Wire Resistance and Ohm’s Law PhET MiniLab Introduction: When an electrical potential exists in a circuit, a current may flow. Current is the flow of electrons in a circuit. Resistance in the circuit slows the flow of the electrons, reducing the current in the circuit.
We will use the mathematical form of Ohm’s Law frequently when we investigate electric current and circuits later in this unit. • Open the PhET Simulation Electricity, Magnets, and Circuits ( Resistance in a Wire[pic] As wire length (cm) increases, the resistance (? _________________ As wire area (cm2) increases, the resistance (? ) __________________As wire density (? cm) increases, the resistance (? ) _______________ Procedure: Ohm’s Law: Electricity, Magnets, and Circuits ( Ohm’s Law [pic] 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.
( ? pt each ) • Remember, the simulation shows milliamps. You should show Amperes V =I * R |8. 0 V |A |800 ? | |2. 0 V |. 044 A |? | |V |. 0058 A |430 ? | |V |.
069 A |100 ? | |6. 4 V |A |300 ? |Conclusion Questions: ( ? 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 ? ? ____________ 4. How many volts must an iPod charger provide to charge an iPOD using . 85 Amps at 35 ?? _____________ 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? ___________________________________________________________________________________________
