# Mechanical Quiz Set A

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Quizzes Created: 6 | Total Attempts: 4,141
Questions: 100 | Attempts: 952

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• 1.

### An assembly consisting of a pulley wheel, side plates, shaft, and bearings over which a cable or roped is passed.

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

C. Sheave
Explanation
A sheave is a component of an assembly that consists of a pulley wheel, side plates, shaft, and bearings. It is designed to have a cable or rope passed over it. Therefore, the correct answer is sheave.

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• 2.

### The effective room temperature in air-conditioning.

• A.

69-79 ËšF

• B.

68-74 ËšF

• C.

69-75 ËšF

• D.

65-70 ËšF

B. 68-74 ËšF
Explanation
The effective room temperature in air-conditioning is typically set between 68-74 ËšF. This range provides a comfortable and cool environment without being too cold or too warm. It allows for optimal cooling and helps maintain a balance between energy efficiency and comfort.

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• 3.

### A machine that converts mechanical energy into electrical energy is called?

• A.

Compressor

• B.

Alternator

• C.

Generator

• D.

Rectifier

C. Generator
Explanation
A machine that converts mechanical energy into electrical energy is called a generator. Generators work by using a rotating coil of wire within a magnetic field. As the coil spins, it creates a flow of electrons, generating an electric current. This process allows generators to produce electricity for various applications, such as powering homes, businesses, and other electrical devices. Therefore, the correct answer is Generator.

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• 4.

### Device used only to add humidity in the air

• A.

Humidifier

• B.

Compressor

• C.

Condenser

• D.

Evaporator

A. Humidifier
Explanation
A humidifier is a device specifically designed to add humidity or moisture to the air. It helps to increase the moisture levels in dry indoor environments, which can be beneficial for respiratory health, preventing dry skin, and reducing static electricity. Unlike a compressor, condenser, or evaporator, which are components of a refrigeration system and have different functions, a humidifier serves the sole purpose of adding humidity to the air.

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• 5.

### A machine that decreases the volume and increases the pressure of a quantity of air by mechanical means.

• A.

Humidifier

• B.

Compressor

• C.

Condenser

• D.

Evaporator

B. Compressor
Explanation
A compressor is a machine that decreases the volume and increases the pressure of a quantity of air by mechanical means. It is commonly used in various applications such as air conditioning systems, refrigeration units, and industrial processes. The compressor works by drawing in air and then compressing it, resulting in higher pressure and temperature. This process is essential for the efficient operation of many systems that require pressurized air or gas.

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• 6.

### A vessel where vapor is liquefied to remove heat.

• A.

Humidifier

• B.

Compressor

• C.

Condenser

• D.

Evaporator

C. Condenser
Explanation
A condenser is a vessel where vapor is liquefied to remove heat. In a condenser, the vapor is cooled and converted back into its liquid form by transferring heat to a surrounding medium, such as air or water. This process is commonly used in refrigeration and air conditioning systems, where the condenser plays a crucial role in removing heat from the system and maintaining the desired temperature.

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• 7.

### A process which refrigerant turns from liquid to gas

• A.

Humidifier

• B.

Compressor

• C.

Condenser

• D.

Evaporator

D. Evaporator
Explanation
The evaporator is the correct answer because it is the part of a refrigeration system where the refrigerant turns from a liquid to a gas. This process occurs when the warm air from the surroundings comes into contact with the cold refrigerant inside the evaporator coils. As the refrigerant absorbs heat from the air, it evaporates and changes into a gas state. This gas is then sent to the compressor to be pressurized and continue the refrigeration cycle.

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• 8.

### In elevator, these prevent the excessive car travel at the highest and lowest floor.

• A.

Knife Switch

• B.

Disconnect Switch

• C.

Handrail Guard Switch

• D.

