13.6: Perform an Activity
pg. 562
Key Concepts:
1. Circuits are a part of electrical technology. They can be connected in
series and in parallel.
2. Current is the rate of electron flow.
3. Potential difference is a measure of the difference in electric potential
energy per unit of charge between two points.
Measuring Voltage and Current in Circuits
Purpose:
To measure electric and potential differences in DC circuits using meters.
Hypothesis:
Equipment and Materials:
- Variable DC power supply
- switch
- ammeter
- 2 lamps
- 6 to 8 conducting wires
- voltmeter
Simulation web site:
https://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
Procedures:
Part A: Measuring Quantities in Series Circuit
1. Obtain the required materials from your teacher. Design a table to
record your observations.
2. Turn off the power supply. Connect the circuit shown in Figure 1.
Figure 1
3. Make sure the power supply is at its lowest setting as instructed by
your teacher (9.0 V). Close the switch.
4. Slowly increase the power until the lamps turn on. Once they are lit,
leave the power supply at this setting.
5. Use an ammeter to measure the current going into the first lamp
(Figure 2). Recorded the measurement in your table 1. Repeat this
step for the second lamp.
6. Use a voltmeter to measure the potential difference across the first
lamp. Record the measurement in your table 1. Repeat this step for the
second lamp and for the power supply.
7. Slightly increase the setting on the power supply (12.0 V). Repeat
steps 5 – 6. Note the brightness of the lamps. Record current and
potential difference in table 2.
8. Turn off the power supply and disconnect your circuit.
Part B: Measuring Quantities in a Parallel Circuit
1. Construct a table to record your observations. Turn off the power
supply. Connect the circuit shown in Figure 3.
Figure 3
2. Make sure the power supply is at its lowest setting (9.0 V). Close the
switch.
3. Slowly turn up the power until the lamps turn on. Once they are lit,
leave the power supply at this setting.
4. Remove one of the lamps from the socket. Use an ammeter to
measure the current going through the lamp that is still lit. Record the
measurement in table 3.
5. Use an ammeter to measure the current going through the unlit lamp.
Record the measurement in your table.
6. Use the voltmeter to measure the potential difference across the lamp
that is still lit (Figure 4). Record the measurement in your table.
Repeat this for the unlit lamp.
7. Repeat steps 4 – 6, but do not remove the second lamp from the
circuit. Record your data in table 4.
8. Turn off the power supply and disconnect your circuit.
Observation:
Table 1: Series Circuit 1
Power source 9.0 V
Lamp #1
Lamp #2
Table 2: Series Circuit 2
Power source 12.0 V
Lamp #1
Lamp #2
Voltage (V)
Current (A)
Voltage (V)
Current (A)
Table 3: Parallel Circuit 1
Power source 9.0 V
Lamp #1
Lamp #2 (unlit)
Table 4: Parallel Circuit 2
Power source 9.0 V
Lamp #1
Lamp #2
Voltage (V)
Current (A)
Voltage (V)
Current (A)
Analyze and Evaluate:
a) Write a concluding statement about the electric current in a series
circuit. [t/i, com]
b) Write a concluding statement about the electric current in a parallel
circuit [t/i, com]
c) How does the potential difference affect the brightness of a light bulb?
[t/i]
d) On step 5 of part ‘B’, you were asked to measure the current going
through the unlit lamp. Refer to your table for this data. Did your
results for this measurement surprise you? Explain. [t/i]
Apply and Extend:
e) It is easy to test whether or not a lamp is working. However, there are
some devices in electric circuits that do not move, make sounds, or
produce light. Each of these devices does perform a specific task.
How would you apply the procedure in Part B to a malfunctioning
circuit that did not make sounds or produce light? [t/i]
Conclusion: