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Physics > Topic 1-Energy > Flashcards

Topic 1-Energy Flashcards

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1
Q

What is specific heat capacity?

A

The amount of energy requires to raise the temperature of 1kg of a material by 1°C

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2
Q

What is a closed system?

A

A system that experiences no net change in its total energy when energy transfers occur within it

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3
Q

What is the definition of ‘Power’?

A

The rate at which energy is transferred (or rate at which work is done)

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4
Q

What does it mean to say energy is dissipated?

A

Energy has spread out and become less useful

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5
Q

What is friction?

A

A force that opposes motion between objects in contact with each other

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6
Q

State 4 different stores of energy

A

Kinetic energy
Gravitational potential energy
Elastic potential energy
Chemical energy

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7
Q

Give examples of chemical energy stores

A

Food
Fuel
Batteries

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8
Q

State the law of energy conservation

A

Energy cannot be created or destroyed (it can only be transferred into different forms)

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9
Q

How can friction be increased?

A

Making the surface rougher

Adding a rougher material

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10
Q

How can friction be reduced?

A

Lubrication

Adding a liquid between the two surfaces

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11
Q

What is energy waste?

A

The energy that is not used by the device for its desired purpose

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12
Q

How can you reduce energy waste?

A

Lubrication
-Oil in a motor reduces friction so less energy is lost (as heat) through friction

Thermal insulation
-Double glazing means that less useful thermal energy is lost

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13
Q

What is thermal energy?

A

Heat

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14
Q

What causes thermal energy to transfer from one object to another?

A

If there is a difference in temperature between one object and another, thermal energy will move from the hotter object to the colder object until they are both at the same temperature

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15
Q

How does thermal energy transfer by conduction?

A

Heating a fluid (liquid or gas) causes the particles to vibrate with more kinetic energy. These vibrations are passed on from one particle to the next through the solid

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16
Q

How does thermal energy transfer by convection?

A

Heating a fluid (liquid or gas) causes the particles to move with more kinetic energy. The warm fluid becomes less dense and rises above colder areas of the fluid

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17
Q

How does thermal energy transfer by radiation?

A

Infrared radiation is electromagnetic radiation emitted by hot objects and absorbed by other objects

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18
Q

What colours absorb the most/least infrared radiation?

A

Black/dull surfaces are the best absorbers of infrared

Light/shiny surfaces are the worst absorbers of infrared

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19
Q

What colours emit the most/least infrared radiation?

A

Black/dull surfaces are the best emitters of infrared

Light/shiny surfaces are the worst emitters of infrared

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20
Q

What does it mean if a material is a good insulator?

A

The material does not allow thermal energy to pass through easily

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21
Q

How can the efficiency of a system be increased?

A
  • Reducing waste output (lubrication, thermal insulation)

- Recycling waste output (absorbing thermal waste and recycling as input energy)

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22
Q

What key factors affect the rate of cooling of a building?

A

The thickness of the walls

The thermal conductivity of the walls

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23
Q

State three methods of reducing heat loss in a building

A

Double glazing
Loft and wall insulation
Thicker walls

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24
Q

How can the efficiency of a mechanical machine with moving parts be improved?

A

Lubricate any moving parts to reduce the friction and therefore energy loss due to heating

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25
Q

How can the efficiency of a radiator be improved?

A

Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls

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26
Q

How can the efficiency of boiling water in a pan be improved

A

By placing a lid on the pan to reduce heat loss from the top

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27
Q

What is a renewable energy source?

A

An energy source which can be replenished as it is being used up and therefore will not run out

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28
Q

Give four examples of renewable energy resources

A

Wind energy
Hydro-electricity
Tidal energy
Solar energy

29
Q

Give an example of a non-renewable energy resource

A

Fossil fuels (coal, oil and gas)

30
Q

What are the advantages of generating power using gas rather than coal?

A

Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily

Lower emission of carbon dioxide

31
Q

What is are some advantages of non-renewable energy?

A

Non-renewable energy is used for more large-scale energy supplies due to the large energy output per kilogram of fuel.

