P1 - Conservation and Dissipation of Energy Flashcards

1
Q

What is conservation of energy?

A

energy cannot be created or destroyed

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2
Q

What is dissipated energy?

A

the energy that is not usefully transferred and stored in less useful ways

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3
Q

What is efficiency?

A

useful energy transferred by a device / total energy supplied to the device

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4
Q

What is elastic potential energy?

A

energy stored in an elastic object as a result of it being deformed. For example, a stretched spring

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5
Q

What is Hooke’s law?

A

the extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded

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6
Q

What is input energy?

A

energy supplied to a device

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7
Q

What is power?

A

the energy transformed or transferred per second. The unit of power is the watt (W)

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8
Q

What is spring constant?

A

force per unit extension of a spring

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9
Q

What is useful energy?

A

energy transferred to where it is wanted in the way that is wanted

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10
Q

What is wasted energy?

A

energy that is not usefully transferred

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11
Q

What is work?

A

the energy transferred by a force. Work done (joules, J) = force (newtons, N) x distance moved in the direction of the force (metres, m)

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12
Q

What are all the 8 energy stores?

A
°Kinetic
°Thermal
°Chemical
°Nuclear
°Gravitational Potential
°Elastic Potential
°Magnetic
°Electrostatic
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13
Q

Where is a kinetic energy store?

A

In a moving object

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14
Q

Where is a chemical energy store?

A

Chemical energy is stored in the bonds that connect atoms with other atoms and molecules with other molecules

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15
Q

Where is a gravitational energy store?

A

an object above ground

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16
Q

Where is an elastic energy store?

A

a stretched or squashed object

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17
Q

What is a thermal energy store?

A

due to a substances temperature

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18
Q

What is a magnetic energy store?

A

The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart

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19
Q

What is a nuclear store?

A

energy stored in the nucleus of an atom

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20
Q

What are all the energy transfer pathways?

A
  • Mechanically,
  • Electrically,
  • by Heating
  • by Radiation
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21
Q

What is mechanical energy transfer?

A

When a force acts and energy is transferred

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22
Q

What is electrical energy transfer?

A

When a current flows

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23
Q

What is energy transfer by heating?

A

Due to temperature difference

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24
Q

What is energy transfer by radiation?

A

A wave such as light, microwaves or sound

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25
Q

What is the equation for Gravitational Potential Energy?

A

ΔEp = mass (m) x gravitational field strength (g) x change in height (Δh)

26
Q

What is the equation for kinetic energy?

A

Ek = 1/2 x mass (m) x velocity² (v²)

27
Q

What is the law of conservation of energy?

A

Energy cannot be created or destroyed

28
Q

What is an efficient lightbulb?

A

CFL bulb

29
Q

What does CFL Bulb stand for?

A

Compact Fluorescent Light Bulb

30
Q

What is an inneficient bulb?

A

A filament light bulb

31
Q

What is useful energy?

A

energy transferred to where it is wanted and in the form it is wanted

32
Q

What is wasted energy?

A

Energy that is not usefully transferred

33
Q

What is the equation for efficiency?

A

Efficiency % = (Useful energy out/total energy in) x 100

34
Q

What is the equation for Elastic Potential Energy?

A

Ee = 1/2 x spring constant (k) x extension² (e²)

35
Q

What is the unit of measurement for Work Done?

A

Joules (J)

36
Q

What is the equation for work done?

A

Work Done (J) = Force (N) x Distance (m)

37
Q

What is a Watt?

A

a J/s

38
Q

What is the unit for power?

A

A Watt

39
Q

What is the equation for power?

A

Power (W) = Energy Transferred (J)/Time (s)

40
Q

The power rating will be greater is work is done over a ………………… period of time

A

shorter

41
Q

What is the origin of the word ‘Kinetic’?

A

The greek word ‘kinesis’

42
Q

What happens to wasted energy?

A

wasted energy is dissipated to the surroundings

43
Q

Why can no device be more efficient than 100%?

A

you can never get more energy from a machine than you put into it

44
Q

What is one of the most efficient appliances?

A

A heater/radiator

45
Q

How many watts is 1kW?

A

1000

46
Q

The more powerful an appliance is the …………… the rate which it transfers energy

A

faster

47
Q

Wasted energy is …………. to the surroundings

A

dissipated

48
Q

What is a closed system?

A

An object or group of objects in which no energy transfers take place out of or into the energy stores of the system

49
Q

What is energy?

A

Energy is the ability to do work

50
Q

What is the unit of measurement for energy?

A

Joules (J)

51
Q

What is a sankey diagram?

A

A diagram representing the amount of useful and wasted energy

52
Q

What does the top path on a sankey diagram represent?

A

Useful energy

53
Q

What does the bottom path on a sankey diagram represent?

A

Wasted energy

54
Q

What are the 4 energy transfer pathways?

A
  • Mechanical work - a force moving an object through a distance
  • Electrical work - charges moving due to a potential difference
  • Heating - due to temperature difference
  • Radiation - energy transferred as a wave, eg light and infrared - the Sun emits light radiation and infrared radiation
55
Q

What is resolution?

A

the minimum distance at which two distinct points can be identified.

56
Q

What is the resolution of the measurement 25.3cm?

A

0.1cm

57
Q

What is the resolution of the measurement 67.5*C?

A

0.1

58
Q

What is the form of wasted energy from friction?

A

Thermal energy

59
Q

What is a source of random error?

A

unknown and unpredictable changes in the experiment, such as room temperature

60
Q

what is the main way in which a motor wastes energy:

A

Thermal energy

61
Q

Explain how the kinetic energy of the air passing a specific point would change if the wind speed is halved.

A

The mass of air passing past the point would half, causing the kinetic energy to half. The velocity if halved, therefore causing the kinetic energy to decrease by a factor of 4. Therefore halving the wind speed causes the kinetic energy to decrease by a factor of 8

62
Q

How do you reduce wasted energy due to friction?

A

Lubrication