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Physics CGP > Energy > Flashcards

Energy Flashcards

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1
Q

How is energy transfered

A

Mechanically (by a force doing work), eletrically (work done by moving charges), by heating or by radiation

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2
Q

What is a system

A

It is a word for a single object or a group of objects

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3
Q

Where is the energy stored when transfered to an object

A

The energy is stored in one of the object’s energy stores.

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4
Q

What happens when a system changes

A

Energy is transfered into or away from the system, between different objects or types of energy stores in the system.

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5
Q

What are closed systems

A

Where niether matter nor energy can enter or leave.

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6
Q

Net change in the total energy of a closed system is always…

A

zero

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7
Q

Work done

A

It is energy transferred and csn be done when current flows (resistance in a circuit) or by a force moving an object

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8
Q

Kinetic energy store

A

Kinectic energy store depends on the object’s mass and speed

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9
Q

The amoutn of gravitational potential energy depends on

A

Object’s mass, height and strength of gravitational field

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10
Q

When something falls energy from its gravitational potential energy store is…

A

Transfered into its kenetic energy store

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11
Q

Are you falling object with this new every assistance is energy lost from the gravitational potential energy store=

A

Energy gained in the kinetic energy store

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12
Q

If Limit of proportionnality has not exceeded then…

A

Energy in the elastic potential energy store of a stretched spring can be found using the equation of elastic potential energy

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13
Q

Specific heat capacity

A

How hard it is to heat something up (the amount of energy needed to raise the temp

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14
Q

Materials that need to gain thermal energy stores to warm up to what

A

Transfer loads of heat when they cool down again. They can store lots of energy

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15
Q

Conservation of energy

A

Energy can be transfered or stored or dissipated but not created or destroyed

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16
Q

Some energy is always dissipated when

A

Energy is wasted because the energy is stored in a way that is not useful.

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17
Q

What is power the rate of

A

Energy transfer or the rate of doing work (energy transfered/time)

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18
Q

Power is measured in…

A

Watts (1 joule trasfered per sec)

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19
Q

What is a powerful machine

A

One that transferes lots of energy in a short space of time.

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20
Q

What is conduction

A

The progress where vibrating particles transfer energy to neighbouring particles

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21
Q

How is thermal energy store shared across an object

A

Energy is shared across the kinetic energy stores of the particles in a object. Then particles begin to vibrate as they are heated and collide more causing enrgy to be transferred between particles in the kinetic store.

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22
Q

Thermal conductivity is the measure of…

A

How quickly energy is transferred through a material in this way.

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23
Q

What is convection

A

Where energy particles move away from hotter to cooler regions

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24
Q

Where does convection happen

A

In gases and liquids

25
Q

How is energy teansfered in convection

A

Like conduction by the thermal store

26
Q

What is the difference of convection and conduction

A

In convection, unlike solids thenpartilces in liquids and gases are able to move. The particles space between individual particles increases causing density if the region being heated to decrease.

27
Q

Because liquods and gases can flow, how will it effect convection

A

The warmer and less dense region will rise above denser, cooler regions. If there is a constant heat source, a convection current can be created.

28
Q

How can a radiator creatw convection currents.

A

Heating a room with a radiator requaites energy to be transfered from the radiator to the air particles by conduction. Then the convection current processes begins.

29
Q

How lubrication reduces frictional forces

A

Frictional force causes some energy to be dissipated, but for objects being rubbed together, lubricants can be used to reduce the friction between the object’s surfaces as they move.

30
Q

Examples of lubricants

A

Liquods like oil, so they can flow easily between objects and coat them.

31
Q

Things to prevent energy loss through heating.

A

Thick walls that are made of material with low thermal conductivity cause a slower rate of enrgy transfer so the building will cool slower.

Thermal insulation

32
Q

Cavity walls

A

Cavity walls made up of inner and outer wall with air gaps in the middles. The air gap reduces the amount of energy transfer by conduction. You can fill them with foam to reduce energy transfer by convection currents created in the loft

33
Q

Loft insulation

A

Can reduce convection currents created in the loft.

34
Q

Double grazed windows

A

Work in the same way as cavity walls as they have an air gap inside them

35
Q

How do draught exluders act as thermal insulation

A

You can put them around doors and windows to reduce energy transfers by convection

36
Q

How can you improve efficiency of energy transfers

A

By insulating objects, lubricating or making them more streamline.

