Agenda1. Warm Up2. Review Homework3. Electric Force 4. Electric Force Guided

Practice5. Practice E#2

HomeworkE#2

AP PhysicsMonday 14.03.03 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.

Warm Up

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.

Agenda1. Warm Up2. 2D Force interactions

Warm UpIn 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.

HomeworkE#3

AP PhysicsTuesday 14.03.04Standards: 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.

AP PhysicsWednesday 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.

Objective: Students will be able to solve electric field problems.

Agenda1. Warm Up2. Electric Field vs Gravitational

Field3. Guided Practice: Electric Field4. E#4

HomeworkE#4

Warm UpFind the net electric force on charge a.

1nC 1nC 1nC

4m 3m

a b c

AP PhysicsThursday 14.03.06Standards: 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.

Objective: Students will be able to solve electric field problems.

Homework#E5

Warm Up

Agenda1. Warm Up2. Electric Field Lines3. Create a Field Line Diagram of an

electron

a b

Find the Net Electric Field at the red dot.

4m

-2nC 2nC

4m 4m

60° 60°

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)

AP PhysicsFriday 14.03.07

HomeworkE#6

Warm UpA 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

Agenda1. Warm Up: answer E= -1.38x10-9

N/C or 1.38x10-19 N/C to the left2. Electric Force & Electric Field

Extension Due Monday

e- e+4m1m

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.

Objective: Students will be able to solve electric field problems. 1 electron or proton is ±1.6x10-19 C

E#2 Coulomb’s Law Practice

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?

b. F=? q1=3.9x10-6C q2=2.2x10-7C r= 2.6x103m

b. F=? q1=8C q2=4C r= 2m

c. F=? q1=40μC q2=20μC r= 1x10-3 m

d. F=200N q1=1x10-4C q2=2x10-4C r= ?

1μC=1x106C 1nC=1x109C

E#3 Force between multiple charges

A

-20nC

CD

-30nC200nC

30cm5 cm

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

1C -2C

3C

4m

2m

Find the Net Electric Force on the 1C Charge

Electric Field Guided Practice

1μC 10m1μC 5m

Find the electric field at the red dot.

Electric Field Practice E#4 a. E=? q=1.6x10-6C r=20m 1μC

b. Find the electric field at the red point. --->>>

2x103m

1μC

c. Find the net electric field at the red point.--->>>

10m

1μC

5m

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 Rules1. 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.

4. At locations where electric field lines meet the surface of an object, the lines are perpendicular to the surface.

3. Electric field lines are most dense around objects with the greatest amount of charge.

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.

1C 1Ca.

2C -1Cb.

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. What is the potential difference between a point 0.48 mm from a charge of 2.9 nC and a point at infinity.

2. 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?

3. 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? 4. (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.

a) What is the change in electrical potential energy of the ionb) What is the electrical potential at the final position of the ion?