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Chapter 37 Electromagnetic Induction: Faraday’s Law
What is electromagnetic
induction?
Electromagnetic induction: The phenomenon of inducing a voltage in a
How can magnetism
create electricity?
When a magnet is plunged into a coil, voltage is induced and the charges in
the coil are set in motion
What determines the
amount of EM
induction?
Amount of induction depends on rate of motion and number of coils.
What happens to the
magnetic field as the #
of coils increase?
As the number of coils increase, the magnetic field also increases. This
makes pushing the magnet through more difficult.
State Faraday’s Law
The induced voltage in a coil is proportional to the product of the number
of loops and the rate at which the magnetic field changes within those
loops
Explain why Faraday’s
Law only applies to
voltage.
Applies only to voltage because current is determined by the resulting
voltage and the resistance of the conductor.
conductor by changing the magnetic field near the conductor
Current as well as voltage is induced in a wire by electromagnetic induction. Why then
is Faraday’s Law expressed in terms of induced voltage and not current?
Summary
Chapter 37 Electromagnetic Induction: Induction of EM Fields
What is a transformer?
A transformer is a device for increasing or decreasing voltage through
EM induction
 Two coils, one with a voltage source (primary) and one with a meter
How do transformers
work?
(secondary) stand in close proximity.
 When current changes in the primary coil (turning on and off a switch), the
changing magnetic field that builds up in the primary coil will extend to the
secondary coil.
 If an iron core is placed inside both coils, the effect is intensified.
 By using alternating current, the current changes automatically (you don’t
have to keep switching on and off).
How can transformers
modify voltage?
By changing the number of loops on either the primary or the secondary,
voltage can be in creased or decreased.
What is the relationship
between primary and
secondary voltages with
respect to # of turns?
Can energy (power) be
increased through this
process? Why or why not?
What does Faraday’s law
say about changing
magnetic fields?
What is the corollary to
Faraday’s law?
How are all electromagnetic
waves generated?
At what speed must EM
waves travel in order to
maintain induction?
Ohm’s Law Applies: As voltage increases, current decreases power is
the same
A changing magnetic field creates a proportional electric field.
The created electric field is at right angles to the changing magnetic
field.
A changing electric field creates a proportional magnetic field.
The created magnetic field is at right angles to the changing electric
field.
Shaking a charged stick will create a changing electric field.
At the speed of light 300,000 km/s
Explain why it is better to transmit energy at very high voltages instead of low voltages.
Summary