Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 123L
Section:
Basic Circuits
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Follow the procedure as outlined in your lab manual.
Answer all questions in complete sentences using the space provided or on attached sheet
of paper.
Be sure to include the correct units in the tables or sentences. Empty parenthesis in the
column or row headers are for units. The cells of the table are for the numbers (or words
or symbols as appropriate).
Use Appendix B to calculate the uncertainty in your current and voltage measurements
and record with your data in tables 1-4. Make sure the numbers are properly rounded.
A real circuit diagram is made to look like reality (boxes, wires, light bulbs, etc). This type of
diagram must be drawn as you perform the lab – not at home later. You don’t always have to
connect your wires exactly as shown in the lab manual, as long as you have set up the circuit
correctly (series or parallel, and with the correct meter in the correct place). Draw the diagram
as you have hooked up your circuit – not what the lab manual shows. Be sure to label the power
supply in your diagram with + and -, and “PS” or “power supply.” Meters should be labeled
either as “ammeter” or “voltmeter” as appropriate. In your diagram, wires should attach to the
boxes (power supply, ammeter, or voltmeter) in the approximately correct locations.
A schematic diagram shows all the circuit elements using symbols. If needed, you may draw
this diagram at home, using your real circuit as a guide. For full credit, do all of the following.
 Include all elements that are in you real circuit (power supply, wires, resistors, ammeter
or voltmeter).
 Put a “+” and “–“ at your power supply symbol to indicate positive and negative sides of
the circuit.
 Use arrows to indicate the flow direction of conventional current.
o If there is a junction, mark the flow direction with arrows along the different
pathways.
 Label the current with the symbol “i_”.
o If there is a junction, label the different pathways “i1”, “i2”, etc as described in the
lab manual procedure for the particular step. You can use ‘iPS’ for current
provided by the power supply.
 Use resistor symbols to indicate the light bulbs – Don’t use a light bulb symbol.
o Label the resistors as “bulb 1” and “bulb 2”, or “R1” and “R2”, as appropriate
based on the procedure in the lab manual for that particular step. Please keep bulb
1 and bulb 2 consistent throughout the lab.
 Use a circle with an “A” inside to represent an ammeter. This should be in series with
the resistor (light bulb).
 Use a circle with a “V” inside to represent a voltmeter. This should be in parallel with
the circuit element or portion of the circuit it is measuring. A voltmeter measures the
change in voltage from one side of the circuit element or portion of a circuit, to the other
side.
Lab: Basic Circuits
Updated 4/6/14
Data & Reporting score:
Part A: Series Circuit
Page 3: Draw both a schematic diagram and a sketch of the real circuit for the series circuit.
Schematic diagram
Real circuit
Question 1: What happens when you unscrew one of the light bulbs from its socket? Be specific
and explain why it happened.
Connecting an ammeter:
For all of the ammeter readings, make sure that you DO NOT change the voltage setting on
the power supply. Simply turn off the power supply to connect or reconnect the ammeter.
Page 4: Connect the ammeter in series BEFORE the first bulb to measure the current going into
the first bulb, I1. Then, connect the ammeter between the two bulbs to measure the current going
into the second bulb, I2.
Table 1: Current measurements for series circuit
Current (bulb 1), Current (bulb 2),
I1 (
)
I2 (
)
±
±
Relationship between I1 and I2
Connecting a voltmeter:
For all of the voltmeter readings, make sure that you DO NOT change the voltage setting
on the power supply. Simply turn off the power supply to connect or reconnect the
voltmeter.
Page 5: Connect the voltmeter in parallel with the first bulb to measure the voltage across (from
one side of the bulb to the other) the one light bulb, V1. Next connect the voltmeter in parallel
with the second bulb only to measure the voltage, V2. Then, connect the voltmeter across both
bulbs to measure the voltage across the combination of light bulbs, V.
Table 2: Voltage measurements for series circuit
Voltage (bulb 1), Voltage (bulb 2), Voltage (combination),
V1 (
)
V2 (
)
V(
)
Lab: Basic Circuits
Updated 4/6/14
Relationship between
V, V1 and V2
±
±
±
Part B: Parallel Circuit
Page 6: Connect your light bulbs and power supply in a parallel circuit
Question 2: What happens when you unscrew one of the light bulbs from its socket? Be specific
and explain why it happened.
For all of the following, make sure that you DO NOT change the voltage setting on the
power supply. Turn off the power supply each time BEFORE you reconnect the circuit.
Page 7: Connect the ammeter in series between power supply and only one of the bulbs. Draw a
schematic drawing to show the connections. Measure the current, I1. Reconnect the ammeter so
it reads current through the other bulb only, I2. Reconnect the ammeter so it reads current
through the combination of both bulbs, I. Draw a schematic diagram to show the ammeter
reading current going into both bulbs.
Schematic diagram (measuring one bulb)
Schematic diagram (combination of bulbs)
Table 3: Current measurements for a parallel circuit
Current (bulb 1), Current (bulb 2), Current (combination),
I1 (
)
I2 (
)
I(
)
±
±
±
Relationship between
I, I1, and I2
Page 8: Connect the voltmeter to measure the voltage, V, across the combination of the two
bulbs. Draw a schematic diagram for this set-up. Next, connect the voltmeter across just one of
the bulbs and measure the voltage, V1. Draw a schematic diagram for this set-up.
Schematic diagram (combination of bulbs)
Schematic diagram (one bulb only)
Lab: Basic Circuits
Updated 4/6/14
Table 4: Voltage measurements for parallel circuit
Voltage (combination), Voltage (one bulb),
V(
)
V1 (
)
±
±
Relationship between V and V1
Calculations: In the space below or on an attached sheet of paper, show the calculation of the
uncertainty in the electronic meter for all of the current and voltage values recorded in tables
1thru 4.
Series circuit bulb 1 current uncertainty:
Series circuit bulb 2 current uncertainty:
Series circuit bulb 1 voltage uncertainty:
Series circuit bulb 2 voltage uncertainty:
Series circuit combo voltage uncertainty:
Parallel circuit bulb 1 current uncertainty:
Parallel circuit bulb 2 current uncertainty:
Parallel circuit combo current uncertainty:
Parallel circuit one bulb voltage uncertainty:
Parallel circuit combo voltage uncertainty:
Question 3 (Instead of summary): What was the goal of, reason for, or purpose of the Basic
Circuits lab? (Write your answer as if you were writing the introductory sentence to your
summary/conclusion paragraph. Do NOT plagiarize the lab manual or fellow students.)
Lab: Basic Circuits
Updated 4/6/14