Go to http://phet.colorado.edu/simulations/sims.php?sim=Ohms_Law and click on Run Now.

Wire Resistance and Ohm’s Law

Procedure Part I Wire Resistance: open the PhET Simulation Electricity, Magnets, and Circuits Resistance in a Wire.

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

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

As wire resistivity (Ωcm) increases, the resistance (Ω) ____increases______

Procedure Part II: Ohm’s Law: Electricity, Magnets, and Circuits Ohm’s Law mA is milliamps, and 100) milliamps equals one Ampere.

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

As voltage increases, current increases.

As resistance increases, current decreases

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

8.0 V

0.01 A

800 Ω

2.0 V

.044 A

45.5 Ω

2.5 V

.0058 A

430 Ω

6.9 V

.069 A

100 Ω

6.4 V

0.0213 A

300 Ω

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? 0.48 Ω

3. A “2D” Maglite flashlight runs on 3.0V. What is the current through the bulb if resistance is 15 Ω? 0.2 A

4. How many volts must an iPod charger provide to charge an iPOD using .85 Amps at 35 Ω? 29.75 V (~ 29.8 V)

5. 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?

This is NOT a very good idea. Connecting four 50 foot cords to make 200 feet increases the resistance of the