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Series Circuits lab
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Or Google: “PhET electricity DC circuit simulation”
Go to: http://phet.colorado.edu/simulations/sims.php?sim=Circuit_Construction_Kit_DC_Only
Background: A series circuit consists of resistors connected with the voltage source in such a way that
the total current must flow through each resistor in turn. The effective resistance of a series circuit is the
sum of the resistances of the individual resistors in the circuit.
Reffective  R1  R2  R3
Throughout this lab, you will apply Ohm’s Law:
V  IR
Above, The circuit diagram for measuring the current and voltage across (a) one resistor, (b) two
resistors, (c) three resistors in series.
Objective: During this investigation you will use Ohm’s Law to determine the effective resistance in
series circuits.
Hints & Tips:
 If you want to delete a component, click on it until it is highlighted in yellow, then hit delete.
 If you want to disconnect something that is connected, right click on the connection point and
select “Split Junction,” they should separate.
 If you want to start all over from scratch, on the right hand side menu, you will see a “clear”
button, select that and it will clear your whole screen.
 Check the voltmeter and ammeter box on the right to see those two devices.
 Check the “schematic” box on the right see the more familiar symbols.
Procedure:
A. One Resistor
1. Drag wires and parts over to create a circuit like (a). Make sure that all of your wires are
connected. Arrange the single resistor in series with the ammeter, open switch, and voltage.
Arrange the voltmeter in parallel with the resistor as shown in the figure. Set the voltage source
at 6 volts by right clicking on the battery and selecting “change voltage.” The battery has a small
internal resistance, right click on the battery, select “Change Internal Resistance” and set it to
“0.00Ω.”
2. Close the switch and read the meters. Open the switch as soon as your readings are complete.
Record your observations in Table 1.
B. Two Resistors
1. Arrange two resistors in series with each other. Change the second resistor so that its different
than the first resistor. Connect the resistors in series with the ammeter, open switch, and voltage
source and in parallel with the voltmeter as in Figure (b). Keep the voltage at 6 volts.
2. Close the switch long enough to read the meters and record your observations in Table 2.
C. Three Resistors
1. Arrange three resistors in series with each other. Change the third resistor so that its different
than the first and second resistors. Connect the resistors in series with the ammeter, open switch,
and voltage source and in parallel with the voltmeter, as in Figure (c). Keep the voltage at
approximately 6 volts.
2. Close the switch long enough to read and record your meter readings in Table 3.
3. With the three resistors still in series, use the voltmeter to find the voltage drop across each
resistor individually. Touch the lead wires of the voltmeter to each end of resistor R1, close the
switch, and read the meter. Record the reading in Part C of the Data and Calculations.
4. Repeat Step #3 for R2 and R3.
5. Find the voltage drop across all three resistors (V1,2,3) by holding one lead of the voltmeter on
one side of R1 and then the other all the way over to the opposite end of R3.
Data and Calculations:
A. One Resistor
1. Given value of R1
2. Measured value of
Table 1: One Resistor
Ammeter Reading (A)
Voltmeter Reading (V)
B. Two Resistors
1. Given value of R1
and R2
2. Calculated equivalent resistance (R1+R2) =
3. Measured value of
Table 2: Two resistors
Ammeter Reading (A)
Requivalent 
V
 _________
I
Voltmeter Reading (V)
V1,2
V1
V2
R1 
V
 _______
I
C. Three Resistors
1. Given value of R1
, R2
and R3
2. Calculated equivalent resistance (R1+R2+R3) =
3. Measured value of
Requivalent 
V
 _________
I
4. Total measured voltage drop across the three resistors (V1+V2+V3) =
Table 3: Three resistors
Ammeter Reading (A)
Voltmeter Reading (V)
V1,2,3
V1
V2
V3
Conclusion Questions:
1. When a circuit consists of resistors in series, how is the effective resistance determined?
2. How are the voltage drops across individual resistances related to the total voltage drop in a series
circuit?
3. What determines the total current in a series circuit?
4. How is Ohm’s Law applied to find the current in a series circuit?
5. A circuit contains four 15 Ω resistors connected in series. What is the effective resistance of the
circuit?
6. The circuit of #5 is placed across a 120 V source.
a. What current will flow in the circuit?
b. What will be the voltage drop across each resistor?
7. A 15 Ω resistor, a 10 Ω resistor and a 5 Ω resistor are connected in series and then placed across a 45
V source.
a. What is the effective resistance of the circuit?
b. What current flows in the circuit?
c. What is the voltage drop across each resistor?