Renewable resources cannot provide such a large amount of energy as easily

Reliable. Not dependant on external factors so can generate power anytime

Still relatively abundant so cost-effective

32
Q

Explain the environmental impacts of burning fossil fuels

A

Carbon dioxide contributes to the greenhouse effect, and causes global warming

Sulphur dioxide leads to acid rain, which can damage buildings and crops

33
Q

What process is used to produce heat in nuclear power stations?

A

Nuclear fission

splitting atoms to release energy

34
Q

What are some of the advantages of nuclear power?

A

Very large amounts of energy for relatively small quantities of fuel

Doesn’t release greenhouse gases and so doesn’t contribute to climate change

Low fuel costs

35
Q

What are the disadvantages of nuclear power?

A

Produces radioactive nuclear waste which is harmful to humans and must be stored safely for centuries

Power stations are expensive to build and decommission

Risk of nuclear accidents, which have fatal consequences on humans and the environment

36
Q

How does hydroelectric power produce energy?

A

Rainwater collects behind a dam

When this water is released from a high place (GPE -> KE), it is used to turn a turbine (KE->KE)

This turbine turns a generator which produces electricity (KE->Electrical)

37
Q

What are the advantages of using hydroelectric systems to generate electricity?

A

Renewable
No atmospheric pollution at point of use
Low operating costs

38
Q

What are the disadvantages of using hydroelectric systems to generate electricity?

A

Only suitable in certain areas (eg somewhere where a damn and reservoir can be built)

It can cost a lot to install the required infrastructure

The dam may cause flooding

39
Q

Describe how geothermal energy can be used to generate electricity

A

Geothermal power stations use heat from below the Earth’s surface to heat water

This hot water can be used directly in heating systems or to produce steam to drive turbines and generate electricity

40
Q

Describe how wave energy can be used to generate electricity

A

The motion of waves in the sea is used to move a floating generator up and down. This motion is used to generate electricity

41
Q

Describe how tidal energy can be used to generate electricity

A

Water from each high tide is trapped behind a barrage/dam and then released past turbines

The turbines drive a generator to produce electricity

42
Q

What are biofuels?

A

Biofuels are taken from living or recently living organisms

  • Methane from animal waste
  • Woodchip
  • Vegetable oil/ethanol from sugar cane
43
Q

What are some of the disadvantages of using biofuels?

A

-When plants are burned or decayed they release CO2

In order to grow biofuels, you need to destroy land which leads to problems because

  • Naturals habitats
  • May involve burning plants (CO2)

Growing biofuels reduces the land available for growing food

44
Q

What are the advantages of tidal energy sources?

A

They do not produce greenhouse gases

They are quite reliable, as tides happen twice a day

They are cheap to run as tides are natural and so are free

45
Q

What are some advantages of solar panels?

A
  • They don’t cause harm to the environment
  • They are a renewable resource
  • They can be used in remote areas where other types of energy are less a accessible
46
Q

What are some disadvantages of solar panels?

A

Expensive to produce

Inefficient

Lower power output

Cannot be stored and therefore may not be able to meet an always changing demand

47
Q

What are some advantages of using wind to generate electricity?

A

Renewable
No atmospheric pollution at point of use
Low operating costs

48
Q

What are some disadvantages of using wind to generate electricity

A

Only works when it’s windy

Low power output (you need hundreds to replace a power station)

Visual pollution

49
Q

In addition to power input, light bulbs should also be labelled with the rate at which they emit visible light

Suggest why

A

Bulbs also transfer thermal energy

The efficiency of the light bulb also needs to be considered

50
Q

Describe a method the student could use to investigate the insulating properties of newspaper

A

Wrap certain amount of layers of newspaper around the metal can

Heat water in can and put water into can

Use measuring cylinder to measure the volume of the water

Measure initial and final temp with digital thermometer

Use stopwatch to measure a time of 5 minutes

Calculate temp decrease then repeat with different numbers of layers

Use same initial temp and same volume of water

51
Q

As a person moves down the zipwire her increase in kinetic energy is less than her decrease in gravitational potential energy

Explain why

A

Work done against air resistance creates thermal energy to be transferred to surroundings

