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