P7.2 Power And Efficiency Flashcards

1
Q

What is electrostatic store associated with

A

Separation of charges

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2
Q

What is chemical store associated with

A

Rearranging atoms

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3
Q

Law of Conservation of Energy

A

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

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4
Q

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

A

Mechanical

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5
Q

How do you convert from milliamps to amps

A

Divide by 1000

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6
Q

Name something that has a thermal energy store

A

A warm bath

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7
Q

Describe how bread is toasted

A

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

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8
Q

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

A

Cost of electricity = energy transferred x cost per unit

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9
Q

Define dissipated energy

A

Energy with no use, lost in the environment

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10
Q

What kind of wall would lose heat the quickest

A

Thin wall
With high thermal conductivity

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11
Q

Why do high thermal conductivities cool quicker

A

Energy can be transferred quicker

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12
Q

Efficiency

A

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

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13
Q

Sankey diagram

A

How energy is redistributed when a system is changed

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14
Q

8 energy stores

A

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

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15
Q

Example of object with energy in kinetic store

A

Anything moving

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16
Q

Example of object with energy in thermal store

A

Anything with temperature

17
Q

Example of object with energy in chemical store

A

Anything that can release energy by chemical reaction

18
Q

Example of object with energy in elastic potential store

A

Anything stretched like strings and rubber bands

19
Q

Example of object with energy in gravitational potential store

A

Anything in gravitational field

20
Q

Example of object with energy in nuclear store

A

Atomic nuclei when nuclear reactions happen

21
Q

Example of object with energy in electrostatic store

A

2 charges that attract or repel each other

22
Q

Example of object with energy in magnetic store

A

2 magnets that attract or repel each other

23
Q

4 ways energy can be transferred

A

Mechanically, electrically, by heating, by radiation

24
Q

How energy is transferred mechanically

A

Object moving due to force acting on it

25
Q

How energy is transferred electrically

A

Charge moving through a potential difference

26
Q

How energy is transferred by heating

A

Energy transferred from hotter object to colder object

27
Q

How energy is transferred by radiation

A

Energy transferred by light / sound waves

28
Q

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

A

…energy can never be created or destroyed