3. PLASTICS AND TEXTILES.

3. Plastics and textiles.

Keys Concepts.

1. Plastic materials.

• Plastics consist of long chains of atoms which are mostly composed of carbon. 
• Plastics can be classified into natural and syhnthetic plastics.
• The process of manufacturing plastic is called polymerisation.
• There are three types of plastic recycling processes: chemical and mechanical recycling and energy recovery. 

2. The classification by internal structure.

• Thermoplastics are usually madre from petroleum products. The most common thermoplastics are: polyethylene terephthalate, high-density polyethylene, polyvinyl chloride, low-density polyethylene, polypropylene, moulded polystyrene, expanded polystyrene or styrofoam.
• Thermosetting plastics are made from petroleum products. They include: polyurethane, bakelite, melamine, polyester resins.
• Typical elastomers include rubber and neoprene. 

 3. Plastic forming techniques.

• Various industrial techniques can be used to manufactures plastic products, such as: extrusion, calendering, vacuum forming and moulding.
• The main techniques for using moulds are as follows: blow moulding, injection moulding and compression moulding.

4. Modification techniques.

•  Modification techniques use tools and machines to make changes to prefabricated materials, such as sheets, bars or mouldings.

5. Textiles.

• Both natural and synthetic fibres can be oven to make a variety of textiles.
• Natural fibres may come from animal sources (wool, silk), plant sources (cotton, linen, esparto, bamboo) and mineral sources (gold, silver and copper fibres).
• Synthetic fibres, such as nylon, polyester, rayon and lycra, are plastic materials.

 

8. ELECTRONS

 8.1. Electronic components.
  
Fixed resistance or resistor.

A fixed resistance or resistor opposes the flow of electric currents, Its value, which we measure in ohms, is indicated by a code of colours and numbers.





Variable resistance or ptentiometer.
The value of a variable resistance or potentiometer can be adjusted between zero and the maximum value specified by the manufacturer.





Resistance that depends on a physical factor.
The physical factors that effect resistance may be temperature or the amount of light:
  -Resistance that depends on temperature is called a thermistor. There are two types of thermistors:

• Negative temperature coefficient (NTC) : The resistance decreases as the temperature rises.
• Positive temperature coefficient (PTC) : The resistance increases as the temperature rises.

 -LDR: Resistance that varies according to the amount of light received. The resistance decreases as the amount of light increases.

Capacitors.
A capacitor can store electrical energy from a battery and then use it to power a light bulb until the charge is totally depleted.
Capacitors are components that can store an electrical charge.
The value of a capacitor indicates the charge in volts that it can store. This is measured in farads (F).

Diodes.
A diode is an electronic component made from semiconductor materials. A diode has two electrodes: an anode (A) and a cathode (K).
A LED only gives off light when an electric current flows throught it.

Transistors.
They are made from semiconductor materials and have three electrodes called the base, the collector and the emitter.
There are two types of transistor: NPN and PNP.

• When no electrons are flowing through the base, then no electrons can pass from the collector to the emitter. The transistor is in cut off.
• When many electrons are flowing through the base, the route between the collector and the emitter will be completely open. The transistor is in saturation.
• When the flow of electrons through the base is between the cut off and saturations levels, it will be proportional to th flow of electrons between the collector and the emitter. The transistor is in the active region.

8.2. Basic devices made with eletronic components.
Timers.
A timer is a device that operates for a cetain period of time and then shuuts itself off automatically.
Integrated circuits.
Integrated circuits consist of miniature electronic components, such as transistors, resistors and capacitors.

7. ELECTROMAGNETIC CONTROL SYSTEMS.

7. ELECTROMAGNETIC CONTROL SYSTEMS.

An electromagnetic control system activates the various parts of a machine, at the right moment and for the right amount of time, ensuring that the machine functions properly.

