Physics 102
Building Circuits and Using the Oscilloscope
January 25, 2006
Elizabeth Silva and Maria Zavala
Abstract:
The purpose of this experiment is to introduce the student to the idea of circuits, so that
one may be able to build a circuit. In addition, the student will learn to use and read the
oscilloscope and function generator.
Equipment:
● Light bulbs
● Wire
● Battery or power supply
● Digital voltmeter
● Function generator
● Oscilloscope
Procedure:
1. Collect all required equipment.
2. Build a series circuit with the three bulbs and wires. Attach the power source.
3. Using the same series circuit (make sure all bulbs are lit) measure the voltage
across each light, record results.
4. Remove one wire that connects the power source to the series circuit, replace it
with the VOM probe set to DCA, and record the current.
5. Using the same bulbs and wires construct a circuit that has two bulbs in series
attached to the power source.
6. Using the same bulbs and wires construct a parallel circuit. Attach the circuit to
the power source.
7. Measure the voltage across each bulb in the parallel circuit and record the results.
8. Remove one wire that connects the power source to the parallel circuit, replace it
with the VOM probe set to DCA, and record the current.
9. Wire two bulbs in series and the third bulb in parallel with the other two.
10. Put away power source and the bulbs with wires.
11. Retrieve the function generator and oscilloscope.
12. Connect the function generator to the oscilloscope; attach the red to red wire and
black to black wires, use banana-to-BNC connectors on the oscilloscope for the
connection.
13. Adjust the frequency generator:
- Set the frequency dial to about 0.9.
- Set the waveform to sine.
- Set the multiplier to X100.
- Turn up the gain (or amplitude) to about three o’clock.
- Set the offset to zero.
14. Adjust the oscilloscope to get a clear waveform on your screen:
- Adjust the voltage/div dial.
- Adjust the trigger dial.
- Adjust the time/div dial.
- Adjust red position dials.
- Adjust the intensity and focus adjustment.
15. Get the largest waveform that fits on the screen at 2ms (Time/div dial).
16. Turn the frequency dial on the function generator and record the effect it has on
the oscilloscope.
17. Turn off and put away the function generator and oscilloscope.
Data:
1. Series Circuit: (3 Bulbs)
A. The voltage measurement across each lit bulb.
VA = 1.440 V
VB = 1.383 V
VC = 1.447 V
VInitial = 4.460 V
B. The current measurement of a series circuit.
I = 0.14 A
2. Series Circuit: (2 Bulbs)
A. The voltage measurement across each lit bulb.
VA = 2.109 V
VB = 2.140 V
VInitial = 4.460 V
3. Parallel Circuit: (3 Bulbs)
A. The voltage measurements across each lit bulb in a parallel circuit.
V1 = 4.460 V
V2 = 4.460 V
V3 = 4.460 V
VInitial = 4.460 V
B. The current measurement for the parallel circuit.
I = 0.73 A
4. Measure the largest wavelength seen on the oscilloscope at 2ms?
The largest wavelength on the ‘scope at 2ms is 9.6 ms.
5. Find the frequency of the wave by measuring its period on the oscilloscope.
ƒ = 104.2 Hz
6. Find the amplitude of the wave in volts.
Amplitude = 8 V
Analysis:
Calculations:
1.This experiment only called for one calculation, frequency.
ƒ = 1/ T ; where T is the period measured in seconds.
Error Analysis:
This experiment was simple to perform. The only place that some variation came up was
with the voltage readings. For example the resulting voltages for a 3 bulb series were:
VA = 1.440 V
VB = 1.383 V
VC = 1.447 V
VInitial = 4.460 V
Yet upon adding VA + VB + VC the sum is 4.270 V. This does not match the initial
voltage reading of 4.460 V. The drop in potential may have come from the springs.
Likewise the voltage totals for all the varies circuits tested in this experiment may have
been off because of the drop in potential from the springs in the circuit.
Questions:
1. Series Circuit: (3 Bulbs)
A. Do all three bulbs light?
Yes, all three light bulbs light up.
B.What happens if any one bulb is removed?
The circuit is broken and the light goes out when one bulb is removed.
2. Series Circuit: (2 Bulbs)
A. Are the two bulbs brighter, dimmer, or the same as they were when all three
bulbs were wired?
The bulbs are brighter.
3. Parallel Circuit: (3 Bulbs)
A. Do all three bulbs light?
Yes, all three light bulbs light up.
B. What happens if any one bulb is removed?
Nothing happens the remaining two bulbs remain lit.
C. When one bulb is removed, what happens to the brightness and the voltage
across the remaining two bulbs?
The brightness was observed; it remained the same when one bulb was
removed.
4. One Circuit - 2 bulbs in series, 1 bulb in parallel with the other 2 bulbs:
A. Do all three bulbs light?
Yes, all three light bulbs lit up.
B. What happens if any one bulb is removed? Record all possible results.
- When the light bulb from the parallel circuit was removed both the series
light bulbs remain lit.
- When one of the light bulbs from the series circuit was removed only the
light bulb from the parallel circuit remained lit. The remaining light bulb in
the series circuit turned off.
C. When one bulb is removed, what happens to the brightness of the remaining
two bulbs?
No change in brightness was observed when the above procedure of 13b
was performed.
5. Turn the frequency dial on the function generator and record the effect you see on the
oscilloscope.
When the frequency dial on the function generator is turned the period of the sine
wave increases.
6. Are the circuits in your car connected in a parallel or series? Why?
The circuits in cars are connected in parallel. When the fuse for your car stereo
blows out it does not stop your car from working, this indicates it is in parallel.
Another example is light from the dashboard, if it goes out it also does not stop
the car from working. The front lights is another example to prove that it is in
parallel, if one light goes out it does not turn off the other light nor does it stop the
car from working.
7. Construct on your paper a single circuit that has two series branches and two parallel
branches. There are many possible answers.
See attachment
8. Schematic diagram A is a circuit with two bulbs in series and one bulb in parallel.
9. Schematic diagram B is a circuit in series.
10. Schematic diagram C is a parallel circuit.
Conclusion:
The purpose of this experiment was to introduce us to the idea of circuits, so that
we may be able to build a circuit. The circuits introduced were series circuits, parallel
circuits, and a combination of both. In addition, the oscilloscope and function generator
were used to familiarize us with its’ functions. By constructing our own circuit boards we
were able to have a better understanding of how the connections within the circuit work
together.
Grade = 89/100