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Electromagnetism

Experiment of Hans Christian Oersted- He found a link between electricity and magnetism

Oersted

Any current carrying conductor creates a magnetic field

Deflection of the needle

Direction

Needle deflects only when current passes, so current carrying conductor has magnetic field

Direction

Reverse

Experiment and right hand thumb rule

Rule

1. They are in circles around the wire

2. More current more strength of field

3. Direction is reversed, the deflection of compass needle is also reversed

Properties

4. Magnetic field at any point is the combined effect of earths field and current

Magnetic field in a circular coil

Loops

Properties

1.Near the wires the magnetic field are circular

2. Near the centre the field lines are parallel, uniform

3. More current more strength of magnetic field

Properties

4. More turns more strength

5. Loop acts like dipole and behaves like magnetic disc of same radius

6.At the centre ,field lines are along the axis of loop and normal to its plane

Clock rule

Solenoid

What is a solenoid?

Solenoid

A solenoid is a long piece of wire which is wound in the shape of a coil. When the electric current passes through the coil it creates a relatively uniform magnetic field inside the coil.

Rule for determining north and south poles

Rule

Identify the poles

B

A

B

More examples

Properties

  • Magnetic field lines inside solenoid are straight and parallel to the axis of solenoid
  • more current magnetic field lines are denser
  • more turns more field lines
  • soft iron core increases field strength

Properties

Similarity and Dissimilarity

Similarity

Properties

Bar magnet

Solenoid

Magnetic lines

From north to south

Same from north to south

North south

North south

Suspended freely

Yes

Attractive property

Yes

Between magnet and solenoid

Dissimilarity

Strength can be increased for solenoid not for magnet

Polarity can be reversed for solenoid

Electromagnets

I shaped electromagnets

U shaped electromagnets

Electromagnets

More current

More turns

Increasing the strength

Differences

Permanent

Electromagnet

Steel

Made of iron

Difference between electro and permanent magnet

Cannot be increased

Strength can be increased

Cannot be

Demagnetized

Cannot reverse

Reverse the polarity

Uses

Current carrying conductor placed under the influence of external field

https://flexbooks.ck12.org/cbook/cbse-physics-class-10/section/4.6/primary/lesson/force-on-a-current-carrying-conductor-in-a-magnetic-field/

Force on a conductor

Fleming's left hand rule

Fore finger- field

Central finger- current

ThuMb- motion

Identify the direction of motion

S

N

Examples

S

N

Identify the direction of motion

S

N

Changing magnetic field

S

N

Factors affecting thrust

Current

Magnetic field strength

Factors affecting force

Length of the conductor

Principle

Current carrying conductor placed in a magnetic field experiences a force

Parts

DC Motor

Coil

Magnet

Commutator

Brushes

Electromagnetic induction

Electromagnetic Induction or Induction is a process in which a conductor is put in a particular position and magnetic field keeps varying or magnetic field is stationary and a conductor is moving. This produces a Voltage or EMF (Electromotive Force) across the electrical conductor.

Electromagnetic induction

https://phet.colorado.edu/sims/cheerpj/faraday/latest/faraday.html?simulation=faraday

Faraday's law

Faraday's second law of electromagnetic induction states that, the magnitude of induced emf is equal to the rate of change of flux linkages with the coil. The flux linkages is the product of number of turns and the flux

Faraday's law

Lenz law

Lenz's law of electromagnetic induction states that, when an emf is induced according to Faraday's law, the polarity (direction) of that induced emf is such that it opposes the cause of its production.

Lenz law

Fleming's right hand rule

Fleming’s Right - hand Rule

This rule states that if we stretch the thumb, middle finger, and an index

finger in such a way that they are mutually perpendicular to each other.

Such that:

1. Thumb: It is along the direction of motion of the conductor.

2. Middle Finger: It points in the direction of the induced current.

3. Index Finger: It points in the direction of the magnetic field.

Fleming's right hand rule

Parts of AC generator

AC generator

Transformers

Transformer

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