Working of a Thermos flask

Q. Usually, umbrellas are Black and black colour absorbs heat.Then why do we use black umbrellas to get protected from the sun?

Q. Why do certain colours absorb heat and certain colours reflect

Q.

Which of the following materials is not lustrous?

1. Gold

2. Silver

3. Wood

4. Diamond

Q.

Why should we always use glass utensils while microwaving something in the microwave and not in steel utensils?

Q. Why thermos flask have a stopper made from plastic?

Q. A thermos flask is designed to prevent the contents of the flask from losing heat. Which of the following statements concerning the design of thermos flasks is incorrect?

1. The stopper helps reduce heat loss by convection
2. The glass walls are silver coated to reduce emitted radiation
3. The flask is designed to prevent heat loss by conduction, convection and radiation
4. The vacuum between the glass walls prevents heat loss by preventing radiation

Q. Explain how the different forms of heat losses are minimized in a thermos flask.

Q.

A _______ surfaces are good absorbers of heat.

Q.

Sir. What is the difference between heat and light?

Yours sincerely

Shubhajeet Das

Q.

Choose the correct answer.

Shiny objects are

1. Good reflectors and good absorbers of heat.

2. Poor reflectors and poor emitters of heat.

3. Good reflectors and poor absorbers of heat.

4. Poor reflectors and good emitters of heat.

Q. In a thermos flask, vacuum between its walls reduces the heat loss by

1. conduction
2. radiation
3. conduction and convection both
4. convection

Q. In a thermos flask, give reason for the following:
(a) A vacuum is created between the two walls of the glass bottle.
(b) The two walls of glass bottle are highly silvered on their vacuum side.
(c) The glass bottle is covered with a cork stopper.
(d) The glass bottle is placed in a plastic case by surrounding it with cork.

Q. The silver coating on the inner bottle of a thermos flask

1. prevents heat transfer by conduction
2. prevents heat transfer by convection
3. prevents heat transfer by radiation
4. prevents heat transfer by absorption

Q. A thermos flask maintains temperature of objects. It

1. containing some kind of heating element to keep hot things hot.
2. containing some kind of heating element to keep cold things cold.
3. keeps hot things hot by not allowing heat to escape.
4. All of the above

Q. A device in which heat loss is minimalized due to three modes of heat transfer is

1. Thermometer
2. Heater
3. Cooker
4. Thermos flask

Q. Thermos flask is a special kind of

1. Process
2. Bottle
3. Apparatus
4. Weighing machine

Q. The vacuum between the walls of the flask prevents the transfer of heat by

1. Conduction
2. Convection
3. Radiation
4. All

Q. Thermos flask was deviced by

1. Fischer
2. Joseph Lister
3. Joseph Fourier
4. Sir James Dewar

Q.

What is a thermos flask?

Q. Vacuum in a vacuum flask prevents heat transfer through process of-

1. Conduction only
2. Conduction and Convection
3. Convection only
4. Radiation only

Q. Four identical conical flasks A, B, C & D each are filled with 500 ml of water. The flasks A, B, C & D are heated till the water attain temperatures of $45{}^{\circ }C,55{}^{\circ }C,65{}^{\circ }C$ and $85{}^{\circ }C$ respectively. Which of the following flasks, contain the highest water level?

1. Flask A
2. Flask B
3. Flask C
4. Flask D

Q. The shining surface in a thermos flask decreases the outgoing heat by ______________.

1. conduction
2. refraction
3. convection
4. reflection

Q. Liquid nitrogen is stored at $77K$ in a vacuum flask. The surrounding atmospheric temperature in the lab is $33K$.

1. After a few days, the temperature of liquid nitrogen will increase.
2. After a few days, the temperature of the lab will decrease.
3. After a few days, the temperature of liquid nitrogen will decrease
4. After a few days, the temperature of liquid nitrogen will remain unchanged.

Q.

What contribution does an evacuated double-wall give to the functioning of a thermos flask?

Q. A polished silver surface is

1. good absorber of heat
2. good reflector of heat
3. poor reflector of heat
4. none of these

Q. A thermos flask:

1. Keeps hot liquids hot and cold liquids hot
2. Keeps cold liquids hot and hot liquids cold
3. Keeps both cold and hot liquids cold
4. Keeps cold liquids cold and hot liquids hot

Q. If you put hot water in thermos flask, it will remain at the same temperature forever.

1. True
2. False

Q. Thermos flask, when closed, is an approximate

1. open system.
2. None of these
3. isolated system.
4. closed system.

Q. A themoflask prevent heat loss from-

1. Conduction
2. Convection
3. radiation
4. all of these

Q. Which of the following is an insulating component in thermos flask?

1. plastic foam
2. air
3. vacuum
4. All of the above