Purpose:
The purpose of this lab is to see if and how Ohm’s Law applies in a circuit that doesn’t have a resistor.
Theory:
Equations
Resistance = Voltage/Current
R = V/I
Voltage = Current * Resistance
V = I * R
Current = Voltage/Resistance
I = V/R
Hypothesis:
I hypothesize that the resistance will be between 8 and 10 ohms.
Procedures:
Assemble a circuit with a multimeter, to measure the current, a voltmeter, to measure the volts, and a resistor that will provide the resistance. Next, a hand-held generator will power the circuit. Record the voltage and current while keeping the generated voltage at a constant rate. Record an estimate of the absolute uncertainty for both the voltage and the current. Choose five target voltages. Then, graph the Voltage versus the Current to get the resistance of the light bulbs. Use uncertainty bars on your graph of Voltage versus Current to get a best fit.
Data:
Voltage (V)
.1
.3
.5
.7
.9
1
Current (A) Low, Average, High
10, 14, 18
45, 55, 65
120, 127.5, 135
120, 135, 150
180, 187.5, 195
180, 190, 200
·Voltage = # of volts = V
·Current = # of amps/1000 = A
·Voltage = + or – .1 V
·Current = high and low given
·Actual Resistance = 6.7 Ohms
Analysis:
Voltage (V)
.1
.3
The Term Paper on Resistance Ohms Law
... circuit is being calculated. To calculate the resistance of the wire using Ohms Law, both an ammeter and a voltmeter will be required: Voltage / Current = Resistance ... The wire in question will have to be attached in this circuit in series so that the current flows directly ...
.5
.7
.9
1
Average Current (A)
14
55
127.5
135
187.5
190
Resistance in Ohms
7.14
5.45
3.92
5.18
4.8
5.26
Results:
The resistance we got from the calculations was close to the actual resistance of 6.7 ohms. However, the 7.14 ohms with a voltage of 0.1V and 3.92 ohms for the voltage of 0.5 ohms were not very accurate.
We could have made many mistakes when doing this lab. Of course, the main error we made was when trying to keep the voltage constant using the generator we were unable to be perfect. This could have been improved had we used a motor for example, that kept the voltage at a constant rate. It was also hard to read the measurements on for example the voltage meter. This could have been improved if we used a digital one.
Conclusion:
This lab’s purpose was to see if Ohm’s Law could actually be applied to a circuit board. In order to test this, we made a “circuit board” that had a resistor. We connected it to a voltmeter, a multimeter, and generator.
My hypothesis was close, but not correct. I hypothesized that the resistance would be between 8 and 10 ohms, but it was only about 6.7 ohms.
This lab could have been done better if we had a generator that provided a constant voltage, and if our voltmeter and multimeter were digital.
