U10-Electric Circuits

Slideshow found here: Circuits Notes

Textbook: Chapter 16 in Mastering Physics (get online code for registration on about page of google classroom)

Basic Video tutorials from Dan Fulelrton: https://www.youtube.com/playlist?list=PLd2HWlWc-MszmgWIKnYCtN_3Heo1qroBi

Worked examples and concept tutorials from Mrs. Twu: https://sites.google.com/site/twuphysicslessons/home/circuits

Essential Knowledge:

  • ΔV=change in electrical potential energy per charge moving through a circuit
  • ΣΔV=0 is used to explain conservation of energy in a circuit.
  • ΔV=IR can be used to find ΔV for a single resistor using values of I and R for the resistor or for the overall circuit using the total I and equivalent resistance.
  • Power is a rate of energy transfer and found using P=IV=ΔE/t. Individual resistors use energy (produce heat) as current runs through them.
  • Charge flow is conserved in a closed system. This is demonstrated by the junction rule, where the sum of currents flowing into a circuit equal the sum of currents flowing of of a circuit.

Student Objectives:

  • Use circuit diagrams or descriptions to perform calculations of unknown values of current in different branches in a circuit.
  • Kirchhoff's junction rule (ΣIin = ΣIout)
    • Make claims and predictions about simple circuits based on conservation of charge.
    • Compare currents in parallel branches using the junction rule/conservation of charge
      • In particular, be prepared to discuss what would happen to branches if configurations are changed (double a resistor's value, open a switch, add a parallel path, etc)
    • Design an experiment to show that charge is conserved in a parallel circuit. Plan data collection and analysis.
  • Kirchhoff's loop rule (ΣΔV=0)
    • construct or interpret a graph of energy changes within an electrical circuit
    • design an experiment to demonstrate the validity of Kirchhoff's loop rule.
      • consider how you would use a voltmeter on several components in series or possibly a simple combination circuit.
    • Perform calculations using conservation of energy (loop rule)

Equations:

Common Misconceptions: (these statements all have errors)

    • Resistors consume charge.
    • Electrons move quickly (near the speed of light) through a circuit.
    • Charges slow down as they go through a resistor.
    • Current is the same thing as voltage.
    • There is no current between the terminals of a battery.
    • The bigger the container, the larger the resistance.
    • A circuit does not have form a closed loop for current to flow.
    • Current gets "used up" as it flows through a circuit.
    • A conductor has no resistance.
    • The resistance of a parallel combination is larger than the largest resistance.
    • Current is an excess charge.
    • Charges that flow in circuit are from the battery.
    • The bigger the battery, the more voltage.
    • Power and energy are the same thing.
    • Batteries create energy out of nothing.