Limit Switch

D. Limit Switch
Explanation
A limit switch is a device used in elevators to prevent the car from traveling beyond the highest and lowest floors. It is designed to detect when the elevator has reached its upper or lower limit and then automatically stop the car from moving further. This ensures that the elevator does not exceed its safe operating range and prevents any potential accidents or damage that could occur from excessive travel.

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• 9.

### This switch cuts off all current supply to the escalator for inspection, maintenance, or repairs.

• A.

Disconnect Switch

• B.

Knife Switch

• C.

Handrail Guard Switch

• D.

Limit Switch

B. Knife Switch
Explanation
A knife switch is a type of switch that is manually operated and is used to interrupt the flow of electric current. It is often used in situations where the current supply needs to be completely cut off, such as during inspection, maintenance, or repairs. By flipping the knife switch, all current supply to the escalator can be disconnected, allowing for safe and efficient work to be carried out.

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• 10.

### In escalators, this is located at the bottom truss of the escalator and provided with on and off positions to stop or prevents the escalator from starting during maintenance service.

• A.

Knife Switch

• B.

Limit Switch

• C.

Handrail Guard Switch

• D.

Disconnect Switch

D. Disconnect Switch
Explanation
The disconnect switch is located at the bottom truss of an escalator and has on and off positions. It is used to stop or prevent the escalator from starting during maintenance service. This switch allows the escalator to be safely turned off and disconnected from its power source, ensuring the safety of maintenance personnel and preventing accidental operation while work is being done.

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• 11.

### In escalators, these stop the escalator if a foreign object becomes wedged at the guard.

• A.

Disconnect Switch

• B.

Knife Switch

• C.

Handrail Guard Switch

• D.

Limit Switch

C. Handrail Guard Switch
Explanation
The handrail guard switch is the correct answer because it is specifically designed to stop the escalator if a foreign object becomes wedged at the guard. This switch serves as a safety mechanism to prevent accidents or injuries caused by objects getting stuck in the handrail guard. By activating this switch, the escalator can be immediately stopped, ensuring the safety of the passengers and preventing any further damage to the escalator.

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• 12.

### A controller sensitive to the degree of moisture in the air.

• A.

Humidistat

• B.

Hygrostat

• C.

Thermostat

• D.

Hydronics

A. Humidistat
Explanation
A humidistat is a controller that is sensitive to the degree of moisture in the air. It is used to measure and control the humidity levels in a space. Unlike a thermostat, which controls temperature, a humidistat specifically focuses on the moisture content in the air. It can be used in various applications such as HVAC systems, humidifiers, and dehumidifiers. By monitoring and adjusting the humidity levels, a humidistat helps maintain a comfortable and healthy indoor environment.

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• 13.

### An Instrument which responds to changes in temperature, and directly or indirectly controlstemperature.

• A.

Humidistat

• B.

Thermosetting

• C.

Thermostat

• D.

Hydronics

C. Thermostat
Explanation
A thermostat is an instrument that responds to changes in temperature and can directly or indirectly control the temperature. It is commonly used in heating and cooling systems to maintain a desired temperature by turning the heating or cooling equipment on or off. The thermostat senses the current temperature and compares it to the desired temperature set by the user. If the current temperature is lower than the desired temperature, the thermostat will activate the heating system. If the current temperature is higher than the desired temperature, the thermostat will activate the cooling system. This allows for efficient temperature regulation in various environments.

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• 14.

### Another name for Humidistat.

• A.

Thermosetting

• B.

Hydronics

• C.

Thermostat

• D.

Hygrostat

D. Hygrostat
Explanation
A humidistat is a device used to measure and control humidity levels in the air. It is often used in conjunction with a dehumidifier or humidifier to maintain a desired level of humidity. The term "hygrostat" is another name for a humidistat, as both words refer to the same device. Therefore, the correct answer is "Hygrostat."

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• 15.

### The art and practice of heating and cooling with water.

• A.

Hydraulics

• B.

HypHonics

• C.

Hydronics

• D.

