Physics 2 Lab : Series and Parallel Resistor Circuits (DCP, CE)
Write a lab report including the following:
Test Ohm’s Law for Series and Parallel circuits by testing the voltage across and currents through each resistor in a particular circuit and for the total circuit as well. You will be testing 4 different circuits involving three different resistors.
Materials : Ohmmeter, Ammeter, Voltmeter, power supply, bread board, connecting leads
Procedure : Use the attached procedure. Note the uncertainties in your various meters when you
take your particular data readings; record these in your data chart. You will be
incorporating them into your data analysis. Take several readings each time and
make sure to include these in your report, as well as the average reading you utilize
for subsequent calculations.
Data tables : Create tables for each circuit showing individual resistances, voltages, currents, and
totals (equivalents) for each. Include units, labels, and uncertainties. Consult your
teacher and old lab/worksheet packets showing what is required for obtaining a
maximum score for the IB DCP criteria.
Calculations : Show all your details (on getting averages, or what formulas you used). Units are
crucial; using uncertainties, as well. The rule of thumb for most of these
calculations is to calculate the +/- percentage each uncertainty is and to add these
%’s up for each calculation.
Conclusion Discuss for each circuit the relationship between your variables. Does your
& Evaluation data suggest the different ways that voltage, current, and/or resistance combine or
split in any particular situation? Discuss possible errors or uncertainties and any
impacts they had on your data and results; explain what you could do to improve
your lab procedure or results in a meaningful way.
Note Well : The lab will be graded using IB lab criteria. Students can corroborate on
experimental data gathering during lab time due to the limited amount of working
equipment amongst members of their lab group. The final written report with
analysis, calculations, and conclusions must be each individual’s own work.

In this lab you will study the properties of simple series and parallel circuits.
You will be using several meters in this lab. As a general rule for meters, whenever you are unsure of the size of the value of what you are reading, start with the largest scale available and work down to the scale that seems appropriate. (Needless to say, using the meters properly also involves the proper meters… ammeters for current, and voltmeters for volts…) This prevents damaging the meters (“pegging” the older analog types, or blowing fuses on the newer digital ones). Check that the meters are used correctly with respect to polarity
( + or ).
You have to be especially careful with the ammeter. The meter has a very low resistance and it is easily damaged if used incorrectly. ALWAYS place the ammeter in SERIES ("in line") with the points being measured. This means you need to disconnect the circuit at that place and wire in the meter. NEVER use the ammeter in PARALLEL and never use the meter in a circuit with no resistor. The Voltmeter is ALWAYS place across (in PARALLEL) with what is being measured.
The ohmmeter is used ONLY when there is no current through the circuit. Remember to always “zero” the meter before using and whenever changing scales. Close the switch ONLY when adjusting the power or taking voltage and current readings.
Equipment : Multimeter, (or ammeters and voltmeters), variable power source, circuit board, wires
Procedure:
A) Preliminary data: record the color codes of your 3 resistors . Check the color code sheets available to get the theoretical value. Record this in your data . Call the lowest resistance R
1
, the next highest
R
2
, and largest R
3
. Check the values with the ohmmeter if available; record these values as well. ( You will use the actual values later in processing your data).
Resistor Colors Theoretical values (ohms)
+/- tolerance
R
1
R
2
R
3
Ohmmeter reading
(ohms)
B) Series Circuit
1) Connect the resistors as shown in the diagram. (DO NOT connect the power source in yet) Measure the resistance from A to B using the ohmmeter in the multimeter. Record this on your data sheet next to your nicely reproduced circuit diagram. (be sure to include a schematic sketch in your data section.)
A B
R1 R2 R3
2) Connect the resistors into the following circuit with the power source and switch. Set the voltage of the power supply to 5 volts. This must be done with the switch closed. Measure the terminal voltage V,
V
1
(the potential difference across R
1
), V
2
(the potential difference across R
2
), and V
3
(ditto) with the voltmeter (or the multimeter on the volts setting). Measure the current I (total current going through), and I
1
(the current in R
1
), I
2
(likewise), and I
3
with an ammeter (or the multimeter on the ammeter settings). Record all of this in your data section.
Resistor Voltage
(Volts)
Current
(milliamps)
Current
(amps)
Whole circuit
R
1
R
2
R
3

