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Physics > P7 > Flashcards

P7 Flashcards

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1
Q

What is chemical energy

A

Energy stored in the bonds of compounds

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2
Q

What is thermal energy

A

Energy relating to temperature, or a change in temperature

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3
Q

What is kinetic energy

A

Energy an object has due to motion

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4
Q

What is graviational energy

A

The energy an object has due to gravity

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5
Q

What is elastic energy

A

The mechanical potential energy of a material as work is performed on it

(Energy associated with deforming metals)

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6
Q

What is nuclear energy

A

Energy associated with nuclear fusion or fission

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7
Q

What is electrostatic energy

A

Energy associated with the distortion of electric fields and charges

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8
Q

What i magnetic energy

A

Energy associated with the separation or joining if magnetic poles

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9
Q

What is non-zero speed

A

The speed of any object with kinetic energy

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10
Q

How is GPE calculated

A

Mass × gravity × height

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11
Q

How is kinetic energy calculated

A

1/2mv²

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12
Q

How is thermal energy calculated

A

Mass × SHC × ∆temp

SHC is the energy needed to increase an object by 1°C or 1K

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13
Q

How is elastic energy calculated

A

1/2kx²

K= spring constant
X = extension

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14
Q

How is energy transferred

A

Mechanically → using forces
Electrically → using current
Heating by particles
Heating by radiation
.

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15
Q

In what way is kinetic energy transferred

A

Mechanically

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16
Q

How is efficiency of energy transferr calculated

A

(useful output ÷ output energy)×100

(Useful output ÷ input)×100

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17
Q

How are thermal and chemical energy transferred

A

By heating of particles

Chemical energy can also be transferred mechanically

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18
Q

How do electromagnetic waves transfer energy

A

Heating by radiation
The greater their frequency, the greater their energy transfer

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19
Q

Describe the changes in energy when falling down a steep slope

A

Gravitational energy is transferred mechanically to kinetic energy

Then mechanical again kinetic energy is transferred to chemical energy

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20
Q

What is the conservation of energy

A

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

21
Q

What happens during the transfer of energy in a closed system

A

The increase of energy in one store will be equal to the decrease in another store

22
Q

Where does an electric current transfer energy from

A

From a chemical store in a battery
From a chemical or nuclear store, used to power the mains elesctricity

23
Q

What are power ratings

A

Ratings given to appliances to show how much energy they will transfer faster

24
Q

Whats an advantage to using high energy rated appliances

A

They will complete a task faster, but at a higher price

25
Q

How do you calculate electrical work done

A

Work done = power × time

26
Q

What is electrical work done measured in

A

kWh (killowatt hour)

27
Q

How do you transfer joules to kWh

A

1kWh = 3.6×10⁶ J

1kW = 1000J
Hour = 3600s

28
Q

How do you calculate the cost of an appliance

A

Electrical work done × current rate

29
Q

What do electrical appliances do (energy transfer)

A

Transfer energy electrically from chemical stores

30
Q

How is energy transferred when current flows through a wire

A

When current flows through a wire the wire heats up
This means energy is transferred to a chemical store and is wasted

31
Q

Why cant appliances such as motors be 100% efficient

A

As energy is transferred to the thermal store

32
Q

In what systems is chemical energy lost to the surroundings

A

In all mechanical systems

33
Q

Why is electricity transferred at a high voltage but low current

A

To reduce the heat loss to the environment
(Through heating of particles)

34
Q

What is energy diserpation

A

Loss of energy to the surroundings

35
Q

How is energy loss reduced in mechanical systems

A

Using lubrication reduces friction, and therefore energy loss is reduced

36
Q

How is heat loss by heating of particles reduced

A

By using insulation
(Insulating materials)

37
Q

What is thermal conductivity

A

A measure of how quickly energy is transferred through a material

The thermal conductivity of a material is fixed and doesnt change based on its mass

The higher the thermal conductivity the faster energy is transferred

38
Q

Why are houses built using materials with a low thermal condictivity

A

Prevents hot air entering and making the house hot during summer
Prevents hot air leaving the house during winter

It reduces the transfer of heat to the surroundings

39
Q

What is a cavity wall

A

A method of insulating a building

Insulating material (low thermal conductivity) is placed between the inner and outer walls of a house

40
Q

How does loft insulation help reduce heat loss

A

As hot air rises it is important to have good loft insulation

This will reduce the heat loss to the surroundings

41
Q

How does double glazing reduced a houses thermal conductivity

A

As that is placed between the panes of glass has a low thermal conductivity

Glass also has a relatively low thermal conductivity

42
Q

How does increasing the thickness of a wall affect energy transfer

A

The thicker the wall the slower the transfer of energy

Heat is transferred by conduction at a slower rate
There is a greater distance the energy has to be moved

43
Q

What is conduction

A

Energy transferred between neighbouring atoms or molecules

44
Q

Why are igloos warm

A

Although ice is a ‘cold’ material, they have a low thermal conductivity, and therefore can trap heat inside

45
Q

How do you calculate the efficiency of energy transfer

A

Efficiency = (useful output energy ÷ input energy) × 100

46
Q

What is a sankey diagram

A

A diagram drawn showing total energy, and how much is wasted or useful

The size of an arrow represents the amount of energy transferred

47
Q

How are sankey diagrams drawn

A

You need to use a scale so that the size of the arrow is proportional to the energy

48
Q

How do you improve efficiency

A

Use insulation.
Use materials that reduce unwanted energy transfer
Use technology to produce better devices, e.g LEDs which give of little heat

Physics (10 decks)

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