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energy Flashcards

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1
Q

How is energy transferred?

A

Between energy stores

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2
Q

What is a kinetic energy store?

A

Anything moving has energy in its kinetic energy store

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3
Q

What is 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

What is a chemical energy store?

A

Anything that can release energy in a chemical reaction, e.g. food, fuel

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5
Q

What is a elastic potential energy store?

A

Anything stretched, like springs and rubber bands

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5
Q

What is a gravitational potential energy store?

A

Anything in a gravitational field (anything that can fall)

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6
Q

What is a electrostatic energy store?

A

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

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7
Q

What is a magnetic energy store?

A

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

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8
Q

What is a nuclear energy store?

A

Atomic nuclei release energy from this store in nuclear reactions

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9
Q

What are the four ways energy can be transferred?

A

Mechanically, electrically, by heating, by radiation

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10
Q

How does mechanically transferring energy work?

A

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

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10
Q

How does by transferring energy by radiation work?

A

Energy transferred, e.g. by light/sound waves, e.g. energy from the Sun reaching Earth as light

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11
Q

How does electrically transferring energy work?

A

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

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11
Q

How does by transferring energy by heating work?

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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12
Q

What is the principle of conservation of energy?

A

Energy can be stored, transferred between stores, and dissipated - but it can never be created or destroyed. The total energy of a closed system has no net change.

simple - amount of energy always remains the same

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13
Q

What is a closed system?

A

A system that can be treated completely on its own, without any matter being exchanged with the surroundings

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14
Q

What is the equation for the law of conservation of energy?

A

Total energy input = useful energy output + wasted energy

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14
Q

When is energy useful?

A

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

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15
Q

What is a device more efficient?

A

When it wastes less energy

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15
Q

Give the 8 ways of energy stores

A

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

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15
Q

Can efficiency ever be equal to or more than 100%?

A

No because there is always some force wasted due to friction.

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16
Q

What is the equation for efficiency?

A

Efficiency = useful energy output/total energy input x 100%

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16
Q

How does wasted energy get transferred normally?

A

By heating or by light or sound

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17
Q

What happens to energy as it is transferred away from a device to its surroundings?

A

As energy is transferred away from a device to its surroundings, the energy often spreads out and becomes less concentrated - it dissipates.

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17
Q

Describe the energy transfers in a ball rolling up a slope. (3)

A
  1. energy is transferred mechanically from the kinetic energy store of the ball to its gravitational potential energy store.
  2. some energy is transferred mechanically to the thermal energy stores of the ball and the slope (bc of friction) 3. then by heating to the thermal energy stores of the surroundings - this energy is wasted.
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18
Q

Describe the energy transfers in a bat hitting a ball. (3)

A
  1. energy is usefully transferred mechanically from the kinetic energy store of the bat to kinetic energy store of the ball (the rest of the energy is wasted)
  2. some energy in kinetic store of bat is transferred mechanically to thermal energy stores of bat, ball and surroundings
  3. remaining energy is wasted by sound
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19
Q

Describe the energy transfers in an electric kettle, boiling water. (3)

A
  1. electrically from mains to thermal energy store of kettle’s heating element
  2. by heating to thermal energy store of water (some is wasted)
  3. by heating from thermal energy stores of heating element and water to the thermal energy stores of surroundings
19
Q

Describe the energy transfers in a battery-powered toy car. (2)

A
  1. usefully transferred electrically from chemical energy store of battery to kinetic energy store of car and carried away by light from headlights
  2. wasted energy transfer to thermal energy stores of car and surroundings + sound is wasted
20
Q

Describe the energy transfers in a bunsen burner and beaker. (2)

A
  1. usefully transferred by heating from chemical energy store of gas to thermal energy store of beaker and water
  2. wastefully transferred by heating to thermal energy stores of stand and surroundings + light is wasted
21
Q

Describe the energy transfers when burning coal.

A

There is a chemical reaction, energy is transferred from chemical energy store in coal to thermal energy when burning.

22
Q

Describe the energy transfers in a car using its brakes to slow down (3)

A
  1. A moving car stores kinetic energy
  2. when it stops it transfers into thermal energy as the brakes exert a frictional force and get hot
  3. this energy then gets transferred to surroundings.
23
Q

Describe the energy transfers when dropping an object that doesn’t bounce. (3)

A
  1. Before object falls, it stores kinetic energy -> once it stop
  2. all kinetic energy transfers to thermal energy stores in object and surroundings (due to friction
  3. heat and sound is wasted
24
Q

Describe the energy transfers for a bungee jumper. (3)

A
  1. When falling, the GPE is converted to KE of jumper
  2. As the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE)
  3. At the lowest point, the jumper’s initial GPE equals the EPE stored in the cord
25
Q

What are the three aways that energy can be transferred by heating?

