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## Electromagnetic Induction

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### Electromagnetic Induction Physics La Ca ada High School Dr.E Electromagnetic Induction Motors/Generators http://science.howstuffworks.com/motor4.htm Faraday s Law ... – PowerPoint PPT presentation

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Title: Electromagnetic Induction

1
Electromagnetic Induction
• Physics
• Dr.E

2
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

3
The Magnetic Field
• The electric field proves a useful concept to
explain the effects of charge at a distance
(explains how one charge knows another charge is
there).
• Stationary charges produce only an electric field
• Moving charges (in flux) produce both an electric
field and a magnetic field

4
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

5
Motors
• Motors work due to two major principles
• Opposite poles attract while like poles repel
• Current running through a coiled wire creates a
magnet

6
Theory
7
Mechanics
8
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9
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

10
• The voltage induced in a coil is proportional to
the number of coils times the magnetic flux (rate
at which the magnetic field changes)

11
Wrap Rule to find Magnetic Field
• Wrap your fingers in the direction of the current
• The magnetic field points in the direction of the
thumb (to the left)
• Since the field lines leave the left end of
solenoid, the left end is the North pole

12
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13
• An ammeter is connected in a circuit of a
conducting loop
• When a bar magnet is moved closer to, or farther
from, the loop, an electromotive force (emf) is
induced the loop
• The ammeter indicates currents in different
directions depending on the relative motion of
magnet and loop
• When the magnet stops moving, the current returns
to zero as indicated by the ammeter

14
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15
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16
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17
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18
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

19
Primary Voltage of 1o turns
Secondary Voltage of 2o turns
20
(Power IN)
(Power OUT)
21
(Voltage x Current)secondary
(Voltage x Current)primary
22
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

23
Power Transmission
• Plant
• 6000 V and 20Amps
• Local and Homes
• 120 V and 100 Amps
• Low Voltage Wires
• 2200 V and 54 Amps
• High Voltage Wires in Town
• 120,000 V and 1 Amp
• Ultra High Voltage
• 400,000 V and 0.3 Amps

24
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

25
Solenoids
• The magnetic field of a solenoid is essentially
identical to that of a bar magnet.

The big difference is that we can turn the
solenoid on and off ! It attracts/repels other
permanent magnets it attracts ferromagnets, etc.
26
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27
Solenoid Applications
• Digital on/off
• Doorbells
• Power door locks
• Magnetic cranes
• Electronic Switch relay
• A small current can be used to switch a much
larger one
• Starter in washer/dryer, car ignition,

28
Solenoid Applications
• Analog (deflection a I )
• Variable A/C valves
• Speakers

Solenoids are everywhere!
29
• Electromagnetic Induction
• Motors/Generators http//science.howstuffworks.com
/motor4.htm
• Transformers
• Power Transmission
• Solenoids
• MRI

30
Thanks to
31
MRI / NMR
If we bathe the protons in radio waves at a
particular frequency, the protons can flip back
and forth. If we detect this flipping ?
hydrogen! The presence of other molecules can
partially shield the applied magnetic field, thus
changing the resonant frequency (chemical
shift). Looking at what the resonant frequency
is ? what molecules are nearby. If a strong
magnetic field gradient is produced across the
sample, can look at individual slices, with
millimeter spatial resolution.
32
Bibliography
• Magnetism Examples of Magnetic Field