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Physics GCSE > Energy > Flashcards

Energy Flashcards

1
Q

What is the rule of conservation of energy?

A

Total energy before a process = Total energy after a process

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2
Q

What is the unit of energy?

A

Energy is measured in joules (J)

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3
Q

What the main energy stores?

A
  • kinetic store
  • gravitational potential store
  • chemical store
  • elastic store
  • thermal store
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4
Q

How can we tell if there is a change to the kinetic store?

A

If the object changes speed

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5
Q

How can we tell if there is a change to the gravitational potential store?

A

If the object ends up higher or lower than it started out

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6
Q

how can we tell if there is a change to the chemical store?

A

If a chemical reaction takes place e.g. fuel burns, so you have less fuel than when you started

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7
Q

How to tell if there is a change in the elastic store?

A

If an object changes its shape

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8
Q

How can we tell if there is a change in the thermal store?

A

If the temperature of the object changes

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9
Q

What are the main energy pathways?

A
  • Mechanical working
  • electrical working
  • heating by particles
  • heating by waves
  • light
  • sound
  • electromagnetic radiation
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10
Q

What is the mechanical working pathway?

A

Energy transferred by a force of physical mechanism (e.g. a pulley)

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11
Q

What is the electrical working pathway?

A

Energy transferred by an electric current

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12
Q

What is the heating by particles pathway?

A

Energy transferred from a higher temperature region to a lower temperature by moving particles (conduction, convection)

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13
Q

What is the heating by waves pathway?

A

Energy transferred from a higher temperature region to a lower temperature region by the emission of infrared radiation

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14
Q

What is the light pathway?

A

Energy transferred as visible light

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15
Q

What is the sound pathway?

A

Energy transferred as a sound wave

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16
Q

What is the electromagnetic radiation pathway?

A

Energy transferred as an electromagnetic wave (radio, microwave, infrared, visible, ultraviolet, X ray, gamma)

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17
Q

What is the equation for work done?

A

Work done by a force (joules- J) = force (N) x distance moved in the direction of the force (m)
W=Fs

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18
Q

What is work done?

A

If a force acts on an object, and the object moves in the direction of the force, we say that work has been done by the force

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19
Q

Finish the sentence: When work is done by a force, ________

A

Energy is transferred between stores

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20
Q

What is the equation for gravitational potential energy?

A

Change in the gravitational potential energy store (J) = mass (in kg) x gravitational field strength (N/kg) x height (m)
GPE = mgh

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21
Q

What are the units for power?

A

Watts

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22
Q

What is the equation for power?

A

power (in watts) x time (in seconds) = energy transferred (in joules)/work done (in joules)
P x t = E

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23
Q

What is the definition of power?

A

Rate of energy transfer
Rate at which work is done

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24
Q

equation for efficiency

A

efficiency = (useful energy transferred / total energy input ) x 100
OR
efficiency = (useful power output/total power input) x 100

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25
Q

What does it mean if energy is dissipated?

A

stored in a less useful way

26
Q

What causes non-useful energy transfer and how can this be reduced for each one?

A

friction / air resistance (makes things heat up)
- use lubricants e.g. oil to reduce friction
- streamline your object

heating of surroundings (hot object in cooler surroundings)
- put on a lid
- use insulating materials

electrical resistance of wires (heat up when a current flows)
- use lower resistance cables

27
Q

What factors affect the rate of energy transfer across the material?

A

a) the thickness
the greater the thickness, the smaller the rate of energy transfer across the barrier
b) the temperature difference
The greater the temperature difference, the greater the rate of energy transfer
c) the material itself
Materials with a high thermal conductivity transfer energy at a greater rate
Materials with a lower thermal conductivity transfer energy at a smaller rate

28
Q

What environmental impact is there from using coal?

A

Releases carbon dioxide (greenhouse gas), can produce sulfur dioxide which causes acid rain, produces soot when burned

29
Q

What are the different ways in which energy can be transferred?

A

Mechanical work, electrical work, heating by particles, heating by waves

30
Q

What equation links kinetic energy, mass, and speed?

