Lecture Sixteen
Physics 100
Fall 2012
 Electric Motors
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

Lab WILL BE HELD today and tomorrow as well
as next Tuesday (Thanksgiving week). If you
need to attend an earlier lab due to travel issues,
please let me know today.
Homework due Monday-posted.
Quiz on magnets and variables next Monday
(Thanksgiving week). If you need to take it early
(Friday) please send e-mail today.
In science a field is a
collection of measurements
of the same quantity over a
region of space.
 Common examples
include temperature fields,
elevation fields, magnetic
fields and gravitational
Fields.

A magnetic field is a collection of
measurements across a region of space
that indicates the relative strength of the
magnetic force
and the direction of the force on a north pole of
a magnet placed there.
 The symbol for the magnetic field is B. The
unit is the Tesla or Gauss.

The field lines for a
current carrying wire are
circles.

To find the direction of the field, point your right
thumb in the direction of the current. Curl your
fingers and they will point in the direction of the
field.
i
x
A.
B.
C.
D.
E.
Up toward the wire
Down away from the wire
Into the page
Out of the page
To the right
1. Point your right fingers in the
direction of the current.
2. Keeping your fingers pointed
in the direction of the current,
rotate your hand so that you
can bend your fingers into the
direction of the magnetic field.
3. Your outstretched thumb then
points in the direction of the
magnetic force on the wire.
north magnetic pole
i
south magnetic pole
A.
B.
C.
D.
E.
Up toward the top of the page
Down toward the bottom of the page
Into the page
Out of the page
To the left


An electric motor is a device that
converts electrical energy into
mechanical energy.
Electric motors use magnetic force to
cause motion.