Hygrostat

C. Hydronics
Explanation
Hydronics is the correct answer because it refers to the art and practice of heating and cooling with water. This term specifically relates to the use of water as a medium for transferring heat in heating, ventilation, and air conditioning (HVAC) systems. It involves the circulation of water through pipes, radiators, and other components to regulate temperature. Hydraulics, hyphonics, and hygrostat are unrelated terms and do not involve the use of water for heating and cooling purposes.

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• 16.

### Descriptive of any material such as synthetic resin which hardens when heated or cured, and does not soften when reheated.

• A.

Humidistat

• B.

Thermosetting

• C.

Thermostat

• D.

Hydronics

B. Thermosetting
Explanation
Thermosetting is the correct answer because it accurately describes a material that hardens when heated or cured and does not soften when reheated. This term is commonly used to describe synthetic resins that undergo a chemical reaction when heated, resulting in a permanent change in their physical properties. Unlike thermoplastics, which soften when reheated, thermosetting materials retain their hardened state even when exposed to high temperatures again.

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• 17.

### What is the refrigerant name of R-12?

• A.

Difluoromethane

• B.

Dichlorodifluormethane

• C.

Chlorotrifluoromethane

• D.

Carbon tetrachloride

B. Dichlorodifluormethane
Explanation
Dichlorodifluormethane is the refrigerant name of R-12.

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• 18.

### Parts of an Escalator.

• A.

Main drive chain, step chain, handrail, drive chain, bottom sprocket main drive chain, step chain, handrail, drive chain

• B.

Main drive chain, safety shoe, handrail, drive chain, bottom sprocket

• C.

Main drive chain, step chain, handrail, drive chain, bottom sprocket

• D.

Main drive chain, step chain, handrail, weighing device, bottom sprocket

C. Main drive chain, step chain, handrail, drive chain, bottom sprocket
Explanation
The correct answer is main drive chain, step chain, handrail, drive chain, bottom sprocket. This is because an escalator consists of several important components that work together to transport people between different levels of a building. The main drive chain is responsible for powering the escalator, while the step chain moves the individual steps. The handrail provides support and safety for passengers. The drive chain is another component involved in the movement of the escalator. Finally, the bottom sprocket helps to guide and control the movement of the chains and steps.

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• 19.

### Under NBC, the clearance between the underside of the car and the bottom of the pit  shall not be less than ___.

• A.

558 mm

• B.

330 mm

• C.

600 mm

• D.

30 mm

C. 600 mm
Explanation
Under NBC (National Building Code), the clearance between the underside of the car and the bottom of the pit should be a minimum of 600 mm. This requirement ensures that there is sufficient space for the car to move smoothly and safely within the pit without any obstructions or risks of collisions. A larger clearance also allows for maintenance and repair work to be carried out under the car without any difficulties. Therefore, the correct answer is 600 mm.

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• 20.

### Under NBC, the minimum diameter of hoisting and counterweight rope.

• A.

558 mm

• B.

330 mm

• C.

600 mm

• D.

30 mm

D. 30 mm
Explanation
The given options provide different values for the minimum diameter of hoisting and counterweight rope under NBC. However, the correct answer is 30 mm, which implies that according to NBC regulations, the minimum diameter of the hoisting and counterweight rope should be 30 mm.

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• 21.

### Under NBC, the minimum width between balusters in an escalator.

• A.

558 mm

• B.

330 mm

• C.

600 mm

• D.

30 mm

A. 558 mm
Explanation
The correct answer is 558 mm. Under NBC (National Building Code), the minimum width between balusters in an escalator is 558 mm. This measurement ensures that there is enough space for individuals to pass through safely without any obstruction or risk of injury. It is important to adhere to these regulations to maintain the safety standards of escalators in public spaces.

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• 22.

### Maximum width of the steps.

• A.

558 mm

• B.

330 mm

• C.

600 mm

• D.

