**Short Question Answers**

**1.**

**Explain why air temperature readings are always taken with the thermometer in the shade?**

Ans: Only in the shade, the air, and the thermometer may be in thermal equilibrium. Therefore, air temperatures are always taken in shade.

**2. What is the temperature of the vacuum?**

Ans: Molecules are not found in a vacuum, this means average Kinetic Energy(K.E.) of molecules is zero. Due to this reason, the temperature of the vacuum is zero.

**3. What do you mean by Zeroth law of thermodynamics?**

Ans: if two systems are in thermal equilibrium with a third system, then they must be in thermal equilibrium with each other. This is called the Zeroth law of thermodynamics.

**4. What are the effects of heat?**

Ans: Following are the effects of heat;

- Heat can produce thermoelectric effects.
- Heat can change the temperature of the body, physical properties of the body, volume of the body, and state of the body.
- In living things it causes physiological changes and effects.

**5. A student claimed that thermometers are useless because a thermometer always registers its own temperature. How would you respond?**

Ans: when a thermometer is used to measure the temperature of a body then there will be an exchange of heat until the body and thermometer attain a common temperature. The student’s claim is true that the thermometer registered its own temperature but the temperature registered is also the temperature of the body. Hence, the registered temperature is the temperature of the thermometer as well as the body.

**6. At what temperature will the Celsius scale reading double the Fahrenheit reading?**

Ans: According to question,

C=2F

We know,

(C-0)/100 = (F-32)/180

or, 2F/100 = (F-32)/180

or, 36F = 10F-320

or, F = -320/26

so, F = - 12.3

^{◦}FTherefore, at -12.3

^{◦}F, the Celsius scale reading doubles the Fahrenheit reading.**7. Define absolute temperature.**

Ans: The temperature measure in Kelvin scale is known as absolute temperature.

**8. At what temperature, do the Fahrenheit thermometer and Celsius thermometer show the same reading?**

Ans: According, to the question

Let x be the required value on both scales. So

C = F = x

We know,

(C-0)/100 = (F-32)/180

(C-0)/100 = (F-32)/180

or, x/100 = (x-32)/180

or, 18x = 10x - 320

or, x = - 320/8

Therefore x = -40

Thus, the required value is -40

^{◦}C or -40^{◦}F.**9. At what point of the thermometric scale does Kelvin scale reading coincide with Fahrenheit scale reading?**

Ans: Here,

Let x be the required value on both scales. So

k = F = x

We know,

(K-273)/100 = (F-32)/180

(K-273)/100 = (F-32)/180

or, (x-273)/100 = (x-32)/180

or, (x-273)/10 = (x-32)/18

or, x = 574.25

Thus, the required value is 574.25 K or 574.25

^{◦}F.
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