Physics Energy

Question 1

State the unit of energy.

Answer 1

Joules or kilojoules.

Question 2

Name three fuels that are good sources of energy.

Answer 2

Oil
Wood
Coal
Food that we eat

Question 3

What does a human need energy for?

Answer 3

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

You need energy for your bones, muscles and brain.

Question 4

Describe what is meant by a fossil fuel.

Answer 4

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.

Question 5

What is a non-renewable source of energy?

Answer 5

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.

Question 6

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

Answer 6

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

Question 7

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

Answer 7

Sulfur dioxide.
Nitrogen oxides.
Particulates.

Question 8

What happens in a power station?

Answer 8

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.

Question 9

Name some renewable sources of energy

Answer 9

Wind
Tidal
Waves
Biomass
Solar
Hydroelectric
Geothermal

Question 10

Describe what is meant by a renewable source of energy.

Answer 10

One that will not be used up.

It also does not produce much carbon dioxide.

Question 11

What is a unit of power?

Answer 11

Watt (w)

Question 12

What is the formula to calculate power?

Answer 12

Time (s)

= Power (w)

Question 13

Define power.

Answer 13

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

Question 14

Define a kilowatt

Answer 14

1000 watts (kw)

Question 15

State the unit of energy that electricity companies use?

Answer 15

Kilowatt hours (kWh) or joules.

Question 16

What could you do to save energy in your house?

Answer 16

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.

Question 17

State the law of conservation of energy.

Answer 17

Energy cannot be created or destroyed - only transferred.

This is the law of the conservation of energy.

Question 18

Define a chemical energy store.

Answer 18

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

Question 19

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

Answer 19

chemical energy store.

Question 20

Energy to do with hot objects has a….

Answer 20

thermal energy store.

Question 21

Energy to do with moving objects has a…

Answer 21

kinetic energy store.

Question 22

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

Answer 22

gravitational potential energy store.

Question 23

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

Answer 23

elastic energy store.

Question 24

Name types of energy store.

Answer 24

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

Question 25

State three ways that energy is transferred between stores.

Answer 25

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

Question 26

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

Answer 26

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.

Question 27

What does dissipation mean?

Answer 27

Becoming spread out wastefully.

Question 28

Name two ways to reduce dissipation in a car.

Answer 28

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

Friction - ensure tyres are properly inflated to reduce friction.

Question 29

How is energy efficiency (%) calculated?

Answer 29

energy input

= efficiency (%)

Question 30

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

Answer 30

the amount of energy transferred.

Question 31

Efficiency can never be more than…… %

Answer 31

100%

Question 32

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

Answer 32

Thermal insulation
Lubrication