30 mm

B. 330 mm
Explanation
The maximum width of the steps is 330 mm. This means that the steps cannot be wider than 330 mm.

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• 23.

### Under NBC, the maximum rated speed of an escalator along the angle of travel.

• A.

37 Meters/Min

• B.

38 Meters/Min

• C.

39 Meters/Min

• D.

40 Meters/Min

B. 38 Meters/Min
Explanation
The correct answer is 38 Meters/Min. This is the maximum rated speed of an escalator under NBC along the angle of travel.

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• 24.

### The total cooling output of an airconditioner during its annual usage, in BTU/hr divided by the energy input during the same period, in watt-hours is known as_____.

• A.

Energy Efficiency Rating

• B.

Seasonal energy efficiency ratio

• C.

• D.

Seasonal cooling efficiency ratio

B. Seasonal energy efficiency ratio
Explanation
The seasonal energy efficiency ratio (SEER) is a measure of the cooling efficiency of an air conditioner over an entire cooling season. It is calculated by dividing the total cooling output of the air conditioner in BTU/hr by the energy input in watt-hours during the same period. SEER is a useful metric for comparing the energy efficiency of different air conditioners and determining their overall performance in terms of cooling output relative to energy consumption.

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• 25.

### A factor used in calculating cooling load that includes heat transferred from walls, doors, ceilings, etc. is known as _____.

• A.

Energy Efficiency Rating

• B.

Seasonal energy efficiency ratio

• C.

• D.

Seasonal cooling efficiency ratio

Explanation
Thermal load is the correct answer because it refers to the factor used in calculating cooling load that includes heat transferred from walls, doors, ceilings, etc. This term encompasses the heat that needs to be removed from a space in order to maintain a desired temperature, taking into account the heat gain from various sources. The other options, such as Energy Efficiency Rating and Seasonal Energy Efficiency Ratio, are not directly related to the calculation of cooling load.

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• 26.

### What is the rating index of an airconditioning/ refrigeration system which rates the unit for thenumber of BTU's of heat removed per watt of electrical input energy? (EER)

• A.

Energy Efficiency Rating

• B.

Seasonal energy efficiency ratio

• C.

• D.

Seasonal cooling efficiency ratio

A. Energy Efficiency Rating
Explanation
The rating index of an air conditioning/refrigeration system that rates the unit for the number of BTU's of heat removed per watt of electrical input energy is called the Energy Efficiency Rating (EER).

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• 27.

### Which of the following is not a component of a hydraulic elevator?

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

D. Counterweight
Explanation
A hydraulic elevator consists of several components that work together to facilitate its operation. The safety shoe is an essential component that prevents the elevator from falling in case of a hydraulic failure. The weighing device ensures that the elevator does not exceed its maximum weight capacity. The sheave is responsible for guiding and supporting the elevator cables. However, the counterweight is not a component of a hydraulic elevator. Counterweights are typically used in traction elevators to balance the weight of the elevator car and reduce the amount of energy required for operation.

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• 28.

### In theater stage house, a weight usually of iron or sand used to balance suspended scenery, or the like.

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

D. Counterweight
Explanation
A counterweight is a weight, typically made of iron or sand, that is used to balance suspended scenery or other objects in a theater stage house. It helps to ensure stability and prevent accidents by counterbalancing the weight of the scenery or equipment being suspended. This allows for smooth and controlled movement of the objects on the stage, enhancing the overall performance and safety of the production.

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• 29.

### In elevator, it detects the obstacles during the door closing, and reopens the door if there is something. Photocell can be used together with this.

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

A. Safety Shoe
Explanation
A safety shoe is a device used in elevators to detect obstacles during the door closing process. It ensures the safety of passengers by reopening the door if it detects any obstruction. This device can be used in conjunction with a photocell to enhance the accuracy of obstacle detection.

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• 30.

### In elevator, it makes the buzzer alarm when the car is overloaded and the door remains open until overloading is eliminated.

