22 Ohms Law_GB

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Tidewater Community College *

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Computer Science

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Apr 3, 2024

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Computer 22 Ohm’s Law The fundamental relationship among the three important electrical quantities current , voltage , and resistance was discovered by Georg Simon Ohm. The relationship and the unit of electrical resistance were both named for him to commemorate this contribution to physics. One statement of Ohm’s law is that the current through a resistor is proportional to the voltage across the resistor. In this experiment you will see if Ohm’s law is applicable to several different circuits using a Current Probe and a Voltage Probe. Current and voltage can be difficult to understand, because they cannot be observed directly. To clarify these terms, some people make the comparison between electrical circuits and water flowing in pipes. Here is a chart of the three electrical units we will study in this experiment. Electrical Quantity Description Unit Water Analogy Voltage or Potential Difference A measure of the Energy difference per unit charge between two points in a circuit. Volt (V) Water Pressure Current A measure of the flow of charge in a circuit. Ampere (A) Amount of water flowing Resistance A measure of how difficult it is for current to flow in a circuit. Ohm ( W ) A measure of how difficult it is for water to flow through a pipe. Figure 1 Physics with Vernier 22 - 1
Computer 22 OBJECTIVES Determine the mathematical relationship between current, potential difference, and resistance in a simple circuit. Compare the potential vs . current behavior of a resistor to that of a light bulb. MATERIALS computer Vernier Circuit Board, or Vernier computer interface wires Logger Pro clips to hold wires one Vernier Current Probe and switch one Vernier Differential Voltage Probe two resistors (about 10 and 50  W ) adjustable 5 volt DC power supply light bulb (6.3 V) PRELIMINARY SETUP AND QUESTIONS 1. Connect the Current Probe to Channel 1 and the Differential Voltage Probe to Channel 2 of the computer interface. 2. Open the file “22 Ohms Law” in the Physics with Vernier folder. A graph of potential vs . current will be displayed. The meter displays potential and current readings. 3. With the power supply turned off, connect the power supply, 10 W resistor, wires, and clips as shown in Figure 1. Take care that the positive lead from the power supply and the red terminal from the Current & Voltage Probe are connected as shown in Figure 1. Note: Attach the red connectors electrically closer to the positive side of the power supply. 4. Click . A dialog box will appear. Click to zero both sensors. This sets the zero for both probes with no current flowing and with no voltage applied. 5. Have your teacher check the arrangement of the wires before proceeding. Turn the control on the DC power supply to 0 V and then turn on the power supply. Slowly increase the voltage to 5 V while holding the switch closed. Monitor the meter in Logger Pro and describe what happens to the current through the resistor as the potential difference across the resistor changes. Use the multi-meter to independently measure the voltage and current at a few points to verify your values. If the voltage doubles, what happens to the current? What type of relationship do you believe exists between voltage and current? How did the multi-meter readings compare to the Vernier values? PROCEDURE 1. Record the value of the resistor in the data table. 2. Make sure the power supply is set to 0 V. Click to begin data collection. Monitor the voltage and current. Click . 3. Increase the voltage on the power supply to approximately 0.5 V. Click . 4. Increase the voltage by about 0.5 V. Click . Repeat this process until you reach a voltage of 5.0 V. 22 - 2 Physics with Vernier
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