Heat and Temperature MCQ Quiz in मल्याळम - Objective Question with Answer for Heat and Temperature - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

There are two types of heat.

• Sensible heat: It is the energy required to change the temperature of a substance with no phase change.
• Latent heat: It is the energy absorbed by or released from a substance during a phase change from a gas to a liquid or a solid or vice versa, at constant temperature.

The amount of heat required to convert per unit mass of the ice into water at 0°C temperature is called latent heat of fusion of ice.

Latent heat of fusion of ice (L) = 80 cal/gram

Concept:

Freezing point and the boiling point of water at different temperature scales are:

Temperature Conversions:

\(\begin{array}{l} F = \frac{9}{5}C + 32\\ C = \left( {F - 32} \right) \times \frac{5}{9}\\ \frac{C}{{100}} = \frac{{F - 32}}{{180}} = \frac{R}{{80}}= \frac{{K - 273}}{{100}}\\ K = C + 273\\ K = F + 460 \end{array}\)

Calculation:

\(F=\frac{9}{5}C +32=\frac{9}{5}\times 45 +32 =113^\circ F\)

Explanation:

Absolute zeroTemperature:

• Absolute zero temperature is the lower limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach its minimum value, taken as 0.
• It is 0 K i.e. −273.15° C or −459.67° F.
• It is impossible to reach zero temperature.
• In practice, work can never achieve absolute zero temperature because as it is impossible to have a source to supply an infinite amount of work.

Explanation:

Instruments

• The instruments used to measure and read temperature takes into account changes in the properties of materials, electrical phenomena incandescence, radiation and melting.
  1. Thermometer
  2. Pyrometer

Pyrometer

1. Thermoelectric pyrometer
   • It is based on the principle that the soldering point between the wires of different metals, when heated a contact voltage is generated.
   • The voltage depends upon the temperature difference between the hot measuring point and the cold end of the wire.
   • Thermocouple elements are constructed of copper and Constant (up to 600°C) or of platinum and platinum-rhodium (up to 1600°C)
2. Radiation pyrometers
   • They are used to measure temperatures of red hot metals up to 3000°C.
   • These concentrate thermal rays through an optical lens and focus them on to a thermo element.
   • The scale of the ammeter is calibrated in degrees Celsius or Kelvin.

Concept:

• Heat is a form of energy that is measured in terms of Joule or calories.
• Heat is transferred from a hotter body to a colder body when there is a temperature difference.
• There are three modes of heat transfer:
  • Conduction, convection, and radiation.
• Heat transfer may occur with or without any medium.

Explanation:

• Conduction:
  • It is a mode of transfer of heat which occurs when the molecules collide with each other.
  • During collisions, the heat from one molecule is transferred to the others.
  • There is direct contact with the nearer molecules without the actual movement of the molecules.
  • The process of conduction takes place in solids and only because the molecules are closer in them and their movement is restricted.
• Convection:
  • It is a mode of transfer of heat where there is the actual movement of molecules.
  • The molecules move and transfer heat to the other molecules.
  • This type of heat transfer occurs in liquids and gases because the movement of the molecules is not restricted.
• Radiation:
  • The transfer of heat which doesn't require any mode for its transfer is known as Radiation.
  • Heat transfer occurs via thermal emission.
  • The heat that comes from the sun to our earth reaches via radiation.

Hence, the heat transfer method when molecules themselves move from one place to another to transfer heat is called Convection.

The correct answer is 298K.

• The basic formula is °C + 273.15 = K.
  So, reading on a Kelvin scale is 25^∘C + 273 = 298K. So, option 1 is correct.

• 0°C is equal to 273.15 Kelvins.
• To convert Fahrenheit degrees into Kelvins, (°F − 32) × 5/9 + 273.15 = K.
• Absolute zero is 0 Kelvins. This is the lowest temperature of any substance.
• Water freezes at 0 degrees Celsius or 32 Degrees Fahrenheit, or 273.15 Kelvins.
• Water boils at 100 degrees Celsius or 212 degrees Fahrenheit, or 373.15 Kelvins.

Important Points

• The formula conversion between Fahrenheit and Celsius is: C/5 = (F-32)/9
• The Celsius scale and the Fahrenheit scale coincide at -40°, which is the same for both.

When a substance is heated, it expands, and volume is increased. Similarly, when it is cooled, it contracts (shrinks) and volume is decreased.

While true, density is not a direct geometrical change—it’s a derived property (mass/volume). The question specifies geometrical changes.

Concept:

\(^\circ F = \frac{9}{5}C + 32\)

\(C = \frac{5}{9}\left( {F - 32} \right)\)

Calculation:

Explanation:

Expansion due to heat

• When a solid, liquid, or gaseous substance is heated, it expands and volume is increased.
• Similarly, when it is cooled, it contracts (shrinks), and volume is decreased.
• E.g: small gaps are left in between the lines of railway track to allow for expansion during summer. If this is not done, the rails would expand and bend thereby causing derailment of trains.
• Except for a few substances, all solids, liquids and gases expand.
• For the same amount of heat given, the expansion of liquids is greater than solid and the expansion of gas is more than liquid.
• The volume of water is reducing while heating from 0°C to 4°C.
• After that volume is increasing.
• The data at 4°C of water will be taken as a reference point for any calculations relating to water.

The correct answer is -40°.

Key Points

• The Celsius scale and the Fahrenheit scale coincides at -40°, which is the same for both.
• The formula conversion between Fahrenheit and Celsius is: C/5 = (F-32)/9

Additional Information

• Water boils at 100 degrees Celsius or 212 degrees Fahrenheit, or 373.15 Kelvins.
• Water freezes at 0 degrees Celsius or 32 Degrees Fahrenheit, or 273.15 Kelvins.
• Absolute zero is 0 Kelvins, this is the lowest temperature of any substance.
• 0°C is equal to 273.15 Kelvins, The basic formula is °C + 273.15 = K.
• To convert Fahrenheit degrees into Kelvins, (°F − 32) × 5/9 + 273.15 = K.