P7

Question 1

Which are the eight stores in which energy can be held?

Answer 1

1) Kinetic
2) thermal
3) chemical
4) gravitational potential
5) elastic potential
6) electrostatic
7) magnetic
8) nuclear

Question 2

What are the four ways energy can be transferred between stores?

Answer 2

1) Mechanically – an object moving due to a force acting on it
2) electrically – a charge moving through potential difference
3) heating – energy transferred from the hotter to call object
4) radiation – energy transferred by waves

Question 3

What is the law of conservation of energy ?

Answer 3

Energy can be stored, transferred or dissipated but it can never be created or destroyed. The total energy of a close system has no net change

Question 4

When is energy useful?

Answer 4

Energy is useful when it is transferred from one store to useful store

Question 5

Efficiency=

Answer 5

Efficiency= Useful output energy/ input energy

Question 6

Which three ways can energy by heating be transferred?

Answer 6

1) Conduction- vibrating particles pass extra energy in their kinetic energy stores to the kinetic energy stores of surrounding particles in solids
2) convection - particles with more energy move from a hotter region to a cooler region where particles with less energy take their place .
3) radiation- energy carried by waves

Question 7

How can we reduce unwanted energy transfers in the home ? Give Fiveways

Answer 7

1) loft insulation – fibreglass wool laid on loft floor and ceilings reduces energy loss by conduction and convection .
2) Cavity walls and cavity wall installation – cavity walls have a To reduce conduction and cavity walls insulation such as insulation foam minimises convection .
3) Double glazing – gap between glass sheets reduces conduction .
4) Thick curtains – reduces convection and conduction.
5) Draft proofing – strips of foam/ plastic around doors/windows reduces convection

Question 8

How can unwanted energy transfers be prevented in the boiler and hot water pipes?

Answer 8

Hot water tank jacket – reduces conduction.
Covering pipes and installation – reduces conduction and convection.
Short pipes – or to spend less time in them. Wide pipes – smaller surface area to volume ratio so less water is near the surface and less energy is lost by conduction.
White pipes – reduces loss by radiation

Question 9

Kinetic energy=

Answer 9

Kinetic energy= gravitational potential energy