4.3.THE EFFICIENCY OF ALTERNATING CURRENT:
The average power of alternating current is equal to the direct current that is needed to produce the same effect.In the case of an alternating sinosoidal current,the average power would be as follows:
Vef= Vmax/√2
4.4.TRANSFORMERS:
Transformers consist of two windings made of cooper wire.If we apply an alternating current to one of them(V1), it will produce a certain voltage in the other (V2) the value will depend on the number of times that the cooper wire has been wrapped around each winding,represented as N1 and N2:
V1/V2=N1/N2.
4.TYPES OF CURRENT
4.1.DIRECT CURRENT:
Between the terminals of a battery,theree is a continuous,stable flow of energy.If we use a voltemeter to measure the current in a car battery,the result will always be 12 volts.This is called direct current.In the same way,if we connect a light bulb to a battery,the electrons always flow in the same direction with the same current.
4.2.ALTERNATING CURRENT:
If we measured the voltaje of an electrical socket,the results could be represented in a graph like the one below:
- The current begins at 0V and increases to 325V.
- The current decreases from 325V to 0V.
- The current becomes negative and decreases to -325V.
- The current increases to 0V.
The variation of any electrical parameter over a period of time is an electric signal.
The tensión or voltage of domestic electricity is an alternating signal becouse it alternates between positive and negative values.Its waveform is also sinusoidal,with a smooth,regular shape.
3.TYPES OF CIRCUITS
3.1.SERIES CIRCUIT:
Two or more elements from a series circuit when the output of one element provides the input for the next element.
To calculate the total resistance of a circuit,we add the resistance values of each load:
R=R1+R2+R3+....
3.2.PARALLEL CIRCUIT:
If identical batteries are connected in parallel,the voltaje of a circuit will not increase.However,the total compsumition of energy will be shared between the batteries,so each one will last longer.
3.3.COMBINATION CIRCUIT:
A combination circuit has some elements connected in series and other elements connected in parallel.
- Three loads in a combination circuit.
- Four loads in a combination circuit.
2.3.ELECTRICAL RESISTANCE: Ohm's LAW:
The resistance (R) of a material is equal to the voltaje divided by the intensity of the electric current which travels through the material.This ratio,which is called Ohm's law,can be expresed as follows: R=V/I.
2.4.ELECTRICAL ENERGY AND POWER:
ELECTRICAL ENERGY: If an electric current (I) flows at a particular tension (V) for a certain amount of time (t) ,we can calculate the energy (E) that is consumed: E=V*I*t
In the SI,this electrical energy is measured in joules.(J).
ELECTRIC POWER: If an electric current (I) flows at a particular tension (V),we can calculate the power (P) that is consumed: P=V*I.
If we know the power of a load,we can calculate the electrical energy that it cosumes over a certain amount of time.We simply multiply the power in kilowatts by the amount of time in hours.E=P*T
2.ELECTRICAL QUANTITIES
2.1.VOLTAGE OR POTENTIAL DIFFERENCE:
The amount of energy that of generator (electrochemical cell or battery) can transfer to electrons depends on its voltaje (V) or electric tension.This is measured in volts (V).
2.2.MEASURING ELECTRIC CURRENT:
Electric current (I) is the charge or number of electrons that flow throungh the cross-section of a conductor every second. We can express this methemetically as follows: I = Q/t
Electric current is measured in amperes or amps (A) in the international system or SI.
1.2. DIAGRAMS AND SYMBOLS:
7.2.EFFECTS ON THE ENVIRONMENT:
Energy production includes many steps,from the extraction of natural resources to the transportation and final distribution of energy to consumers.Each of these steps can have an impact on the environement.
- Extracting natural resources
- Transporting fuel
- Generating fuel
- Waste treatment.
7.3.CLIMATE CHANGE:
- When we burn fossil fuels,gases such as carbón dioxide and methane are released into the air.These gases contribute to the greenhouse effect,which increases the earth's average temperature.
- Alredy we can observe some of the effects of global warmig,such as the melting of our polar ice caps and glaciers which lead to rising sea levels,and more extreme weather conditions in many places around the world.
- Power stations that burn fossil fuels also reléase other pullution into the air,such as sulphur oxide and nitrous oxide.These pollutants combine with wáter vapour in the air to produce acid rain,which damages our forest,lakes and rivers.It also contributes to the acidification of our oceans.
- These power stations effect plant and animal life because they use refrigeration systems that pump hot wáter into our rivers and oceans.This increases the local wáter temperature and also reduces the amount of oxygen in the wáter.
7.4.ENERGY CONSUMPTION:
The fossil fuels that consumers use in their cars or home heating systems also have an effect on the evironment.
6.5.MARINE POWER STATIONS:
Use the movement of ocean wáter to generate electricity.
- Tidal power stations,which use the energy of tides.
- Wave power stations,which use the energy of waves.
- Ocean thermal conversión stations,which use the difference in wáter temperatura between the surface of the ocean and deeper áreas to produce energy.
6.6.GEOTHERMAL POWER STATIONS:
- It can be used directly to provide hot wáter for heating and industrial uses.In some places,this hot wáter is used for bathing and health spas.
- It can be used indirectly to drive generators and produce electricity.