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

B. Weighing Device
Explanation
The correct answer is "Weighing Device" because in elevators, a weighing device is used to measure the weight of the passengers inside the car. When the weight exceeds a certain limit, it triggers the buzzer alarm to indicate overloading. The door remains open until the excess weight is eliminated to ensure the safety of the passengers and prevent any potential accidents.

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• 31.

### An assembly consisting of a pulley wheel, side plates, shaft, and bearings over which a cable or roped is passed.

• A.

Safety Shoe

• B.

Weighing Device

• C.

Sheave

• D.

Counterweight

C. Sheave
Explanation
A sheave is a component of an assembly that consists of a pulley wheel, side plates, shaft, and bearings. It is designed to guide and support a cable or rope as it is passed over it. The other options, safety shoe, weighing device, and counterweight, do not match the given description of the assembly.

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• 32.

### A package assembly of air conditioning components which provides for the treatment of air it is distributed to an air conditioned space.

• A.

Air Conditioner

• B.

Air Handling Unit

• C.

Air Conditioning

• D.

Refrigeration

B. Air Handling Unit
Explanation
An air handling unit is a package assembly of air conditioning components that is responsible for treating the air before it is distributed to an air conditioned space. It typically includes components such as filters, fans, heating and cooling coils, and dampers. The air handling unit plays a crucial role in maintaining the desired temperature, humidity, and air quality within the conditioned space.

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• 33.

### An apparatus that can heat, cool, clean and circulate air

• A.

Air Conditioner

• B.

Air Handling Unit

• C.

Air Conditioning

• D.

Refrigeration

A. Air Conditioner
Explanation
An air conditioner is an apparatus that can heat, cool, clean, and circulate air. It is a device used to regulate the temperature, humidity, and air quality in a specific space. It works by extracting heat from the indoor air and transferring it outside, thereby cooling the room. Additionally, it can also provide heating during colder months by reversing the cooling process. The air conditioner also filters and cleans the air, removing dust, allergens, and pollutants. Overall, an air conditioner is a versatile appliance that can provide comfort and improve indoor air quality.

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• 34.

### Is the achievement of a temperature below that of the immediate surroundings.

• A.

Air Conditioner

• B.

Air Handling Unit

• C.

Air-Conditioning

• D.

Refrigeration

C. Air-Conditioning
Explanation
Air-conditioning refers to the process of controlling and regulating the temperature, humidity, and air quality of a confined space to create a comfortable environment. It involves the use of various equipment such as air conditioners and air handling units to achieve a temperature lower than that of the immediate surroundings. Therefore, the achievement of a temperature below that of the immediate surroundings is a characteristic of air-conditioning.

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• 35.

### A device that maintains, control of the indoor environment—its desirable temperature, humidity, air circulation, and purity for the occupants of that space or for the industrial materials that are handled or stored there.

• A.

Air Conditioner

• B.

Air Handling Unit

• C.

Air-Conditioning

• D.

Refrigeration

C. Air-Conditioning
Explanation
Air-conditioning is the correct answer because it is a device that maintains control of the indoor environment by regulating the temperature, humidity, air circulation, and air purity. It is commonly used in homes, offices, and other buildings to provide a comfortable and healthy indoor environment for the occupants. Air-conditioning systems can also be used for industrial purposes to control the temperature and humidity levels for materials that are handled or stored in a specific space.

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• 36.

### Where the endless belt of steps pass around during operation of an escalator.

• A.

Sprocket Assembly

• B.

Closed Nipple

• C.

Coil

• D.

Relay

A. Sprocket Assembly
Explanation
The correct answer is "Sprocket Assembly." In the context of the question, an escalator is being described, and the phrase "endless belt of steps" suggests that the escalator has a continuous loop of steps. The sprocket assembly is responsible for driving and guiding the steps, ensuring their smooth movement around the escalator. It consists of sprockets, chains, and other components that work together to rotate the steps, allowing passengers to move up or down the escalator.

