Transcript SPH3U: Energy, Work, Power

SPH3U: Electricity
Overview of
Electromagnetism
Electricity & Magnetism

Electricity and Magnetism are very
closely related, since both are based on
the properties of electrically charged
particles.

The Electromagnetic force is one of the
four fundamental forces in nature
(including the strong nuclear, the weak
nuclear, and gravity).
Magnetic Fields and Current
When an electric current moves through
a wire, a magnetic field is produced.
 The magnetic field exists in circular rings
around a straight conductor.
 The direction of the magnetic field
depends on the direction of the current.

Magnetic Fields and Current

Oersted’s principle: Whenever a
charge moves through a straight
conductor, a circular magnetic field is
created around the conductor.
Magnetic Fields and Current

The Right-hand Rule:
when holding a straight
conductor with your right
hand and thumb pointing
in the direction of
conventional current,
your curled fingers will
point in the direction of
the magnetic field lines.
Practice

Draw the magnetic field lines around each
wire.
Current going into the page
Current going out of the page
Practice

Draw the magnetic field lines around each
wire.
The Motor Principal

Since a current carrying wire has a magnetic
field around it, an external magnetic field
around the wire can cause the wire to move.

This is because of the attraction or repulsion of
the two magnetic fields (the one around the
wire and the external one).

http://www.youtube.com/watch?v=tUCtCYty-ns
The Motor Principal

This property is called the Motor Principal:
A current-carrying conductor that cuts across
external magnetic field lines experiences a
force that is perpendicular to both the
magnetic field and the direction of the
electric current.
The Motor Principal
The force is caused
because the magnetic
field lines on the magnet,
and on the wire, are going
in the same direction.
Therefore there is a
repulsion.
The Motor Principal

Right-hand Rule for
the Motor Principal:
If the fingers of your
open right hand point
in the direction of the
external magnetic
field, and your thumb
points in the direction
of the conventional
current, then your
palm faces in the
direction of the force
on the conductor.
Practice

Determine the direction of the force on
the wire.
X
Electromagnetic Induction

Because of the relationship between
electricity and magnetism, when a
magnetic field changes near a
conductor, an electric current can be
produced.
Electromagnetic Induction

This is how electricity is produced in a
power-plant:
When water (or steam) pushes the turbine,
it will rotate a magnet.
 When the magnet is rotated, the magnetic
field changes.
 When the magnetic field changes, a current
is produced.
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Videos
Overview of the entire unit
 http://www.youtube.com/watch?v=XiHVe
8U5PhU
Homework
Read section 12.2 (pg. 553-556) and
12.5 (pg. 563-566).
 Supplement your notes by adding
information from these sections.
 Do the following questions:

Page 556 # 1-7
 Page 566 # 1-2
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