Energy transfer and efficiency

Question 1

What is thermal energy?

Answer 1

Thermal energy is where an object at a higher temperature has greater thermal energy.
examples: heater, the Sun and hot water

Question 2

What is light energy?

Answer 2

Light energy is where light is a wave that is emitted from anything at a very high temperature.
examples: lamps, stars and fire

Question 3

What is electrical energy?

Answer 3

Electrical energy is usually associated with electric current
examples: mains supply, overhead cables and output from a transformer

Question 4

What is sound energy?

Answer 4

Sound energy is where an object vibrates and emits sound.

examples: buzzer, bell, siren and person talking

Question 5

What is kinetic energy?

Answer 5

Kinetic energy is energy due to movement.

examples: person running, high-speed train and planet orbiting the Sun

Question 6

What is chemical energy?

Answer 6

Chemical energy is energy stored by atoms.

examples: food, chemical cell and coal

Question 7

What is nuclear energy?

Answer 7

Nuclear energy is energy stored by the nuclei of atoms.

Question 8

What is elastic potential energy?

Answer 8

Elastic potential energy is where an object that has been pulled or squashed.
example: a stretched rubber band and cables supporting a bridge

Question 9

What is gravitational potential energy?

Answer 9

Gravitational potential energy is energy due to an object’s position in the Earth’s gravitational field. An object lifted higher will have greater gravitational potential energy.
examples: aeroplane in the sky and person up a ladder

Question 10

What does chemical energy produce?

Answer 10

chemical energy -> thermal energy + light energy + sound energy

Question 11

What is the principle of conservation of energy?

Answer 11

This is where energy can’t be created or destroyed but can be transferred from one form to another.

Question 12

Give one reason why heat energy might be wasted?

Answer 12

Heat energy might be wasted due to electric currents following in wires of due to friction between moving surfaces.

Question 13

What is efficiency?

Answer 13

Efficiency is a measure of how well a device transfers energy in the form we can.

Question 14

How is efficiency calculated?

Answer 14

efficiency = useful energy transferred by the device / total energy supplied by the device x 100%

Question 15

What are sankey diagrams?

Answer 15

Sankey diagrams are energy-transfer diagrams that show the different forms of energy takes during a transfer. The thickness of the arrow in the diagram is drawn to scale to show the amount of energy transferred.

Question 16

What can all object do to do with infrared radiation?

Answer 16

All objects can emit infrared radiation, absorb infrared radiation and reflect infrared radiation.

Question 17

What does the amount of infrared radiation emitted by an object depend on?

Answer 17

The amount of infrared radiation emitted by an object depends on its temperature and its surface.

Question 18

Give 2 reasons to why a dull black surface loses energy more quickly than a bright shiny surface:

Answer 18

• a dull black surface is a good radiator of heat

- a bight shiny surface is a poor radiator of heat

Question 19

What is the difference between a dull black surface and a bright shiny surface?

Answer 19

A dull black surface is a good absorber of heat radiation where as a bright shiny surface is a poor absorber, as it reflects the heat radiation away.

Question 20

What is thermal equilibrium?

Answer 20

Thermal equilibrium is where eventually, the rate of heat absorption will equal the rate of heat radiation and the temperature remains steady.

Question 21

What do all atoms have?

Answer 21

All atoms have both kinetic energy and potential energy.

Question 22

What happens when substances are heated?

Answer 22

When substances are heated, the temperature increases and the atoms gain more kinetic energy.

Question 23

What is the heat energy of a substance the total of?

Answer 23

The heat energy of a substance is the total kinetic energy and potential energy of all the atoms in the substance.

Question 24

How can you investigate the different rates of heat radiation of different surfaces?

Answer 24

To investigate the different rates of heat radiation of different surfaces, you can compare the temperature over time of a silvered beaker and blackened beaker.

Question 25

How can you investigate the different rates of heat absorption?

Answer 25

To investigate the different rates of heat absorption, you can use a radiant heater between two plates - one silvered and one blackened. Then time how long it takes for each plate to get hot enough to melt some wax.