P2

using the sun energy

the sun is the ulimate source of loads of our energy

you can capture the sun energy using photocells

photocells (solar cells) generate electricity directly from sunlihgt.

photocells are usually made of silicon. when sunlight falls on the cell :

the silicon atoms absorb some of the enrgy, knocking loose some electrons, these electrons then flow atound a circuit - which is electricity

the current and output of a photocell depends on

it surface area

the intensity of lihgt

the distance from the light

advantages: low maintenance, last long, no pollution and renewable

disadvantages: no sunlight, no power

solar and wind power

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

glass lets in heat and light from the sun which is absorbed by thing within the room heating them up.

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

heated thing in the room emit infared radiation of a longer wavelength, which cant escape though the glass - its reflected back instead

this works to heat and keep heat inside a building

solar water heaters - glass lets heat and light from the sun in which is then absorbed by the black pipes and heats up the water.

wind turbines

wind turbine convert the kinetic energy of moving air into electricity. the wind turns the blade, which turn a generator

advantages: cheap, doesnt pollute waste, renewable

disadvantage: loads of turbine in replace of one coal power station, noise pollution, difficult to find a suitable place - spread out , expensive to set up

producing and distributing electricity

power stations

1) fuel produce heat which then generates steam

2) the moving steam drives the blades of a turbine

3) rotating movement from the turbine is converted to electricity by the generator

dynamo effect

elecctromagnetic induction: the creation of a voltage in a wire which is experiencing a change in magnetic field

using electromagnetic inductor to transform kinetic energy into electrical energy is called the dunamo effect.

two different situation where you get em induction:

A)  electrical conductor move through a magnetic field B)nagnetic field through a electrical conductor changes

to get a bigger voltage and current you can increase:

the strength of the magnet, the numbers of turns on the coils or the speed of moverment

generators roatae a coil in a magnetic filed

every half time the current in the coil swaps direction. this means the generator produces a alternating current.

turning the coil faster produces not only more peaks , not  a higher voltage and current to.

frequency of ac electrical supplies is the number of cycle per second and measure in hertz

supplying electricity efficiently

electricity is transfromed to high voltage before distrubuting

high voltage or high current is needed to transmit electical power. cables get hot with high currents, this is inefficent.

cheaper to increase the voltage. this keep the current very low, meaning less wasted energy because…