Sources of Heat

Q. The amount of heat gained or lost by a body is directly proportional to its________.

1. Change in its temperature
2. Nature of the substance of the body
3. All the above
4. Mass

Q.

Name the following :

Energy obtained from the sun.

Q.

1. Name the star nearest to the Earth.
2. Why does it appear brighter and hotter than other stars ?
3. How much time is required for light to reach the Earth from this star ?
4. Give the composition of this star.
5. What is the source of energy of this star ?

Q.

A newly laid quilt is_________than an old one because it contains______________.

Q.

Explain how the sun is the ultimate source of energy, by taking any one example.

Q. The quantity of heat which crosses per unit area of a metal plate during condition depends upon

1. The density of the metal
2. The temperature to which the metal is heated
3. The temperature gradient perpendicular to the area d
4. The area of the metal plate

Q.

___ is a natural source of light.

Q. A water cooler of storage capacity $120$ litres can cool water at a constant rate of P watts. In a closed circulation system (as shown schematically in the figure), the water from the cooler is used to cool an external device that generates constantly $3$ kW of heat(thermal load). The temperature of water fed into the device cannot exceed $30$ ${}^{o}C$ and the entire stored $120$ litres of water is initially cooled to $10$ ${}^{o}C$. The entire system is thermally insulated. The minimum value of P(in watts) for which the device can be operated for $3$ hours is? (Specific heat of water is $4.2$ kJ $k{g}^{-1}{K}^{-1}$ and the density of water is $1000$ kg $m^{-3}$).

1. $1600$
2. $2067$
3. $2533$
4. $3933$

Q. When we rub two bodies together, heat is generated.

1. False
2. True

Q.

The surface temperature of the sun is about

1. ${10}^6$${}^{°}C$

2. ${5800}^{\circ }C$

3. ${10}^4$${}^{°}C$

4. ${1000}^{\circ }C$

Q. Which of the following is a bad conductor of heat?

1. Steel
2. Copper
3. Ceramic
4. Iron

Q.

A new quilt is warmer than an old one?

Q. The area of a hole of heat furnace is ${10}^{-4}{m}^2$. It radiates $1.58\times {10}^{5}cal$ of heat per hour. If the emissivity of the furnace is $0.80$, then its temperature is

1. $1500K$
2. $2000K$
3. $2500K$
4. $3000K$

Q. Two thin blankets are warmer than a single one of the same thickness because.

1. The air layer trapped in between the two blankets is a bad conductor
2. The distance of heat transmission is increased
3. The total mass of the blankets will be more
4. None of these

Q. is the ultimate source of energy.

1. Sun
2. Wind
3. Moon

Q. is the ultimate source of energy.

1. Sun
2. Wind
3. Moon

Q.

Which is the ultimate source of energy?

1. Water

2. Sun

3. Uranium

4. Fossil fuels

Q. Even after wearing a woollen cloth Vidya feels cold.Choose a best option that can keep her warmer
a)use blanket over woollen cloth
b)use a cap to cover her ears
c)cover her nose which is sensitive

Q. Name two factors on which the heat energy liberated by a body depend.

Q. In which among the following, heat transfer happens through conduction:

1. Solids
2. Liquids
3. Gases
4. All of the above.

Q. Why do most stainless steel pans have copper bottoms?

1. Copper bottom makes the pan more durable.
2. Copper is cheaper than steel.
3. Copper is a worse conductor of heat than steel.
4. Copper is a better conductor of heat than steel.

Q. Identify the mode of heat transfer as labelled in the image below.

1. A-Convection, B-Conduction, C-Radiation
2. A-Conduction, B-Convection, C-Radiation
3. A-Radiation, B-Conduction, C-Convection
4. A-Radiation, B-Convection, C-Conduction

Q. Solar energy is the energy which is obtained from the radiations of the Sun.

1. False
2. True

Q. Solar energy is the energy which is obtained from the radiations of the Sun.

1. False
2. True