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IGCSE PHYSICS > Unit 1 - Energy > Flashcards

Unit 1 - Energy Flashcards

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1
Q

Unit of measure for power

A

Watts (W)

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2
Q

Power (W) =

A

Power (W) = energy transferred (J) / time (S)

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3
Q

Formula to calculate average power

A

P = Fv

Power (W) = force (N) X velocity (m/s)

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4
Q

Definition for work

A

“work” is when you are moving a subject over a certain distance, with a certain force. This movement is called work

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5
Q

Work is measured in

A

Joules (J)

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6
Q

Work done (J) =

A

Work done (J) = Force (N) X distance (M)

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7
Q

What are the main components of a power station (fossil fuel)

A

Generator, turbines, boiler, condenser, fuel

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8
Q

Problems with fossil fuel power stations

A

Cause global warming and air pollution

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9
Q

Gravitational potential energy (GPE) is measured in

A

Joules (J)

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10
Q

GPE (J) =

A

Gravitational potential energy (J) = mass (kg) X gravity (g / usually 10 on Earth) X height (m)

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11
Q

Kinetic energy (J) =

A

KE (J) = 0.5 X mass (kg) X velocity²

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12
Q

GPE on earth is usually

A

10 N/Kg

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13
Q

Define energy

A

Energy is the capacity to do work. Measured in Joules (J)

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14
Q

What happens when force is applied perpendicular to the direction of movement ?

A

No work is done (not useful)

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15
Q

Elastic potential energy =

A

Energy stored (J) = average force (N) X distance (m)

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16
Q

Unit of measure for energy

A

Joule (J), kilojoule (KJ)

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17
Q

Breaking distance (m)

A

Breaking distance (m) = Kinetic energy (J) / force (N)

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18
Q

( When thrown vertically )

Height (m) =

A

Height (m) = KE / (mass X gravity)

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19
Q

State the law for conservation of energy

A

Energy cannot be created or destroyed, only transferred

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20
Q

Work done (J) =

A

Work done (J) = force (N) X distance (M)

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21
Q

Time (s) =

A

Time (s) = energy (j) / power (w)

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22
Q

Energy transferred (j) =

A

Energy (j) = power (w) X time (s)

23
Q

Efficiency (%) =

A

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

24
Q

Name the types of energy

A

Chemical, thermal, kinetic, gravitational potential (GPE), elastic potential, sound, light

25
Q

Speed (or velocity) =

A

Speed (m/s) = distance (m) / time (s)

26
Q

What is conduction

A

Conduction is direct transfer by contact.

27
Q

Why is conduction best in metals

A

Metals are the best conductors of energy because they have free electrons

28
Q

How does conduction take place

A

Atoms vibrate and pass that vibrations on to the atom nearest to them by colliding and ‘shaking’ them. Because of this, conduction a works best where atoms are closer together (best in solids, worst in gases)

29
Q

What is convection

A

Convection is the circulation of a fluid (liquid or gas) caused by heating it

30
Q

How does convection occur

A

Heating a fluid makes it less dense so the hot fluid rises. Once the fluid rises, it cools and falls back towards the heat source causing a convection currant. This circulation continued until the fluid is in equilibrium

31
Q

What is infrared radiation

A

Infrared radiation is energy transfer by electromagnetic waves

32
Q

What objects emit infrared radiation

A

All object that are above absolute zero (-273C or 0K) emit infrared radiation.

Hotter objects emit more infrared radiation

33
Q

How does infrared travel

A

As electromagnetic waves.

Because of this, infrared can travel through a vacuum as it does not need particles to be transferred.

34
Q

What objects reflect the most infrared radiation

A

Light coloured, shiny, smooth objects reflect the most infrared radiation

35
Q

What objects absorb the most infrared radiation

A

Dark coloured, rough, matt surfaces absorb the most infrared

36
Q

What role does convection take in everyday phenomena

A

Coastal wind is caused by convection currants.
Air above land warms up quicker than the air above the sea. The air above land rises and moves towards the sea, cools and is pushed back towards land causing an inward wind. This cycle in reversed at night.

37
Q

How is insulation used in buildings

A

Insulation is used to stop heat transfers.
Examples of insulation is double glazed windows (air in between glass reduces conduction) and cavity wall insulation (foam in between walls containing small pockets of gas to reduce conduction and convection)

38
Q

How is insulation used to reduce energy transfers from the human body.

A

Layers of fat under the skin insulate the human body.

Clothes are also used to stop conduction away from the body.

39
Q

Describe the energy transfers involved in harnessing wind energy

A

Kinetic energy (wind) –> mechanical + kinetic energy (turbines) –> electrical energy + heat

40
Q

Describe the energy transfers involved in generating water power (aka hydropower)

A

GPE (height of water) –> kinetic energy (water dropping)

–>mechanical / kinetic energy (turbines) –> electrical energy + heat

41
Q

Describe the energy transfers involved in harvesting geothermal energy

A

Thermal energy (heat from geothermal resource) –> thermal energy (water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electrical energy + heat

42
Q

Describe the energy transfers involved in solar cells

A

Infrared radiation (sun) –> electrical energy + heat

43
Q

Describe the energy transfers involved in solar heating systems

A

Thermal energy (sun) –> thermal energy (heating water)

44
Q

Describe the energy transfers involved in harvesting energy through fossil fuels

A

Chemical energy (fuel) –> thermal energy (burning fuel) –> thermal energy (heating water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electric energy + heat

[ the smoke and pollution are produced in the 2nd step when the fossil fuels are burnt and smoke is produced ]

45
Q

Describe the energy transfers involved in harvesting nuclear power

A

Thermal energy (nuclear reactor) –> thermal energy (heating water) –> kinetic energy (steam) –> mechanical / kinetic energy (turbines) –> electrical energy + heat

46
Q

Describe the pros and cons of wind energy

A

Pro: wind is free, renewable energy source

Con : unreliable, eyesore, high maintenance, low efficiency

47
Q

Describe the pros and cons of water energy

A

Pro : can re-use water, no greenhouse gases produce

Con : dam failure will cause mass destruction, very noisy

48
Q

Describe the pros and cons of geothermal energy

A

Pro: renewable energy, no pollution, very efficient
Con: can only be harvested in certain areas, can’t be moved easily

49
Q

Describe the pros and cons of solar heating systems

A

Pro: lowers water bill, renewable energy
Con: not efficient, expensive to purchase and install

50
Q

Describe the pros and cons of solar cells

A

Pro: renewable, can be used anywhere sunny
Con: not efficient, expensive

51
Q

Describe the pros and cons of fossil fuels

A

Pro : produce lots of energy cheaply, very efficient

Con: produces lots of greenhouse gases

52
Q

Describe the pros and cons of nuclear power

A

Pros : produce LOADS of energy, energy sources not likely to run out of thousands of years

Cons: produce nuclear waste, can be used to make nuclear weapons

53
Q

Velocity (speed) =

A

Speed (m/s) = distance (m) / time (s)

IGCSE PHYSICS (8 decks)

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