Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 133L
Section:
Basic Circuits



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).
A real circuit diagram is required for all circuits in this lab except steps A-1 and A-3. This
diagram is made to look like reality (boxes, wires, light bulbs, etc). These diagrams 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 is required for all circuits in this lab except steps A-1 and A-3. This
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 09/18/13
Data & Reporting score:
Part A: Series Circuit
A-1: Connect the series circuit shown in figure 3 of your lab manual.
Question A-1a) What happens when you unscrew one of the light bulbs from its socket? Be
specific and explain why it happened. (Replace the bulb when done.)
Question A-1b) What happens if you increase the power supply voltage slightly?
Question A-1c) What would happen if you were to unscrew the other light bulb?
Connecting an ammeter:
Make sure that you DO NOT change the voltage setting on the power supply. Simply
unplug the banana plug from the positive terminal of the power supply.
A-2: Connect the ammeter as shown in the left hand circuit drawing of figure 5. (Connect the
ammeter in series BEFORE the first bulb to measure the current going into the first bulb, I1.)
Schematic diagram
Real circuit
Connect the ammeter as shown in the right hand circuit drawing of figure 5. (Connect the
ammeter BETWEEN the two bulbs to measure the current going into the second bulb, I2.)
Schematic diagram
Real circuit
Table 1: Current measurements for series circuit
Current (bulb 1), I1 (
) Current (bulb 2), I2 (
Lab: Basic Circuits
Updated 09/18/13
)
Relationship between I1 and I2
Connecting a voltmeter:
Make sure that you DO NOT change the voltage setting on the power supply.
A-3: Connect the voltmeter as shown in the center circuit drawing of figure 7. Connect the
voltmeter in parallel with the first bulb to measure the voltage across (from one side of the bulb
to the other) the first light bulb, V1.
Schematic diagram
Real circuit
Without changing the voltage on the power supply, connect the voltmeter in parallel with the
second bulb only (left hand circuit drawing of figure 7) to measure the voltage, V2.
Schematic diagram
Real circuit
Then, without changing the voltage on the power supply, connect the voltmeter across both
bulbs (right hand circuit drawing of figure 7) to measure the voltage across the combination of
light bulbs, V3.
Schematic diagram
Real circuit
Table 2: Voltage measurements for series circuit
Voltage (bulb 1), Voltage (bulb 2), Voltage (combination),
V1 (
)
V2 (
)
V3 (
)
Lab: Basic Circuits
Updated 09/18/13
Relationship between
V1 V2, and V3
Part B: Parallel Circuit
B-1: Connect the parallel circuit shown in figure 8 of your lab manual.
Question B-1a) What happens when you unscrew one of the light bulbs from its socket? Be
specific and explain why it happened. (Replace the bulb when done.)
Question B-1b) What happens if you increase the power supply voltage slightly?
Question B-1c) What would happen if you were to unscrew the other light bulb?
For B-2 and B-3, DO NOT change the voltage setting on the power supply between the
various circuit configurations. Simply unplug the banana plug from the positive terminal
of the power supply to change your circuit.
B-2: Connect the ammeter in your circuit as shown in figure 10. (Connect the ammeter in series
between power supply and only one of the bulbs, the top bulb.) Measure the current through the
top bulb, I1, and record the value in table 3.
Ammeter reading of current through top bulb only
Schematic diagram
Real circuit
Without changing the voltage on the power supply, reconnect the ammeter so it reads current
through the bottom bulb only, I2.
Ammeter reading of current through bottom bulb only
Schematic diagram
Real circuit
Lab: Basic Circuits
Updated 09/18/13
Without changing the voltage on the power supply, reconnect the ammeter so it reads current
through the combination of both bulbs, I3.
Ammeter reading of current through combination of both bulbs
Schematic diagram
Real circuit
Table 3: Current measurements for a parallel circuit
Current (top),
Current (bottom), Current (combination),
I1 (
)
I2 (
)
I3 (
)
Relationship between
I1, I2, and I3
B-3: Connect the voltmeter in your circuit as shown in figure 11. (Connect the voltmeter across
just one of the bulbs (the top one) and measure the voltage, V1. Record the value in table 4.
Voltmeter reading across top bulb only
Schematic diagram
Real circuit
Without changing the voltage on the power supply, reconnect the voltmeter so it reads the
voltage across the bottom bulb only, V2. Record the value in table 4.
Voltmeter reading across bottom bulb only
Schematic diagram
Real circuit
Lab: Basic Circuits
Updated 09/18/13
Without changing the voltage on the power supply, reconnect the voltmeter so it reads the
voltage across the power supply output, V3. This is equivalent to the voltage across the
combination of both bulbs in the parallel circuit. Make sure the rest of the circuit is still attached
and the light bulbs are lit when you take your reading. Record the value in table 4.
Voltmeter reading across power supply
Schematic diagram
Real circuit
Table 4: Voltage measurements for parallel circuit
Voltage (top),
Voltage (bottom),
Voltage (across PS),
V1 (
)
V2 (
)
V3 (
)
Relationship between
V1, V2, and V3
Turn the voltage on the power supply to zero. Turn off power supply. Dismantle your circuit.
Questions: Answer the following questions on an attached sheet of paper (hand-write on lined
paper, green engineering paper, or type).
1. (Instead of summary/conclusion paragraph): In one sentence, tell me 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)
2. Using only words (no symbols or variables), state the relationship for current in series circuits
that you identified in table 1. How does this relate to the current provided by the power
supply?
3. Using only words (no symbols or variables), state the relationship for voltage in series circuits
that you identified in table 2. How does this relate to the voltage provided by the power
supply?
4. Using only words (no symbols or variables), state the relationship for current parallel circuits
that you identified in table 3. How does this relate to the current provided by the power
supply?
5. Using only words (no symbols or variables), state the relationship for voltage in parallel
circuits that you identified in table 4. How does this relate to the voltage provided by the
power supply?
There is no conclusion/summary paragraph for this lab experiment.
Lab: Basic Circuits
Updated 09/18/13