AT Cycle 18

🔴❗2: M 1/5, 🟡❗4: M 1/5a, 🔵❗7: M 1/5 - 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 be able to calculate the resistance in a wire  R = ρL/A.

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

• To understand why and how to calculate power lost in a resistor  P = IV = I²R = V²/R.

• 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 23: circuit analysis, "challenge 2" work problems only (just 4 problems).  Look on Google Classroom at the bottom of the Classwork page in topic Account Set-up & Tech to see how to set up your ➕ Positive Physics account.

Homework:  Assessment on Electrostatics on Friday, January 9th.  ➕ Positive Physics is due on tonight Monday, January 5th 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!!!  It is best to try to finish these well before they are due because there will be no excuse for late work.  Watch the following two videos on Kirchhoff's Laws:

More Resources for equivalent resistance review: 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.  

🟥 2: T 1/6a, 🟨 4: M 1/5b, 🟦 7: T 1/6a - Kirchhoff's Laws

Check In: Kirchhoff's Laws

Today, we'll review Kirchhoff's Loop Rule and Junction Rule by doing an example problem.  Although you may have already learned about the technique of using "equivalent resistance," this technique does not work well if we have more than one battery.  Kirchhoff's Laws are a much more general technique for solving any circuit.  We will be using this technique throughout this unit, so make sure you write down any questions you have and find the answers since it's very important you are an expert in using Kirchhoff's Laws.  Pay special attention to sign conventions.  Rewatch videos from last post if you need to.

Homework: Assessment on Electrostatics on Friday, January 9th.  Finish doing  Kirchhoff's Laws Intro Problems (SOLUTIONS) and write down any questions you might have.  Finish at least 3 of these problems.  Also watch the following videos on Capacitors:

❤️ 2: T 1/6b, 💛 4: W 1/7, 💙 7: T 1/6b - time-dependent RC circuits

Today, we'll learn what a capacitor does when it's in a circuit.  This PhET simulation will assist with our investigation.  We will compare and contrast a capacitor with a battery.  Then, we'll use Kirchhoff's Laws to determine an expression for the charge of a capacitor as time changes.  

Then, we will collaborate to understand Jon Ting's video by forming heterogeneous groups/pairs to ensure everyone understood the derivation.  NOTE: When Jon Ting talks about the "area under the curve," he made a mistake - it's not area under the curve.  Try to make sense of it without thinking about area.

Homework:  Rewatch Jon Ting's video and learn to recreate it.  Assessment on Electrostatics on Friday, January 9th.  

📕 2: W 1/7, 📒 4: Th 1/8, 📘 7: Th 1/8 - extra practice

Check-In:  Deriving Capacitor Charging/Discharging Equations

Finish doing  Kirchhoff's Laws Intro Problems (SOLUTIONS) if you haven't finished.  Practice deriving capacitor charging and discharging equations.

If you would like, you may start the following problems, but we'll have more time to do these in the next couple weeks:   
Required 1:  2007E1, 2013E2, and Chapter 27 #59 & 60. 

Homework:  Assessment on Electrostatics next class - Friday, January 9th.