8. ELECTRONICS (8.1)

Electronics involves the study of circuits that modify the intensity, direction or properties of electric currents.

8.1. ELECTRIC COMPONENTS

Here, we'll analyse the most common 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.
The first two stripes are replaced by two numbers, according to their colour.The third stripe indicates the number of zeroes that we must add to the previous figure.The fourth stripe indicates the tolerance or the maximum deviation from the theorical value.

Variable resistance or potentiometer
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
There are two types of resistances that depend on a physical factor:
  -Resistance that depends on temperature, that 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 ligth received.The resistance decreases as the amount of ligth increases. These devices ,like potentiometers, are often used in security systems, where they are parts of sensors.
Capacitors
A capcitor can store electrical energy from a battery and then use it to power a ligth bulb until the charge is totally depleted.
Capacitors are componets 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.It only allows electric current to flow in one direction. A diode has two electrodes: an anode(A) and a cathode (K).
A LED (ligth emitting diode) only gives off ligth when an electric current flows through it.

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 abovee is a cam. The shape of this device allows us to control the moment and duration of an activity.

 

7.2. Limit switches

There are two types of switches:

-Normally open
-Normally closed

6. ELECTROMAGNETIC MECHANISMS

These are devices that can convert movement into electricity or vice versa.

6.1. Electromagnetic generators

These generators transform mechanical energy into electricity. There are two types of generators:

Dynamos

It consists of a magnet and a rotary coil. The coil is located between the two poles of the magnet. The ends of the coil have two semicircular conductors, which form the commuttator. When electricity is applied to the coil, it rotates and begins to generate direct current in the coil.

  

Alternators

A simple alternator is almost identical to a dynamo, except the commutator, which consists of two metallic rings connected to carbon brushes.

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

It's an electromagnetic component that works such as a switch. When electricity passes through the coil, it acts like a magnet. The coil attracts a moveable metal contact towards another fixed contact.

5. EFFECTS OF ELECTRIC CURRENT (5.3 + 5.4)

5.3. Electromagnetic effects

The following pictures show us how to create a magetic field with daily materials.

 

This effect can be used to pruduces movement, for example in electric motors.

To generate an electric current with a magnet, we can move the conductor or we can move the magnet. 

5.4. Sound

We can transform elecric current into sound by using diverse electromechanical devices, such as bells. Some of these devices are based on the piezoelectric effect.

5. EFFECTS OF ELECTRIC CURRENT ( 5.1 + 5.2)

The movement of electrons trhough conductive  materials produces effects that have useful applicattions.

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

There are various ways that electricity can be used to produce light:

Incandescent bulbs

When an electric current passes trough the metalic filament of a light bulb, it produces light. This is called incandescense.

Fluorescents tubes

Inside a fluoreescent tube, there is a metallic filament, normally, made of tungsten. When an electric current passes trough the filament, electrons are emitted into the inert gas. These react with mercury, creating invisible, ultraviolet light. Then the phosphor coating inside the tube transforms the ultraviolet light into visible light.

Light-emitting diodes (LED)

A LED has layers of semiconductors materials. When the electricity is applied to it, the electrons and holes cross over into the active layer, where they combine and produce photons or particles of light.