37
Q

Why is no device 100% efficient

A

Wasted energy also occurs like thermal stores. An exception is electric heaters as all energy is electrostatic

38
Q

Renewable transport

A

Vehicles running on pure biofuels or electricity

39
Q

Renewable heating

A

Geothermal heat pump, solar water heaters, burning biofuels or using electricity

40
Q

Wind turbine disadvantages

A

A disadvantage of them is that they spoil the View, you need about 1500 wind turbines to replace one coal-fired power station as well as they are very noisy. Also, there is a problem of when the wind doesn’t stop or it’s too strong meaning that on average wind turbines produce electricity 70 to 85% of the time. The intitail costs are high but there are no fuel costs and minimal running costs.

41
Q

Solar cells disadvantages

A

In sunny countries solar power is very reliable but only in the daytime, and so the power can still be affected by cloudy atmospheres, like wind you can’t increase the power output when there is extra demand and the initial costs are high but after that the energy is free and running costs almost nil. Solar cells are usually used to generate electricity on the relatively small scale

42
Q

How do you solar cells work

A

I generate electric currents straight directly from the Sunlight

43
Q

Geothermal power disadvantages

A

The main drawbacks with geothermal power is that there aren’t very many suitable locations for power plants the cost of building the power plant is often high compare to the amount of energy it produces

44
Q

How does geothermal power work

A

In volcanic areas where hot rock like quite near the surface the source of much of the energy is the slow decay of various radioactive elements including uranium deep inside the Earth. This is free energy that’s reliable and has very little damage to the environment

45
Q

Hydroelectric power disadvantages

A

There is a big impact on the environment due to the flooding of the valley and possible loss of habitats for some species. The reservoir can also look on sightly when they dry up. They can be unreliable in terms of a drought and initial costs are high and there are no fuel costs and minimal running costs

46
Q

How does hydroelectric power work

A

Hydroelectric power usually requires the flooding of the valley by building a big dam. There is no pollution as the water is allowed out through turbines which creates electricity from the kinetic store. A big advantage is that it can provide an immediate response to any increased demand for electricity

47
Q

Wave power disadvantages

A

You need lots of small wave power turbines located on the coast. You are Disturbing the seabed and the habitats of marine animals and spoiling the view and could be a hazard to boots. They are unreliable since the waves tend to die out when the wind drops and initial costs are high but there are no fuel costs and minimal running costs. Wave power is never likely to provide energy on a large scale

48
Q

How does wave power work

A

You need lots of small wave power turbines that would have turbines connected to a generator moved by the waves

49
Q

Disadvantages of tidal barrages which use the Sun and moon gravity

A

Preventing free access by boats, spoiling the view and altering the habitat of wildlife, tides are reliable in the sense that they happen twice a day without fail but height of the tide is variable so lower tides will provide significantly less energy and they also don’t work when the water level is the same either side of the barrage. Initial costs are moderately high but there are no fuel costs and minimal running costs so it can only be used in some of the most suitable estuaries tidal power has the potential for generating a significant amount of energy.

50
Q

How do you tidal barrage is work

A

They are big dams built across the river estuaires, With turbines in them. As the tide comes in it fills up the Estuary and the water is an allowed through the turbines out of control the speed. Tides are produced by Gravitational pull of the sun and moon

51
Q

How do you biofuels work

A

They are created from either plant products or animal dung and can be solid liquid or gas and can be burnt to produce electricity or fuels

52
Q

Advantages of biofuels

A

They are supposedly, neutral and reliable as crops take relatively short time to grow different crops can be grown all year round

53
Q

Environmental problems from nonrenewables

A

Greenhouse effect, a release of sulphur dioxide causing acid rain, coal mining, oil spillages, nuclear waste

54
Q

Disadvantages of nuclear power

A

It always carries the risk of major catastrophes, the overall cost of nuclear power is high due to the cost of the power plant and final decommissioning, new killer waste is very dangerous in disposing of it

55
Q

Loft insulation

A

Lots of layers of foam to reduce convection inbetween the air gaps and reduces the heat loss of radiations as it has to get through lots of layers

56
Q

Black body radiation

A

Radiation emitted by a perfect balck body

57
Q

Infared radiation

A

Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum

58
Q

Specific heat capacity

A

Enrgy needed to raise the temp of 1kg of a substance by 1°C

59
Q

How to keep something as a constant heat

A

It absorbs the same amount of enrgy as emitted.

Physics CGP (7 decks)

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