TEXTILES

• Natural and synthetic fibres can be woven to make a variety of textiles.
• Natural fibres may come from animal sources (wool, sik), plant sources (cotton, linen, esparto, bamboo) and mineral sources (god, silver and copper fibres)
• Synthetic fibres, such as mylon, polyester, rayon and Lycra, are plastic materials.

         

                     

                              MODIFICATION TECHNIQUES

• Modifications techniques use tools and machines to make changes to prefabricated materials, such as sheets, bars or mouldings.
• Examples of these techniques include: measuring→marking→cutting→drilling→filing and sanding→joining
• You must always pay special attention to health and safety rules

PLASTING FORMING TECHNIQUES

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

THE CLASSIFICATION OF PLASTICS

• Thermoplastics are usually made from petroleum products. The most common thermoplastics are:

1. Polyethylene terephthalate (PET)
2. High-density polyethylene
3. Polyvinyl chloride (PVC)
4. Low-density polyethylene
5. Polypropylene
6. Moulced polystyrene
7. Expanded polystyrene or Styrofoam

• Thermosetting plastics are made from petroleum products. They include:

1. Polyurethane
2. Bakelite
3. Melamine
4. Polyester reisns

• Typical elastomers includ rubber and neoprene

PLASTIC MATERIALS

• Plastics consist of long chains of atoms wich are mostly composed of carbon.
• Plastics can be classified into natural and synthetic plastics.
• The process of manufacturing plastic is called polymerisation.
• Plastic material are resistant, insulating ( against electricity, heat and sound), ductile, malleable, impermeable and light.
• There are three types of plastic recycling processes: chemical and mechanical recycling and energy recovery.

ELECTROMAGNETIC CONTROL SYSTEM
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.
Electromagnetic control systems often use cams and limit switches.

CAM SWITCH CONTROLLER
A camshaft is a cylindrical device with protrusions that make contact with other devices in order to activate or desactivate them.
The shape of a cam allows us to  control the moment and duration of an activity, such us the running of a motor or the illumination of a light bulb.

LIMIT SWITCHES
A limit switch detects when preassure is being applied to it. There are two types of limit switch: NORMALLY CLOSED (N/C) and NORMALLY OPENED (N/O)

EFFECTS OF ELECTRIC CURRENT

Heat

The energy that an electric current produces in the form of heat is called the Joule Effect. It is expressed by the following formula:

                                     E=I2xRxt

Light
There are varioues ways that electricity can be used to produce light 

Incandescent bulbs
When an electric current passes through the metallic filament of a light bulb , it produces light. This phenomenon is called a light-emitting diode (LED)

Fluorescent tubes
Inside a fluorescent tube, there is a metallic filament. There is also an inert gas, and a small amount of mercury. When an electric current passes trough the filament , electrons are emitted into the inert gas. This react with the mercury, creating ultraviolet light. Then the phosphor coating insisde the tube transforms the ultraviolet light into visible light.

Light emitting diodes (LED)
A LED has layers of of semiconductor materials. When electricity is applied to the LED, the electrons and holes cross over into the active layer, where they combine and produce photos, or particles of lights.

Electromagnetic effect
The scientist Michael Faraday discovered the opposite effect . He noticed that electricity could be generated by using a magnet and an electrical conductor. This principle allows us to build dynamos and alternators. Electromagnets use electric current to create magnetic fields.

Sound
We can transform electric current into sound by using electromechanical devices, such as bells and buzzers. The piezoelectric effect lets us use electricicty to produce sounds.

TYPES OF CURRENT
Some electrical devices use batteries and some must be connected to the electric mains. Both provide electricity, but in different ways.

Direct current
Between the terminals of a battery, there is a continuous, stable flow of energy. If we use a volmmeter to measure the direct current in  a car battery, the result will always be 12 volts. This is called direct current. The value of direct current doesn't change over time.

Alternating current
The tension or voltage of domestic electricity is an alternating signal because it alternates between positive and negative values.
If we measure the voltage of an electrical socket, the results could be represented in 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 value of alternating current changes over time. The flow of energy also changes direction in a cyclical way.


The efficiency of alternating current
The average power of alternating current is the power that a direct current should have in order to produce the same electrical effect. The average power would be as follows:
                                  Vef= Vmax/√2


Transformers
Alternating current can be increased or decreased by a transformer. They consist of two windings made of copper wire. If we apply an alternating current to one of them (V1) it'll produce a certain voltage in the other (V2). 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

TYPES OF CIRCUITS

SERIES CIRCUIT

Two or more elements are connected in series when the output of one element is the input of the next element. In this type of circuit, the current flowing through all the elements is the same.

To calculate the total resistance we use this formula: R=R1+R2+R3+...

PARALLEL CIRCUIT

Two or more elements are connected in parallel when they share the same input and output. In this type of circuit, the potential difference of each element is the same.

To calculate the total resistance we use this formula:

1/R=1/R1+1/R2+1/R3+...

If identical batteries are connected in parallel, the voltage of the circuit wil not increase.

COMBINATION CIRCUIT

If a circuit has some elements in series and others in parallel, it is a combination circuit.

                 

In this type of circuit, the current remains constant between elements that are connected in series. At the same time, the voltage remains constant between elements that are connected in parallel.

If you click here, you will see another explication of series and parallel circuit.

ELECTRICAL QUANTITIES

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)

If we want to measure voltage, we can use a volmeter and it must be connected in parallel.

