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CGP Physics > Section 4-Energy Resources and Energy Transfer P1 > Flashcards

Section 4-Energy Resources and Energy Transfer P1 Flashcards

1
Q

What are the 8 different types of energy stores that energy can be transferred between?

A
  • Kinetic
  • Thermal
  • Chemical
  • Gravitational Potential
  • Elastic Potential
  • Electrostatic
  • Magnetic
  • Nuclear
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2
Q

Define a kinetic energy store:

A

Anything moving has energy in its kinetic energy store

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3
Q

Define a thermal energy store:

A

Any object - the hotter it is the more energy it has in this store

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4
Q

Define a chemical energy store:

A

Anything that can release energy by a chemical reaction (e.g. food, fuel)

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5
Q

Define a gravitational potential energy store:

A

Anything in a gravitational field (i.e. anything which fall)

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6
Q

Define a elastic potential energy store:

A

Anything stretched, like springs and rubber bands

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7
Q

Define a electrostatic energy store:

A

E.g. two charges that attract or repel each other

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8
Q

Define a magnetic energy store:

A

E.g. two magnets that attract or repel each other

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9
Q

Define a nuclear energy store:

A

Atomic nuclei release energy from this store in nuclear reactions

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10
Q

What four main ways can energy be transferred between stores?

A

Mechanically
Electrically
By heating
By radiation

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11
Q

How can energy be transferred between stores mechanically?

A

An object moving due to a force acting on it (e.g. pushing, pulling, stretching or squashing)

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12
Q

How can energy be transferred between stores electrically?

A

A charge moving through a potential difference (e.g. charges moving round a circuit)

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13
Q

How can energy be transferred between stores by heating?

A

Energy transferred from a hotter object to a colder object (e.g. heating a pan of water on a hob)

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14
Q

How can energy be transferred between stores by radiation?

A

Energy transferred (e.g. by light/sound waves, e.g. energy from the sun reaching earth as light)

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15
Q

What’s the principle of conservation of energy?

A

Energy can be stored, transferred between stores, and dissipated(spread out) - but it can never be created or destroyed. The total energy of a closed system(a system that can be treated on its own without any matter being exchanged with the surroundings) has no net change.

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16
Q

When is energy useful?

A

Energy is only useful when it’s transferred from one store to a useful store.

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17
Q

What does the law of conservation of energy also mean that?

A

Total energy input = useful energy output + wasted energy

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18
Q

Most energy transfers involve some wasted energy often to thermal energy stores. What is it called when less energy is wasted?

A

More efficient

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19
Q

What’s the equation to calculate efficiency of an energy transfer?

A

useful energy output
Efficiency = ————————————x 100(%)
total energy output/input

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20
Q

What happens to wasted energy?

A
  • We generally can’t do anything with wasted energy
  • Wasted energy is an output that is transferred to less useful stores(normally thermal, light, sound) this energy is transferred away from the source and dissipates
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21
Q

Describe the energy transfer of a ball rolling up a slope:

A

Energy is transferred mechanically from kinetic energy to gravitational potential and thermal energy(due to friction the thermal energy is wasted)

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22
Q

Describe the energy transfer of a bat hitting a ball:

A

Some useful energy is transferred mechanically from the kinetic store of the bat to the kinetic store of the ball. The rest of the energy is wasted transferred from kinetic mechanically to thermal and sound.

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23
Q

Describe the energy transfer of an electric kettle boiling water:

A

Energy is transferred electrically from the thermal store of the kettles heating element to the thermal in the water. Some thermal energy is wasted to the surroundings.

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24
Q

Describe the energy transfer of a battery-powered toy car:

A

Energy is usefully transferred electrically from the chemical energy store of the battery to the kinetic energy store of the car and carried away by light from the headlights. Wasted energy are also from chemical to thermal and sound

25
Q

Describe the energy transfer of a Bunsen burner and a beaker:

A

Energy is usefully transferred by heating from the chemical energy store of gas to the thermal energy stores of the beaker and water. Energy is also wastefully transferred by heating as light.

26
Q

What’s a Sankey diagram?

A

Sankey(energy transformation) diagrams are a way of representing how much of the input energy is being usefully employed and how much is being wasted.
-The thicker the arrow the more energy it represents

27
Q

What are the three different ways energy can be transferred by heating?

A

Radiation
Conduction
Convection

28
Q

Define thermal radiation:

A

Thermal radiation is the transfer of energy by heating by infrared electromagnetic waves.

29
Q

Define conduction:

A

Conduction is the main form of energy transfer by heating particles in solids

30
Q

Define convection:

A

Conduction is the main form of energy transfer by heating particles in liquids and gases

31
Q

What state(s) of matter can thermal radiation be absorbed or emitted in?

A

Solid, Liquid and Gas

Any object can absorb or emit thermal radiation whether or not conduction or convection are also taking place

32
Q

What’s the correlation between temperature difference and the rate by which energy is transferred?

A

The bigger the temperature difference, the faster energy is transferred.

33
Q

What’s thermal radiation?

