AT Cycle 19

🔴 1: M 1/4, 🟡 3: M 1/4a equipotential lines lab (1)

Today, we'll learn how to draw equipotential lines with a lab. Read the instructions for the equipotential lines lab, and complete the questions in the ✏️ Google Classroom assignment, which will require you to screenshot your work, posting it on a Jamboard, and then drawing electric field lines overtop. We'll continue with this lab next period. The lab is due Wednesday at 10pm.

🟥 1: T 1/5, 🟨 3: M 1/4b equipotential lines lab (2)

Today, we'll finish up the equipotential lab. Then, we'll do 2005E1 and make sure that you understand the relationship between equipotential lines and electric field lines. With any remaining time, try finding some AP practice problems.

Homework: The equipotential lab is due Wednesday at 10pm. THINK ABOUT THIS: If you can calculate V by integrating E, can't you find E by taking the derivative of V? Kind of, but the problem is that E is a vector, so how do we get a vector from a scalar? First, for a conceptual explanation, check out the video below. Then, read section 24-6 on page 701-702 in your textbook, and work through Sample Problem 24.05. For some good practice, you may want to derive the expression for the electric potential at any point on the central axis of a uniformly charged disk. Additionally, make sure to think about why E_x and E_y are zero. Using the gradient method E=-∇V is a cool different way of finding the electric field. In a lot of ways it's easier than the electric field integral, since you don't have to ever deal with component geometry. Check it out!

❤️ 1: W 1/6a, 💛 3: W 1/6 electric field gradient

Today, we'll review getting the electric field with the gradient of the potential E=-∇V . We'll do an example together. With any time remaining, we'll practice additional electrostatics AP problems. Look in Google Classroom for additional posted problems.

To think about the whole unit, here are the topics in electrostatics we have studied:

• Coulomb's Law

• Finding electric field

  • E = F/q

  • electric field integral (superposition of dq)

  • Gauss's Law

• Electric potential energy of a configuration of charges

• Finding electric potential

  • potential integral (superposition of dq)

  • Path integral if we know electric field (compatible with Gauss's Law)

• Calculating field and potential due to non-uniform charge distributions (integrals)

You may watch a review video below:

📕 1: W 1/6b, 📒 3: Th 1/7 equivalent resistance, ➕ Positive Physics problems

Today, we'll review what you should know about circuits from last year. If you need to review videos from last year, then you can do that. There are several goals today:

• To understand the link between electrostatics and circuits.

• To understand and know how to use Ohm's Law.

• To understand why and how to calculate power lost in a resistor.

• To be able to solve simple series and simple parallel circuits with equivalent resistance.

• To be able to solve combination circuits with equivalent resistance.

The output is ➕ Positive Physics unit 20: circuit analysis, "challenge 2" work problems only (just 4 problems) due Sunday at 10pm.

Homework: Quiz on all of electrostatics, with a focus on potential energy and potential, next class - Friday, January 8th. ➕ Positive Physics is due on Sunday at 10pm. Make sure you know how to solve circuits with equivalent resistance by then. Only completion score counts, so try the problems till you get them right. No late work will be accepted. Watch the following two videos on Kirchhoff's Laws:

More Resources: Equivalent resistance is a very useful and fast way of solving circuits with multiple resistors and only one battery. I am assuming you know all about solving series, parallel, and combo circuits using equivalent resistance from last year. If you do not, you may want to review the material by looking at Electrical Circuits Lesson 4 (The Physics Classroom website), or watching videos on Series Circuits and Parallel Circuits (both by Dan Fullerton) and on a Combo Circuit Example (by Ron Call). Remember that the key to success with combo circuits is redrawing every time you combine resistors simply in series or simply in parallel. Work your way forward to find equivalent resistances and then work your way backward to get the currents through and voltage drops across each resistor.