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🟢 8: M 3/16 - E-field superposition
🟢 8: M 3/16 - E-field superposition
"If there is more than one charge creating an electric field, then the total, or net, electric field at any point is found using the superposition principle for electric fields, which can be stated as follows: For a configuration of charges, the total, or net, electric field at any point is the vector sum of the electric fields due to the individual charges of the configuration."
We'll learn about the superposition of electric field by going through some problems in this Electric Field Presentation. When you're doing these types of problems, imagine that you are putting a small POSITIVE test charge at the location where you're trying to find the electric field, and draw the electric field contributions from each individual charge in the configuration (same as the direction of force on the positive test charge). Then add vectors in a vector kind of way: separate into x- and y-components, add x-components, add y-components, put together with Pythagorean Theorem to find magnitude, and use arctan to find direction.
Then, we'll try to collectively figure out what an electric field looks like around various configurations of charges by using the simulation found at https://phet.colorado.edu/sims/html/charges-and-fields/latest/charges-and-fields_en.html. Read the beginning of section 20.5 on pages 713-714 in your textbook to get an idea of how to draw electric field vectors using superposition.
Watch directions for this activity here (sorry for the low res, but you'll get the idea), and review the Electric Field Superposition "May the Field Be With You" activity.
Also, read the five general rules for electric field lines:
The general rules for sketching and interpreting electric field lines are as follows:
The closer together the field lines, the stronger the electric field.
At any point, the direction of the electric field is tangent to the field lines.
The electric field lines start at positive charges and end at negative charges.
The number of lines leaving or entering a charge is proportional to the magnitude of the charge.
Electric field lines never cross.
Finally, you'll practice solving problems with electric fields in 📖 electric fields textbook problems #20, 21, 44, 60, 65, 71, plus "electric field due to two point charges", but I recommend you finish these by next class so you can ask questions if you have them before the quiz.
Handout: Electric Field Superposition "May the Field Be With You"
Homework: QUIZ on Electric Force and Field on Wednesday, March 18th! Finish 📖 electric fields textbook problems and Electric Field Superposition "May the Field Be With You" before next class.
Optional Extra Practice: 📄 Electric Field Worksheet (PH). FYP: Coulomb's Law. Solutions (plus #9 solution)
🟩 8: T 3/17🎯 - problem solving
🟩 8: T 3/17🎯 - problem solving
Test - 7:40 - 9:35 (115)
1 - 9:40 - 10:20 (40)
2 - 10:25 - 11:05 (40)
3 - 11:10 - 11:50 (40)
L - 11:54 - 12:35 (41)
4 - 12:40 - 1:20 (40)
5 - 1:25 - 2:05 (40)
6 - 2:10 - 2:50 (40)
We'll spend the period demonstrating our understanding by doing problem solving on electric force and electric field.
Homework: QUIZ on Electric Force and Field next class - Wednesday, March 18th!
Here's a helpful video that will talk you through how to find where the electric field will be zero when there are two charges on the x-axis. By the way, this is the same process you'd use to figure out where to put a third charge so that the net force on that charge is zero (since that is the same thing as saying the electric field is zero). Here's another version - I like how they ultimately solve the equation here; taking the square root of both sides for me is easier than dealing with a quadratic.
💚❗8: W 3/18🎯 - electric field quiz
💚❗8: W 3/18🎯 - electric field quiz
Test - 7:40 - 10:35 (175)
1 - 10:40 - 11:10 (30)
2 - 11:15 - 11:45 (30)
3 - 11:50 - 12:20 (30)
L - 12:25 - 1:06 (41)
4 - 1:10 - 1:40 (30)
5 - 1:45 - 2:55 (30)
6 - 2:20 - 2:50 (30)
QUIZ on Electric Force and Field TODAY!
After the quiz, we'll just continue to work on problem solving.
Homework: Unit Assessment on Electrostatics - Charging, Electric Force, and Electric Field on Tuesday, March 24th!
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