# HP Cycle 35

## 4/7 - 4/12 Th 4/7 F 4/8 M 4/11 T 4/12

### 🟢❗ 6: Th 4/7, 🔵❗ 8: Th 4/7 - ➕ Positive Physics superposition of force

QUIZ Today on the electroscope lab and charging.

Today, after the the quiz, we will learn about the principle of superposition by finishing the Coulomb's Law Presentation. Remember that force is a vector quantity.

Then, we'll practice superposition of electric force by doing ➕ Positive Physics unit 22: Electric Charges & Force "work" problems from the sections:

• electric force problems 2

• challenge

Homework: Finish these ➕ Positive Physics problems by Sunday, April 10th at 10pm. Only completion score counts. No late work will be accepted. If you missed class or are looking for additional support on the principle of superposition, watch the following video:

### 🟩 6: M 4/11, 🟦 8: F 4/8 - electric field

Today, we'll discover what a field is by looking a gravitational fields with which we are a little bit familiar. We'll discuss what an electric field looks like and how to represent it with electric field lines. Finally, we will learn how to characterize and quantify the strength of an electric field by expressing the force per Coulomb.

First, you will watch the following video at your own pace. Pause, rewind, re-watch, and take notes. Then, in ✅ GoFormative, complete the "Electric Field Worksheet."

If you finish early, move on to the next lesson which is longer.

Homework: ✅ GoFormative "Electric Field Worksheet" due Tuesday at 10pm. No late work will be accepted on this assignment. QUIZ on electric field and force Wednesday, April 27th.

### 💚 6: T 4/12, 💙 8: M 4/11 - 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, you'll try to figure out in your lab groups 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. Page 544 in your textbook may help you to understand how to make your predictions: Constructing Electric Field Pattern Due to a Dipole.

Watch directions for this activity here (sorry for the low res, but you'll get the idea), and complete the Electric Field Superposition "May the Field Be With You" activity.

Also, read the five general rules for electric field lines on the bottom of page 543 of your textbook (also copied below).

The general rules for sketching and interpreting electric field lines are as follows:

1. The closer together the field lines, the stronger the electric field.

2. At any point, the direction of the electric field is tangent to the field lines.

3. The electric field lines start at positive charges and end at negative charges.

4. The number of lines leaving or entering a charge is proportional to the magnitude of the charge. (See Learn by Drawing 15.2, Sketching Electric Lines of Force for Various Point Charges.)

5. Electric field lines never cross.

Homework: Complete "Electric Field Superposition" by next class. QUIZ on electric field and force Wednesday, April 27th.