Chapter
15 & 16
Electrostatics:
Forces & Energy
Electric
Field
Definition
of the Electric Field, 
If
a test charge  experiences
a force  at
a given location, the electric field at
that location is
Units:
N/C
The
electric field is the force per charge at a given location.
Video of Electric Field
Solving
for the force gives us the force on a given charge:
 
Example
15-10
In
a certain region of space, a uniform electric field has a magnitude
of  and
points in the positive x direction. Find the magnitude and direction
of the force this field exerts on a charge of (a) +2.80 µC
and (b) -9.30 µC.
Solution:
(a) 
(b) 
Electric
Field of a Point Charge
Magnitude
of the Electric Field Due to a Point Charge
Example
15-11
Find
the electric field produced by a 1.0 µC point charge at a distance
of (a) 0.75 m and (b) 1.5 m.
Solution:
(a) 
(b) 
Example
15-12
Two
charges,  and  ,
have equal magnitudes q and are placed as shown in the figure. The
net electric field at point P is vertically upward. We conclude that
(a) is
positive, is
negative; (b) is
negative, is
positive; or (c) and have
the same sign.
Solution:
(b) is
negative, is
positive.
Example
15-13
Two
charges, each equal to +2.90 µC, are placed at two corners
of a square 0.500 m on a side, as shown. Find the magnitude and
direction of the net electric field at a third corner of the
square, the point labeled 3 in sketch.
Solution:
On to Electric Field Lines |
:
:
:
