Electric generator - class-IX

The working of a generator in based on the phenomenon of electromagnetic induction.

The laws of electromagnetic induction has been used in the construction of a electric generator. In electric generator, emf is induced by changing the flux.
Galvanometer is used to detect current. So, no use of electromagnetic induction.
Voltmeter is used to measure voltage. Again, no use of electromagnetic induction.
Electric motor changes electrical energy into mechanical energy, which has no use of laws of electromagnetic induction.

Answer is D.

Electromagnetic induction is a process where a conductor placed in a changing magnetic field (or a conductor moving through a stationary magnetic field) causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current - it is said to induce the current.
Hence, the D.C. generator is based on the principle of electromagnetic induction.

Answer is B.

The electric generator is devised to convert mechanical power into electrical power. Permanent magnet (PM) current converts into electrical energy through the interaction of two magnetic fields. One field is produced by a permanent magnet assembly, the other field is produced by an electrical current flowing in the rectangular coil ABCD, through the brushes and split-ring commutators. These two fields result in a torque which tends to rotate the coil. As the coil turns, the current in the winding is commutated to produce a continuous torque output. 
The split ring commutator is made from 2 pieces of copper that are held apart in the center from touching each other. They look like a copper ring split in the middle. The effect of using split rings in a electric generator is that the direction of the current flowing in the coil is reversed and DC current is generated.

If the speed of rotation of armature coil is increased in an AC generator

Electric generator, also called dynamo, any machine that converts mechanical energy to electricity for transmission and distribution over power lines to domestic, commercial, and industrial customers. Generators also produce the electrical power required for automobiles, aircraft, ships, and trains.A feature common to both AC and DC generator is Mechanical energy is converted to electrical energy

In an AC generator,  Magnetic flux $= NAB\sin\phi$

A dynamo converts mechanical energy into electrical energy.

The slip rings allow the transfer of alternating e.m.f. induced in the rotating coil to the external circuit. Each ring is connected to one end of the coil wire and is electrically connected to the external circuit via the conductive carbon brushes.

An electric generator is a machine which generates electricity by using the principle of EMI. It converts mechanical energy into electrical energy.

An electric generator is a machine which generates electricity by using the principle of electromagnetic induction. It converts mechanical energy to electrical energy.

The generator/dynamo is made up of stationary magnets (stator) which create a powerful magnetic field, and a rotating magnet (rotor) which distorts and cuts through the magnetic lines of flux of the stator. When the rotor cuts through lines of magnetic flux it makes electricity.

An electric generator (Dynamo) is a machine which generates electricity by using the principle of electromagnetic induction.

Electric generator is the application of EMI. The electric generator woeles on the principle that when a straight conductor is moved in magnetic field, then current is induced in the conductor.

AC generators are used in power station to generate electricity, which is supplied to our hours. AC generator is also h/a alternator.

There is no commutator in AC generator. In DC generator, we connect the two ends of the coil to the commutator consulting two half rings of copper.

The power house AC generators have a fixed site of coil arranged around a relating electromagnet. Thus, in large power house generators, the coils are stationary are the electromagnet rotates.

Magnets are also used in making electric generators and electric motors. Magnetic resources imagine also use magnets

AC generator means alternating generator. i.e. AC generator produces current that revenues its direction continuously.

A small generator is called or dyanamo. Ex. Dynamo are used in bicycles for lighting purposes.

Electric Motor
1. It converts electrical energy into mechanical energy.
2. It needs electrical energy for its working.
3. They are used as water pumps, marble grinders e.t.c Generator
1. It converts mechanical energy into electrical energy
2. It needs mechanical energy for its working.
3. They are used as water pumps, marble grinders e.t.c
3. Diesel generator, hydro-electric generator are the examples of it.

Dynamo produces Direct current by process of commutation.

When a conductor moves in a magnetic field, an emf is induced across the conductor. This is the only basis on which each and every rotating electric generator works. Let us discuss the matter in a little bit details so that we can easily understand how does an electrical generator actually work. According to Faraday's law of electromagnetic induction, when a conductor links with a changing flux, it will have an induced emf across it. The value of induced emf across the conductor depends on the rate of change of flux linkage with the conductor. 

When the plane of the rectangular coil is parallel to the magnetic field, angle between the magnetic field and the area vector of coil  $\theta = 90^o$
Flux passing though the coil  $\phi = BA \ \cos\theta = BA \ \cos90^o = 0$
Thus no emf is induced in the coil and induced current is zero.

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because It is not necessary to reverse the direction of the current.The brushes transfer the electricity from outside the motor to the spinning winding in the center of the motor. They undergo quite a lot of friction, and after a while wear out. Carbon is used as it is a reasonable conductor, and is soft enough to wear down instead of wearing down the "comutator" - the ring the brushes press against. Brushes are designed to be replaceable in large motors because of this.

A small AC dynamo is connected to a galvanometer and gently rotated, then the needle of the galvanometer moves towards both right and left The deflection of the needle of a galvanometer indicates a current flowing through the small stator winding (wound coil) inside the device. The more current flowing through the coil the greater the magnetic disturbance 

A dynamo is an electrical generator that produces direct current or (Electromotive force) with the use of a commutator.

Dynamo is an electric generator where shaft is rotated mechanically and electric energy is produced. It converts the mechanical motion of the driven shaft into electrical motion,with the aid of a magnet.

The armature current will increase if the speed of the DC generator start decreasing due to an increase in voltage drop at armature resistance.

A dynamo (generator) works on the principle of electromagnetic induction, where a changing magnetic flux induces an electromotive force.

The main difference  between $A.C$ generator and $D.C$ generator is carbon brushes.

For a generator with fixed field excitation, the induced EMF is directly proportional to the speed of rotation (E = k * N). Given 100V at 1500 rpm, the constant k is 100/1500. To find the speed for 120V, we solve 120 = (100/1500) * N, which yields N = 1800 rpm.

A dynamo converts mechanical energy to electrical energy, producing a DC current, using a commutator.
A motor converts various type of energy like fossil fuel, steam an electrical energy to mechanical energy.
A transformer magnetically couples different electrical circuits. 

An electric generator converts mechanical energy into electrical energy based on Faraday's law of electromagnetic induction. An electric motor works on the force exerted on a current-carrying conductor in a magnetic field, while a fuse and bell operate on thermal and magnetic effects respectively.

Answer is D.

The emf is actually induced by a change in the quantity called the magnetic flux rather than simply by a change in the magnetic field. Magnetic flux is proportional to both the strength of the magnetic field passing through the plane of a loop of wire and the area of the loop. The value of the magnetic flux is proportional to the total number of lines passing through the loop. When the area is perpendicular, that is, at right angles (90 degrees) to the lines, the maximum number of lines passes through the area and the flux is a maximum. When the area is parallel to the lines, no lines pass through the area and the flux is 0.
Hence, maximum number of lines of force passes though the coil when the angle between the plane of coil and lines of force is 90 degrees.

The a.c dynamo has step rings because it changes polarity in every half cycle.

The electric generator works on the principle of Faraday's Law of electromagnetic induction.

A generator is a device that converts mechanical energy into electrical energy. It is the source of electricity used to generate large amounts of electricity in power house.

Generally a small dynamo require a permanent magnet. Using the Faraday's law of induction, rotating a coil of wire and magnetic fields to convert mechanical rotation into a direct electric current. Thus, a dynamo converts mechanical energy to electrical energy.  

When the number of turns in the coil increases, the strength of the voltage induced in the coil will also increase as the number of turns and induced voltage are directly proportional to each other.
Therefore, if the number of turns in the coil of this dynamo is doubled, then the voltage in the bulb will also be doubled.

In a DC generator, the ends of the coil are connected to the split ring commutator.

Voltage/current produced in a generator can be increased by: 
a) Using a powerful electromagnet to make the magnetic field stronger in place of a permanent magnet.
b) By winding the coil round a soft iron core to increase the strength of magnetic field.
c) By using a coil with more turns.
d) By rotating the coil faster.
e) By using a coil with a larger area.

If a powerful electromagnet is used instead of a permanent magnet, magnetic field strength increases. This increase in magnetic field strength leads to the increase in induced voltage in the coil. An increased voltage leads to an increased induced current in the generator.

The only difference between a DC generator and an AC generator is in the way the two ends of the generator coil are linked to the outer circuit.

A device that reverses the direction of flow of current through a circuit is called a commutator. In electric motors, the split ring acts as a commutator.

AC generator produces alterating current which reverses its direction continuously. It is also h/a alternator.

An electric generator is classified on the basis of type of electric current it produces

Voltage/current produced in a generator can be increased by:
a) Using a powerful electromagnet to make the magnetic field stronger in place of a permanent magnet.
b) By winding the coil round a soft iron core to increase the strength of magnetic field.
c) By using a coil with more turns.
d) By rotating the coil faster.
e) By using a coil with a larger area.

Dynamo is a type of electrical generator and produces dc current as output.

A dynamo consists of 
1) A horse-shoe magnet 
2) An armature coil 
3) Two slip rings
4) Two carbon brushes
5) The external circuit (or load)

A dynamo consists of 
1) A horse-shoe magnet 
2) An armature coil  
3) Two slip rings
4) Two carbon brushes
5) The external circuit (or load)

A dynamo is a device which converts mechanical energy into electrical energy. 

Dynamo consists of horse-shoe magnet, armature coil, two slip rings, two carbon brushes, external circuit/load

Dynamo produces DC as output while transformer can be used to step-up or step-down AC voltage only.

Output emf is induced in armature coil which delivers power to the load.

DC motor is a device which coverts electrical energy into mechanical energy. It employs Fleming's left hand rule.
DC generator converts mechanical energy into electrical energy in from of DC. It employs Fleming's right hand rule.

The EMF generated by Faraday's law of induction due to relative movement of a circuit and a magnetic field is the phenomenon underlying electrical generators. When a permanent magnet is moved relative to a conductor, or vice versa, an electromotive force is created. If the wire is connected through an electrical load, current will flow, and thus electrical energy is generated, converting the mechanical energy of motion to electrical energy.

The frequency of AC current produced is same as the frequency of rotation of dynamo which is given 100 cycles per second that is $100Hz$.

Induced voltage in the rotating loop is given by   $\mathcal{E} = NBAw \ \sin wt$
where $N$ is the number of turns in the loop, $A$ is the area of the loop, $B$ is the magnetic field and $w$ is the angular speed of rotation of loop.
$\implies \ \mathcal{E}\propto w$
So, the induced voltage increases on increasing the speed of rotation of loop.

Generator is the device used for the production of electric current.

The voltage generated by a generator , whether AC or DC , depends upon the rate of change of flux linked with coil .

The AC dynamo (generator) is made up of stationary magnets (stator) which create a powerful magnetic field, and a rotating magnet (rotor) which distorts and cuts through the magnetic lines of flux of the stator. When the rotor cuts through lines of magnetic flux it makes electricity. Thus mechanical energy is converted into electrical energy. 

An electric generator works on the principle of Electromagnetic Induction.

A  dynamo converts mechanical energy into electrical energy according to Faraday's Law of Electromagnetic Induction.

Dynamo is a device which converts mechanical energy into electrical energy.

After every half rotation, the direction of e.m.f reverses and hence current changes its direction after a regular interval.