Miscible with HFCs. Polyolester (POE) synthetic oils are formulated specifically because they exhibit excellent chemical miscibility with hydrofluorocarbon (HFC) refrigerants like R-134a and R-410A.

Question 55

Which of the following is a correct characteristic of a window AC unit?
1. It is ideal for large, open spaces and requires separate ductwork.
2. It is generally more energy-efficient than split systems in larger installations.
3. It is a self-contained unit and often used for cooling individual rooms.
4. It operates primarily on water-cooled condensers.
Which of the above statement are correct?

Accepted Answer

Option C: 3 only. Statement 3 is correct. A window AC is a packaged, self-contained single-chassis room air conditioner requiring no ductwork and utilizing an air-cooled condenser.

Question 56

In air-conditioning systems, air may be cooled and dehumidified by
1. Spraying chilled water to air in the form of fine mist.
2. Circulating chilled water or brine in a tube placed across the air flow.
3. Placing the evaporator coil across the air flow.
Which of the above statements are correct?

Accepted Answer

Option D: 1, 2 and 3. Cooling and dehumidification occurs whenever moist air contacts a cooling medium maintained below the air's dew point temperature, via chilled water spray (1), chilled water/brine coils (2), or direct expansion DX coils (3).

Question 57

In an arc welding process, welding speed is doubled. Assuming all other process parameters to be constant, the cross sectional area of the weld bead will

Accepted Answer

Option D: Reduce by 50%. Weld bead volume per unit time $= A 	imes v = 	ext{constant wire feed rate}$. If welding travel speed $v$ is doubled, the cross-sectional bead area $A$ is reduced by $50\%$.

Question 58

Match List-I (types of cooling tower) with List-II (operation) and select the correct answer using the codes given below the lists:
List -I:
i. Natural draft
ii. Induced draft
iii. Forced draft
iv. Cross flow

List-II:
1. Fan is installed centrally at the top
2. Based on free convection heat transfer
3. Hot water sprayed from the top
4. An exhaust fan placed at the base

Which of the above is/are correct?

Accepted Answer

Option A: i-2, ii-1, iii-4, iv-3. Natural draft -> Chimney effect / Free convection (i-2); Induced draft -> Suction fan mounted on top discharge (ii-1); Forced draft -> Blower fan mounted at the base intake (iii-4); Cross flow -> Air flows horizontally while water sprays vertically (iv-3).

Question 59

Arrange the following pressure control valves in ascending order based on their setpoint pressures:
1. Back-pressure regulator
2. Relief valve
3. Pressure-reducing valve
4. Pressure-relief switch
Which of the above is/are correct?

Accepted Answer

Option B: 3, 1, 4, 2. Ascending setpoint pressure order: Pressure-reducing regulator (low side, 3) -> Evaporator back-pressure regulator (1) -> High-pressure cutout switch (4) -> Mechanical emergency relief valve (highest safety margin, 2).

Question 60

How does the capillary length change when retrofitting a CFC-based unit with an HFC-based unit?

Accepted Answer

Option D: 20% more of old capillary. When retrofitting from R-12 to R-134a, R-134a operates at slightly higher head pressures and lower mass flow rates, requiring approximately 15–20% longer capillary tube (or smaller internal diameter) to maintain correct expansion pressure drop.

Question 61

Match List -I (Refrigerator problems) with List-II (possible reason) and select the correct answer using the codes given below the lists:
List -I:
i. Uneven Cooling
ii. Excessive Frost Buildup
iii. Water Leakage
iv. Door Seal Problems

List-II:
1. Faulty defrost system
2. Blocked air vents
3. Cracks or tears on gasket
4. Clogs formation or leaks

Which of the above is/are correct?

Accepted Answer

Option A: i-2, ii-1, iii-4, iv-3. Uneven cooling -> Blocked vents (i-2), Excessive frost -> Faulty defrost heater/bi-metal (ii-1), Water leakage -> Clogged drain hole (iii-4), Door seal issues -> Torn gasket (iv-3).

Question 62

The moisture in a refrigerant is removed by

Accepted Answer

Option D: Driers. Filter driers containing solid desiccant cores (molecular sieves or activated alumina) chemically adsorb moisture and filter particulates from circulating liquid refrigerant.

Question 63

Which one of the following is a CFC refrigerant?

Accepted Answer

Option C: R502. R-502 is a chlorofluorocarbon azeotropic blend (R-22 / R-115, containing CFC R-115); R744 is $CO_2$, R290 is Propane, R718 is Water.

