Presentation is prepared by: Guided By:•Meet Patel(13BEEEM052) Prof. Krishna Chauhan•Jaydev Kubavat(13BEEEG049) Electrical Engg. Dept.•Mayur Patel(13BEEEM053) S.V.I.T. Vasad.•Parth Gupta(13BEEEG013)

Elements of Electrical Engineering(2110005)

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Meet Patel(13BEEEM052)

Mayur Patel(13BEEEM053)

Jaydev Kubavat (13BEEEG049)

Parth Gupta(13BEEEG016)

Of Electrical-1 has completed their Active learning Assignment for term ending in December 2013

DATE:25/11/2013

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It is the process by which an emf (voltage) is produced in a wire by a changing magnetic flux.

Magnetic flux is the product of the magnetic field and the area through which the magnetic field passes.Electromagnetic induction is the principle behind the electric generator.The direction of the induced current due to the induced emf is governed by Lenz’s Law.

Electromagnetic induction

It states that an induced emf is produced by changing the flux, but how could the flux be changed?

Turn the field off or on.Move the loop of wire out of the fieldRotate the loop to change the angle between the field and the area of the loop.

Faraday’s law

Faraday’s Law in equation form:

tN

Where

Є = The induced emf (voltage) (V)

ΔΦ = The change in flux (Wb)

Δt = The change in time (s)

N = number of loops.

The induced emf in the wire will produce a current in the wire. The magnitude of the induced current is found using Ohm’s Law:

RI

IR

IRV

Application of Faraday’s Law Generator

Faraday’s LawShow that when you integrate the emf, e

with respect to time you get the average change in flux in time t.

ttdttd mmm )()(

dt

tdt

)()(

Average value

12

2

1

)(

)(tt

dttf

tf

t

t

Two types of electric fields. One is created by charge and the other is created by a changing magnetic field.

The Most Important Point of Faraday’s Law

A changing magnetic field produces

or creates an electric field.

The induced current in a wire produces a magnetic field such the flux of the produced magnetic field opposes the original change in flux. In simple terms the wire resists the change in flux and wants to go back to the way things were.

Lenz’s Law

ExampleExample A current loop has an area of 40 A current loop has an area of 40 cmcm2 2 and is placed in a 3-T B-field at the and is placed in a 3-T B-field at the given angles. Find the flux given angles. Find the flux through the through the loop in each case.loop in each case.

An

nn

A = 40 cm2 (a) = 00 (c) = 600(b) = 900

x x x x x x x x x x x x x x x x

(a)(a) = = BA BA cos 0cos 000 = (3 T)(0.004 m = (3 T)(0.004 m22)(1); )(1); 12.0 mWb12.0 mWb

(b)(b) = = BA BA cos 90cos 9000 = (3 T)(0.004 m = (3 T)(0.004 m22)(0); )(0); 0 mWb0 mWb

(c)(c) = = BA BA cos 60cos 6000 = (3 T)(0.004 m = (3 T)(0.004 m22)(0.5); )(0.5); 6.00 mWb6.00 mWb

Lenz’s LawThe direction of the emf

and thus the current is given by Lenz’s law. The statement in bold in the center of page 789 is a statement of Lenz’s law. Use this to find the direction of the current. If you are looking down on the loop from above, is the current flowing clockwise or counter clockwise? Explain.

Lenz’s Law

The magnetic is moving away from the coil so the magnetic field is decreasing, thus the current is in a direction to off-set the decrease.

The magnetic is moving toward the coil so the magnetic field is increasing, thus the current is in a direction to off-set the increase.

Induced Current

When a conductor moves across When a conductor moves across flux lines, magnetic forces on the flux lines, magnetic forces on the free electrons free electrons induce induce an electric an electric current.current.

When a conductor moves across When a conductor moves across flux lines, magnetic forces on the flux lines, magnetic forces on the free electrons free electrons induce induce an electric an electric current.current.

Right-hand force rule Right-hand force rule shows shows current outward for down and current outward for down and inward for up motion. (Verify)inward for up motion. (Verify)

Right-hand force rule Right-hand force rule shows shows current outward for down and current outward for down and inward for up motion. (Verify)inward for up motion. (Verify)

Down

II

Down

vvB

FF

Up vv

B

FF

Up

II

B

Magnetic Flux Density

Magnetic Flux density:

ABA

• Magnetic flux lines Magnetic flux lines are continuous and are continuous and closed.closed.

• Direction is that of Direction is that of the B the B vector at any vector at any point.point.

; = B BAA

; = B BAA

When area A is perpendicular to flux:

When area A is perpendicular to flux:

The unit of flux density is the weber per square meter.The unit of flux density is the weber per square meter.

alternating current - electric current that rapidly reverses its directionelectric generator - a device that uses electromagnetic induction to convert mechanical energy into electrical energy electromagnetic induction - inducing a voltage in a conductor by changing the magnetic field around the conductorinduced current - the current produced by electromagnetic inductioninduced emf - the voltage produced by electromagnetic induction

Important Terms.

Faraday’s law of induction - law which states that a voltage can be induced in a conductor by changing the magnetic field around the conductorLenz’s law - the induced emf or current in a wire produces a magnetic flux which opposes the change in flux that produced it by electromagnetic inductionmagnetic flux - the product of the magnetic field and the area through which the magnetic field lines pass.motional emf - emf or voltage induced in a wire due to relative motion between the wire and a magnetic field

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