Transcript Electric Field (Continued)

E-Field w3d3
ELECTRIC FIELD (CONTINUED)
HAPPNINS
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Today
 Quiz 2
 Continue with E-Field
 A problem or two
Monday
 7:30 am PROBLEM SESSION
 Electric Flux and Gauss’s Law
Wednesday
 Start Unit on Potential
Sunday
 WebAssign Due
Friday
 Quiz, Etc.
THE COULOMB FORCE
q1q2
FK 2
r
Coulombs Law applies:
 The FORCE is always on a particular charge
 The Force on a particular charge under the
influence of other charges is found by
SUPERPOSITION. (Add em up!!)
 The force is a VECTOR!!! You add them as
vectors!
 A charge cannot apply a force to itself.
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TWO CHARGES
F  1  qq0
q
E     k 2 runit  k 2 runit
q0  q0  r
r
ELECTRIC FIELD
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If a charge Q is in an electric field E then
it will experience a force F.
The Electric Field is defined as the force
per unit charge at the point.
Electric fields are caused by charges and
consequently we can use Coulombs law
to calculate it.
For multiple charges, add the fields as
VECTORS.
An electric field of 10 N/C exists at a point in space. A 5.0
Coulomb charge is placed at the point. The force on the
charge is
A. It can’t be calculated
without additional
information.
B. 5.0 N
C. 10.0 N
D. 50.0 N
E. 2.6 Tharks
WHAT IS THE ELECTRIC FIELD AT THE
CENTER OF THE SQUARE ARRAY?
WHICH ONE OF THE FOLLOWING STATEMENTS IS
TRUE CONCERNING THE MAGNITUDE OF THE
ELECTRIC FIELD AT A POINT IN SPACE?
A) It is a measure of the total charge on the object.
B) It is a measure of the electric force on any charged
object.
C) It is a measure of the ratio of the charge on an object
to its mass.
D) It is a measure of the electric force per unit mass on
a test charge.
E) It is a measure of the electric force per unit charge on
a test charge.
AT WHICH POINT (OR POINTS) IS THE ELECTRIC FIELD ZERO N/C
FOR THE TWO POINT CHARGES SHOWN ON THE X AXIS?
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A) The electric field is never zero in the vicinity of these charges.
B) The electric field is zero somewhere on the x axis to the left of the +4q
charge.
C) The electric field is zero somewhere on the x axis to the right of the –2q
charge.
D) The electric field is zero somewhere on the x axis between the two
charges, but this point is nearer to the –2q charge.
E) The electric field is zero at two points along the x axis; one such point is
to the right of the –2q charge and the other is to the left of the +4q charge.
Let’s Do The QUIZ!
THEN BACK TO UNIT 3 – THE ELECTRIC FIELD.
TRY TO FINISH IT TODAY.