RECALL THE FOLLOWING CONCEPT:
The Motor Principle: Current in the presence of an external magnetic field will produce a force
(motion) [that is perpendicular to the current and the magnetic field].
Current
+
Magnetic Field

Force (Motion)
RHR #3 tells you the direction
of the force
QUESTION: HOW DOES A GENERATOR WORK?
The wind, waterfalls or steam (from fossil fuel burning plants) turn turbines. How is this converted
into electricity? Come up with a prediction.
LAW OF ELECTROMAGNETIC INDUCTION:
The change could be produced by changing the magnetic field strength, moving a magnet toward or away
from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.
In summary:
+

Generators
- Take many loops of wire and spin them (motion) in
the presence of a
- A generator has all the same components as a motor
Motor
Generator
Input
Current
Output
Rotation
FACTORS AFFECTING ELECTROMAGNETIC INDUCTION

: There is more induced electrical current from a



coiled conductor than a straight conductor.
: The number of loop in a solenoid is directly
proportional to the electrical current induced in the conductor for a given magnetic field change.
: The quicker you move a magnet in and out
of a solenoid, the greater the rate of change in the magnetic field and the larger the induced
current.
: The stronger the magnet, the greater the
induced current.
APPLICATIONS OF ELECTROMAGENTIC INDUCTION
Induction Cooking
Cooking involves a transfer of thermal energy from the element
into the metal pot.
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This heats the pot because of the resistance of the pot (iron
works best due to higher resistance); glass (insulating material)
pots don’t work.
Metal Detectors
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As a result, the induced electric field in the metal produces its
own magnetic field as well. Metal detectors are usually used
for detecting landmines and other security purpose.
Induction Chargers
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Examples of typical low-powered devices that can be charged
using induction chargers are electric toothbrushes and cell
phones.
http://phet.colorado.edu/en/simulation/faraday
WEBLINKS FOR
ELECTROMAGNETIC http://micro.magnet.fsu.edu/electromag/java/faraday2/
http://new.wvic.com/index.php?option=com_content&task=view&id=9&Itemid=46
INDUCTION
HOMEWORK: Read Pages 588-591 and Complete Questions #1-6 on Page 591



Recall that when a magnet is pushed into a solenoid (coiled
conductor), the electrons in the coil move in a particular direction and
produce an electric current.
The direction of the current is influenced by the
If a changing magnetic field induces a current in a coil, the induced
current is created so that its own magnetic field
the
motion that produced it
Basically, the coil opposes whatever the magnet is trying to do.
 If north is moving in, the coil
 If north is moving out, the coil
.
.
Example: Determine the direction of the induced current.
(A)
(B)
Hint: Use the RHR for the solenoid to assist in answering your question
Applications:
The Drop-Zone at Canada’s Wonderland involves a thrilling free-fall
towards the ground. The braking system on such a ride must have a
reliable and carefully-executed braking system. The braking system uses
Lenz’s Law. A magnetic field is produced that
.
HOMEWORK:
Read Pages 588-591 and Complete Questions #1-6 on Page 591 (from Section 13.1)
Read Pages 592-594 and Complete Questions #1-4 on Page 594 (from Section 13.2)