CP3 Conservation of Energy

Question 1

What is mass measured in?

Answer 1

Kilograms (Kg)

Question 2

What is energy measured in?

Answer 2

Joules ( J )

Question 3

Conservation of Energy

Answer 3

Energy can not be created or destroyed; Energy can only be transferred from one store to another.

Question 4

What is Energy Efficiency?

Answer 4

A way of describing how good a device is at transferring energy into useful forms.

Question 5

What’s the equation for energy efficiency?

Answer 5

Efficiency = useful energy transferred / total energy

Question 6

Name two things that affect the rate of energy transfer.

Answer 6

• Thickness of material
• Temperature difference

Question 7

Thermal Conductivity

Answer 7

A measure of how well a material conducts energy when it is heated

Question 8

What does a high thermal conductivity mean?

Answer 8

The material is good at conducting thermal energy

Question 9

What is the equation for Kinetic Energy?

Answer 9

KE = 0.5mv^2

Kinetic Energy = 0.5 * Mass * Velocity^2

Question 10

What is Kinetic Energy measured in?

Answer 10

Joules

Question 11

Convert 250g into Kg

Answer 11

250g = 0.25kg

250 / 1000 = 0.25

Question 12

What kind of diagram do we use to show energy transfers?

Answer 12

Sankey Diagram

Question 13

What is a ‘System’ when we talk about energy transfers?

Answer 13

A set of things being studied - for example a kettle, the water in it, and it’s surroundings form a simple system.
An object or a group of objects that interact.

Question 14

Dissipated

Answer 14

Spread out

Question 15

Conduction

Answer 15

The way energy is transferred through solids by heating.
Vibrations are passed from particle to particle.

Question 16

Convection

Answer 16

The movement of particles in a fluid depending on their temperature.
Hotter, less dense regions rise, and cooler, denser regions sink.

Question 17

Emit

Answer 17

To give out

Question 18

What does it mean if an energy source is non-renewable?

Answer 18

It will eventually run out because we cannot renew our supplies of it.

Question 19

What does is mean if an energy source if renewable?

Answer 19

It will never run out

Question 20

Name all 8 energy stores

Answer 20

• Magnetic
• Thermal
• Elastic potential
• Gravitational potential
• Nuclear
• Electrostatic
• Chemical
• Kinetic

Question 21

Define Thermal Energy Store and give an example

Answer 21

The energy a system has because of its temperature.
An example could be that the thermal store of water in a kettle increases when you turn the kettle on.

Question 22

Define Kinetic Energy Store and give an example of one

Answer 22

The energy a system has because it’s moving.
An example could be that if a car speeds up from 30km/h to 60km/h then its kinetic energy store will increase.

Question 23

Define Gravitational Potential Energy Store and give an example of one

Answer 23

The energy a system has because of how high it is above the ground.
An example could be: if you pick up an object off the ground, its gravitational potential will increase.

Question 24

Define Chemical Energy Store and give an example

Answer 24

The energy stored in chemicals including food, fuels, and batteries.
An example could be: If you turn on a battery powered torch, the chemical energy stored in the battery will decrease.

Question 25

Define Elastic Potential Energy Store and give an example

Answer 25

The energy stored in a system when it is stretched or squashed.
Example: A spring that is stretched will have an increased elastic potential store.

Question 26

Define Magnetic Energy Store and give an example

Answer 26

The energy stored when two repelling magnetic poles have been pushed together or two attracting poles have been pulled apart.
Example: If you hold two magnets with opposite poles together, they will attract each other. If you pull them apart then you will have increased the magnetic energy store.

Question 27

Define Electrostatic Energy Store and give an example

Answer 27

The energy stored the repelling charges have been moved closer together or attracting charged have been pulled apart.
Example: If you touch a Van de Graaff generator, then your hair will stick up because the hairs will have a positive charge and repel each other.

Question 28

Define Nuclear Energy Store and give an example

Answer 28

The energy stored in the nucleus of an atom
Example: the huge amount of energy stored in the nuclei of atoms is why nuclear weapons are so devastating.

Question 29

How does energy move from one store to another?

Answer 29

Through an energy transfer pathway

Question 30

Name the 6 Energy Transfer pathways

Answer 30

• Mechanical (forces)
• Electrical
• Heating
• Radiation (waves)
• Light
• Sound

Question 31

What energy is stored in a chocolate bar?

Answer 31

Chemical

Question 32

What type of energy would you find in a train moving at 70km/h ?

Answer 32

Kinetic Energy

Question 33

What energy is stored in a rocket during take off?

Answer 33

Kinetic Energy and Gravitational Potential Energy

Question 34

What type of energy is found in the nucleus of an atom?

Answer 34

Nuclear Energy

Question 35

What happens to wasted energy?

Answer 35

It is dissipated to the surroundings

Question 36

For every 100J of energy put into a lightbulb, 5J is useful.
Calculate the efficiency of the light bulb.

Answer 36

0.05
5J / 100J = 0.05

Question 37

A device transfers 30J of useful energy every second. The total energy transferred to the device each second is 50J.
Calculate its efficiency.

Answer 37

0.6
30J / 50J = 0.6

Question 38

A light bulb transfers 90J of energy by heating every second. 100J of energy is transferred to the light bulb every second by electricity.
Calculate its efficiency.

Answer 38

0.9
90J / 100J = 0.9

Question 39

What number can the efficiency of a device never be greater than?

Answer 39

1 (or 100%)

Question 40

What 3 ways can energy be transferred by heating?

Answer 40

• Conduction
• Convection
• Radiation