# Electromagnetic Induction - PowerPoint PPT Presentation

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## Electromagnetic Induction

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### Electromagnetic Induction Electromagnetic Induction Motion of a magnet in a coil or loop creates (induces) voltage If coil is connected to complete circuit, current ... – PowerPoint PPT presentation

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Title: Electromagnetic Induction

1
Electromagnetic Induction
2
Electromagnetic Induction
• Motion of a magnet in a coil or loop creates
(induces) voltage
• If coil is connected to complete circuit, current
flows
• Relative motion is neededit doesnt matter which
moves, the magnet or the coil
• Amount of voltage depends on rate of motion and
number of loops in coil

3
• The induced voltage is proportional to the number
of loops times the rate of change of the magnetic
field
• Magnetic field is changed by motion or by
changing the strength of the field in an
electromagnet

4
Generators
• Rotating a coil in a magnetic field will create
alternating current
• As coil rotates, amount of magnetic field
enclosed by loop changes, inducing a changing
voltage
• Frequency of alternating current is the same as
frequency of rotation of the coil
• Energy is converted from some mechanical form to
electrical

5
Motors and Generators
• Both have same parts
• Motors convert electrical energy to mechanical
movement using the magnetic force on a moving
charge to move the coil
• Generators convert mechanical to electrical by
using the magnetic force due to the coil movement
to move the charges through the wire

6
Transformers
• Two coils of wire wound on the same iron core so
that changes in the magnetic field of the first
coil (primary) induce voltage across the second
coil (secondary)
• If ac flows through primary, ac is induced in
secondary
• Voltage in secondary depends on ratio of turns in
primary and secondary

7
Transformers
• If secondary has more turns, than transformer is
called step-up and voltage is increases
• If secondary has fewer turns, then is called
step-down and voltage is decreased
• Power is not increased so if voltage is stepped
up, current is reduced

8
Transformer Equations
• Primary turns Primary voltage
• Secondary turns Secondary voltage
• (Voltage x current)p (voltage x current)s

9
Power Transmission
• Almost all electrical energy is sold as ac
because it is easy to change voltage using
transformers
• High voltage and fairly low currents are used to
transmit power over long distances
• This reduces losses due to heating in the wires
• Voltage is stepped down to 120 V for homes

10
Electric and Magnetic Fields
• Faradays law holds even if no conductor is
present
• A changing magnetic field induces an electrical
field
• Maxwell extended Faradays idea to say a changing
electrical field induces a magnetic field

11
Electrical and Magnetic Fields
• Electrical and magnetic fields are perpendicular
to each other
• Magnitude of induced field is proportional to
rate of change of the other field
• Explained operation of electromagnetic waves
• Speed of light is only speed where induction will
continue without energy gain or loss