Phet Wire Resistance and Ohm’s Law

Go to  http://phet.colorado.edu/simulations/sims.php?sim=Ohms_Law

 and click on Run Now.

Procedure Part I Wire Resistance:

open the PhET Simulation Electricity, Magnets, and Circuits à Resistance in a Wire

As wire length (cm) increases, the resistance (Ω) _________________

As wire area (cm²) increases, the resistance (Ω) __________________

As wire density (Ωcm) increases, the resistance (Ω) _______________

Procedure Part II: Ohm’s Law: Electricity, Magnets, and Circuits à Ohm’s Law

mA is milliamps, and _________ milliamps equals one Ampere.

·         Move the potential (volts) and resistance (ohms) sliders and observe the current (amps)

As voltage increases, current  __________________.

As resistance increases, current  ________________.

Fill out the tables below and check your work in the simulation.   ( ½ pt each )

·         Remember, the simulation shows milliamps.

·         You should show Amperes

          V                   =             I                  *              R

Conclusion Questions:  ( ½ pt each)

1.       Incandescent light bulbs have a very thin filament that glows when hot.  Thin filaments have very high / low resistance.

2.       The 12V battery in your car operates a 25 amp car stereo.  What is the resistance of this stereo system? ___________

3.       A “2D” Maglite flashlight runs on 3.0V.  What is the current through the bulb if resistance is 15 Ω ? ____________

4.       How many volts must an iPod charger provide to charge an iPOD using .85 Amps at 35 Ω? _____________

You need to buy a long extension cord to power a stereo at your spring break BBQ.  You need 200feet.  You have a 50 ft cord that will work.  You rationalize that four such 50 ft cords will do the job.  Is this a good idea?  Why or Why not? ________________