Electromagnetic control systems

Activates the various parts of a macine, at the right movement and for the right amount of time, ensuring that the machine functions properly.

Cam switch controller

The device on the side of the pulley in the pictures above is called cam. The shape of this device allows us to control the moment and duration of an activity, such as the rinning of a motor or the illumination of a light bulb

Limit switches

The picture below show an electrical control system for a water tank. 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.

There are two types of limit switch:

ELECTRONAGNETIC MECHANISM

Electromagnetic mechanism are devices that can covert movement into electricity or vice versa. In other words, they use electromagnetic phenomena to produce electricity or convert it into mechanical energy.

ELECTROMAGNETIC GENERATORS

Electromagnetic generators transform mechanical energy into electriciy. There are two types of generators, depending on the type of current that is produce. Generators that produce direct current are called dynamos, and those that produce alternating current are called alternators

-Dynamos

A dynamo consist of a magnet and a rotary coil. The coil is located between the two poles of the magnet. The ends of the coil have tow semi-circulaar conductors, which form the commutator. These conductors are attached to carbon brushes, which in turn are conected to electrical wires. When electricty is applied to the coil, it rotaters and begins to generate direct current in the coil.

-Alternators

A simple alternator is almost identical to a dynamo, except for the commutator, which consist of two metallic rings connected to carbon brushes, Instead of direct current, this produce altenating current

ELECTRIC MOTORS

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

RELAY

A relay os an elctromagnetic component that works 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.

EFFECTS OF ELECTRIC CURRENT

The movement of electrons though conductibe materials produces effects that hava applications. For example, a hair dryer uses the energy of electrons to produce heat and movement-

HEAT

The energy that an electric current produces as heat is called the Joule Effect. It is expressed by the following formula
               
                                                   E= I2xRxt
Most of the energy that is consumed by radiators and heaters is converted into heat.

LIGHT

-Incandescent bulbs

When an electrc current passes through the meatallic filament of a light bulb, iat produce light. This phenomenon is called incandescence.

-Fluorescent tubes

Inside a fluorescent tube, there is a metallic filament, normally made 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 laters of semiconductor materials. The n-type layer has extra electrons with negatively charged particles.

TYPES OF CURRENT

Some electrical devices use batteries and some must ve connected to the electric mains

DIRECT CURRENT

Between the terminals of abattery, there is a continuous, stable flow of energy. of we use a voltmeter 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.

ALTERNATING CURRENT

If we measured the voltage of an electrical socket, the results could be represented in a graph like one below;

-The current egins at 0 V 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 tension of voltage of domestic elctricity is an alternating signal beacause it altenates between positive and negative values. Its waveforms is also sinusoidal, with a smiith, regular shape.

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 te case of an alternating sinusoidal current, 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 form a series circuit when the output of one element provide the input for the next elemenat.

In the following diagram, the same current flows through all the elemnts, and the total volatge is the sum of the tensions at the end of each 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 conection would be a series of generators. The total resistance would be the sum of all the resistance values.

                                      V= V1+V2+V3+...

PARALLEL CIRCUIT

In a parallel circuit, the various components share the same input and output. In other words, the wires from both sides are joined together.

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

If indetical batteries are connected in paralle, the voltage of the circuit will not increase. However, the total consumption of energy will be shared between the batteries, so each one will last longer. 

COMBINATION CIRCUIT

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

In thisa 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

ELECTRICAL QUANTITIES

VOLTAGE OR POTENTIAL DIFFERENCE

In the circuit on the rigth, electrons flow from an electrochemical cell, though a light bulb and the back to the cell.

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 volatage, we can use a voltmeter. This device has two wire that must be connected in parallel to the element athat we are checking.

MEASURING ELECTRIC CURRENT

Electric current (I) is the charge or nmber of electrons that flow throuht the cross-section oof a conductor every second. We can express this mathematically as follows:

                                                    I = Q/t

Electric current is measured in amperes or amps (A) in the International System or SI

ELECTRICAL RESISTANCE: OHM´S LAW

In order to measure the resistance of a lamp, the following experiment was performed with three different circuits

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     and       I=V/R

The ohm (Ω) is the unit of electric resistance. The following equation can be used

                                              1Ω=1V/1A

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 x I x t

In this SI, this electrical energy is measured joules (J)

Electric power 

The electric 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)

1KW/H= 3600000 j = 3600 kJ

Electric circuit and electronics

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

PARTS OF AN ELECTRIC CIRCUIT

Electric circuit consist of various parts:

-Generator: Cells and batteries               Loads: Light bulbs, Motirs, Resistors, Bells



Switching device: Switches, push buttons, 3-way switches

DIAGRAMS AND SYMBOLS