A

Conduction, convection, radiation

26
Q

What is thermal radiation?

A

The transfer of energy by heating by infrared electromagnetic waves which occurs in solids, liquids and gases. Any object can both absorb and emit thermal radiation.

27
Q

What is conduction?

A

The process where vibrating particles transfer energy to neighbouring particles, mainly through solids.

28
Q

What is convection?

A

The process where vibrating particles transfer energy to neighbouring particles, mainly in liquids and gases.

29
Q

What is the relationship between temperature and energy in the thermal energy stores of a body and its surroundings?

A

The bigger the temperature difference, the faster energy is transferred between the thermal energy stores of a body and its surroundings.

30
Q

Are all objects continually emitting and absorbing infrared radiation?

A

Yes

31
Q

What happens when an object is hotter than its surroundings?

A

It emits more radiation than it absorbs (as it cools down)

32
Q

What happens when an object is cooler than its surroundings?

A

It absorbs more radiation than it emits (as it warms up)

33
Q

What is thermal conduction?

A

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

34
Q

What happens when thermal conduction happens in a solid?

A

The energy is gradually passed all the way through the solid, causing a rise in temperature at the other side of the solid then usually transferred as thermal energy storers of the surroundings.

35
Q

Describe an experiment to demonstrate conduction.

A
  1. Attach beads at regular intervals on a metal bar using wax
  2. Hold the metal bar in a clamp stand, and, using a bunsen burner, heat the side of the bar with no beads attached from the end
36
Q

Explain the results of the conduction experiment (2)

A
  • As time passes, energy is transferred along the bar by conduction and temperature increases along the rod
  • The wax holding the beads, gradually melts and the beads will fall as the temperature increases, starting w the bead closest to point of heating.
37
Q

When does convection occur?

A

When more energetic particles move from the hotter region to the cooler region and transfer energy as they do

38
Q

Describe the different ways in which energy is transferred to cook the potatoes. (conduction) (2)

A
  • metal spike conducts the thermal energy
  • thermal energy is conducted into the middle of/inside the potato;
39
Q

Describe the different ways in which energy is transferred to cook the potatoes. (convection) (3)

A
  • convection (current) occurs;
  • due to density of air decreasing / air expanding;
  • potato receives hotter air near the top;
40
Q

Describe the different ways in which energy is transferred to cook the potatoes. (radiation) (2)

A
  • thermal energy is radiated/emitted from the black surface;
  • potato absorbs thermal energy from all sides;
41
Q

Describe the different ways in which energy is transferred to cook the potatoes. (general)

A

electrical energy is transferred into thermal energy in the heating element;

42
Q

What is work done?

A

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

43
Q

What is the formula for work done?

A

Work done (J) = Force (N) X Distance moved in the force’s direction (m).

44
Q

What is power?

A

The rate at which energy is transferred or the rate at which work is done

45
Q

What is the formula for power?

A

Power = work done / time taken

46
Q

When is energy transferred to and away for kinetic energy store?

A

When an object speeds up, energy is transferred to while when an object slows down, energy is transferred away

47
Q

What does the energy in the kinetic energy store depend on?

A

The object’s mass and speed

48
Q

What’s the relationship between mass, speed and energy in kinetic energy store?

A

The greater its mass and the faster it’s going, the more energy there’ll be in its kinetic energy store.

49
Q

What is the formula for energy in kinetic energy store?

A

energy in kinetic energy store = 1/2 x mass x (speed)^2

49
Q

What happens when you lift an object?

A

It causes a transfer of energy to the gravitational potential energy store of the raised object.

50
Q

What does the amount of energy in a gravitational potential energy store depends on?

A

The objects mass, its heights and the strength of the gravitational field the object is in

50
Q

What is the formula of gravitational potential energy? (can also be used to find the change in energy and height)

A

energy in gravitational potential energy store = mass x gravitational field strength x height (mgh)

51
Q

What happens when an object falls?

A

Energy from its gravitational potential energy store is transferred to its kinetic energy store

52
Q

What happens when there is no air resistance on a falling object?

A

Energy lost from the g.p.e store = Energy gained in the kinetic energy store

53
Q

What does air resistance do when acting against falling objects?

A

It causes some energy to be transferred to other energy stores, e.g. thermal energy stores of the object and surroundings.

54
Q

What is the formula related to power, energy and time?

A

power = energy transferred / time (W)

physics (6 decks)

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