7.1. Cam switch controller.
The device on the side of the pulley in the picture above is called a cam.

7.2. Limit switches.
The battery provides power for the pump, which moves water from the lower tank to the upper tank. When the upper tank is full, a limit switch turns off the pump.

Normally closed (N/C)
It opens when it is activated.

Normally open (N/O)
It closes when it is activated.

6. ELECTROMAGNETIC MECHANISMS.

6. ELECTROMAGNETIC MECHANISMS.

They use electromagnetic phenomena to produce electricity or convert it into mechanical energy.

6.1. Electromagnetic generators.

Generators that produce direct current are called dynamos, and those that produce alternating current are called alternators.

Dynamos.
A dynamo consists of a magnet and a rotary coil. The coil is located beteen the two poles of the magnet. The ends of the coil have two semi-circular conductors, which form the commutator.

Alternators.
A simple alternator is almost identical to a dynamo, except for the commutador, which consist of two metallic rings connected to carbon brushes. Instead of a direct current, this produces alternating current.

6.2. Electric motors.

An electric motor is a device that can transform electrical energy into movement. It uses the forces of attraction and repulsion between a magnet and an electrically-charged wire.

6.3. Relays.
A relay is an electromagnetic component that works as a switch. Relays may have a single circuit with one moveable contact. 

5. EFFECTS OF ELECTRIC CURRENT

5.1. Heat.
The energy that an electric current produces as heat is called the Joule Effect.
It is expressed by the following formula:
                                                E = I^2 x R x t

5.2. Light.
Incandescent bulbs.
When an electric current passes through the metallic filament of a lightbulbs, it produces light. This phenomenon is called incandescence.

Fluorescent tubes.
Inside a fluorescent tube, there is a metallic filament, normally of tungsten. There is also an inert gas, such as argon, and a small amount of mercury.

Light-emitting diodes (LED)
A light-emitting diode (LED) has layers of semiconductor materials.

5.3. Electromagnetic effects.
In this experiment, the electric circuit has created a magnetic field. This effect can be used to produce movement.

5.4. Sound.
We can transform electric current into sound by using electromechanical devices, such as bells and buzzers. Some of these devices are based on the piezoelectric effect.

4. TYPES OF CURRENT

4.1. Direct current.
Between the terminals of a battery, there is a continuous, stable flow of energy. If we use a voltmeter to measure the current in a car battery, the result will always be 12 volts. This is called direct current.

4.2. Alternating current.
If we measured the voltage of an electrical socket, the results could be represented in a graph like the one below:

• The current begins at 0 V and increases to 325 V.
• The current decreases from 325 V to 0 V.
• The current becomes negative and decreases to -325 V.
• The current increases to 0 V.

The variation of any electrical parameter over a period of time is an electric signal.
The tension or voltage of domestic electricity is an alternating signal because it alternates between positive and negative values. Its waveform is also sinusoidal, with a smooth, regular shape.

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 sinusoidal current, the average power would be as follows:
                                                            Vef = Vmax/√2
4.4. Transformers.
Transformers consist of two windings made of copper wire. If we apply an alternating current to one of them, it will produce a certain voltage in the other. The value will depend on the number of times that the copper wire has been wrapped around each winding, represented as n1 and n2:
                                                           V1/V2 = n1/n2

3. TYPES OF CIRCUITS

3.1. Series circuit.

Two or more elements form 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 +...
One example of this type of connection would be a series of generators.
In other words:                             V = V1 + V2 + V3 +...
 

3.2. Parallel circuit.
If identical batteries are connected in parallel, the voltage of the circuit will not increase.
The equivalent resistance of this type of circuit would be:
                                                    1/R = 1/R1 + 1/R2 + 1/R3 +...
 

3.3. Combination circuit.
A combination circuit has some elements connected in series and other elements connected in parallel.

2. ELECTRICAL QUANTITIES

2.1. Voltage or potential difference.
The amount of energy that a generator can transfer to electrons depends on its voltage (V) or electric tension. This is measured in volts (V).
This device has two wires that must be connected in parallel to the element that we are checking.

