Physics Experiment
Series & Parallel Resistances - Genecon Version
Purpose:
- to determine the equivalent resistance of two resistors in
series
- to determine the equivalent resistance of two resistors in
parallel
- to practice constructing electric circuits
- to practice using an ammeter and a voltmeter
Discussion:
In this lab, you will construct simple circuits using combinations
of known resistances in series and in parallel. Then you will use an
ammeter to measure the current, I, through the resistor arrangement
and a voltmeter to measure the potential difference, V, across it.
With this data, you determine the equivalent resistance of the
arrangement using Ohm's Law (V = IR) and compare this to the separate
resistor values.
Equipment:
Genecontm generator |
5 connecting wires
|
2 - 3 ,
5 Watt resistors
|
2 - 5 ,
5 Watt resistors
|
2 10 ,
5 Watt resistors
|
2 - 25 ,
5 Watt resistors
|
0-1 A ammeter
|
0-3 V voltmeter
|
|
Procedure:
Resistors
in Series:
- Choose 2 resistors R1 and R2, and enter their values in the
data table.
- Predict the equivalent resistance of these two resistors in
series, and enter your prediction in the data table.
- Wire this series resistor combination into the circuit shown
below.
Here's how:
- Construct the same circuit (one resistor) that you built for the Ohm's Law experiment.
- Clip one end of a new wire to one end of your second resistor.
- Clip the other end of this new wire to one end of the resistor you placed in the circuit.
- Move any wires that were on the resistor in the circuit to the free end of the second resistor.
- You should be able to trace a conducting path from one clip of the Genecontm generator, through one resistor then through the other, through the ammeter, and back to the generator.
- Check to be sure that the voltmeter is attached across both resistors.
- Record the current through the resistor combination and the
voltage across it in the data table.
Resistors
in Parallel:
- Choose 2 resistors R1 and R2 of equal value, and
enter their values in the data table.
- Predict the equivalent resistance of these two resistors in
parallel, and enter your prediction in the data table.
- Wire this parallel resistor combination into the circuit shown
below. Here's how:
- Remove the second series resistor and restore the circuit to the one you built in the Ohm's Law experiment.
- Clip a new wire to each end of the second parallel resistor.
- Clip the other end of each new wire to an end of the original resistor in the circuit.
- Record the current through the resistor combination and the
voltage across it in the data table.
Results:
- For each trial, calculate the equivalent resistance of the
resistor combination based on the measured current and voltage
using Ohm's Law. Record your results in your data table, and be
sure to show a sample calculation.
Conclusions:
- How do you find the equivalent resistance for two resistors in
series?
- How do you find the equivalent resistance for two resistors in
parallel?
last update April 12, 2007 by JL
Stanbrough