Download Ohm's Law Experiment: Measuring Resistances to Verify Ohm's Law and Resistor Combinations and more Exams Law in PDF only on Docsity! OHM'S LAW PURPOSE: To measure voltage across a resistor and current through a resistor to verify Ohm's law and to verify the equations for series and parallel combinations of resistors. APPARATUS: Ohm's Law Board Assorted wire leads DC Power Supply Voltmeter Ammeter METHOD: Three unknown resistances are measured by taking a series of voltage and current readings for each resistor. Since Ohm's law states V IR , a graph of V versus I for each resistor will have a slope R. Therefore each resistance can be determined from the graph. The resistance of the three resistors connected in series is found by taking a sequence of voltage-current readings. The resistance from the slope of the graph may then be compared with the value calculated from the series resistance formula. PROCEDURE: HAVE AN INSTRUCTOR CHECK ALL CIRCUITS BEFORE TURNING ON ANY POWER SUPPLY 1. Individual resistors a. Connect the resistor marked R1 in series with the dc power supply and connect the circuit as shown in Figure 1. Voltmeter Ammeter b. Connect the voltmeter across the resistor. Turn on both digital meters. The current control on the power supply should be near its maximum, the voltage control should be at its minimum. Turn on the power supply and adjust it until the voltmeter reading is 2 volts. Record this voltage and its corresponding current reading. d. Take additional readings at 4, 6, 8 and 10 volts. e. Repeat steps 1a through 1d with each of the other two resistors. (R2 and R3) f. Turn off the digital meters turn the voltage to zero, and then turn off the power supply. 2. Resistors in series a. Connect the three resistors in series with each other and with the dc power supply and and connect the circuit as shown in figure 2. Power Supply Figure 2 I b. Connect the voltmeter so that it is across all three resistors as shown. Turn on both digital meters. c. Turn on the power supply and take readings for voltage and current, but with voltages of 2, 4, 8, and 10 volts. Record these values on the given data table. d. Turn off the digital meters turn the voltage to zero, and then turn off the power supply. 3. Resistors in parallel a. Connect the three resistors in parallel, and the combination in series with the power supply and connect the circuit as shown in figure 3. Power Supply I b. Connect the voltmeter across the parallel combination of resistors. Turn on both digital meters. c. Turn on the power supply and take readings as before for applied voltages of 2, 4, 6, 8 and 10 volts. Record these values on the given data table. d. Turn off the digital meters turn the voltage to zero, and then turn off the power supply. 4. Series-parallel combination a. Connect R2 and R3 in parallel and that combination in series with R1 and connect the circuit as shown in figure 4. Power Supply I b. Connect the voltmeter across the series-parallel combination of resistors as shown. Turn on both digital meters. c. Again make measurements for voltage and current with applied voltages of 2, 4, 6, 8 and 10 volts. Record these values on the given data table. d. Turn the voltage to zero, then turn off the power supply and disconnect the circuit. Make sure that all digital meters are turned off.
