Ohms_law

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Ottawa University *

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MISC

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Electrical Engineering

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Apr 3, 2024

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4

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General Physics II Name: Jamaira Ross Ohm’s Law Goals To investigate the relationship between resistance, current, and voltage involved in Ohm’s Law. Introduction: Ohm’s Law states that the current, I , that flows in a circuit is directly proportional to the voltage, V , across the circuit and inversely proportional to the resistance, R , of the circuit: I = VR (1) Equipment: DC power supply, 5 different resistors between 100 to 10,000 Ω , Digital Multimeter (DMM), necessary wires. Ammeters are connected in series so that the current flows through them. The ideal ammeter has a resistance of zero so that it has no effect on the circuit. Real ammeters have some internal resistance. Voltmeters are connected in parallel to resistive elements in the circuit so that they measure the potential difference across the element. The ideal voltmeter has infinite internal resistance. This keeps the voltmeter from becoming a significant path for current around the element being measured.
Procedure: 1) Construct a series circuit with the power supply, a resistor and ammeter as shown below. 2) Use a DMM to measure the actual resistance of your resistor and record it in the table below. 3) Do not turn on the power supply until you are ready to read the current through the resistor, and Dr. Maughan has approved your setup. 4) Turn on your DMM to measure amps. 5) Turn both dials on your power supply as much as you can counterclockwise. 6) Turn the power supply on turn the current adjustment clockwise a small amount. 7) Turn the voltage adjustment clockwise, if the voltage does not change you may need to turn your current adjustment a bit more. 8) Set your voltage to 6 V . 9) Record the current (careful to make sure and check what units the DDM is displaying) and calculate using Eq 1. What the current should be theoretically. 10) Turn off your power supply and replace your resistor with a new one. 11) Once your resistor is replaced turn on your power supply. (it should stay set at 6 V but if it is not adjusted it to be) 12) Record the current (check the units) and calculate using Eq 1. What the current should be theoretically. 13) Continue this for at least 5 different resistances.
Data: Voltage of DC power supply _____6____ (V) Resistance (Ω) Measured Current (Amps) Theoretical Current(Amps) 1 815 7.4mA .736 2 669 9.01mA 8.96 3 462 13.05mA 12.98 4 986 6.10mA 6.1 5 97 62.0mA 61 Analysis: Construct a graph of Current (vertical axis) vs. 1/Resistance (horizontal axis) using Excel (or another plotting software if you prefer) for the measured values. Do not forget to label your axes including units. 0 0.01 0.02 0.00E+00 1.00E-02 2.00E-02 3.00E-02 4.00E-02 5.00E-02 6.00E-02 7.00E-02 Resistance voltage (V) Questions: 1) Discuss how the theoretical currents compare to the actual currents you measured for each resistor. What may cause any differences you found? There wasn’t a major difference between them.
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2) What shape is the graph? linear 3) What mathematical relationship does the graph illustrate for current and resistance? It gets bigger over time 4) Does this make sense from Ohm’s Law? Yes, the higher the resistance the higher the current 5) What physical quantity does the slope of your plot represent? The change in v over the resistance