Heat Transfer9 Flashcards

1
Q

Anything that is hot…

A

Gives out infrared radiation

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2
Q

A thermal image…

A

Is a picture made using infrared radiation

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3
Q

Infrared radiation can travel through…

A

Space (a vacuum) and transparent material like glass

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4
Q

Heat radiation is also called…

A

Infra red radiation

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5
Q

All objects…and…infra-red radiation.

A

Absorb

Emit

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6
Q

The …an object is, the …infrared radiation it emits in a given time.

A

Hotter

More

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7
Q

Cold objects?

A

Absorb heat radiation

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8
Q

Hot objects?

A

Emit heat radiation

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9
Q

Light/shiny objects?

A

Reflect heat well but doesn’t absorb heat well do not heat up much, emits heat slowly stay hotter for longer

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10
Q

Dark/dull objects?

A

Absorb more heat this means they heat up quickly. Hot dark objects also emit heat radiation very well this means that they cool down quickly.

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11
Q

How does heat travel through a solid?

A

By a process called conduction, caused by particles vibrating and knocking into each other.

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12
Q

Why are metals good conductors?

A

Because they contain “free electrons” which can move around the whole metal and carry the heat energy through more easily.

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13
Q

Why are non-metals bad conductors?

A

They don’t contain free electrons.

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14
Q

Are liquids and gases good conductors of heat?

A

Liquids and gases are bad conductors because the particles are too far apart to knock into each other.

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15
Q

Why does a metal cup feel colder than a polystyrene cup?

A

The metal cup will conduct heat away from your hand.

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16
Q

Heat travels through liquids and gases by a process called?

A

Convection

17
Q

Convection involves hot particles…and cooler particles…in a continuous cycle called a… …

A

Rising
Falling
Convection currents

18
Q

The cycle continues until the whole liquid or gas becomes the same…

A

Temperature

19
Q

Heat can be lost from buildings by conduction through the…

A

Roof, floor, window glass, walls

20
Q

Heat can be lost from buildings by convection through the…

A

Draught

21
Q

How can you save heat?

A

Insulating, double glazing, fitting draught excluders

22
Q

Materials used for insulating often contain… Because

A

Air

A gas such as air is a very poor conductor

23
Q

Why is a foam container a better insulator than a metal?

A
  • foam container is a better insulator

- prevents heat getting in

24
Q

What are the three ways that heat can be transferred?

A

Radiation, convection, conduction

25
Q

How is a fibre sleeping bag designed to reduced heat transfer by which 2 processes?

A
  • Conduction

- Convection

26
Q

Why is a fibre sleeping bag good at reducing heat loss?

A
  • there is air space between the fibre and air isn’t a good conductor
  • the air is trapped in the fibre so it can’t convect either