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