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.