Circuits

Firstly, thank you SO MUCH to the people who handed in their stop motion videos - they look incredible!

Secondly, welcome to the Circuits unit! You probably learned some of this in grade 9 but I'll assume you forgot most of it and start from the beginning. The most foundational equation we need to learn is Ohm's Law (there are some typed notes and an optional worksheet just below).

Your assignment today:

Please watch this lovely video introducing circuits and Ohm's Law on Ohm's law, conductors, insulators, and Power.

• https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/circuits-part-1
• Then go to MS Teams to write your quiz! (see my email from today - April 16th)

Remember the quiz will be CLOSED at 3:00pm tomorrow (Friday April 17th) and I will post the answers to the quiz at that time. Also a reminder that your mark can't go down so have fun with this and give it your best shot!

Notes

Ohm's Law:

• V = IR
  • V is Voltage, measured in Volts (V)
  • I is Current, measured in Amperes (A)
  • R is Resistance, measured in Ohms (Ω)

Current is defined as the amount of charge to pass a point in one second :

• I = q/t
  • I is Current
  • q is Charge, measured in Coulombs (C)
  • t is Time, measured in Seconds (s)

Voltage is defined as energy per charge:

• V = E/q
  • V is Voltage
  • E is Energy, measured in Joules (J)
  • q is Charge

You should also know the different symbols used to draw circuits (resistor, light bulb, battery, switch, ammeter, voltmeter)

I hope everyone is safe and healthy! I am very impressed with the level of engagement so far - thanks for the hard work everyone and keep it up!

Today we are moving on to learn about Resistors. I'm sure you can guess that resistors resist the flow of current. However, there are two rules you need to know about how resistors ADD TOGETHER. There is one rule for resistors in SERIES and one rule for resistors in PARALLEL. Sometimes you will need to use both rules to solve a circuit!

Your assignment today is firstly to watch these two short videos:

• https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/circuits-part-2
• https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/circuits-part-3
• I strongly suggest taking notes during the videos!

Then, answer the questions in your MS Teams assignment.

• There is a challenge question today! Put your thinking boots on :)
• Just like last time, the assignment will be closed tomorrow (Tuesday) at 3pm. Let me know if you have any questions!

Today we have a short lesson on Power in circuits. There are 3 equations for power - each useful in different situations. For Total Power, it doesn't matter if resistors are in series or parallel - just add up the power from each resistor! You may have to find other values in the circuit (like I, V, or R) before you can find P.

Your Assignment:

• Please watch the video here (I suggest taking notes during the video, or at least write down the 3 equations):
  • https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/electric-power
  • https://www.youtube.com/watch?v=WNPFyqkDn6Q (optional video with examples)
• Then, please complete the quiz on MS Teams
• The quiz will close at 3pm on Thursday April 23rd

Hello, I hope everyone is doing well. I would consider this to be the most important part of the Circuits unit - Kirchoff's Laws. In this chapter, every circuit is like a puzzle. You must use the information you have to get to the information you want. There is almost always more than one correct path but some paths will be more efficient. Your tools to solve each puzzle are the Current Law, the Voltage Law, and Ohm's Law. Using these 3 things you can solve an infinite number of circuits problems!

Your assignment today

• Please watch these 2 videos
  • https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/ee-kirchhoffs-current-law
  • https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/v/ee-kirchhoffs-voltage-law
  • Optional Notes and practice problems if you want)
    • https://www.khanacademy.org/science/physics/circuits-topic/circuits-resistance/a/ee-kirchhoffs-laws
  • Optional Example Video - This is not the same circuit as your quiz but it DOES use the same process to "solve" the circuit.
    • https://www.youtube.com/watch?v=0MKcxCHkT1c
• Then, please answer the questions on the MS Teams assignment. Make sure you understand HOW you got to the answer!

Below are the regular notes and regular worksheet if you would like to use them as resources as well. I am not assigning the worksheet but this chapter gets much easier with practice so if you plan on doing engineering or sciences I would recommend practicing some of the problems.

Today we are doing a second class on Kirchoff's laws and Circuit analysis because it is the most important topic in this unit and it also requires the most practice. It is certainly the most applicable skill for those of you who might apply this unit in the future.

Today:

• Please watch this great video on circuit analysis.
  • https://www.youtube.com/watch?v=-PiB2Xd3P94
  • I personally do not put the zero ohm resistor in but if it works for you absolutely do it
• Then, please answer the questions in your Assignment on MS Teams for today.

Thanks! If you have any questions please post them in the other "Chat Or Ask A Question" channel or message me directly through teams. I have the audio figured out for my screen recordings so I should be able to answer questions in detail if needed!

Kirchoff Quiz 2 Key:

Today we have a quick and easy lesson about how batteries work in real life. We have been pretending batteries are a perfect source of voltage but that is not actually true! Here is how batteries really work:

• Vterm = ε - Ir is the formula for terminal voltage.
  • Vterm = terminal voltage or the ACTUAL voltage supplied across the terminals of a battery
  • ε = emf which is the "ideal" voltage produced inside the battery. Still measured in Volts (V)
  • I = current through the battery
  • r = internal resistance of a battery. Must use lower case r.
    • You CAN add the internal resistance to the resistance of the rest of the circuit to find total current in the circuit.
• Basically, some of the voltage is consumed by the internal resistor before it even leaves the battery.
  • This leads to a slightly lower voltage being supplied to the rest of the circuit.
  • The higher the current, the more voltage is lost within the battery.

Please watch the following video for a good example: https://www.youtube.com/watch?v=R1QN_0fcZ_8

Then, please complete the short quiz through MS Teams before 3pm on Wed. May 6th.

Optional:

• Regular notes are below if you want to take a look.
• Scroll to the bottom of worksheet 7.2 (above) to see worksheet 7.3 on Terminal Voltage and EMF

Scroll to the bottom of worksheet 7.2 (above) to see worksheet 7.3 on Terminal Voltage and EMF