52
Q

Different people have different speeds at the end of the zip wire

Explain why

A

Different people have different surface areas so they would be affected by air resistance differently

53
Q

Suggest some potential sources of random error

A

Variation in initial mass of ___

Variation in room temp

if with ice-ice melting while handling`

54
Q

How do you correct a zero error after readings have been taken from the balance

A

Record the value of the zero error when there is no object on the balance

Take away the amount the zero error was from all the readings

55
Q

Give two reasons why a hydroelectric power station is not able to meet an increase in demand

A

the variation in demand is
(much) greater than _____

demand remains high for longer
than __ hours

56
Q

Give two environmental advantages of using a gas-fired power station to generate electricity compared with using a coal-fired power station.

A 
• no sulfur dioxide released
• doesn’t cause acid rain
• no particulates released
• doesn’t cause global dimming
• less carbon dioxide released
(per kg of fuel burned)

less global warming

57
Q

A car driver sees a fallen tree lying across the road ahead and makes an emergency stop

The braking distance of the car depends on the speed of the car

For the same braking force, explain what happens to the braking distance if the speed doubles

A

Doubling speed increase the kinetic energy

Kinetic energy increases by a factor of 4

Work done by brakes to stop the car increases

Work done increases by a factor of 4

Work done is force x distance and braking force is constant

So if work done increases by 4 then the braking distance must increase by 4

58
Q

Give one environmental advantage to turning off electrical appliances when they are not being used

A

Conserves fossil fuels

Less fossil fuels are burnt

Less greenhouse gas is produced

59
Q

The speed of the miner at the bottom of the slide is much less than the calculated maximum possible speed

Explain why

A

Work is done

Against friction between miner and slide

Due to slide not being perfectly smooth

60
Q

A bullet is fired horizontally.

In the short time it takes for the bullet to reach its target, its horizontal speed has fallen to 80% of its initial speed

Explain why the speed of the bullet decreases so quickly

A

Friction with air resistance is high at high speed

61
Q

Give two reasons for taking repeat readings in an investigation

A

To calculate a mean

To spot anomalies

Reduce the effect of random errors

62
Q

The fire in a stove uses wood as a fuel. The fire heats the matt black case of the stove

The air next to the stove is warmed by infrared radiation

How does the design of the stove help to improve the rate of energy transfer by infrared radiation?

A

Black is a good emitter of infrared radiation

It has a large surface area

Matt surfaces are better emitters than shiny surfaces

63
Q

Some people heat their homes using electric heaters. other people heat their homes using a wood burning stove

Give two environmental advantages of using a wood burning stove to heat a home rather than heaters that use electricity generated from fossil fuels

A

Wood is renewable

Using wood conserves fossil fuels

Wood is carbon neutral

64
Q

Give one advantage of using a temperature sensor and data logger instead of a glass thermometer to measure temperature

A

Greater sensitivity/precision

Could link to a computer for data analysis

More frequent readings

Reduces instrument error

65
Q

Explain why the student recommended plastic foam and aluminium foil as the best insulator

A

Aluminium foil is a poor absorber of thermal radiation since it is light and shiny

Plastic foam traps air which is a good insulator

66
Q

Explain, in terms of particles, how heat is transferred through the glass wall of a boiling tube

A

Particles vibrate with more kinetic energy/a stronger amplitude

Energy is transferred by collisions with other particles

67
Q

A vaccum flask has:

  • a plastic cap
  • Double-walled glass container
  • Vacuum
  • Silvered surfaces

How do these features keep the liquid inside hot?

A

Plastic is a poor conductor and stops convection currents forming at the top of the flask so stopping energy transfer by convection

Glass is also a poor conductor so it reduces energy transfer by conduction

Vacuum stops energy transfer by conduction

Silvered surfaces reflect infrared radiation and are also poor emitters of infrared radiation

Instead they reflect the infrared radiation back towards the hot liquid partially.

It therefore stops energy transfer by radiation

68
Q

Arctic foxes have small ears

How does the size of ears help to keep the fox warm in a cold environment?

A

The ears have a small surface area

So it reduces energy radiation/transferred from the fox

Physics (10 decks)

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