6.3.SOLAR POWER STATIONS:
Use energy from sunlight to generate electricity.There are two main types of solar power stations:solar an photovoltaic.
1.Solar termal stations:
- Wich solar collectors that absorb sunlight in order to produce heat.
- With mirrors called heliostarts that reflect and concéntrate sunlight in one place.
2.Photovoltaic stations:
- Small solar power installations can provide energy for homes and rural áreas.Excess power can be stored in batteries or accumulators and used at night.
6.4.BIOMASS POWER STATIONS:
In a biomass power station,the fuel used to produce energy comes from biomass.The steam produced from burning the biomass moves a turbine that is connected to a generator(alternator).
6.POWER STATIONS THAT USE RENEWABLE ENERGY SOURCES:
Some power stations use clean,renewable energy sources to produce electricity.These alternatives help to reduce our dependence on non-renewable sources of energy,such as fossil fuels,which also cause environement problems.
6.1.WIND FARMS:
Wind farms use the kinetic energy of the wind to generate electricity.The wind turns the blades of a turbine,at the top of a tower.The blades are cennected to a gearbox which increases the rotational speed of the generator.
6.2HYDROELECTRIC POWER STATIONS:
- In conventional hydroelectric stations,the wáter flows from the reservoir to the turbines throungh a high-pressure conduit.Then it flows out,usually into a river.
- In pumped-storage hydroelectric stations,the wáter flows from the turbines to a second reservoir.Then it is pumped back up to the higher reservoir and stored for later.These stations are often built in áreas where there isn't enoungh rain or river wáter to keep the upper reservoir full,so the wáter must be reused.
5.ELECTRIC POWER STATIONS THAT USE NON-RENEWABLE ENERGY SOURCES:
There are two types:Thermal power station and nuclear power stations.
5.1.THERMAL POWER STATIONS THAT FOSSIL FUELS:
- Fossil fuels,such as coal,oil and natural gas,are used to heat wáter in a boiler.
COMBINED-CYCLE POWER STATION:
The first system burns natural gas with compresses air.This produce superheated gases,which turn a turbine to generate electricity.The second system uses the hot gases from the first system and uses them to produce steam in a heat recovery boiler.
5.2.NUCLEAR POWER STATION:
The reactor radioactive material as fuel.The most commonly used materials are isotopes of uranium.
Advantages:Of nuclear power stations are their productivity and profitability.They produce lots of electricity that can be sold at a profit.
Disadvantages:Of nuclear power stations are the risks of nuclear accidents an the management and storage of radioactive waste.
4.ELECTRICAL ENERGY:
Is a form of energy that is transported by an electrical current.
Electricity is very common for two reasons:
- It can be easily transformed into other types of energy,such as ligth and heat.
- It can be transported over long distances in ways that are cheap and efficient.
4.1.ELECTRIC POWER STATIONS:
Is a place where energy from natural resources is transformed into energy that we can consume.If the energy obtained is electricity,it is called an electric power stations.
HOW ELETRICITY IS GENERATED:
- They use generators to transform this energy into electricity.
- The electric generators used in power stations are called alternators.
- An alternator usually has a stationary part,called a startor,and a moving part,called a rotor.
The turbine-alternator system is used at all power stations except for photovoltaic station,which use a different type of technology.
4.2.THE TRANSPORTATION AND DISTRIBUTION OF ELECTRICITY:
The transportation of electrical energy includes:
- RAISING VOLTAGE: Electricy must be transported over long distances,so the voltaje is raised to avoid the loss of energy as heat.
- HIGH VOLTAGE LINES: Routes for high voltaje lines are carefully planned and the lines are installed on towers.
- DISTRIBUTIONS: The power distributed to homes,offices,industries and public installations,such as streetlights and traffic lights.
3.ENERGY SOURCES:
Energy sources are natural resources that we can use to generate different forms of energy.Then we can transform that energy for various purposes.
3.1 NON-RENEWABLE ENERGY SOURCES:
They include fossil fuels and nuclear energy,which uses radioactive materials,such as uranium.
COAL.
3.2 RENEWABLE ENERGY SOURCES:
Renewable energy sources come from natural resources that we cannot use up completely.These include hydroelectric,solar,marine,geothermal and biomass resources,as well as energy that we can produce from solid urban waste.
2.ENERGY TRANSFORMATIONS:
A battery constains chemical energy which is transformed into electrical energy.Then a lighbulb transforms the electrical current into luminous and thermal energy.
The chemical energy in our muscles can be transformed into mechanical energy in order to move objects,such as the sofa in the picture.
Chemical energy can be stored in fireworks.When fireworks explode,that chemical energy is converted into light,heat,dsound and mechanical energy.
Photovoltaic solar panels transform luminous energy from the sun into electrical energy.
Internal combustion engines transform the chemical energy of fossil fuels into thermal energy.Most of this thermal energy is transformed into motion,but some is lost as heat.Some energy is also lost as sound when certain parts of the motor hit each other and vibrate.
A kitchen mixer converts electrical energy into kinetic energy to turn the machine's axis.Some of this kinetic energy is passed to the liquid,which moves around.Some energy is also lost as heat.
In stars,the nuclear energy of atoms,such as hydrogen,is transformed into very intense luminous and thermal energy.
