Download Series and Parallel Circuits 1- (Modified) Student Worksheet

SERIES AND PARALLEL
Pre-Lab Question
What is the difference between voltage and current?
EXPLORATION
Materials
1 yellow multimeter (with leads)
1 battery board
1 alligator lead card
1. Build the circuit shown in the schematic below. The numbers indicate contact points
where you will use the multimeter probes to measure voltage.
Figure 1: Simple Circuit
Measure the voltage across the batteries to establish a benchmark. Although they are
labeled 1.5V, the actual voltage may vary. Actual voltage can be greater than the labeled
level with brand new batteries, and less than the labeled level for batteries that have been
used. It is alright if the actual voltage is not exactly 6V.
To measure the battery combination voltage, be sure to measure from tip-to-toe of the
whole combination.
Actual Voltage of Battery Combination:
.
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2.

First, predict and explain what voltages (V) you will measure between the labeled
points on the circuit. After, close the switch, and measure the voltage of the pairs
on the circuit. Place the probes at contact points shown on the circuit diagram above
and record below.

Second, predict and explain what current (I) you will observe at each labeled point
on the circuit. After, measure the current. To measure, you interrupt the circuit with
the multimeter which means you disconnect the circuit at a point and use the
multimeter to complete the circuit. Measure the current at the test points with the
mA setting and record below.
Contact
Points
Predicted
Measured
Explanation of Prediction
V1-2
V2-3
V1-3
I1
I2
I3
Explain your observations. What determines the voltages? How does the voltage of the
components compare to the batteries voltage? Does current behave differently than voltage
in a circuit and how?
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Series Circuits
3. Build the circuit drawn in the schematic below.

First, predict and explain the voltage for
each pair of test points. After, measure the
voltage and record below.

Second, predict and explain the current for
each test point. After, measure the current
and record.
Figure 2: Series Circuit
Contact
Points
Predicted
Measured
Explanation of Prediction
V1-2
V2-3
V1-3
I1
I2
I3
Explain your observations. How do light bulbs in series share voltage? How does this
compare to the voltage of the battery? Why are they the same or different?
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Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109
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Parallel Circuits
4. Build the circuit shown below.
Figure 3: Parallel Circuit
5.

Predict what the voltage will be across each light bulb when you close the switch.
How does this relate to the total voltage potential of the battery? Discuss with your
group. After recording your prediction, close the switch and measure the voltage
across the two light bulbs. Explain what you observe.

Predict the current at each light bulb and for the whole circuit (test points a, b, and
c). Discuss with your group and explain your prediction. Will current behave the
same as with two bulbs in series?
Contact
Points
Predicted
Measured
Explanation of Prediction
V1-4
V2-3
Ia
Ib
Ic
How do voltage and current behave in a parallel circuit compared to a series circuit?
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Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109
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Challenge Work:
1. Describe a fast way to check if a light bulb circuit is series or parallel.
2. Why do you think most Christmas tree lights are wired in parallel?
4. Is the circuit in Fig. 2 or Fig. 3 more of a power drain on the battery? Explain.
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Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109
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APPLICATION
Materials
1 yellow multimeter (with leads)
1 battery board
1 alligator lead card
1. Build the circuit shown below.
Figure 4: Series and Parallel Circuit
2. Predict the voltage across each bulb and across all the bulbs. Once you’ve recorded your
prediction, measure the voltages. Explain your observations.
Contact
Points
Predicted
Measured
Explanation of Prediction
V1-2
V2-3
V2-4
V1-4
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Copyright 2006, The Regents of the University of Michigan, Ann Arbor, Michigan 48109
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3. Predict the current at each point in the circuit. Once you’ve recorded your prediction,
measure the currents at each test point. Explain your observations.
Contact
Points
Predicted
Measured
Explanation of Prediction
Ia
Ib
Ic
Id
Ie
4. Observe the lights with the switch closed. Are all the bulbs equally bright? Explain what
you observe.
What happened to the current after point 2 when there are two paths it could travel on?
Challenge Work: Predict what will happen when you unscrew light bulbs in the series and
parallel circuit.
Figure 5: Series and Parallel Circuit
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a) Predict what will happen if you unscrew bulb 1. Explain your prediction.
b) Predict what will happen if you unscrew bulb 2. Explain your prediction.
c) Predict what will happen if you unscrew bulb 3. Explain your prediction.
6. Unscrew each bulb and observe what happens. Record your observations. Do they agree
with your predictions? Explain.
a) Bulb 1 unscrewed.
b) Bulb 2 unscrewed.
c) Bulb 3 unscrewed.
Summary:
Final Clean-up
Please disconnect all alligator leads and reattach them to the clip card. Replace all
equipment to the carts.
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