P2.3.4P2. Thermal Physics
Consequences of thermal energy transfer — Combined Science 0653 - Physics Revision Notes & Topical Questions
5 min read 9 parts Lesson 11 of 14 1 quiz
Lesson summary
P2.3.4 Consequences of thermal energy transfer — COMBINED SCIENCE notes: Apply conduction, convection and radiation to everyday situations and explain how insulation reduces energy transfer.Good conductors — they move thermal energy quickly.Metal pans pass energy to food.Metal ra…
- Insulators
- Room radiator
- Polished cooking pans
- Solar panels
- Car radiator
- Double-walled glass
Part 1 of 7Applications of conduction
Good conductors
- Good conductors they move thermal energy quickly.
- Metal pans pass energy to food.
- Metal radiators pass energy from the water to the air.
Insulators
- Insulators they slow the transfer of thermal energy.
- Plastic or wooden handles on pans protect the hands.
- Air spaces in walls and windows keep houses warm because air is a poor conductor.
Part 2 of 7Applications of convection
Room radiator
- Room radiator air next to the radiator is heated, expands, becomes less dense and rises,
- while cooler air moves in and the room is heated by the current.
Hot drink
- Hot drink convection currents of warm air carry energy away from the surface of a hot drink.
Part 3 of 7Applications of radiation
Polished cooking pans
- Polished cooking pans a shiny outer surface reduces energy loss by radiation.
Solar panels
- Solar panels pipes are painted dull black to absorb as much infrared radiation as possible.
Car radiator
- Car radiator it is dark in colour and has a large surface area so it emits more radiation.
Part 4 of 7Vacuum flask
Double-walled glass
- Double-walled glass the vacuum between the two walls prevents conduction and convection because there are no particles.
Silvered surfaces
- Silvered surfaces the shiny walls reflect thermal radiation back and reduce radiation losses.
Stopper and support
- Stopper and support they are made of insulating plastic or cork to reduce conduction and convection through the top.
Part 5 of 7Home insulation
Home insulation
Loft and cavity wall insulation
- Loft and cavity wall insulation materials such as fibreglass and foam trap air in small pockets,
- which cannot form convection currents and conduct poorly.
Double glazing
- Double glazing the narrow air gap reduces conduction and prevents convection currents from forming.
- It does not reduce radiation because thermal radiation passes through glass and air.
Rate of loss
- Rate of loss heat loss from a building depends on the temperature difference, the surface area, the surface type and the insulation.
Part 6 of 7Several transfers at once
Cup of tea
- Cup of tea conduction through the cup and into the table, convection from the surface to the air above, and radiation from the sides of the cup.
Wood or coal fire
- Wood or coal fire it heats nearby objects mainly by radiation and the rest of the room by convection currents.
Car radiator
- Car radiator a liquid takes energy from the engine by conduction and passes it to the radiator by conduction.
- The radiator then transfers energy to the air mainly by convection through its fins and partly by radiation.
Part 7 of 7More from the specification
More from the specification
Phonon conduction between lattice atoms
- Phonon conduction between lattice atoms vibrational wave packets propagate through crystal lattices via elastic collisions between bonded atoms.
Conduction in solids
- Conduction in solids vibrating particles pass energy on, and free electrons in metals carry energy so metals conduct well
Greenhouse effect
- Greenhouse effect gases such as carbon dioxide in the Earth's atmosphere absorb emitted infrared and warm the surface
Emission and absorption
- Emission and absorption hotter objects emit more radiation, and dark matt surfaces emit and absorb more than shiny ones
Applications
- Applications insulating tiles reduce heat transfer, and experiments with cans compare the rate of cooling for different surfaces
Conduction in solids
- Conduction in solids vibrating particles pass energy on, and free electrons in metals carry energy so metals conduct well
Greenhouse effect
- Greenhouse effect gases such as carbon dioxide in the Earth's atmosphere absorb emitted infrared and warm the surface
Emission and absorption
- Emission and absorption hotter objects emit more radiation, and dark matt surfaces emit and absorb more than shiny ones
Applications
- Applications insulating tiles reduce heat transfer, and experiments with cans compare the rate of cooling for different surfaces
Carbon dioxide
- Gas that turns limewater cloudy.
Thermal equilibrium
- A state in which objects are at the same temperature.
Electron
- Negative particle that moves around the nucleus.
Lattice
- Regular pattern of particles in a giant structure.
Solid
- A state of matter with a fixed shape and fixed volume.
Vibration
- Rapid backwards and forwards movement.
Key terms
| Term | Meaning |
|---|---|
| Insulation | A material that reduces the transfer of thermal energy. |
| Vacuum flask | A double-walled container with a vacuum and silvered walls that keeps contents hot or cold. |
| Double glazing | Two panes of glass with a narrow air gap that reduces conduction and convection. |
| Cavity wall insulation | Insulating material in the gap between two layers of a wall. |
| Dull black surface | A surface that is the best absorber and emitter of radiation. |
Avoid these mistakes
1
Saying double glazing stops radiation — thermal radiation passes through glass.
2
Saying a vacuum flask works by trapping air — it uses a vacuum with no particles to carry energy.
3
Naming only one method for a real situation — most real cases involve two or three transfers at once.
4
Saying insulators stop thermal energy completely — they only slow the transfer.
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