Question 64

Which of the following statements about the construction of an evaporator is true?
1. The evaporator transfers heat from the refrigerant to the surrounding air, cooling the air in the process.
2. The direct expansion (DX) evaporator is used only in industrial refrigeration systems.
3. Flooded evaporators operate by maintaining a constant refrigerant level in the system.
4. The efficiency of an evaporator is not influenced by the flow rate of the refrigerant.
Which of the above statement are correct?

Accepted Answer

Option C: 3 only. Statement 3 is correct. Statement 1 is inverted (heat transfers from air to boiling refrigerant); DX is used in domestic/commercial units; flow rate strongly impacts heat transfer coefficient.

Refrigerator Mechanic2025

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JKSSB — Refrigerator Mechanic (2025)

Which of the following is NOT a basic refrigeration cycle?

Identify the ongoing operation in the given diagram showing a hand tap inserted into a drilled hole with a tap wrench.

In sheet metal work, the angle of the V-notch is typically represented as X. What is the value of X?

For air with a relative humidity of 80%

Arrange the following AC repair tools in order of price (lowest to highest).1. Refrigerant Gauge Set2. Digital Thermometer3. Vacuum Pump4. Refrigerant Recovery Machine5. Manifold Gauge SetWhich of the above is/are correct?

During the chemical dehumidification process of air

What is the method of varying inductance in a coil?

Which process is being performed with a capacitor using a resistor placed across its terminals?

When two resistors, R1R_1R1​ and R2R_2R2​, are connected in series, what is their combined resistance?

The item consists of two statements; one labeled as Assertion (A) and other as Reason.Assertion (A): Hydrogen is chosen in Electrolux refrigeratorReason (R): It is non-corrosive and insolubleSelect the answers to these items using the code given below:

Which refrigerant is considered ozone-friendly?

In gas welding, the maximum flame temperature occurs

Water at 42°C is sprayed into a stream of air at atmospheric pressure, dry bulb temperature of 40°C and a wet bulb temperature of 20°C. The air leaving the spray humidifier is not saturated. Which of the following statements is true?

What is used to provide thermal insulation in refrigeration systems?

Which is the correct combination for psychrometric process?List-I:i. Activated aluminaii. Water injectioniii. Steam injectioniv. HygroscopicList-II:1. Heating and humidification2. Heating and dehumidification3. Cooling and dehumidification4. Cooling and humidificationChoose the correct Answer:

Consider the following statements about spray humidification process.1. Dry bulb temperature is increased2. Total heat process remains sameChoose the correct statement is

What role does the accumulator play in a refrigerator system?

What could cause a reduction in the suction pressure of a refrigeration system?

Arrange the following AC systems in ascending order of cooling capacity (BTU/h).1. Portable Air Conditioner2. Window Air Conditioner3. Split Air Conditioner4. Central Air Conditioning SystemWhich of the above is/are correct?

Which defective component leads to the formation of frost in a water cooler?

What state is the refrigerant in when it exits the dry expansion evaporator?

Match the type of thermometer and their properties.Thermometer:i. Constant volume thermometerii. Constant pressure thermometeriii. Electric resistance thermometeriv. ThermocoupleThermometric property:1. Volume2. Pressure3. EMF4. ResistanceWhich is the above are correct?

What is the primary characteristic of an air-cooled condenser used in commercial refrigeration systems?

The heat removal rate from a refrigerated space and the power input to the compressor are 7.2 kW and 1.8 kW, respectively. The coefficient of performance (COP) of the refrigerator is

A measure of feeling warmth or coolness by the human body in response to the air temperature, moisture content and air motion is called

Which of the following is commonly used in the descaling procedure of cooling towers?

Which of the following method (s) is/are adopted in the design of air duct system?1. Velocity reduction method2. Equal friction method3. Static regain methodSelect the correct answer using the codes given below:

What could be the reason for a compressor continuing to run after its body has overheated?

Why is a starting capacitor used in the electrical circuit of a deep freezer?

Match List-I (Refrigerant) with List-II (miscibility with oil) and select the correct answer using the codes given below the lists:List -I:i. R-11ii. CO2iii. R-22List-II:1. Partial miscibility2. Good miscibility3. No miscibilityWhich of the above is/are correct?

The phenomenon that enables cooling towers to cool water to a temperature below the dry bulb temperature of air is termed as

Which of the following factors are to be considered while selecting a microcontroller?1. Memory requirements2. Processing speed required3. Number of input/output pinsWhich of the above statements are correct?

What function does the damper serve in a frost-free refrigerator?

In an inverter refrigerator, what role does the pulse-width modulation (PWM) control technique play?

Arrange the cooling technologies in descending order of energy efficiency.1. Air-source heat pump2. Water-cooled chiller3. Evaporative cooling system4. Ground-source heat pumpWhich of the above is/are correct?

Which type of refrigeration system is typically used in an ice plant?

