Physics 2 lab chapter 21

6/26/2015

Procedure Part I Wire Resistance:

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

0.01 A

800 Ω

2.0 V

.044 A

450 Ω

2.5 V

.0058 A

430 Ω

6.9 V

.069 A

100 Ω

6.4 V

0.021 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 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 volt

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? No, since distance L increases the resistance increases. The current and voltage will drop more as it nears the end of the power cord which could cause insufficient voltage once it reached the stereo causing damage.