# Concept of Electric Motor and Generator

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ELECTRIC MOTOR

Electric motor is a rotating device which converts electrical energy into mechanical energy.
Electric motor is used in many components like fans,mixer,washing  machine,computer, mp3 player and many more.

so, now we will discuss abouthow an electric motor works

Working of an Electric motor

• An Electric motor shown here with circuit diagram with ABCD as its coil.
• The coil is placed between between magnetic fields.
• Coil and magnetic field are perpendicular to each other.
• The ends of the coil are connected to the two halves P and Q of a split ring.
• The inner sides of these halves are insulated and attached to an axle.
• The external conducting edges of P and Q touch two conducting stationary brushes X and Y, respectively.
• we know that magnetic field always goes from north pole to south pole.
• The coil is connected to the power source. so current is flowing from A to B to C to D.
• We know that when a current carrying conductor is placed inside a magnetic field it experiences a force.
• In which direction the force will act we can know it from Fleming’s left hand rule.

• If we apply Fleming’s left hand thumb rule to coil AB. then coil AB is the middle finger which shows the direction of current.
• And Index finger will show direction of magnetic field.
• Then then the thumb finger will show the direction of force which is downward direction, So coil AB will experience a downward force.
• In the same way coil CD will experience a upward forceIn this way coil ABCD will rotate.
• In the same way if we will reverse the current then coil will rotate in opposite direction.

Now we will study about Electromagnetic induction.

ELECTROMAGNETIC INDUCTION

We know that if a current carrying conductor is placed inside a magnetic field it
experiences a force.
If we reverse this statement to “if a moving conductor is placed inside a magnetic field will the current will be produced in that conductor“?
This experiment was done by the great scientist Michael Faraday.

He found that Yes the conductor produces current. The detection of current was done by a Galvanometer(Galvanometer is a device which shows the direction of the current).
This happens because of electromagnetic induction.

Now we will do another experiment.

• Take two different coils of copper wire having large number of turns (say 50 and 100 turns respectively).Insert them over a non-conducting cylindrical roll.
• Connect the coil-1, having larger number of turns, in series with a battery and a plug key.Also connect the other coil-2 with a galvanometer as shown.
• when we will plug in the key the galvanometer in coil-2 deflects.
• From these observations, we conclude that a potential difference is induced in the coil-2 whenever the electric current through the coil–1 is changing.
• Coil-1 is called the primary coil and coil-2 is called the secondary coil.
• From this observation we conclude that when current flows in primary coil current induces in secondary coil.
• This principle is used in Transformers.
• The induced current is found to be the highest when the direction of motion of the coil is at right angles to the magnetic field.
• we can use a simple rule to know the direction of the induced current.
• For induced current we will use Fleming’s right hand rule.

ELECTRIC GENERATOR

Electric generator is a device which converts mechanical energy into electrical energy.
In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity.
Generator is used in many places to produce electrical energy.

Now we will study about how an Electric generator works.

Working of an Electric Generator

Based on the phenomenon of electromagnetic induction.
An electric generator, consists of a rotating rectangular coil ABCD placed between the two poles of a permanent magnet.
The two ends of this coil are connected to the two rings R1 and R2. The inner side of these rings are made insulated.
The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2, respectively.
The two rings R1 and R2 are internally attached to an axle.
The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field.
Outer ends of the two brushes are connected to the galvanometer to show the flow of current in the given external circuit.
When the axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet.

By applying Fleming’s right-hand rule, the induced currents are set up in these arms along the directions AB and CD.
Thus an induced current flows in the direction ABCD.
If there are larger numbers of turns in the coil, the current generated in each turn adds up to give a large current through the coil.
This means that the current in the external circuit flows from B2 to B1.

Now we will study about making of domestic electric circuit

DOMESTIC ELECTRIC CIRCUITS

• Domestic electric circuit connection are the type of connection which we generally use in our houses.
• The circuit components are all connected in parallel.
• If any components gets damaged or do not work properly it do not affect other components.
• We can also regulate each of the components using switches.
• We also use protection devices like ‘fuse‘ to protect the components from various electrical damages.
A schematic diagram of one of the common domestic circuits

• we receive supply of electric power through a main supply (also called mains), either supported through overhead electric poles or by underground cables.
• One of the wires in this supply, usually with red insulation cover, is called live wire (or positive).
• Another wire, with black insulation, is called neutral wire (or negative). In our country, the potential difference between the two is 220 V.
• In each separate circuit, different appliances can be connected across the live and neutral wires.
• Each appliance has a separate switch to ‘ON’/‘OFF’ the flow of current through it.
• In order that each appliance has equal potential difference, they are connected parallel to each other.

FUSE

• A fuse in a circuit prevents damage to the appliances and the circuit due to overloading.
• Overloading can occur when the live wire and the neutral wire come into direct contact.
• In such a situation, the current in the circuit abruptly increases. This is called short-circuiting.
• The use of an electric fuse prevents the electric circuit and the appliance from a possible damage by stopping the flow of unduly high electric current.
• Material used in fuse have high resistance and low melting point(to get disconnected easily).
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