P7.2 Power And Efficiency

Question 1

What is electrostatic store associated with

Answer 1

Separation of charges

Question 2

What is chemical store associated with

Answer 2

Rearranging atoms

Question 3

Law of Conservation of Energy

Answer 3

Energy cannot be created or destroyed,
it can only be transferred between stores

Question 4

If work is done on an object, what is the type of transfer

Answer 4

Mechanical

Question 5

How do you convert from milliamps to amps

Answer 5

Divide by 1000

Question 6

Name something that has a thermal energy store

Answer 6

A warm bath

Question 7

Describe how bread is toasted

Answer 7

Toaster is turned on,
electrical energy is transferred to the thermal store of the heating element.
Then thermal energy is transferred by radiation to heat the surface of the bread

Question 8

What equation links cost of electricity, energy transferred, and cost per unit

Answer 8

Cost of electricity = energy transferred x cost per unit

Question 9

Define dissipated energy

Answer 9

Energy with no use, lost in the environment

Question 10

What kind of wall would lose heat the quickest

Answer 10

Thin wall
With high thermal conductivity

Question 11

Why do high thermal conductivities cool quicker

Answer 11

Energy can be transferred quicker

Question 12

Efficiency

Answer 12

Measure of how efficiently a device transfers energy from one store to another

Efficiency = useful energy output / total energy input

How can you improve efficiency
Insulating objects, lubricating, energy efficient light bulbs

Question 13

Sankey diagram

Answer 13

How energy is redistributed when a system is changed

Question 14

8 energy stores

Answer 14

kinetic, thermal, chemical, elastic potential, gravitational potential, nuclear, electrostatic, magnetic

Question 15

Example of object with energy in kinetic store

Answer 15

Anything moving

Question 16

Example of object with energy in thermal store

Answer 16

Anything with temperature

Question 17

Example of object with energy in chemical store

Answer 17

Anything that can release energy by chemical reaction

Question 18

Example of object with energy in elastic potential store

Answer 18

Anything stretched like strings and rubber bands

Question 19

Example of object with energy in gravitational potential store

Answer 19

Anything in gravitational field

Question 20

Example of object with energy in nuclear store

Answer 20

Atomic nuclei when nuclear reactions happen

Question 21

Example of object with energy in electrostatic store

Answer 21

2 charges that attract or repel each other

Question 22

Example of object with energy in magnetic store

Answer 22

2 magnets that attract or repel each other

Question 23

4 ways energy can be transferred

Answer 23

Mechanically, electrically, by heating, by radiation

Question 24

How energy is transferred mechanically

Answer 24

Object moving due to force acting on it

Question 25

How energy is transferred electrically

Answer 25

Charge moving through a potential difference

Question 26

How energy is transferred by heating

Answer 26

Energy transferred from hotter object to colder object

Question 27

How energy is transferred by radiation

Answer 27

Energy transferred by light/sound waves

Question 28

Energy can be stored, transferred between stores and dissipated but…

Answer 28

…energy can never be created or destroyed