A

Thermal radiation/infrared radiation is just electromagnetic waves with a certain range of frequencies.

  • all objects are continually emitting and absorbing infrared radiation
  • an object that is hotter than its surroundings emits more radiation than it absorbs, an object that is cooler than its surroundings emits less radiation than it absorbs
34
Q

Define thermal conduction:

A

Thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles.

35
Q

What’s conduction?

A

In a solid particles are close together so when one vibrates it collides with other nearby particles. This process continues throughout the solid and gradually some of the energy is passed through the solid causing a rise in temperature.

36
Q

Describe an experiment to demonstrate conduction:

A
  • attach beads at regular intervals to a long metal bar using wax
  • hold the metal bar in a clamp stand, use a Bunsen burner to heat the side of the bar with no beads attached from the very end
  • as time goes on energy is transferred along the bar by conduction
  • the wax will gradually melt and the beads will fall as the temperature increases (this illustrates conduction)
37
Q

Define convection of heat:

A

Convection occurs when the more energetic particles move from the hotter region to the cooler region - and transfer energy as they do.

38
Q

What are convection currents about?

A

Convection currents are all about changes in density.

39
Q

Explain convection in an immersion heater:

A
  • energy is transferred from the heater coils to the water by conduction
  • the particles near the coils moved around faster so there’s more distance between them(expands)and becomes less dense
  • reduction in density means the hotter water rises above(displaces) the cooler denser water making the cooler water sink toward the coils
  • the cold water is then heated by the coils and rises and the cycle continues you’ll end up with convection currents circulating the energy throughout the water
40
Q

When is convection most efficient?

A

In roundish or squarish containers because they allow convection currents to work best.

41
Q

What water in the immersion heated wont heat up?

A

The water below the heater coils because convection happens above and there’s almost no conduction

42
Q

Describe a practical to see convection current:

A
  • place purple potassium permanganate crystals in a beaker of cold water(on one side of the beaker)
  • heat the beaker gently with a Bunsen burner underneath the crystals
  • as the temperature of the water increases around the crystals they begin to dissolve forming a bright purple solution
  • this purple solution is carried through the water by convection
43
Q

How can you reduce the rate of thermal conductivity? And what’s an example of a strategy

A

Some materials have low thermal conductivity
An example of a material like this is insulation(air can’t move so energy has to conduct very slowly through the pockets of air

44
Q

How can you reduce the rate of convection? And what’s an example of a strategy

A

To reduce convection you need to stop the fluid moving and prevent convection currents from flowing
Insulation is an example of a poor material for convection

45
Q

How can you reduce the rate of thermal radiation? And what’s an example of a strategy

A

To reduce the amount of energy transfers away from an object by thermal radiation, the object should be designed with a surface that is a poor emitter(e.g. white and shiny)

46
Q

What is a Leslie cube?

A

It’s a hollow, watertight metal cube whose four vertical faces have different surfaces.(e.g. black paint, white paint, shiny metal, dull metal)

47
Q

Describe how you can investigate emissions of thermal radiation with a Leslie cube?

A
  • place a empty Leslie cube on a heat proof mat
  • boil water in a kettle and fill the cube with boiling water
  • wait for the cube to warm up then hold a thermometer against each of the faces you should find all the faces have the same temperature
  • hold an infrared detector a set distance away and record the amount of IR radiation
  • repeat this for each of the faces making sure the detector is the same distance away and compare your results
48
Q

Why is work done the same as energy transferred?

A

When a force moves an object through a distance, work is done on the object and energy is transferred.

  • to make something move some sort of force needs to act on it
  • the force does ‘work’ to move the object and energy is transferred
  • whether energy is transferred usefully or not work is still done and therefore energy transferred=work done
49
Q

When is friction cause and what does it lead to?

A

Friction is caused when you push something along a rough surface
Energy is transferred to kinetic and wasted thermal energy

50
Q

What’s the equation linking Force, Work done and Distance moved? And what are the units?

A

Work done(J) = Force(N) x Distance moved(m)

51
Q

Define power:

A

Power is the rate at which energy is transferred.

52
Q

What’s the equation linking Time taken, Work done and Power? And what are the units?

A 
Work done(J)
Power(W) = ————————
                  Time taken(s)
53
Q

1 Watt = ?

A

1J of energy transferred per second (J/s)

54
Q

What links movement and an objects kinetic energy store?

A

Anything moving has a kinetic energy store

-energy is transferred to this store when something speeds up and away from this store when something slows down

55
Q

What’s the equation linking Kinetic energy, Speed and Mass?

A

Kinetic Energy(J) = 0.5 x Mass(kg) x Speed²(m/s)

56
Q

What’s the equation linking Mass, Height, Gravitational potential energy and Gravitational field strength?

A

Gravitational potential energy(J) = Mass(kg) x Gravitational field strength(N/kg) x Height(m)

57
Q

What’s the gravitational field strength on earth?

A

10N/kg

58
Q

What’s the transfer of energy of a falling object if there’s no air resistance?

A

Energy lost from GPE store = Energy gained in kinetic store

CGP Physics (16 decks)

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