2.2. Measuring electric current.
Electric current is the charge or number of electrons that flo through the cross-section of a conductor every second.
                                                                  I= Q/t 
Electric current is measured in amperes or amps (A).

2.3. Electric resistance: Ohm's Law.
 The resistance (R) of a material is equal to the voltage divided by the intensity of the electric current which travels through the material. This ratio, which is called Ohm's Law, can be expressed as follows:
                                                                              R= V/I
Ohm's Law has two forms:
 V = R x I    and   I = V/R

2.4. Electric energy and power.

Electrical energy.
If an electric current flows at a particular tension for a certain amount of time, we can calculate the energy that is consumed:   E = Vx I x t
Is measured in joules (J).

Electrical power.
The electrical power of a load is the amount of energy that it can transform over a certain amount of time. Electric power is measured in watts (W) or kilowatts (kW).

If an electrical current flows at a particular tension, we can calculate the power (P) that is consumed:
                                                                        P = V x I
We simply multiply the power in kiloatts by the amount of time in hours.
                                                                        E = P x t

7. ELECTRIC CIRCUITS AND ELECTRONICS

1. AN ELECTRIC CIRCUIT.

An electric circuit is a pathway for the flow of electrons.
Electric current is a continuous flow of electrons through a circuit.

1.1. Parts of an electric circuit.
Electric circuits consist of various parts:

• Generators provide the energy that electrons need in order to move.

 

• Loads are devices that transform electric energy into other types of energy that we can use.

   Light bulbs
  Motors

Resistors
 Bells

• Switching devices are used to direct and interrupt the flow of electric current.

  Switches
Push buttons
3-Way switches


1.2. Diagrams and symbols.
Generators: electrochemical cell and battery.
Loads: Light bulb or lamp, resistor, motor, bell, relay.
Switching devices: switch, push button, 3-way switch.
Safety elements: fuse.
Measuring instruments: ammeter, voltmeter.
Other parts: connection and bridge.

8. HOW CAN WE SAVE ENERGY?

8. HOW CAN WE SAVE ENERGY?

There are two important ways we can save energy: by increasing the energy efficiency of the devices that we use and by recycling as much as possible.

8.1. Energy efficiency.

An energy-efficient device requires less energy to perform the same work.

• Lighting: We can reduce the amount of electric light that we use by taking advantage of natural lighting.
• Domestic appliances: New appliances have energy efficiency labels to indicate how much energy they consume.
• Air conditioning and heating: We use a lot of energy to keep our homes at a comfortable temperature, but there are ways we can be more efficient.
• Transport: The best way to consume less energy is to use public transport or to travel with other people when going long distances.

8.2.. Recycling.

Our consumption of manufactured products generates waste and uses energy. We can reduce these negative effects by recycling as much as possible.

8.3. Positive impact.

Energy efficiency has a beneficial effect on the environment.
There are various projects to develop clean energy, such as nuclear fusion, which is the source of our Sun's energy.

7. ENVIRONMENTAL IMPACT.

7. ENVIRONMENTAL IMPACT.

7.1. Environmental impact assessment.

Any proposed new technological project should include an environmental impact assessment. There should also be an assessment of the economic and social repercussions of the project before any important decisions are made.

Wind: it is non-polluting, but it has visual and acoustic impacts, renewable, it is clean and it helps to replace our dependency on fossil fuels and output is low, discontinuous and random.
Hydroelectric: it has a major impact because it changes the flow of rivers and floods large areas, reneable, output is high and efficient and it a dam breaks, the could be a disaster.
Solar: it is non-polluting, but large power stations take up a lot of land, renewable, it is clean and it helps to replace our dependency on fossil fuels and installations are expensive.
Marine: the construction of marine stations affects the local environment, renewable, it is clean and it helps to replace our dependency on fossil fuels and installations are expensive.
Biomass: the technology is beneficial when it is used properly, renewable, it helps to replace our dependency on fossil fuels and it requires an excessive use of natural resources.
Fossil fuels: air pollution contributes to climate changes, non-renewable, output is high and efficient and air pollution causes respiratory illnesses.
Nuclear: radiation is very dangerous if there are accidents, non-renewable, output is high and effcient and it produces radioactive waste.

