Wire Resistance and Ohm’s Law
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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 _1,000_____ 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 (slows)__.
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 |.01 A |800 Ω | |2.0 V |.044 A |450 Ω | |0.2 V |.0058 A |430 Ω | |6.9 V |.069 A |100 Ω | |6.4 V |.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 / 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 ? _.20 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? _No, because resistivity is lost through all of the cords. When resistance is lost, the power doesn’t have the current needed to power your stereo.___