# P2 Revision

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• Created by: Spanish
• Created on: 07-03-16 17:03
How can the current from a dynamo be increased?
- Using a stronger magnet, increasing the number of turns on the coil, rotating the magnet faster
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What is the equation used to calculate energy efficiency?
efficiency= useful energy output/ total energy input
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Yes. Most wavelength of electromagnetic radiation can pass through the Earth's atmosphere, but infrared radiation is absorbed
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How is methane produced?
Methane is produced when organic matter decomposes in an environment lacking oxygen
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Briefly describe the greenhouse effect?
The electromagnetic radiation from the Sun has a relatively short wavelength. This radiation is absorbed by and warms the Earth. The Earth then re-radiates the energy as infrared radiation with a longer wavelength.
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What is the equation used for calculating power?
power= voltage x current
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What is the equation used to calculate energy supplied?
energy supplied = power x time
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What is the equation used to calculate the cost of electricity used?
cost of electricity used = energy used x cost per kWh
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What time of the day is electricity at its cheapest?
We pay less for electricity during the night when not as much is needed, but it still has to be produced.
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What factors does the choice of energy source depend on?
availability, ease of extraction, effect on the environment, associated risks
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Why do moons orbit planets?
Moons orbit planets and planets orbit stars because centripetal force acts on them
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What is a meteor?
A meteor is made from grains of dust that burn up as they pass through the Earth's atmosphere
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What do probes measure?
temperature, gravitational forces, radiation, magnetic fields, a planet's atmosphere and surroundings
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Give two ways in which spacesuits protect astronauts?
1. A dark visor stops the astronaut being blinded 2. The suit is pressurized and has an oxygen supply for breathing
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What is the order of the planets?
Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune
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How was the moon formed?
The moon was formed after a collision between Earth and another planet
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What is an asteroid?
An asteroid is a large rock in orbit around the Sun. It is a mini planet or planetoid
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How have asteroids affected the Earth?
they have created enormous craters, caused tsunamis to flood large areas, hot rocks rained down
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How old are the Earth and Moon estimated to be?
The Earth and Moon are estimated to be 4.6 billion years old
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What prevents an asteroid joining with other asteroids to form another planet?
Jupiter has a very large mass compared to the mass of an asteroid, so its gravitational force prevents it from joining with other asteroids to form a planet.
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Why can we see other planets, satellites, meteors and comets?
We can see other planets, satellites, meteors and comets because they reflect the Sun's light
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What are the advantages of nuclear power?
Fossil fuel reserves are not used and no greenhouse gases are discharged into the atmosphere
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What are the disadvantages of nuclear power?
Its very high maintenance, decommissioning costs, and the risk of accidents similar to the one at Chernobyl
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What comes from the nucleus of an atom?
Alpha, beta and gamma radiations come from the nucleus of an atom
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Which type of radiation causes most ionisation?
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What is alpha radiation absorbed by?
Alpha radiation is short ranged (a few centimetres) and is easily absorbed by a sheet of paper or card
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What is beta radiation absorbed by?
Beta radiation has a range of about 1m and is absorbed by a few millimetres of aluminium
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Gamma radiation is much more penetrating and, although a few centimetres of lead will stop most of the radiation, some can pass through several metres of lead or concrete
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What can gamma radiation be used for?
Gamma radiation kills microbes and bacteria so it can be used for sterilisng medical instruments
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What do transformers do?
Transformers change the size of the voltage and current
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What are some advantages of photocells?
they are robust and do not need much maintenance, they need no fuel and do not need long power cables, they cause no pollution and do not contribute to global warming, they use a renewable energy source
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What does a photocell contain?
A photocell contains two pieces of silicon joined together to make a p-n junction
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What does the output from a photocell depend on?
the light intensity, the surface area exposed, the distance from the light source
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Wind farms do not contribute to global warming, nor do they pollute the atmosphere but they can be noisy, take up a lot of space and people sometimes complain that they spoil the view
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## Other cards in this set

### Card 2

#### Front

What is the equation used to calculate energy efficiency?

#### Back

efficiency= useful energy output/ total energy input

### Card 4

#### Front

How is methane produced?

### Card 5

#### Front

Briefly describe the greenhouse effect?