7.2. Effects on the environment.

 Extracting natural resources.
Fossil fuels and radioactive elements, such as uranium, must be extracted from underground deposits. Large areas of forest have been destroyed to provide wood for fuel.
Transporting fuel.
Most oil is transported over land through pipelines and by sea in large ships called oil tankers. Natural gas is transported over land through gas pipelines or by sea in tankers as liquid natural gas. These tankers are called LNG carriers.
Generating electricity.
Hydroelectric power stations require large amounts f water hich must be stored behind dams in reservoirs.
Waste treatment.
Some steps can be taken to reduce waste and its effects:

• Filters can reduce pollutants, such as nitrous oxide and sulphur.
• Low-sulphur coal can also be used to reduce sulphur emissions.
• Large forests should be protected because they remove C02 from the air.

7.3. Climate change.
This situation has negative effects on the envinment, and the most serious is climate change, a problem that is associated specifically with fossil fuels. Our use of fossil fuels generates air pollution, such as carbon monoxide gas and heavy metal particles in the air.

• These gases contribute to the greenhouse effect, which increases the Earth's average temperature.
•  We can observe some of the effects of global warming, such as the melting of our polar ice caps and glaciers lead to rising sea levels.
• These pollutants combine with water vapour in the air to produce acid rain.

7.4. Energy consumption.

 The fossil fuels that consumers use in their cars or home heating systems also have an effect on the environment.

6. POWER STATIONS THAT USE RENEWABLE ENERGY SOURCE.

6. POWER STATIONS THAT USE RENEWABLE ENERGY SOURCE.

Some power stations use clean, renewable energy sources to produce electricity.

They have several problems:

• They are 'greener' than conventional power stations because they produce less pollution.
• They use renewable energy, so they don't consume limited natural resources.
• They reduce our dependence on other countries that produce fossil fuels such as oil and natural gas.
• They are relatively cheap, in comparison to other energy sources.

6.1. Wind farms.

Wind farms use the kinetic energy of the wind to generate electricity. The wind the blades of a turbine, at the top of a tower.

The output and efficiency of a wind farm depend on two factors:

• The location of the farm, which determines the speed and strength of the winds.
• The number of turbines that can be installed there.

6.2. Hydroelectric power stations.

There are two main types of hydroelectric power stations:

• In conventional hydroelectric stations, the water flows from the reservoir to the turbines through a high-pressure conduit.

 

• In pumped-storage hydroelectric stations, the water flows from the turbines to a second reservoir. Then it is pumped back up to the higher reservoir and stored for later.
  
  6.3. Solar power stations.
  
  Solar power stations use energy from sunlight to generate electricity. There are to main types of solar power stations: solar thermal and photovoltaic.
  
  Solar thermal stations.
  
  
  Solar thermal stations can use sunlight in two ways:
  
  • With solar collectors that absorb sunlight in order to produce that.
  • With mirrors called heliostats that reflect and concentrate sunlight in one place.

Photovoltaic stations.
Small solar power installations can provide energy for homes and rural areas. Excess poer can be stored in batteries or accumulators and used at night.









6.4. Biomass power stations.

Biomass is any material that is produced by natural processes.
In a biomass power stations, 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).








 6.5. Marine power stations.

There are three general types of marine power stations:

• Tidal power stations, which use the energy of tides.
• Wave power stations, which use the energy of tides.
• Ocean thermal conversion stations, which use the difference in water temperature between the surface of the ocean and deeper areas to produce energy.

