Heat And Thermodynamics — Part 1 MCQs with Explanations

The heat stored in water vapor is called latent heat. Latent heat is a form of thermal energy that is stored when a substance changes phase, such as from a liquid to a gas.

Refrigerators work by using a special substance that changes easily between liquid and gas. Option A is incorrect because the ice in the freezer is a *result* of the cooling, not the *cause*. Option B is the correct answer. The refrigerator uses a compressor to squeeze a gas, making it very hot. This hot gas then passes through coils (usually on the back of the fridge) where it releases its heat into the surrounding air. After that, the gas expands suddenly, and this expansion makes it much colder. This cold gas then absorbs heat from the inside of the refrigerator, cooling it down. Option C is partially correct . While the *evaporation* of a liquid does cool things down, in a refrigerator, the cooling is mainly due to the sudden expansion of the compressed gas . The evaporation plays a supporting role in the cycle. Option D is incorrect because the correct answer is Option B.

The correct answer is B: 298 K . Here's why: Room temperature is generally considered to be around 25 degrees Celsius (°C) . The Kelvin scale is related to the Celsius scale by a simple formula: Kelvin (K) = Celsius (°C) + 273.15 . So, to convert 25°C to Kelvin, we add 273.15 to 25, which gives us approximately 298.15 K. Therefore, 298 K is the closest and most accurate representation of room temperature on the Kelvin scale. The other options are incorrect: 98 K is extremely cold. 273 K is the freezing point of water (0°C). 373 K is the boiling point of water (100°C).

Real gases behave like ideal gases when the intermolecular forces become negligible. At low pressure , gas molecules are far apart, reducing intermolecular attractions. At high temperature , molecules move rapidly, so the effect of intermolecular forces becomes very small. Therefore, under low pressure and high temperature, a real gas shows ideal gas behavior.

Second Law of Thermodynamics is the correct answer to “The statement that 'heat cannot flow by itself from a body at a lower temperature to a body at a higher temperature', is known as”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

301 is the correct answer to “A Kelvin thermometer and a Fahrenheit thermometer both give the same reading for a certain sample. What would be the corresponding reading in a Celsius thermometer”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

all wavelengths is the correct answer to “A black body can absorb radiations of”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Alcohol has a lower freezing point is the correct answer to “In cold countries, alcohol is preferred to mercury as a thermo-metric liquid because”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

20% RH, 60°C temperature is the correct answer to “In which of the following conditions wet clothes will dry earliest”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Water is the correct answer to “Which one of the following has the highest value of specific heat”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

0° Celsius is the correct answer to “Which temperature can water exist in both liquid and solid conditions”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

our perspiration evaporates rapidly is the correct answer to “A fan produces feeling of comfort during hot weather, because”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

temperature is the correct answer to “A thermometer is used to measure”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

has high specific heat is the correct answer to “Water is used in hot water bags because it”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Increase is the correct answer to “A metal plate with a circular hole at the centre is heated. What will happen to the area of the hole”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Add 273 to the given temperature is the correct answer to “To convert temperature from Celsius to Kelvin scale, you must:”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Humidity is the correct answer to “Decrease in which of the following factors leads to an increase in the rate of evaporation”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

A pin hole in a box is the correct answer to “Which of the following is the example of ideal black body”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

$$\overline F = \frac{9}{2}\overline C + 32$$ is the correct answer to “Let the average temperatures in Centigrade (C) and Fahrenheit (F) be $$\overline C $$ and $$\overline F $$. If $$\overline C $$ and $$\overline F $$ are related to $$F = \frac{9}{2}C + 32,$$ then $$\overline F $$ and $$\overline C $$ have the relation”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

absolute humidity is the correct answer to “Amount of water vapour (gaseous) in a given volume of air (cubic metre) is known a”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

When two systems are in heat balance with the third system, they will also be in equilibrium with each other is the correct answer to “In Thermodynamic, Zero Law states that-”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Black is the correct answer to “Which color is inside the solar cooker”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Friction is the correct answer to “The heat conduction in a cubic object does not depend on-”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Otto-cycle is the correct answer to “The four storke petrol engine is based on”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

convection is the correct answer to “Ocean currents are an example of”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Both cups reached room temperature at the same time is the correct answer to “On a specific day and time, the temperature was 48°C in Churu and 24°C in Shimla. Two metallic cups identical in all respects contained water at 95°C in Churu and 71°C in Shimla. Which one of these two cups reached room temperature first”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Wood is the correct answer to “Which of the following a bad conductor of heat”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

reflect back the heat given by the Earth is the correct answer to “Cloudy nights are warmer compared nights because clouds mainly”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

0°C = 273 K is the correct answer to “What is the relationship between Celsius to Kelvin temperature-”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

high specific heat capacity is the correct answer to “Water is used in car radiator because of its”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

These are all good conductors is the correct answer to “Find the similarity of the following silver, copper, gold, aluminium.”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

double is the correct answer to “When temperature difference between liquid and its surroundings is doubled, the rate of loss of heat will”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Maximum is the correct answer to “The universe has a tendency to entropy-”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

327°C is the correct answer to “If a gas is compressed to half of its original volume at 27°C, to what temperature should it be heated to make it occupy its original, volume”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Adiabatic demagnetisation is the correct answer to “Which of the following principle is used to produce low temperatures”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

Infinite is the correct answer to “A conductor is said to be perfect if it has . . . . . . . . electrical conductivity.”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

104°F is the correct answer to “The value of 40 degrees Celsius in Fahrenheit scale is”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

A is true, but R is false is the correct answer to “Assertion (A) The boiling point of water decreases as the altitude increases. Reason (R) The atmospheric pressure increases with altitude.”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

green is the correct answer to “When red glass is heated in dark room it will seem”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.

At all temperatures is the correct answer to “Water evaporates-”. This question is standard in competitive examination syllabi for Heat And Thermodynamics.