Download Name:

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.
Part A: Series Circuit
A-1: Connect the series circuit shown in figure 3 of your lab manual. Note what symbols are
used to represent the light bulbs and the power supply in the figure, as well as the arrow showing
the direction of conventional current flow.
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 to connect or
reconnect the ammeter in the circuit.
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.)
Draw both a schematic diagram and a sketch of the real circuit for the left hand series circuit.
The schematic diagram must include all of the elements in your real circuit , + and – signs at the
power supply symbol indicating the positive and negative sides of the circuit, an arrow indicating
the direction of the conventional current, and the resistors (light bulbs) labeled as bulb 1 (or R1)
and bulb 2 (or R2). Use resistor symbols to represent the light bulbs since we are only concerned
with the bulb’s electrical resistance. Please keep bulb 1 and 2 consistent throughout the lab.
Schematic diagram
Real circuit
Lab: Basic Circuits
Updated 09/13/12
Data & Reporting score:
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 (
)
Relationship between I1 and I2
Connecting a voltmeter:
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 to connect or
reconnect the voltmeter in the circuit.
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. 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. 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.
Table 2: Voltage measurements for series circuit
Voltage (bulb 1), Voltage (bulb 2), Voltage (combination),
V1 (
)
V2 (
)
V3 (
)
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?
Lab: Basic Circuits
Updated 09/13/12
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. Draw both a schematic diagram and a sketch of the
real circuit that you made.
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. Draw both a schematic diagram and a sketch of the real circuit
that you made.
Ammeter reading of current through bottom bulb only
Schematic diagram
Real circuit
Without changing the voltage on the power supply, reconnect the ammeter so it reads current
through the combination of both bulbs, I3. Draw both a schematic diagram and a sketch of the
real circuit that you made.
Ammeter reading of current through combination of both bulbs
Schematic diagram
Real circuit
Lab: Basic Circuits
Updated 09/13/12
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.
Draw both a schematic diagram and a sketch of the real circuit that you made.
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. Draw both a schematic diagram and a sketch of the real
circuit that you made.
Voltmeter reading across bottom bulb only
Schematic diagram
Real circuit
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. Draw both a schematic diagram and a
sketch of the real circuit that you made.
Voltmeter reading across power supply
Schematic diagram
Real circuit
Lab: Basic Circuits
Updated 09/13/12
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.
Question 1 (Instead of summary/conclusion paragraph): 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)
Question 2: What do your observations of current in this lab experiment you about the
relationship of current from the power supply and through the resistors in (a) series
circuits and (b) parallel circuits?
Question 3: What do your observations of voltage in this experiment tell you about the
relationship of voltage provided by the power supply and across the resistors in (a)
series circuits and (b) parallel circuits?
There is no conclusion/summaryparagraph for this lab experiment.
Lab: Basic Circuits
Updated 09/13/12