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AP Physics-Electric Circuits Experiments Rice-2014 Page 1
Electric Circuit Experiments 1. Using the resistor RX on the 5-resistor block, vary the
potential difference across it in approximately equal increments for eight different values (i.e. use one to eight D-cells). a. Measure the potential difference between the ends of
the resistor. (Voltmeter Range-DCV-20) b. Measure the current through the resistor. (Ammeter
Range - DCA-200m) c. Touch the resistor at various times during the
experiment. What do you feel? What does this mean? d. Plot a graph of V vs. I (even though this violates our
normal convention.) Repeat this experiment for RY and RZ in your kit. Plot all three graphs on one set of axes. What is the significance of the slope of these graphs? Use the resistor color code chart in your textbook to determine the accepted value of the resistance of your resistor. Measure the resistance with the ohmmeter. Calculate experimental error using both the resistor color code value and the measured resistance from the ohmmeter.
e. Draw conclusions. 2. Using the 9-resistor block, connect the resistor network to a
battery whose potential difference is approximately 3 V(2 D-cells). Vary the resistance from 100 to 900 in increments of 100 as shown on the block. a. Measure the potential difference between the ends each
new resistance. (Voltmeter Range-DCV-20) b. Measure the current through the resistor. (Ammeter
Range - DCA-200m, Drop to DCA-20m when the current drops below 20 mA)
c. Plot a graph of current vs. resistance and find an equation which describes the relationship between them. What is the significance of the constant of proportionality? Determine your experimental error.
d. Draw conclusions. 3. Connect three long bulbs in series with a battery as shown in
the circuit to the right. Vary the potential difference of the battery from about 1.5 V (one cell) to about 10.5 V (7 cells) in increments of 1.5 V (one cell). a. Measure the potential difference across the first long
bulb. (Voltmeter Range-DCV-20) b. Measure the current through the first long bulb.
(Ammeter Range - DCA-2) c. Plot a graph of V vs. I (even though this violates our
normal convention.) What is the significance of the slope of this graph? Do whatever is necessary with your data to develop a mathematical model relating potential difference and current for a long bulb.
d. Draw conclusions.
VRX
A
VR
A
V
A
L
L
L

4. Using the five resistor block, connect RA, RB, and RX, in series with a battery whose potential difference is approximately 6 V (4 D-cells) a. Measure the potential difference across
each resistor and across the battery. (Voltmeter Range-DCV-20)
b. Measure the current in each connecting wire. (Ammeter Range - DCA-200m, Drop to DCA-20m if the current is below 20 mA)
c. Use the mathematical model developed in experiments 1 and 2 to determine the equivalent resistance of this circuit as viewed from the terminals of the battery. How does this resistance relate to the individual resistances of the resistors?
d. Draw conclusions from your measurements and calculations.
5. Using the five resistor block, connect RA,
RB, and RX, in parallel with a battery whose potential difference is approximately 6 V (4 D-cells). a. Measure the potential difference across
c. Use the mathematical model developed in experiments 1 and 2 to determine the effective resistance of this circuit as viewed from the terminals of the battery.
d. Draw conclusions from your measurements and calculations.
6. Using the five resistor block, connect RX, RY,
and RZ, in series with a battery whose potential difference is approximately 6 V (4 D-cells). a. Measure the potential difference across
c. Use the mathematical model developed in experiments 1 and 2 to determine the effective resistance of this circuit as viewed from the terminals of the battery.
d. Draw conclusions from your measurements.
A
V
RX
A
V
A
V
A
VRA RB
A A
A A
V V
V
V
RA
RB
RX
A A
A A
V V
V
V
RX
RY
RZ

7. Using the five resistor block, connect RX,
RY, and RZ, in parallel with a battery whose potential difference is approximately 6 V (4 D-cells). a. Measure the potential difference
across each resistor and across the battery. (Voltmeter Range-DCV-20)
c. Use the mathematical model developed in experiments 1 and 2 to determine the effective resistance of this circuit as viewed from the terminals of the battery. Draw conclusions from your measurements and calculations.
Writeup notes: For each investigation described above you should include the following: Briefly discuss the purpose and procedure of the experiment.
Draw a schematic diagram using proper circuit symbols. Include meter placement in your schematic diagram.
Include a data table which shows each of the measured and calculated values. Show your calculations. An appropriate data table for experiments 4 through 7 might look like the following:
Circuit Element V (V) I (A) Published R () Measured R () Calculated R ()
RX
RY
RZ
Battery/ External Circuit
For experiments 1, 2, and 3, include each graph and, where appropriate, a mathematical analysis. Each section of the lab report should have its own independent conclusion outlining the important ideas of that investigation. Experiments 1, 2, and 3 should discuss slope significance and the final mathematical model that results from the analysis of the experiment. Experiments 4 through 7 should relate the resistances of the individual resistors to the equivalent resistance of the entire circuit as measured at the terminals of the battery. Experiments 4 through 7 should also discuss the relation among the potential differences measured in each circuit as well as the relation among the measured currents. Error analysis: For investigations 1 and 2, error calculations should be performed with respect to the slope of your final graphs and the significance of those slopes. For investigations 4 through 7, you should perform error calculations comparing the equivalent resistance as calculated using the potential difference and current as measured at the terminals of the batteries to the equivalent resistance as calculated using the resistor values. When you have completed all seven investigations, you should write a final conclusion which discusses the general principles shown by the set of experiments.
A
V
RZ
A
V
A
V
A
VRX RY

Useful Information for DC Circuits Measuring Current--Ammeters When using an ammeter, always connect it in series with the circuit element through which you wish to measure
the current. Ammeters have very low resistance, and if connected in parallel (even for a fraction of a second) the current through the meter will be high enough to cause a fuse to blow if your meter is fused, or can destroy the meter if you are not so fortunate as to be using a setting that is fused. If you are unsure of the approximate value of the current that you are measure, start with the ammeter set to the highest available range and work down to the appropriate range for the measurement you are making. For the Cen-Tech P30756 meter, a DCA range of 200 mA should be fine if you stay within the potential difference and resistance values suggested in the experiments. The red test lead should be connected to the VmA hole (high potential) and the black test lead should be connected to the COM hole (low potential). If you get a negative current reading it means that the meter is connected backwards, i.e. high potential to the COM hole and low potential to the VmA hole.
Connect the test leads to these two holes for measuring currents of 200 mA or less. For currents greater than 200 mA (up to 10 A) the top and bottom holes are used with the meter switched to the 10 A position.
Note: Be very careful when using the 10 A range because the meter is not fuse protected in this mode. Measuring Potential Difference--Voltmeters
When using a voltmeter, always connect it in parallel with the circuit element across which you wish to measure the potential difference. Voltmeters have very high resistance and are therefore unlikely to be damaged if connected improperly. Because of this high resistance, however, your readings will be nonsensical if the meter is connected in series with a circuit element. Start with the highest range and work down to the appropriate range for the measurement you are making. Setting your multimeter at the 20 DCV range should work fine for measuring all of the potential differences you will encounter in this set of experiments.
Use these two holes when measuring potential difference.

electric circuit experiments - school district of · pdf fileelectric circuit experiments 1....

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