M. RahmanP1 TOPIC 6

1) Name the 9 types of energy giving examples.

AnswerElectricityLight SoundKineticNuclear Thermal Gravitational potential energyElasticChemical

M. RahmanP1 TOPIC 6

2) Name the two types of stored Energy. (2)

Answer

• Potential energy eg: Elastic and gravitational

• Chemical energy eg: food, fuels and batteries

M. RahmanP1 TOPIC 6

3) What is the conservation of energy (2).

• Energy cannot be created or destroyed and can only be converted from one form to another.

• For example all energy supplied to a system needs to be accounted for.

If 300J of electrical energy is supplied to a system, the total useful energy and wasted energy must equal 300j

M. RahmanP1 TOPIC 6

4) Explain how energy is conserved in the following ;a) Solar panel (Light to--______)b) Falling object (Gravitational potential -______)c) TV (Electrical ----- ______ +________)d) Batteries (Chemical-- _________ ------__________

Ans:a) Solar panel (Light to-- Electricity)b) Falling object (Gravitational potential -Kinetic)c) TV (Electrical ----- Sound + Light)d) Toy car batteries (Chemical-- Electrical Kinetic.

M. RahmanP1 TOPIC 6

5) Why is the total input energy not the same as the useful output energy?Ans:

a) Energy could be wasted eg as heat or sound

M. RahmanP1 TOPIC 6

6) What kind of energy transfers happen to a person who is running (2).Ans:Chemical energy(food) to kinetic energy (movement

M. RahmanP1 TOPIC 6

7) A machine has an input of 500W. It wastes 300W. (3)a) Calculate the useful energy b) b) Calculate the efficiency.

Answera) Total input energy= Useful energy+ wasted energy. Useful energy = 500-300= 200W

b) Efficiency= useful 200 = 0.4 or 40% Total input 500

M. RahmanP1 TOPIC 6

8)

a) Calculate the energy suppliedb) What form is the energy wasted?c) What is the efficiency of the light bulb?

Answera) Total input energy= Useful energy + wasted energy. = 300 + 30 = 330b) Heat

c) Efficiency= useful 300 = 0.91 or 91% Total input 330

Light bulb 300 J of light energy

30 J of wasted energy

Energy supplied

M. RahmanP1 TOPIC 6

9) For an object to stay at the same temperature what needs to happen.

AnswerThe energy absorbed must = The energy emitted

Or

Power absorbed must = The power emitted

M. RahmanP1 TOPIC 6

10) a) Describe how the earth is kept at a constant temperature. b) Describe why a radiator will reach a constant temperature.

Answer

a) The amount of heat absorbed by the earth from the sun will become equal to the amount of heat emitted.

b) The amount of heat supplied will equal to the amount of heat emitted (lost)

M. RahmanP1 TOPIC 6

11) Which colours are the best absorbers and emittersa) Blackb) Whitec) Silver

Answer

a) Black

M. RahmanP1 TOPIC 6

12) What type of materials are the best absorbers.a) Mat/roughb) Shiny/gloss

AnswerMat/rough

M. RahmanP1 TOPIC 6

13) Why are solar panels painted black(6)

Answer• Heat radiation from the sun is

absorbed by the black surfaces.

M. RahmanP1 TOPIC 6

14) Why is a silver coloured blanket used by athletes to cover themselves after a race?

Answer.The silver colour helps to stop the body heat from radiating away keeping the athlete warm.

M. RahmanP1 TOPIC 6

15) What are the three ways energy is transferred.(3)

AnswerConductionConvectionRadiation

M. RahmanP1 TOPIC 6

16) The thermal heat is transferred to earth from the sun by (infra red) radiation. Why is thermal heat not transferred through convection or conduction (3).

Answer• Convection and conduction

require particles, radiation does not. As there are no particles in space (vacuum) convection and conduction cannot happen.

M. RahmanP1 TOPIC 6

17) Solar hot water panels contain water pipes. At the start the temperature of the water in the pipe increases. After a while, the temperature becomes constant. Suggest changes which would increase the constant temperature reached.

Answer• Paint the solar panels black• Cover pipe with insulation.

M. RahmanP1 TOPIC 6

18)

• Using the information in the diagram, describe the energy transfers involved in producing electrical energy in a fossil fuel powered power station.

Answer• Heat and light energy supplied by the sun,• for photosynthesis of plants, or energy for animals stored as

chemical energy• plants and animals die over million years become fossil fuels• Fossil fuels (chemical energy) burnt to produce thermal

energy,• to boil water produces steam.• Steam (kinetic energy) turns turbine,• this turns generator ((kinetic energy) which produces

electricity

Underlined and in bold are the energy transfers