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• 37.

### Pipe fitting with outside threads use for connecting pipes.

• A.

Sprocket Assembly

• B.

Closed Nipple

• C.

Coil

• D.

Relay

B. Closed Nipple
Explanation
A closed nipple is a type of pipe fitting that is used to connect pipes with outside threads. It is designed to create a tight and secure connection between two pipes, preventing any leakage or loss of pressure. The closed nipple is threaded on both ends, allowing it to be easily screwed into the pipes. This type of fitting is commonly used in plumbing and industrial applications where a strong and reliable connection is required.

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• 38.

### What is a cooling or heating element which is made of pipe or tubing?

• A.

Sprocket Assembly

• B.

Closed Nipple

• C.

Coil

• D.

Relay

C. Coil
Explanation
A coil is a cooling or heating element made of pipe or tubing. It is designed to transfer heat from one medium to another. The pipe or tubing is usually wound into a spiral shape to increase the surface area for better heat transfer. Coils are commonly used in HVAC systems, refrigeration units, and heat exchangers to regulate the temperature of air or fluids.

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• 39.

### A safety device of a passenger elevator which reduces the collision shock of a car or counterweight due to over travel beyond the lowest stop. It stops the car or counterweight safely.

• A.

Pit

• B.

Winding Drum Machine

• C.

Buffer

• D.

Governor

C. Buffer
Explanation
A buffer is a safety device in a passenger elevator that helps reduce the impact or shock when the elevator car or counterweight travels beyond the lowest stop. Its purpose is to safely stop the car or counterweight and prevent any damage or injury that could occur from overtravel.

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• 40.

### Safety device of  a passenger elevator which activates if the car travels faster  than its rated speed by grasping the guide rail to stop the car safely.

• A.

Governor

• B.

Pit

• C.

Winding Drum Machine

• D.

Buffer

A. Governor
Explanation
The correct answer is "Governor." A governor is a safety device in a passenger elevator that activates if the car travels faster than its rated speed. It works by grasping the guide rail to stop the car safely. The governor is designed to prevent the elevator from exceeding its maximum speed and ensure the safety of passengers.

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• 41.

### On elevators, a gear-driven machine having a drum to which the wire ropes that hoist the car are fastened, and on which they wind.

• A.

Governor

• B.

Pit

• C.

Winding Drum Machine

• D.

Buffer

C. Winding Drum Machine
Explanation
The correct answer is "Winding Drum Machine." This is because the given explanation describes a gear-driven machine with a drum to which the wire ropes that hoist the elevator car are attached and wound. This accurately describes a winding drum machine, which is commonly used in elevators for vertical transportation. The other options, governor, pit, and buffer, do not match the given description and are not related to the function of hoisting the elevator car.

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• 42.

### That portion of the hoistway in the elevator extending from the threshold level of the lowest landing floor of the hoistway.

• A.

Governor

• B.

Pit

• C.

Winding Drum Machine

• D.

Buffer

B. Pit
Explanation
The correct answer is "Pit" because the pit refers to the portion of the hoistway in the elevator that extends from the threshold level of the lowest landing floor. This is the area below the elevator where the elevator car descends and comes to a stop. The pit is an essential component of the elevator system as it allows for the proper functioning and safety of the elevator by providing space for the elevator car to fully descend and align with the landing floor.

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• 43.

### The criteria in the selection of an elevator other than interval and average waiting time.

• A.

Travel Time

• B.

Power Consumption

• C.

Speed

• D.

Electric Consumption

A. Travel Time
Explanation
The selection of an elevator is based on various criteria other than interval and average waiting time. One important factor is the travel time, which refers to the time it takes for the elevator to reach its destination. This is crucial in ensuring efficient and quick transportation of people or goods. Additionally, power consumption is another consideration as it affects the energy efficiency of the elevator. Speed is also an important factor as it determines how quickly the elevator can transport passengers. Lastly, electric consumption is another aspect to consider in terms of the elevator's energy usage.