What is the primary advantage of the Cassette Type Air Conditioning system?

Which property is considered ideal for POE lubricant in refrigeration systems?

In air-conditioning systems, air may be cooled and dehumidified by1. Spraying chilled water to air in the form of fine mist.2. Circulating chilled water or brine in a tube placed across the air flow.3. Placing the evaporator coil across the air flow.Which of the above statements are correct?

In an arc welding process, welding speed is doubled. Assuming all other process parameters to be constant, the cross sectional area of the weld bead will

Arrange the following pressure control valves in ascending order based on their setpoint pressures:1. Back-pressure regulator2. Relief valve3. Pressure-reducing valve4. Pressure-relief switchWhich of the above is/are correct?

How does the capillary length change when retrofitting a CFC-based unit with an HFC-based unit?

The moisture in a refrigerant is removed by

Which one of the following is a CFC refrigerant?

A Comfort Air Conditioning System primarily focuses on:

Which of the following materials is commonly used for ductwork in HVAC systems?

Why the filler metal does not melt and flow into the joint in bronze welding of copper?

Match the Column A (Refrigerant) with Column B (colour code).Column-A:i. Ammoniaii. Methyl Chlorideiii. Freon-12iv. Freon-22v. Freon-113Column-B:1. Light Blue2. Orange3. White4. Green5. PurpleChoose the correct option:

What is the advantage of super heating the vapour in suction line?

Which component these symbols represent in electrical schematics (showing two parallel lines with curved plates and polarity marks)?

Arrange the refrigerants in descending order of Global Warming Potential (GWP).1. R-410A2. R-134a3. R-224. R-32Which of the above is/are correct?

What is the primary function of a Heat Recovery Wheel (HRW) in an HVAC system?

What is the name of component used in electronic circuit shown in the diagram with a 3-pin TO-92 plastic package?

Which of the following is an advantage of Thermo-Acoustic refrigeration over conventional refrigeration systems?

The Bypass Factor of an air conditioning system refers to:

Which tool is used for bending, seaming and forming of sheet metal?

Arrange the following refrigerant flow control devices in descending order of their capacity to handle flow rate:1. Solenoid valve2. Capillary tube3. Thermostatic expansion valve (TXV)4. Electronic expansion valve (EEV)Which of the above is/are correct?

Which method is commonly used to control the capacity of commercial compressors?

Which of the following is true about the Electronic Expansion Valve (EEV)?

What is the part marked as X in the flaring set diagram (pointing to the clamping bar with precision chamfered holes)?

What is the part marked as X in the vapour compression system diagram (pointing to the narrow coiled metering line connecting condenser outlet to evaporator)?

Which of the following is a key characteristic of scroll compressors used in commercial refrigeration?

Arrange the temperature in ascending order for a vapor-compression refrigeration cycle:1. Condensing temperature range (°C)2. Evaporating temperature range (°C)3. Superheat temperature range (°C)4. Subcooling temperature range (°C)Which of the above is/are correct?

Which of the following is a key advantage of a flooded chiller over a DX chiller?

Which material used for making integrated circuit?

Which process of copper tubing is in progress in the diagram showing a punch tool expanding the end of a copper tube into a cylindrical socket?

Arrange the following refrigeration and air conditioning repair tools by size (smallest to largest).1. Multimeter2. Refrigerant Recovery Machine3. Vacuum Pump4. Leak Detector5. Brazing TorchWhich of the above is/are correct?

Which substance absorbs heat and directly changes its state from solid to vapour?

Overcharging a refrigeration system with refrigerant can cause:

What is the main feature of a Precision Air Conditioning System?

In a typical starting procedure for a Central Air Conditioning Plant, which component should be started first?

In a Direct Expansion (DX) chiller, the refrigerant:

Moisture should be removed from refrigerants to avoid1. Compressor seal failure2. Freezing at the expansion valve3. Restriction to the refrigerant flow4. Corrosion of steel partsWhich of the above is correct?

Which component of a refrigeration system is used to control refrigerant flow?

Arrange the following materials by their max operating temp in descending order:1. Fiberglass2. PVC Louvers3. Aluminum Alloy Fan Blades4. Stainless Steel FastenersWhich of the above is/are correct?

Which type of compressor is generally used in larger refrigeration systems?

Match List -I with List-II and select correct answerList-I:i. Bell Coleman Refrigerationii. Reverse Carnot Cycleiii. Milk Chilling Plantiv. Superheating Refrigeration CycleList-II:1. Expansion Cylinder2. Heat Pump3. Brine4. Decrease COPChoose the correct Answer:

Arrange the following AC repair tools in order of price (lowest to highest).
1. Refrigerant Gauge Set
2. Digital Thermometer
3. Vacuum Pump
4. Refrigerant Recovery Machine
5. Manifold Gauge Set
Which of the above is/are correct?

