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_1000_ 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

.010A

800 Ω

2.0 V

.044 A

45.45Ω

2.5V

.0058 A

430 Ω

6.9V

.069 A

100 Ω

6.4 V

.0213A

300 Ω

Conclusion Questions: ( ½ pt each)

1. Incandescent light bulbs have a very thin filament that glows when hot. Thin filaments have very 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 ohms___

3. A “2D” Maglite flashlight runs on 3.0V. What is the current through the bulb if resistance is 15 Ω ? __0.2 amps__

4. How many volts must an iPod charger provide to charge an iPOD using .85 Amps at 35 Ω? ___29.75 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 would not be favorable because using four 50ft cords vs. one 200ft cord would increase the overall resistance and this would result in less voltage