Physics 2

The sun is ultimate source of loads of our energy. 

Direct Current - just means the current flows the same way round the circuit all the time. E.g. Photocells are example of direct current. 

Advantages of photocells:

• There are no moving parts
• Low maintenance
• Don't need power cables

Disadvantages:

• No sunlight, no power

Curved mirrors focus the sun's light and heat. 

It can concentrate energy from the sun. 

Solar heating is when energy from the sun is used to heat something directly. 

The light from the sun has a short wavelength, so it can pass through the glass into a room. 

Wind turbines convert kinectic energy of moving air into electricity. 

Advantages: 

• Quite cheap to run
• Renewable
• Doesn't produde polluting waste 

Disadvantages

• Noise pollution
• Expensive to set up
• Not fast enough to generate any power 

The national grid connects power stations to cosumers. It is a network of pylons and cables which covers the whole country. 

Power stations convert one kind of energy into electricity:

1) Use the fuel to produce heat which generates steam.

2) The moving steam drives blades of turbine

3) The rotating movement from turbine is converted to electricity. 

Fossil Fuels are burnt to release their heat energy and they are concentrated source of energy. 

There are step up and step down transformers. Step up increases the voltage of and step down decreases to safe level which can be used at homes. 

Electromagnetic Induction: The creation of a voltage in a wire which is experencing a change in magnetic field. 

To get a bigger voltage and current, you can increase..

1) The strength of the Magnet

2) The number of turns on the coil

3) The speed ofmovement

Alternating Current is produced in generators

This is when the current changes direction. 

The greenhouse effect helps regulate earth's temperature

1) Energy from the sun is absorbed by the earth

2) The earth radiates heat...

3) ...Which is absorbed by greenhouse gases

4) ... and re-radiated in all directions. 

Natural:                                                                        Humans:

Carbon dioxide - burning fossil fuels                            Chopping down trees 

Methane - Cattle digestion produces methane             Decaying Waste in landfill sites

Water Vapour - As global temperature increases, so could the amount of water vapour. 

Nuclear Radiation causes Ionisation. Postive ions formed when atoms lose electrons. Negative ions are formed when atoms gains electrons. 

Alpha radiation: Are strongly ionising and can be stopped by paper or skin. 

It can be used for smoke detectors

Beta radiation: Are moderatly ionising and stopped by a thin sheet of metal

Used for medical usues such as traces 

Gamma radiation: Weakly ionising and stopped by thick concrete or sheet of lead. 

It had medical and inductrial uses. 

Can be used to sterilise. 

Nuclear power uses uranium as fuel. 

Advantages:

• Make lots of energy without releasing lots of Carbon dioxide
• Relatively Cheap
• Release lot more energy than chemical reaction 

Disadvantages: 

• Expensive to build and maintain
• Causes pollution
• Longer to start up
• Non-renewable energy source
• Difficult to dispose off 

Asteroids usually stay in their orbits but sometimes can be pushed or pulled

Meteors are rocks that have crashed down to earth. We see them as 'shooting stars' 

Layers of unusal elements in rocks 

Sudden chnages in fossil numbers between adjacent layers of rock 

Comets orbit the sun in very ellpitical orbits. 

Comets are baslls of rock, dust and ice which orbit the sun in very elongated ellipses. 

Near Earth Objects are asteroids or comets which might be on a collision course with earth. 

The moon may have come from a colliding planet. The moon has a lower density and moon rocks contain few substances which evaporate at low temperatures. 

Our sun is just on of the many billions of strs which form the milky way galaxy. 

Galaxies themselves are often millions of times further apart than the stars are within a galaxy. So even the slowest among you will have worked out that the universe is mostly empty space. 

A light year is the distance that light travels through a vaccum in one year. 

Advantages of Unmanned Probes:

• They don't have to carry food or water
• They're cheaper
• Withstand conditions that would be lethal to humans

Disadvantages of Unmanned Probes:

• They can't think for themselves
• Can't do maintenance or repairs