When two resistors, $R_1$ and $R_2$ , are connected in series, what is their combined resistance?

The item consists of two statements; one labeled as Assertion (A) and other as Reason.
Assertion (A): Hydrogen is chosen in Electrolux refrigerator
Reason (R): It is non-corrosive and insoluble
Select the answers to these items using the code given below:

Consider the following statements about spray humidification process.
1. Dry bulb temperature is increased
2. Total heat process remains same
Choose the correct statement is

Arrange the following AC systems in ascending order of cooling capacity (BTU/h).
1. Portable Air Conditioner
2. Window Air Conditioner
3. Split Air Conditioner
4. Central Air Conditioning System
Which of the above is/are correct?

Match the type of thermometer and their properties.
Thermometer:
i. Constant volume thermometer
ii. Constant pressure thermometer
iii. Electric resistance thermometer
iv. Thermocouple

Thermometric property:
1. Volume
2. Pressure
3. EMF
4. Resistance

Which is the above are correct?

Which of the following method (s) is/are adopted in the design of air duct system?
1. Velocity reduction method
2. Equal friction method
3. Static regain method
Select the correct answer using the codes given below:

Match List-I (Refrigerant) with List-II (miscibility with oil) and select the correct answer using the codes given below the lists:
List -I:
i. R-11
ii. CO2
iii. R-22

List-II:
1. Partial miscibility
2. Good miscibility
3. No miscibility

Which of the above is/are correct?

Which of the following factors are to be considered while selecting a microcontroller?
1. Memory requirements
2. Processing speed required
3. Number of input/output pins
Which of the above statements are correct?

Arrange the cooling technologies in descending order of energy efficiency.
1. Air-source heat pump
2. Water-cooled chiller
3. Evaporative cooling system
4. Ground-source heat pump
Which of the above is/are correct?

In air-conditioning systems, air may be cooled and dehumidified by
1. Spraying chilled water to air in the form of fine mist.
2. Circulating chilled water or brine in a tube placed across the air flow.
3. Placing the evaporator coil across the air flow.
Which of the above statements are correct?

Arrange the following pressure control valves in ascending order based on their setpoint pressures:
1. Back-pressure regulator
2. Relief valve
3. Pressure-reducing valve
4. Pressure-relief switch
Which of the above is/are correct?

Match the Column A (Refrigerant) with Column B (colour code).
Column-A:
i. Ammonia
ii. Methyl Chloride
iii. Freon-12
iv. Freon-22
v. Freon-113

Column-B:
1. Light Blue
2. Orange
3. White
4. Green
5. Purple

Choose the correct option:

Arrange the refrigerants in descending order of Global Warming Potential (GWP).
1. R-410A
2. R-134a
3. R-22
4. R-32
Which of the above is/are correct?

Arrange the following refrigerant flow control devices in descending order of their capacity to handle flow rate:
1. Solenoid valve
2. Capillary tube
3. Thermostatic expansion valve (TXV)
4. Electronic expansion valve (EEV)
Which of the above is/are correct?

Arrange the temperature in ascending order for a vapor-compression refrigeration cycle:
1. Condensing temperature range (°C)
2. Evaporating temperature range (°C)
3. Superheat temperature range (°C)
4. Subcooling temperature range (°C)
Which of the above is/are correct?

Arrange the following refrigeration and air conditioning repair tools by size (smallest to largest).
1. Multimeter
2. Refrigerant Recovery Machine
3. Vacuum Pump
4. Leak Detector
5. Brazing Torch
Which of the above is/are correct?

Moisture should be removed from refrigerants to avoid
1. Compressor seal failure
2. Freezing at the expansion valve
3. Restriction to the refrigerant flow
4. Corrosion of steel parts
Which of the above is correct?

Arrange the following materials by their max operating temp in descending order:
1. Fiberglass
2. PVC Louvers
3. Aluminum Alloy Fan Blades
4. Stainless Steel Fasteners
Which of the above is/are correct?

Match List -I with List-II and select correct answer
List-I:
i. Bell Coleman Refrigeration
ii. Reverse Carnot Cycle
iii. Milk Chilling Plant
iv. Superheating Refrigeration Cycle

List-II:
1. Expansion Cylinder
2. Heat Pump
3. Brine
4. Decrease COP

Choose the correct Answer:

Arrange the following pressure control devices in ascending order based on their typical operating pressure range:
1. Evaporator pressure regulator
2. Condenser pressure regulator
3. High-pressure cutout switch
4. Low-pressure cutout switch
Which of the above is/are correct?