 

 6.6. Geothermal power stations.

Geothermal energy can be used in two ways:

• It can be used directly to provide hot water for heating and industrial uses.
• It can be used indirectly to drive generators and produce electricity.

 

5. ELECTRIC POWER STATIONS THAT USE NON-RENEWABLE ENERGY SOURCES.

5. ELECTRIC POWER STATIONS THAT USE NON-RENEWABLE ENERGY SOURCES.

Most of the electricity that we use comes from electric power stations that use non-renewable energy sources. There are two types: thermal power stations and nuclear power stations.

5.1. Thermal power stations that use fossil fuels.

Thermal power stations use fossil fuels to produce thermal energy. Then the thermal energy is converted to mechanical energy, in order to generate electricity.

Combined-cycle power stations.
In combined-cycle or  cogeneration power stations, electricity is generated in two systems. The first system burns natural gas with compressed air. This produces superheated gases, which turn a turbine to generate electricity.
The second system uses the hot gases from the first system and them to produce steam in a heat recovery boiler. Then the steam turns a turbine to generate more electricity.

5.2. Nuclear power stations.

A nuclear  power station is a thermal power station that uses a nuclear reactor to produce heat. The reactor uses radioactive material as fuel. The most commonly used materials are isotopes of uranium.
 

The main advantages of nuclear power stations are their productivity and profitability. They produce lots of electricity that can be sold at a profit.
The main disadvantages of nuclear power stations are the risks of nuclear accidents and the management and storage of radioactive waste.

4. ELECTRICAL ENERGY

4. ELECTRICAL ENERGY.

Electrical energy is a form of energy that is transported by an electrical current.
Electrical energy is the most commonly used energy in modern, industrialised societies. There are many technological objects around us that use electricity.

Electricity is very common for two reasons:

• It can be easily transformed into other types of energy, such as light and heat.
• It can be transported over long distances in ways that are cheap and efficient.

4.1. Electric power stations.

A power station or generating station 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 station.

How electricity is generated.
Electric power stations require sources of energy, such as the mechanical energy of falling water. 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 stator, and a moving part, called a rotor.
The turbine-alternator system is used at all power stations except for photovoltaic stations, which use a different type of technology.

4.2. The transportation and distribution of electricity.

Electric energy cannot be stored. As a result, it must be transported from power stations to the places where it is needed, such as industries and urban areas.

The transportation of electrical energy includes:

• Raising the voltage: Electricity must be transported over long distances, so the oltage is raised to avoid the loss of energy as heat.
• High voltage lines: Routes for high voltage lines are carefully planned and the lines are installed on toers.
• Reducing the voltage: Electrical substations are installed between high voltage lines and final consumers.
• The power is distributed to homes, offices, industries and public installations, such as streetlights and traffic lights. The electric lines are usually supported by posts or installed underground.

3. ENERGY SOURCES

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.
We can classify energy sources into two general categories: renewable and non-renewable.

3.1. Non-renewable energy sources.

Non-renewable sources come from natural resources that are limited and can be exhausted. At the moment, the most commonly used energy sources are non-renewable. They include fossil fuels (oil, coal and natural gas) and nuclear energy, which uses radioactive materials, such as uranium.

                                                                                                                                            
       Coal                        Uranium    

Gas tanks    
                   Pretroleum extractor





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

2. ENERGY TRANSFORMATIONS.




A battery contains chemical energy which is transformed into electrical energy. Then a lightbulb 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 object.





Chemical energy can be stored in fireworks, When fireworks explode, that chemical energy is converted into light, heat, sound 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. 







A kitchen mixer converts electrical energy into kinetic energy to turn the machine's axis.







In stars, the nuclear energy of atoms, such as hydrogen, is transformed into very intense luminous and thermal energy.



Energy can be transformed, but it cannot be created or destroyed. This is the principle of energy conservation.