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ohms law

# ohms law - Laboratory Report PHYS 122L Ohm’s Law and...

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Unformatted text preview: Laboratory Report PHYS 122L Ohm’s Law and Resistivity Purpose of the Experiment: • To become familiar with the use of voltmeters and ammeters in DC electrical measurements • To examine the characteristics of DC circuits in which ohmic devices (resitors) are connected in series and parallel • To measure the resistivity of a metal wire • To observe the non-ohmic behavior of a semiconductor diode Experimental Procedure Series and Parallel Resistors: The current through, and potential drops across three resistors (10Ω, 16Ω, and 27Ω) connected in different ways will be measured and analyzed, using Ohm’s Law and Kirchoff’s junction and loop relations. For each of the three cases described below we had to decide how to connect the power supply, the resistors, the voltmeter, and the ammeter in order to get the necessary data. In each case, I R and V R are recorded for each resistor, along with I power supply and V power supply . Case I: All three resistors are connected in series R 1 = 10 Ω Ρ 2 = 16 Ω Ρ 3 = 27 Ω Case II: All three resistors are connected in parallel R 1 = 10 Ω Ρ 2 = 16Ω Ρ 3 = 27 Ω Case III: The 16Ω and 27Ω resistors in parallel with the 10Ω resistor in series with the other two R 1 = 10 Ω R 2 = 16 Ω R 3 = 27 Ω Resistivity of Two Metals: A series circuit consisting of the DC power supply, a length of nichrome wire, and the 10 ohm resistor are connected. The ammeter and voltmeter are connected in such a way that they can record the potential difference across the wire and the current through it. Ten readings of V wire and I wire are taken for currents uniformly spaced between 50 and 300 mA. The polarity is then reversed and another ten readings are taken, uniformly spaced from 50 mA to 300 mA. The length and diameter of the wire, along with the temperature of the room are measured. This procedure is repeated for the steel wire. I-V Characteristic for a Diode: The 10 ohm resistor is connected in series with the semiconductor and the DC power supply. The ammeter and voltmeter are arranged to measure I diode and V diode . Twenty readings of I diode and V diode are taken for currents approximately uniformly spaced between 0 and 300 mA. Experimental Data Series and Parallel Resistors: Case I Power Supply R 1 = 10 Ω R 2 = 16 Ω R 3 = 27Ω V (V) 4.19 ± 0.01 0.78 ± 0.01 1.25 ± 0.01 2.11 ± 0.01 I (mA) 78 ± 1 78 ± 1 78 ± 1 78 ± 1 Case II Power Supply R 1 = 10 Ω R 2 = 16 Ω R 3 = 27Ω V (V) 1.08 ± 0.01 1.08 ± 0.01 1.08 ± 0.01 1.08 ± 0.01 I (mA) 217 ± 1 108 ± 1 69 ± 1 41 ± 1 Case III Power Supply R 1 = 10 Ω R 2 = 16 Ω R 3 = 27Ω V (V) 1.82 ± 0.01 0.90 ± 0.01 0.9 ± 0.01 0.9 ± 0.01 I (mA) 89 ± 1 89 ± 1 56 ± 1 34 ± 1 Uncertainties in values are from the ILE of the voltmeter and ammeter. Resistivity of Two Metals: Room temperature: 21.6 ºC Length of nichrome wire: 49.5 ± 0.3 cm (uncertainty from unknown length of enclosed wire at the ends) Diameter of nichrome wire: 0.10 ± 0.01 mm (uncertainty from ILE of micrometer)Diameter of nichrome wire: 0....
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ohms law - Laboratory Report PHYS 122L Ohm’s Law and...

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