AP Physics
Monday 14.03.03
Warm Up
Standards: III A 1 b Calculate
the magnitude and direction of
the force on a positive or
negative charge due to other
specified point charges
Objective: SWBAT calculate the
force due to electric charges.
Agenda
1. Warm Up
2. Review Homework
3. Electric Force
4. Electric Force Guided
Practice
5. Practice E#2
If the rod touches the sphere, how
many charges will leave the the sphere
for the rod. Will the sphere have a net
positive or negative charge.
Homework
E#2
AP Physics
Tuesday 14.03.04
Standards: III A 1 b Calculate
the magnitude and direction of
the force on a positive or
negative charge due to other
specified point charges
Warm Up
In 1990, a French team flew a
kite that was 1034 m long.
Imagine two charges, +2.0 nC
and -2.8 nC, at opposite ends
of the kite. What would be
the electric force between
them.
Objective: SWBAT calculate the
force due to electric charges.
Agenda
1. Warm Up
2. 2D Force interactions
Homework
E#3
AP Physics
Wednesday 14.03.05
Standards: 3a2a Students should
understand the concept of electric field, so
they can: Calculate the magnitude and
direction of the electric field produced by
two or more point charges.
Warm Up
Find the net electric force on
charge a.
a
b
c
1nC
1nC
1nC
4m
Objective: Students will be able to solve
electric field problems.
Agenda
1. Warm Up
2. Electric Field vs Gravitational
Field
3. Guided Practice: Electric Field
4. E#4
Homework
E#4
3m
AP Physics
Warm Up
Thursday 14.03.06
Find the Net Electric Field at the red dot.
Standards: 3a2a Students should
4m
understand the concept of electric field,
2nC
so they can: Calculate the magnitude-2nC a 60°
60° b
and direction of the electric field
produced by two or more point charges.
Objective: Students will be able to solve
electric field problems.
4m
4m
Hint: Find the x and y component of each charge,
and then add/subtract the x components and
add/subtract the y components. (Don’t forget to
find the direction of the Net Electric Field)
Agenda
1. Warm Up
2. Electric Field Lines
3. Create a Field Line Diagram of an
electron
Homework
#E5
AP Physics
Friday 14.03.07
Standards: 3a2a Students
should understand the concept
of electric field, so they can:
Calculate the magnitude and
direction of the electric field
produced by two or more point
charges.
Warm Up
A single negative and positive charge
are 1 meter apart. What is the
magnitude and direction of the
electric field at the specified point
below - 8 minutes
Objective: Students will be able
to solve electric field problems.
Agenda
1. Warm Up: answer E= -1.38x10-9
N/C or 1.38x10-19 N/C to the left
2. Electric Force & Electric Field
Extension Due Monday
1m
e-
4m
e+
1 electron or proton is ±1.6x10-19 C
Homework
E#6
E#2 Coulomb’s Law Practice
b. F=?
q1=8C
q2=4C
r= 2m
b. F=?
q1=3.9x10-6C
q2=2.2x10-7C
r= 2.6x103m
c. F=?
q1=40μC
q2=20μC
r= 1x10-3 m
d. F=200N
q1=1x10-4C
q2=2x10-4C
r= ?
1.(4) In 1990, a French team flew a kite that was 1034 m long.
Imagine two charges 2.0 nC and -2.8 nC, at opposite ends of the
kite. Calculate the magnitude of the electric force between
them. If the separation of charges is doubled, what absolute
value of equal and opposite charges would exert the same
electric force?
2. (2) Kalyan Ramji Sain, of India, had a mustache that
measured 3.39 m from end to end in 1993. Suppose two
charges, q and 3q, are placed 3.39 m apart. If the magnitude of
the eletric force btween the charges is 2.4x10-6N, what is the
value of q?
1μC=1x106C
1nC=1x109C
E#3 Force between multiple charges
200nC
D
-30nC
5 cm
C
-20nC
30cm
A
1. Find the net force on A
2. Find the net force on C.
1. American athlete Jesse Castenada walked 228.930 km in 24 h in 1976, setting a new
record. Consider an equilateral triangle with a perimeter equal to the distance
Castenada walked. Suppose the charges are placed at the following vertices of the
triangle: q1=-2.4 nC at the bottom right vertex, and q3=4.0 nC at the top vertex. Find the
magnitude and direction of the resultant electric force acting on q1.
Practice: Charges in 2 Dimensions
Find the Net Electric Force on the 1C Charge
1C
4m
-2C
2m
3C
Electric Field Guided Practice
Find the electric field at the red dot.
1μC
5m
1μC
10m
Electric Field Practice E#4
a. E=?
q=1.6x10-6C
r=20m
b. Find the
electric field
at the red
point. --->>>
2x103m
1μC
1μC
c. Find the net
electric field
at the red
point.--->>>
5m
1μC
10m
1. The world’s largest tires have a mass of almost 6000 kg and a diameter of 3.72 m
each. Consider an equilateral triangle with sides that are 3.72 m long each. If equal
positive charges are placed at the points on either end of the triangle’s base, what is
the direction of the resultant electric field strength vector at the top vertez? If the
magnitude of the electric field strength at the top vertex equals 0.145 N/C, what are
the two quantities of charge at the base of the triangle?
Electric Field Lines Rules
1. Electric field lines always extend from a positively charged object to
a negatively charged object, from a positively charged object to
infinity, or from infinity to a negatively charged object.
2. Electric field lines never cross each other.
3. Electric field lines are most dense around objects
with the greatest amount of charge.
4. At locations where electric field lines meet the surface of an object,
the lines are perpendicular to the surface.
Electric Field of an electron
Electric Field of a proton
Electric Field Lines Examples
Electric Field Lines Examples
Electric Field Lines Examples
Drawing & Understanding
Electric Field Lines
-- The idea behind drawing Electric field lines is easy. You
calculate the electric field (like we did yesterday) at different
points, with an emphasis on the direction of the electric field. If
you find the direction of the Electric field at enough points, you
will get something that looks very similar to the electric field
diagrams from previous slides.
Guided Practice: Electric Field Diagrams
Estimate the magnitude and direction of the electric field
at each point shown. Use these vectors to draw an
electric field diagram.
+
-
E#5 Electric Field Diagrams.
Make an electric field diagram for the following configurations.
Use the guided practice as your model.
a.
b.
1C
1C
2C
-1C
36. The diagram above shows electric field lines in an
isolated region of space containing two small charged
spheres, Y and Z. Which of the following statements is
true? (A) The charge on Y is negative and the charge on Z
is positive. (B) The strength of the electric field is the
same everywhere. (C) The electric field is strongest
midway between Y and Z. (D) A small negatively charged
object placed at point X would tend to move toward the
right.(E) Both charged spheres Y and Z carry charge of the
same sign.
E#7 Electrical Potential Energy & Difference
1.
2.
3.
4.
a)
b)
What is the potential difference between a point 0.48 mm from a
charge of 2.9 nC and a point at infinity.
The potential energy of an electron (q=-1.6x10-19C) increases by
3.3x10-15 J when it moves 3.5 cm parallel to a uniform electric
field. What is the magnitude of the electric field through which
the electron passes?
A charged particle 3.1x10-12J of potential energy when it moves
4.7 cm through a uniform electric field. The potential difference
across this distance is -73 V.
a. What is the magnitude of the electric field?
b. What is the magnitude of the charge on the particle?
(8) A negative ion (q=-4.8x10-19C) moves 0.63cm through a
uniform electric field in a direction opposite to the direction of the
field. The magnitude of the electric field is 279 volts per meter.
What is the change in electrical potential energy of the ion
What is the electrical potential at the final position of the ion?