Physics P2 Ocr Gateway (1)

Front 1

What kind of current do photocells produce? What does this mean?

Back 1

A direct current - the current flows the same way round the circuit all the time

Front 2

What are photocells made of?

Back 2

Silicon (a semi-conductor)

Front 3

What happens when sunlight falls on the cell? (2 points)

Back 3

- The silicon atoms absorb some of the energy, knocking loose some electrons
- These electrons then flow around the circuit = electricity

Front 4

What 3 things does the current and power output of a photocell depend on?

Back 4

- Surface area
- The intensity of the light
- The distance from the light

Front 5

What are 6 advantages of photocells?

Back 5

Sturdy
Low maintenance
Last a long time
No power cables or fuel
Renewable
Doesn't pollute environment

Front 6

What is a major disadvantage of photocells?

Back 6

No sunlight = no power

Front 7

What are curved mirrors used for?

Back 7

To focus the Sun's light and heat
Single curved mirror = eg. solar oven
Large curved mirror = generate steam to produce elec

Front 8

How do you make devices that collect energy from the Sun most efficient?

Back 8

Most efficient if they track the Sun's movement across the sky

Front 9

When can energy collectors capture the maximum amount of light and heat?

Back 9

When they are pointed directly at the Sun

Front 10

What is passive solar heating?

Back 10

Involves any system that can capture the Sun's energy directly eg. greenhouse

Front 11

How do solar water heaters work?

Back 11

Glass lets in heat and light from the sun and is absorbed by the black pipes to heat the water

Front 12

How does a greenhouse work? (5 points)

Back 12

1) The sun produces radiation with a very short wavelength
2) Transparent glass allows heat and light through
3) The ground and plants absorb radiation and heat up
4) They re-radiate the infrared but because they are much cooler than the sun = longer wavelength
5) Won't pass through and is reflected back

Front 13

How is wind produced?

Back 13

Energy from the sun heats up the atmosphere which causes convection currents

Front 14

How do wind turbines generate electricity?

Back 14

Wind turbines convert kinetic energy of moving air into electricity. The wind turns the blades = turn a generator

Front 15

What are 4 advantages of wind-turbines?

Back 15

Renewable energy source
Robust
Cheap to run
No pollution

Front 16

What are 5 disadvantages of wind-turbines?

Back 16

Unreliable (depends on the wind speed)
Eye sore
Space required
Considered noisy
Expensive to set up

Front 17

What is the National Grid?

Back 17

The network of pylons and cables which cover the whole country, taking electricity from power stations to homes and industry

Front 18

What are the 3 stages of how energy is converted to electricity in power stations?

Back 18

1. BOILER: Fuel produces heat to genetate steam
2. TURBINE: The moving steam turns the turbine
3. GENERATOR: Rotating movement from turbine is converted to electricity by electromagnetic induction

Front 19

What is electromagnetic induction?

Back 19

Creation of voltage (maybe current) in a wire which is experiencing a change in magnetic field

Front 20

Why do generators produce an alternating current (AC)?

Back 20

1. Generators rotate a coil in a magnetic field
2. Every 1/2 turn, the current in coil swaps direction

Front 21

What happens if you turn a coil in a magnetic field faster?

Back 21

Higher voltage and current

Front 22

What is the dynamo effect?

Back 22

Using electromagnetic induction to transform kinetic energy into electrical energy

Front 23

What are the 2 different situations where you get electromagnetic induction?

Back 23

1) An electrical conductor moves through a magnetic field
2) The magnetic field through an electrical conductor changes

Front 24

What happens if the direction of movement is reversed in a magnetic field?

Back 24

The voltage/current is reversed to

Front 25

What 3 things can you increase to get a bigger voltage/current?

Back 25

1) Strength of magnet
2) No. of turns in coil
3) Speed of movement

Front 26

What are two advantages of burning fossil fuels for energy?

Back 26

Readily available at the moment
Concentrated source of energy (a little fuel gives a lot of energy)

Front 27

What are four disadvantages of burning fossil fuels for energy?

Back 27

Produces acid rain and carbon dioxide
We have no control of the price or supply as we buy it from other countries
Non-renewable

Front 28

What are four advantages of biomass?

Back 28

Renewable
Quickly make more
"carbon neutral process" = produces CO2 when burnt but plants take in this CO2
Doesn't need to be imported

Front 29

What are two disadvantages of biomass?

Back 29

Need a lot of space
Needs a lot to produce energy

Front 30

What do you need to transmit lots of electrical power?

Back 30

High voltage OR current

Front 31

Why can a high current be inefficient?

Back 31

Because the cables get hot (heat wasted)

Front 32

What happens to the voltage before the electricity is sent round the country? Why?

Back 32

The voltage is transformed to 400,000V
This keeps the current low so less energy is wasted by heating cables

Front 33

How do you increase the voltage?

Back 33

A step up transformer

Front 34

How do you bring voltage down to safe usable levels?

Back 34

A step down trnasformer

Front 35

Why is mains electricity an alternating current (AC)?

Back 35

Transformers only work on AC

Front 36

What is the equation for total energy input?

Back 36

Total energy input = useful energy output + waste energy output

Front 37

What is the equation for efficiency?

Back 37

Efficiency = Useful energy output / total energy input (x100)

Front 38

What is power?

Back 38

A measure of the rate at which energy is used

Front 39

What is the equation for power?

Back 39

Power (W) = Voltage (V) x Current (A)

Front 40

What is the equation for the energy supplied (in kWh)

Back 40

Energy supplied = Power x time

Front 41

How do you work out the cost of energy?

Back 41

Cost = number of units x price per unit

Front 42

What are two advantages of off-peak electricity?

Back 42

Cheaper for the consumer
Cost effective for the electricity company as the power stations cannot be turned off at night

Front 43

What are two disadvantages of off-peak electricity?

Back 43

Risk of fire if no one is watching appliances over night
People start to fit their routine around off peak rates

Front 44

What do the gases in the atmosphere do with radiation? How do they do this?

Back 44

They filter out certain types of radiation from the sun by absorbing or reflecting radiation of certain wavelengths (infrared)

Front 45

How does the greenhouse effect help regulate Earth's temperature? (5 points)

Back 45

1) Earth absorbs short wavelength EM radiation from the sun. This warms the earth and the eart emits some of this EM radiation back
2) Most that is emitted back is longer wavelength infrared radiation (heat)
3) A lot of this is absorbed by atmospheric gases like carbon dioxide, methane and water vapour
4) The gases re-radiate heat in all directions
5) Atmosphere = insulating layer = stops earth losing heat at night

Front 46

Give three things that are increasing carbon dioxide levels

Back 46

1)People use more energy (cars) = releases CO(2)
2)More land is needed for houses and food = trees chopped down and burnt = less CO(2) absorbed, more released
3)Natural sources like respiration and volcanic eruptions

Front 47

Give three things that are increasing methan levels

Back 47

1) Cattle farming increased = more methane
2) Decaying waste in landfill
3) Naturally = volcanoes and animals

Front 48

Give two things that are increasing water vapour levels

Back 48

1) Natural sources like oceans
2) Power stations

Front 49

Why is the climate changing?

Back 49

More fossil fuels are being burnt and so the level of carbon dioxide has increased. The global temperature has a link between the concentration of CO(2).

Front 50

What can we expect from changes in the weather?

Back 50

1) Many regions suffer more extreme weather
2) Increased number of hurricanes
3) Affects food production = regions too dry/wet to grow

Front 51

What are 2 human causes of temperature change?

Back 51

1) The rising CO(2) level
2) Soot and gases from factories can reflect heat from cities = increases local temperatures

Front 52

What are 2 natural causes of temperature change?

Back 52

1) Ash and gases thrown into the atmosphere by volcanoes can reflect radiation from the Sun back into space = cools earth down
2) Changes in our orbit around the sun can cause ice ages

Front 53

When is nuclear radiation given off?

Back 53

When an unstable nucleus decays

Front 54

Give properties of alpha particles on:
1) Size and movement
2) Penetration
3) Ionisation

Back 54

1) Relatively big, heavy and slow moving (2 protons and 2 neutrons)
2) Stopped quickly and don't penetrate far into materials
3) Strongly ionising

Front 55

Give properties of beta particles on:
1) Size and movement
2) Penetration
3) Ionisation

Back 55

1) They're electrons = small and move fast
2) Penetrate moderately
3) Moderately ionising

Front 56

Give properties of gamma particles on
1) Size and movement
2) Penetration
3) Ionisation

Back 56

1) No mass
2) Penetrate a long way into materials
3) Weakly ioning

Front 57

What can a) alpha b) beta and c) gamma be stopped by?

Back 57

a) Skin or paper
b) A few mm of aluminium
c) A few cm of lead

Front 58

How can you identify the type of radiation?

Back 58

By it's penetrating power
Place paper, aluminium and lead between the source and a detector and see if the radiation is detected

Front 59

What is a use of alpha radiation?

Back 59

Smoke detectors

Front 60

How do smoke detectors work? (3 points)

Back 60

1)The smoke detectors have a weak source of alpha radiation close to two electrodes
2)The radiation ionises the air and a current flows between the electrodes
3) If there's a fire the smoke absorbs the radiation - the current stops - alarm sounds

Front 61

What is are two uses of beta radiation?

Back 61

Tracers and thickness gauges

Front 62

How is beta used as a tracer?

Back 62

Radioactive source injected in to the body
A radiation detector is used to follow its progress to see if the body is working properly

Front 63

How is beta used as in thickness gauges?

Back 63

1) The radiation source is placed above a detector with the paper in-between
2) If the paper is too thick = beta detected decreases and makes rollers pinch up
3) If the paper is too thin = beta reading increases and makes rollers open a bit

Front 64

Why are gamma and beta used as tracers in the body?

Back 64

They are able to pass out of the body

Front 65

What two uses does gamma radiation have?

Back 65

1) Cancer treatment
2) Sterilise medical equipment

Front 66

How is gamma used to treat cancer?

Back 66

1) High doses kill all living cells
2) Directed carefully at the cancer at the correct dosage to kill the cancerous cells without damaging too many normal cells

Front 67

How is gamma used to sterilise medical equipment

Back 67

Kills all the microbes

Front 68

What are 4 advantages of nuclear power?

Back 68

- Lots of energy without releasing CO(2)
- Release lots more energy than chemical reactions (eg. burning)
- Nuclear fuel = cheap
- Plenty of uranium in the ground

Front 69

What are 5 disadvantages of nuclear power?

Back 69

- Power stations = expensive to build
- Processing uranium before use = expensive
- Risk of leak or major catastrophe
- Radioactive waste produced = dangerous and difficult to dispose of
- Uranium = non-renewable