Convection Heat Transfer - Class IX
applications of convection
Questions
In which of the following process, convection does not takes place primarily?
- sea and land breeze
- Boiling of water
- warming of glass of bulb due to filament
- heating air around a furnace
While measuring the thermal conductivity of liquids, the upper part is kept hot and lower one cool so that :
- convectional flow is stopped
- radiation is stopped
- conduction is easier
- it is easier to perform the experiment
Fireman crawl when entering a burning building because:
- It is easier to crawl
- Smoke rises high in the air
- It helps to move faster
- To resist more heat
Convection of heat takes place in:
- Metals only
- Liquids only
- Gases only
- Liquids and gases
Birds glide effortlessly in the air with the help of
- Conduction of heat in the air
- Radiation of light through the atmosphere
- Convection currents of air
- More sugar
It is hotter at the same distance over the top of a fire than it is on the side of it mainly because
- Heat is radiated upwards
- Air conducts heat upwards
- Convection takes more heat upwards
- Conduction, convection and radiation all contribute significantly in transferring heat upwards
Why it is more hotter for same distance over the top of a candle than it in the side of its flame?
- Conduction of heat in air is upward
- Heat is maximum radiated in upward direction
- Radiation and conduction both contribute in transferring heat upwards
- Convection takes more heat in upward direction
In natural convection, a heated portion of a liquid moves because
- Its molecular motion becomes aligned
- Of molecular collisions within it
- Its density is less than that of the
surrounding fluid - Of currents of the surrounding fluid
The correct statement of the following:
A) Water can be boiled inside the artificial satellite by convection
B) Heavy liquid can be boiled in artificial satellite by convection
Mark correct option/s
- Both statements are correct
- Both statements are wrong
- A is correct but B is wrong
- B is correct but A is wrong
It is hotter at some distance over the flames than in front of it because :
- air conducts heat upwards only
- heat is radiated upwards only
- convection of heat occurs upwards only
- heat is radiated downwards only
Which of the following process(es) occur(s) during the convective transfer of heat within a large volume of air?
- A continuous flow of warmer and cooler parts of air is established.
- The flow of air molecules results in flow of heat.
- The cooler portion of the air surrounding a warmer part exerts a buoyant force on it.
- As the warmer part of the air moves, it is replaced by cooler air that is subsequently warmed up.