YR 9 - Energy stores and Transfers

Question 1

what happens when an object is raised up?

Answer 1

when an object is raised up, there is an increase in its gravitational store.

Question 2

what happens when an object moves faster?

Answer 2

when an object lives faster, there is an increase of energy in its kinetic store

Question 3

what happens when an objects temperature increases?

Answer 3

when an objects temperature increases, there is an increase of energy in its thermal store.

Question 4

what happens when a fuel burns?

Answer 4

when a fuel burns, energy is transferred from its chemical store.

Question 5

what happens when an object is stretched or compressed?

Answer 5

when an object is stretched or compressed, there is an increase of energy in its elastic store

Question 6

what is the Law of Conservation of Energy?

Answer 6

Energy cannot be created not destroyed, but can be stored, dissipated or transferred usefully.

Question 7

what are ways energy can be transferred?

Answer 7

energy can be transferred by:
- doing electrical work
- heating
- radiation
- mechanical work

Question 8

what is in a closed system?

Answer 8

in a closed system there is no net energy change to the total system.

Question 9

what is wasted energy?

Answer 9

energy which is dissipated to the surroundings is often described as wasted

Question 10

what can reduce unwanted energy transfers?

Answer 10

Lubrication and thermal insulators reduce unwanted energy transfers.

Question 11

what happens when the thermal conductivity of a material increases?

Answer 11

the higher the thermal conductivity of a material, the higher the energy transfer by conduction across the material.

Question 12

Finish the sentence:

objects with thin walls and ____ thermal conductivity ____ quicker than objects with _____ walls and low thermal conductivity.

words: low, large, small, high, heat, melt, radiate, hard, thick

Answer 12

objects with thin walls and high thermal conductivity cool quicker than objects with thick walls and low thermal conductivity

words: high, cool, thick

Question 13

how do you calculate the efficiency of a transfer?

include: the equation

Answer 13

efficiency = useful energy output energy transfer / total input energy transfer.

OR (it may also be calculated as)

efficiency = useful power output / total power input.