A

Kinetic energy = 0.5 x mass x (speed)^2
KE = 1/2 mv^2

31
Q

Give five examples of a reliable energy resource

A

Coal, oil, gas, uranium, hydroelectric, biofuel, geothermal

32
Q

Define the term “power”

A

Power is the rate of energy transfer

33
Q

Give an example of a non-useful energy transfer

A

e.g. transfer to the thermal store of the surroundings

34
Q

What are the different ways in which energy can be stored in a system?

A

Kinetic store, gravitational potential store, elastic store, thermal store, chemical store

35
Q

Define the specific heat capacity of a material

A

The amount of energy needed to raise the temperature of 1 kg of an object by 1 degrees Celsius

36
Q

Give five examples of a renewable energy resource

A

e.g. wind, solar, tidal, hydroelectric, bio-fuel, geothermal, waves

37
Q

What are the effects of thermal conductivity of the walls of a building on the rate of cooling?

A

The greater the thermal conductivity, the greater the rate of cooling

38
Q

In physics, what is a system?

A

An object or a group of objects

39
Q

What is meant by the dissipation of energy?

A

Energy becomes stored in non-useful ways (usually the thermal store of the surroundings)

40
Q

What are the effects of thickness of the walls of a building on the rate of cooling?

A

The thicker the wall, the smaller the rate of cooling

41
Q

What are the changes to stored energy when an object is accelerated by a constant force?

A

The kinetic energy store of the object increases

42
Q

What equation links changes to the gravitational potential energy, mass, gravitational field strength, and height?

A

Change in gravitational potential energy = mass x gravitational field strength x height
GPE = mgh

43
Q

What environmental impact is there from using wind?

A

Wind turbines can be noisy, and are often considered an eye-sore

44
Q

What are the changes to stored energy when an electric kettle brings water to the boil?

A

Energy is transferred to the element by electrical working and the thermal store of the element increases. Energy is then transferred to the thermal energy store of the water by heating

45
Q

State the equation for efficiency

A

Efficiency = useful power output / total energy input

46
Q

What is meant by a renewable energy resource?

A

One that is being (or can be) replenished as it is used

47
Q

What are the changes to stored energy when an object is projected up a slope?

A

The kinetic energy store of the object decreases, and the gravitational potential store of the object increases

48
Q

What environmental impact is there from using biofuel made from crops?

A

Land needed could be used to grow food. Can be close to carbon neutral as the CO2 released when burned was taken in when the plant was growing

49
Q

What is the equation that links power, energy transferred, and time?

A

Energy transferred = power x time
E = Pt

50
Q

What environmental impact is there from using hydroelectricity?

A

Dam needs to be built, and land flooded to make the reservoir

51
Q

Explain what is meant by the conservation of energy

A

The total energy before a process = the total energy after a process

52
Q

Suggest ways in which the efficiency of a machine could be increased

A

Use lubrication to reduce friction, use wires of a lower resistance

53
Q

Give four examples of a non-renewable energy resource

A

Coal, oil, natural gas, uranium

54
Q

What is meant by the term “energy resource”?

A

A material or mechanism used for the generation of electricity, for transport, and for heating of homes and workplaces

55
Q

What are the changes to stored energy when a vehicle slows down?

A

The kinetic energy store of the object decreases, and the thermal energy store of the brakes increases

56
Q

What unit is power measured in?

A

Watts (W)

57
Q

What environmental impact is there from using uranium?

A

Uranium has to be mined, byproducts are highly radioactive and last for a long time

58
Q

What are the changes to stored energy when a moving object hits an obstacle?

A

The kinetic energy store of the object decreases, and the thermal energy store of the obstacle and the surroundings increases

59
Q

A car driver sees a fallen tree lying across the road ahead and makes an
emergency stop.
The braking distance of the car depends on the speed of the car.
For the same braking force, explain what happens to the braking distance if the
speed doubles.
You should refer to kinetic energy in your answer.

A
  • doubling speed increase the kinetic energy
  • kinetic energy increases by a factor of 4
  • work done (by brakes) to stop the car increases
  • work done increases by a factor of 4
  • work done is force × distance and braking force is constant
  • so if work done increases by 4 then the braking distance must increase by 4
60
Q

Give one environmental advantage to turning off electrical appliances when
they are not being used.

A

e.g.
- conserves fossil fuels
- less (fossil) fuels burned
- less pollutant gas (produced)
- less greenhouse gas (produced)

Physics GCSE (8 decks)

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