      



MEASURING ELECTRIC CURRENT
Electric current is the number of electrons that flow through the cross-section of a conductor every second. We can express this mathematically as follows:
                                        I=Q/t
I=electric current
Q=coulomb
t=time (s)
Electric current is measures in amps (A) in the S.I.

If we want to measure the electric current we use an ammeter, and it must be connected in series.

               
              


ELECTRICAL RESISTANCE: Ohm's Law
The resistance (R) of a material is equal to the voltage divided by the intensity of the electic current wich travels trough the material. This ratio, wich is called Ohm's Law, can be expressed as follows:
                                      R=V/I

Ohm's Law has two forms:
                                  V=RxI       I=V/R

The resistance is measured in omh (Ω)

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= VxIxt 

The energy is measured in joules (J)

ELECTRIC POWER
Electrical power is the energy consumed over a certain amount of time. It is measured in watts (W) or kilowatts (kW)

If an electric current (I) flows at a particular tension (V) we can calculate the power that is consumed:
                                        P=VxI

You can click here and you will learn more about power 

 

ELECTRIC CIRCUITS AND ELECTRONICS

AN ELECTRIC CIRCUIT
This is a pathway for the flow of electrons. It consists of the following parts, wich are connected by wires, a generator that provides energy, elements that provide control and protection, loads that receive and use energy.

PARTS OF AN ELECTRIC CIRCUIT

Electric circuits consists of various parts:

1-GENERATORS: batteries and cells

2-LOADS: light bulbs, motors, resistors and bells

3-SWITCHING DEVIDES: switches, push buttons, 3-way switches.    

DIAGRAM AND SYMBOLS

ENVIRONMENTAL IMPACT

CLIMATE CHANGE
Most of our electricity comes from power stations that use non-renewable energy sources, as a result, it causes an impact in the environment.
For example:
-Air pollution
-Greenhouse effect
-Global warming
-Acid rain

POWER STATIONS THAT USE RENEWABLE ENERGY SOURCES
There are many types of power stations that use renewable sources, such us: wind power, hydroelectric power, solar power, marine power, geothermal power and biomass power.
Some advantages of these types of power stations:
-They are greener than conventional power stations
-They don´t consume limited natural resources
-They reduce our dependence to use fossil fuels

WIND FARMS
They are a totally clean source of electricity. Wind farms use the kinetic energy of the wind to produce energy. The wind turns the blades of a turbine, and the blades are connected to a gearbox.

HYDROELECTRIC POWER STATIONS
They use the energy of falling water to produce energy. There are two types of hydroelectric stations:

-Conventional hydroelectric stations: here, the water flows from the reservoir to the turbines through a high preasure conduit. Then it flows out, usually into a river.

-Pumped-storage hydroelectric stations: here, the water flows from the turbines to a second reservoir. Then it is pumped back up to a higher reservoir and stored for later.

SOLAR POWER STATIONS
They use energy from sunlight to generate electricity. There are two types of solar power stations:

Solar thermal stations
They can use sunlight in two ways:
-With solar collectors that absorb sunlight to produce heat
-With mirrors called heliostats, that reflects and concentrate sunlight in one place.

Photovoltaic stations
Here, solar panels convert sunlight directly into electricity. Each panels contains many photovoltaic cells.

BIOMASS POWER STATIONS
Biomass is any organic material that is produced by natural processes.
In a biomass power station, the fuel used to produce energy comes from biomass. The steam from burning the biomass moves a turbine connected to a gerenator (alternator)

MARINE POWER STATIONS
They use the movement of ocean water te generate electricity. They are very expensive and not vere efficient. There are three types of marine power stations:
-Tidal power stations
-Wave power stations
-Ocean thermal conversion stations

GEOTHERMAL POWER STATIONS
They use heat from the deepest underground layers of our planet. This energy can be used in two ways:
- Directly, to provide hot water for heating and industrial uses.
-Indirectly: to drive generators to produce electricity.

ELECTRIC POWER STATIONS THAT USE NON-RENEWABLE ENERGY SOURCES
There are two types: Thermal power stations and nuclear power stations.

THERMAL POWER STATIONS
Thermal power stations use fossil fuels to produce thermal energy. Than the thermal energy is converted to mechanical energy, in order to generate energy.

Combined-cycle power stations

A combined-cycle station is more efficient than single-cycle stations because it has two systems that produce more energy.
The first system burns natural gas with compressed air, and the gases that it produced, they turn a turbine.
The second system uses the steam from the first system. That steam turns another turbine to produce more electricity.

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.

ELECTRICAL ENERGY

WHAT IS ELECTRICAL ENERGY?
It is a form of energy that is transported by an electrical current. It is very usually used because:
1-It can be easily transformed in other types of energy.
2-It can be transported over long distances in ways that are cheap and efficient.

ELECTRIC POWER STATIONS
A power station is a place where energy from natural resources is transformed into energy that we can consume. After the electricity has been generated, it can be transported to locations where energy is needed.

How electricity is generated
In electric power stations they use generators to transform energy into electricity. The electric generators used in power stations are called alternators.
An alternator usually has a stationary part, called stator, and a moving part, called a rotor.

THE TRANSPORTATION AND DISTRIBUTION OF ELECTRICITY
Electrical energy must be transported from power stations to the places where it is needed. The transportation of electrical energy includes:
-Raising the voltage: it is to avoid the loss of energy as heat
-High voltage lines: routes for high voltage lines are carefully planned
-Reducing the voltage: (they use substation transformers)
-Final: now, the power is distributed where it´s necessary.