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Science > Physics Energy > Flashcards

Physics Energy Flashcards

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1
Q

State the unit of energy.

A

Joules or kilojoules.

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2
Q

Name three fuels that are good sources of energy.

A

Oil
Wood
Coal
Food that we eat

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3
Q

What does a human need energy for?

A

To keep your body warm, to breathe, to move, to talk.

You need energy for your bones, muscles and brain.

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4
Q

Describe what is meant by a fossil fuel.

A

Coal, oil and gas - energy resources formed millions of years ago.

Oil and gas are made from fossilised remains of sea creatures.

Coal is made from the fossilised remains of trees.

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5
Q

What is a non-renewable source of energy?

A

Coal, oil and gas.
They can’t be used again and it is not easy to get more of them when we have used them up.

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6
Q

Name the greenhouse gas that is produced when fossil fuels are burned.

A

Carbon dioxide.
CO2.
A greenhouse gas can contribute to climate change.

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7
Q

Apart from CO2, what other pollutants are made when burning fossil fuels?

A

Sulfur dioxide.
Nitrogen oxides.
Particulates.

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8
Q

What happens in a power station?

A

Thermal power stations burn coal and gas.
The fuel is burnt to heat water and produce steam.
The steam turns a turbine (like a big fan).
The turbine dives a generator which sends electricity to homes and factories etc.

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9
Q

Name some renewable sources of energy

A

Wind
Tidal
Waves
Biomass
Solar
Hydroelectric
Geothermal

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10
Q

Describe what is meant by a renewable source of energy.

A

One that will not be used up.

It also does not produce much carbon dioxide.

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11
Q

What is a unit of power?

A

Watt (w)

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12
Q

What is the formula to calculate power?

A

Time (s)

= Power (w)

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13
Q

Define power.

A

How quickly energy is transferred be a device (w).

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14
Q

Define a kilowatt

A

1000 watts (kw)

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15
Q

State the unit of energy that electricity companies use?

A

Kilowatt hours (kWh) or joules.

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16
Q

What could you do to save energy in your house?

A

Insulation in the house reduces the rate at which energy is transferred into the surroundings, so it reduces the rate at which you need to supply energy to heat the house.

17
Q

State the law of conservation of energy.

A

Energy cannot be created or destroyed - only transferred.

This is the law of the conservation of energy.

18
Q

Define a chemical energy store.

A

Emptied during chemical reactions when energy is transferred to surroundings, for example when you burn a fuel.

19
Q

Energy to do with food, fuels, batteries has a ….

A

chemical energy store.

20
Q

Energy to do with hot objects has a….

A

thermal energy store.

21
Q

Energy to do with moving objects has a…

A

kinetic energy store.

22
Q

Energy to do with position in a gravitational field has a…

A

gravitational potential energy store.

23
Q

Energy to do with changing ape, stretching or squashing has a….

A

elastic energy store.

24
Q

Name types of energy store.

A

Chemical energy store.
Elastic energy store.
Thermal energy store.
Kinetic energy store.
Gravitational potential energy store.
Mechanical energy store.
Radiative energy store.

25
Q

State three ways that energy is transferred between stores.

A

Electric current
Radiation (like light)
Waves (like sound)
Heating

26
Q

Explain a bouncing ball in terms of the transfer of energy.

A

When the ball is lifted up, it is cooler and the surroundings are cooler. There is more energy in the gravitational potential energy store of the ball and less energy in the thermal energy stores of the ball and surroundings.

When the ball is at the top of the first bounce, it is a warmer ball and also warmer surroundings. There is less energy in the gravitational potential energy store of the ball and more energy in the thermal energy stores of the ball and surroundings.

27
Q

What does dissipation mean?

A

Becoming spread out wastefully.

28
Q

Name two ways to reduce dissipation in a car.

A

Air resistance - reduce by closing windows, have an aerodynamic car design.

Friction - ensure tyres are properly inflated to reduce friction.

29
Q

How is energy efficiency (%) calculated?

A

energy input

= efficiency (%)

30
Q

In a Sankey diagram, the thickness of an arrow corresponds to…

A

the amount of energy transferred.

31
Q

Efficiency can never be more than…… %

A

100%

32
Q

We can reduce unwanted energy transfer by ….. and ……

A

Thermal insulation
Lubrication

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