C) Parallel Circuit
1) Connect the resistors as shown in the diagram. (DO NOT connect the power source
in yet) Measure the resistance from A to B using the ohmmeter in the multimeter.
Record this on your data sheet next to your nicely reproduced circuit diagram.
A B
R1
R2
R3
Resistor
2) Connect the resistors to the power source. Measure and record I, I
1
, I
2
, I
3
, V, V
1
, V
2
,
and V
3
in your data section.
Voltage
(Volts)
Current
(milliamps)
Current
(amps)
Whole circuit
R
1
R
2
R
3
D) Series- Parallel Circuit I
1) Connect the resistors as shown in the diagram. (DO NOT connect the power source
in yet) Measure the resistance from A to B using the ohmmeter in the multimeter.
Record this on your data sheet next to your nicely reproduced circuit diagram.
R1
A
R2
R3 B
Resistor
2) Connect the resistors to the power source. Measure and record I, I
1
, I
2
, I
3
, V, V
1
, V
2
,
and V
3
in your data section.
Voltage
(Volts)
Current
(milliamps)
Current
(amps)
Whole circuit
R
1
R
2
R
3
E) Series- Parallel Circuit II
1) Connect the resistors as shown in the diagram. (DO NOT connect the power source
in yet) Measure the resistance from A to B using the ohmmeter in the multimeter.
Record this on your data sheet next to your nicely reproduced circuit diagram.
R1 R2
A R3 B
Resistor
2) Connect the resistors to the power source. Measure and record I, I
1
, I
2
, I
3
, V, V
1
, V
2
,
and V
3
in your data section.
Voltage
(Volts)
Current
(milliamps)
Current
(amps)
Whole circuit
R
1
R
2
R
3

Calculations and processing your data: Show the setups and calculations for each step. Include labels and units to somehow indicate what you are calculating.
Series Circuit:
1) Calculate the equivalent resistance of your circuit, R eq
. What is the % difference between this theoretical value and the one obtained in lab?
2) Calculate I (the total current) using Ohm’s Law, V and R eq
( the equivalent resistance, your answer to #1).
What is the % difference between this theoretical value and the one obtained in lab?
3) Calculate V
1
, V
2
, V
3
using your theoretical I (what you just calculated) and the actual resistances of each resistor as measured in your preliminary data. Compare these to your experimental values measured in lab.
4) What is the relationship between the voltage drop at a resistor and the value of the resistor?
5) What statement can be made about the current through each resistor in a series circuit?
Parallel Circuit:
1) Calculate the equivalent resistance of your circuit, R eq
. What is the % difference between this theoretical value and the one obtained in lab?
2) Calculate I (the total current) using Ohm’s Law, V and R eq
( the equivalent
resistance, your answer to #1).
What is the % difference between this theoretical
value and the one obtained in lab?
3) Calculate I
1
, I
2
, I
3
using your measured voltage and the actual resistance of each resistor as measured in your preliminary data. Compare these to your experimental values measured in lab.
4) What is the relationship between the current through a branch and the value of the resistor in the branch of a parallel circuit?
5) What statement can be made about the voltage across each branch in a parallel circuit?
Series - Parallel Circuit I:
1) Calculate the equivalent resistance of your circuit, R eq
. What is the % difference between this theoretical value and the one obtained in lab?
2) Using your experimental data, calculate the % difference between I
1
and the sum of I
2
+ I
3
.
3) Using your experimental data, calculate the % difference between V and the sum of V
1
+ V
2
.
Series - Parallel Circuit II:
1) Calculate the equivalent resistance of your circuit, R eq
. What is the % difference between this theoretical value and the one obtained in lab?
2) What is the % difference between the sum of the voltages across the top branch and the voltage across the bottom branch?
3) What is the % difference between the sum of the current in the top branch and the current in the bottom branch as opposed to the total current measured?
General Questions:
1) Suppose the resistors in each of the 4 circuits (Series, Parallel, Series-Parallel 1 & Series-
parallel II) were light bulbs. What would happen to the light bulbs if a) R
2
burned out in the Series circuit? b) R
1 burned out in the Parallel circuit? c) R
3
also burned out in the Parallel circuit? d) R
3
burned out in the Series-Parallel I circuit? e) R
3
burned out in the Series-Parallel II circuit?
2) Given the three resistors, there are many possible different resistance values which could be obtained using one or more resistors you used in the lab. List and sketch the 17 possible combinations (such as R
1 alone, R
2
alone, R
1
and R
2
in series, etc.) Determine the total resistance of each setup (using the resistances measured in your lab).