Question 1

Which of the following is the condition to use two compressors in the refrigeration system?
A)the desired temperature is 3°c
B)the desired temperature is -3°c
C)the desired temperature is -50°c
D)the desired temperature is -5°c

Accepted Answer

When the desired temperature in a refrigeration system is very low, such as -50°C, using two compressors (or a multi-stage compression system) is often necessary. This approach improves efficiency and reliability for achieving and maintaining such low temperatures.

Question 2

Centrifugal compressors are used to handle------------------ volume of refrigerant.
A)small
B)medium
C)large
D)very large

Accepted Answer

Centrifugal compressors are typically used to handle large volumes of refrigerant due to their design and efficiency in moving large quantities of gas.

Question 3

Which of the following cooling towers possess maximum heat transfer from air to water?
A)natural draft
B)mechanical draft
C)natural and mechanical draft
D)atmospheric draft

Accepted Answer

Mechanical draft cooling towers are designed to maximize heat transfer by using fans or blowers to force air through the tower, enhancing the cooling efficiency compared to natural draft towers which rely solely on natural convection.

Question 4

Which of the following is true about the optimum effective temperature for human comfort?
A)same in winter and summer
B)not dependent on season
C)lower in winter than in summer
D)higher in winter than in summer

Accepted Answer

The optimum effective temperature for human comfort is generally lower in winter than in summer. This is because people tend to wear heavier clothing in winter, which insulates them better, allowing for a lower ambient temperature to be comfortable.

Question 5

When the heat stored in the body is-------------- the human body feels comfortable.
A)zero
B)infinite
C)positive
D)negative

Accepted Answer

The human body feels comfortable when the heat stored in the body is zero, meaning there is a balance between heat production and heat loss.

Question 6

Room air conditioners and packaged units are examples of
A)direct expansion systems
B)indirect expansion systems
C)chilled water systems
D)indirect contraction systems

Accepted Answer

Room air conditioners and packaged units directly cool the air by expanding refrigerant in the evaporator coil, which classifies them as direct expansion systems.

Question 7

Which of the following types of filters used in the air conditioning system is made of cloth that is discarded on getting dirty?
A)viscous type filters
B)dry filter
C)spray washers
D)electric precipitators

Accepted Answer

Dry filters in air conditioning systems are often made of materials like cloth or fiberglass that are designed to trap particulates from the air. When these filters become dirty, they are typically discarded and replaced, as opposed to being cleaned and reused.

Question 8

The process of extraction of the certain required amount of water from air is known as                        
A)heating
B)cooling
C)humidification
D)dehumidification

Accepted Answer

Dehumidification is the process of removing moisture from the air, which effectively extracts water from the air to achieve a certain required humidity level.

Question 9

Which of the following is capable of absorbing excess moisture from the air?
A)silica gel
B)charcoal
C)salts of calcium or ammonia
D)activated alumina

Accepted Answer

The answer of Which of the following is capable of...

Question 10

Magnetic materials are heated with the help of
A)hysteresis loss
B)electric arc
C)electric current
D)radiation.

Accepted Answer

Hysteresis loss in magnetic materials occurs due to the lag between the change in magnetization and the external magnetic field, which generates heat.

Question 11

In the indirect resistance heating method, heat is delivered to the charge
A)direcly
B)by radiation
C)by convection
D)both (b) and (c).

Accepted Answer

In the indirect resistance heating method, heat is delivered to the charge not directly but through radiation and convection. This means the heating element itself gets hot and then transfers the heat to the charge via radiating the heat through space (radiation) and by heating the air around the charge, which then heats the charge (convection).

Question 12

Electric ovens using heating elements of........................... can produce temperatures up to 3000°C
A)nickel
B)graphite
C)chromium
D)iron.

Accepted Answer

Graphite is capable of producing very high temperatures up to 3000°C in electric ovens due to its high melting point and excellent electrical conductivity.

Question 13

Which of the following heating method is based on the transformer principle ?
A)resistance heating
B)eddy-current heating
C)induction heating
D)dielectric heating.

Accepted Answer

Induction heating works on the principle of the transformer, where an alternating current flows through a primary coil, generating a varying magnetic field that induces a current in the secondary material (the workpiece), heating it up due to its electrical resistance.

Question 14

Which of the following furnace suffers from pinch effect?
A)resistance furnace
B)core type induction furnace
C)coreless induction furnace
D)vertical core type induction furnace.

Accepted Answer

The answer of Which of the following furnace suffers from...

Question 15

The coreless induction furnace uses high-frequency electric supply in order to obtain high
A)flux density
B)eddy-current loss
C)primary resistance
D)power factor.

Accepted Answer

High-frequency electric supply in a coreless induction furnace is used to increase eddy-current loss, which generates heat for melting metals.

Question 16

Spot welding is used for
A)thin metal sheets
B)rough and irregular surfaces
C)costings only
D)thick sections

Accepted Answer

Spot welding is primarily used for joining thin metal sheets together because it applies heat and pressure to the weld area through electrodes, making it ideal for materials like thin sheets of metal where minimal distortion is desired.

Question 17

Which of the following is an advantages of heating by electricity?
A)quicker operation
B)higher efficiency
C)absence of flue gases
D)all of the above

Accepted Answer

The answer of Which of the following is an advantages...

Question 18

...... has the highest value of thermal conductivity.
A)copper
B)aluminium
C)brass
D)steel

Accepted Answer

Copper has the highest thermal conductivity among the options listed, making it an excellent material for applications requiring efficient heat transfer.

Question 19

...... method has leading power factor
A)resistance heating
B)dielectric heating
C)arc heating
D)induction heating

Accepted Answer

Dielectric heating involves the use of high-frequency electromagnetic fields to heat dielectric materials, which can lead to a leading power factor due to the capacitive nature of the process.

Question 20

Which of the following methods of heating is not dependent on the frequency of supply?
A)induction heating
B)dielectric heating
C)electric resistance heating
D)all of the above

Accepted Answer

Electric resistance heating is not dependent on the frequency of the supply. It relies on the resistance of the material to convert electrical energy into heat, which is independent of the electrical supply frequency. Induction and dielectric heating methods, on the other hand, are frequency-dependent.

Quiz 2: HVAC and Heating Systems: Understanding Compressors, Cooling Towers, Filters, and Heat Transfer Methods

Which of the following is the condition to use two compressors in the refrigeration system?

Centrifugal compressors are used to handle------------------ volume of refrigerant.

Which of the following cooling towers possess maximum heat transfer from air to water?

Which of the following is true about the optimum effective temperature for human comfort?

When the heat stored in the body is-------------- the human body feels comfortable.

Room air conditioners and packaged units are examples of

Which of the following types of filters used in the air conditioning system is made of cloth that is discarded on getting dirty?

The process of extraction of the certain required amount of water from air is known as

Which of the following is capable of absorbing excess moisture from the air?

Magnetic materials are heated with the help of

In the indirect resistance heating method, heat is delivered to the charge

Electric ovens using heating elements of........................... can produce temperatures up to 3000°C

Which of the following heating method is based on the transformer principle ?

Which of the following furnace suffers from pinch effect?

The coreless induction furnace uses high-frequency electric supply in order to obtain high

Spot welding is used for

Which of the following is an advantages of heating by electricity?

...... has the highest value of thermal conductivity.

...... method has leading power factor

Which of the following methods of heating is not dependent on the frequency of supply?