Download Project 3: Tricky Electrical Circuits

Cornell Science Inquiry Partnerships
Cornell University
http://csip.cornell.edu
Tricky Electrical Circuits
Teacher’s Guide
by Tom Oberst, CSIP Graduate Student Fellow, Cornell University
Description
Aided by a large demonstration circuit with five light bulbs in parallel and in series, the
teacher will ask students to make quick calculations and guesses to answer “trick”
questions about what would happen to the circuit if certain light bulbs are removed. This
is a fun project because the results can be anti-intuitive.
Subject: Physics
Grade Level: 9-12
Time required: 1 class period (45 minutes)
Background
Students should be familiar with electric current, voltage, resistance, power, Ohm’s Law,
and how to add voltages, currents, and resistances in series and in parallel.
Learning & Behavioral Objectives
Give students a fundamental understanding of how electric circuits work and of the
physical meaning of current, voltage, and resistance.
National Science Education Standards Addressed:
 Electricity and magnetism
 Transfer of energy
 Structure and properties of matter
 Evolution and equilibrium
 Abilities necessary to do scientific inquiry
 Evidence, models and explanation
Assessment Strategy
Students answer questions verbally and interact through student-student and studentteacher discussion.
Teaching Tips
Keep a spare light bulb on hand in case one burns out or gets dropped. Also think about
the answers to the questions you will ask the students (and any they may come up with on
their own) before beginning. Sometimes these things can even be tricky. For example, the
resistance of the light bulbs cannot simply be measured across the light bulb because it
will change substantially when the light bulb is in use and gets hot.
This material was developed through the Cornell Science Inquiry Partnership program (http://csip.cornell.edu), with
support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program
(DGE # 0231913 and # 9979516) and Cornell University. Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.