energy stores and transfers ༊*·˚

Question 1

what happens to the gravitational energy store of an object when you raise it up?

Answer 1

there is an increase of energy in its gravitational store.

Question 2

what happens to the kinetic energy store of an object when it speeds up?

Answer 2

there is an increase of energy in its kinetic store.

Question 3

how does an increase in temperature effect the internal thermal energy store of an object?

Answer 3

there is an increase of energy in its thermal store.

Question 4

what must you do to a fuel to release its internal energy store and transfer it from the fuel?

Answer 4

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

Question 5

when you stretch or compress an object, what are you doing to its elastic energy store?

Answer 5

there is an increase of energy in its elastic store.

Question 6

what is the principal of the conservation of energy?

Answer 6

energy can be transferred usefully, stored or dissipated, nut cannot be created or destroyed.

Question 7

by what means can energy be transferred?

Answer 7

electrical work, heating, radiation, or mechanical work

Question 8

what is the definition of a closed system?

Answer 8

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

Question 9

how do we describe the energy transferred to the surroundings that does not serve a useful purpose?

Answer 9

wasted energy.

Question 10

how do we reduce the wasted energy in a system?

Answer 10

lubrication and thermal insulation.

Question 11

if an object conducts a large amount of thermal energy across it, what must be true about its thermal conductivity?

Answer 11

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

Question 12

how will the time taken for an object with thin walls and high thermal conductivity to cool down compared with sn object with thick walls and low thermal conductivity, assuming they start at the same temperature?

Answer 12

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

Question 13

what is the equation used to calculate the efficiency of thermal energy transfer?

Answer 13

efficiency = useful energy / total energy.

Question 14

if you know the power transferred, how can you use that to calculate efficiency?

Answer 14

useful power output / total power input.