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• 44.

### Heat rating for a fixed temperature heat detector.

• A.

138-195 F

• B.

150-200 F

• C.

135-197 F

• D.

130-190 F

C. 135-197 F
Explanation
The correct answer is 135-197 F because this range falls within the specified temperature range for the heat detector. The heat detector is designed to activate when the temperature reaches a certain threshold, and this range encompasses that threshold.

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• 45.

### Heat is transferred through materials

• A.

Reflection

• B.

• C.

Polarization

• D.

Conduction

D. Conduction
Explanation
Conduction is the transfer of heat through materials by direct contact between particles. When two objects with different temperatures come into contact, the particles with higher energy transfer their energy to the particles with lower energy. This transfer of energy continues until both objects reach thermal equilibrium. Unlike convection and radiation, which involve the movement of fluids or electromagnetic waves, conduction relies on the physical contact between objects. Therefore, conduction is the most appropriate explanation for the transfer of heat through materials.

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• 46.

### The following are ways in which heat may be transferredexcept____.

• A.

Reflection

• B.

• C.

Polarization

• D.

Conduction

C. Polarization
Explanation
Heat can be transferred through three main mechanisms: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between objects or substances. Convection is the transfer of heat through the movement of fluids or gases. Radiation is the transfer of heat through electromagnetic waves. However, polarization is not a method of heat transfer. Polarization refers to the orientation of electromagnetic waves, and it does not involve the transfer of heat. Therefore, polarization is the correct answer as it is not a way in which heat can be transferred.

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• 47.

### What is also known as a synthetic chemical refrigerant?

• A.

Plenum

• B.

Ammonia

• C.

Carbon

• D.

Freon

D. Freon
Explanation
Freon is also known as a synthetic chemical refrigerant. It is a trademarked name for a group of chemicals called chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs). These chemicals are commonly used as refrigerants in air conditioning systems and refrigerators. They have excellent heat transfer properties and are non-toxic, non-flammable, and stable. However, they have been found to contribute to ozone depletion and have been phased out in many countries due to their harmful environmental effects.

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• 48.

### Gas used as refrigerant with water

• A.

Nitrogen

• B.

Ammonia

• C.

Carbon

• D.

Freon

B. Ammonia
Explanation
Ammonia is commonly used as a gas refrigerant with water due to its favorable thermodynamic properties. It has a low boiling point and high heat transfer coefficient, making it efficient in absorbing heat from the surroundings. Ammonia is also non-toxic, non-flammable, and has low global warming potential, making it a safer and more environmentally friendly option compared to other refrigerants like Freon.

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• 49.

### An air compartment or chamber

• A.

Compressor

• B.

Plenum

• C.

Buffer

• D.

Damper

B. Plenum
Explanation
The correct answer is plenum. A plenum refers to an air compartment or chamber that is used to distribute air in a building's heating, ventilation, and air conditioning (HVAC) system. It acts as a buffer or reservoir for the conditioned air before it is delivered to different areas of the building through ductwork. The plenum helps to ensure even airflow and pressure throughout the system, improving the efficiency and effectiveness of the HVAC system.

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• 50.

### Device that convert electrical energy into mechanical energy, by electromagnetic means.

• A.

Compressor

• B.

Alternator

• C.

Generator

• D.

Rectifier

B. Alternator
Explanation
An alternator is a device that converts electrical energy into mechanical energy, by electromagnetic means. It does this by using a rotating magnetic field to induce an alternating current in the stator windings. This alternating current can then be used to power electrical loads or charge a battery. Unlike a generator, which typically uses brushes and slip rings to transfer the electrical energy, an alternator uses a rectifier to convert the alternating current into direct current. Therefore, an alternator is the correct answer in this case.

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• Mar 21, 2023
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• Sep 10, 2015
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