Printer Friendly Version
of this lab is to use a Wheatstone Bridge to investigate the resistance of resistors wired in series and in parallel.
slide-wire Wheatstone bridge
3 100-W resistors
1 500-W resistor (to be used as R
2 50-W resistors
2 uncovered alligator clips
1 DC 6V power supply
leads and test probe
Initially, set-up your circuit as shown in the diagram below. Be careful to not accidentally release the slide wire - it is very difficult to reconnect! Since your leads have alligator clips, merely clamp them over the screw heads.
Do NOT turn on the power supply until Mrs. Colwell has "okayed" your equipment. PLEASE, handle the resistors carefully - do not twist their leads, they break off VERY easily. The alligator clips are to help you "connect" the resistors into each of the combinations listed in the data chart on page 2.
Kirchoff's Loop Rule
states that the sum of the voltage changes around a CLOSED loop in a circuit equals zero. Using this rule generates the following equations which when solved simultaneously can be used to determine an experimental value for the unknown resistance.
1a. Which combination (A through F) represented the largest resistance?
1b. Which combination (A through F) represented the smallest resistance?
2. Does combining resistors in series increase or decrease their effective resistance?
3. Does combining resistors in parallel increase or decrease their effective resistance?
4. In general, were your percent errors larger or smaller when the null point was located in the middle third (35 cm - 65 cm) of the slide wire?
5. Why do you think this result was true?
6. Why was it important to only "tap" the test probe to the slide wire and not "hold it down" for extended periods of time?
7. Why is this technique of measurement called a "null method?"
Series and Parallel Circuits
Parallel and Series Circuits
RC Time Constants
Resistance and Resistivity
Resistance, Gauge, and Resistivity of Copper Wires
Terminal Voltage of a Lantern Battery
A Comparison of RC and RL Circuits
An Introduction to DC Circuits
Capacitors and Dielectrics
Dielectrics: Beyond the Fundamentals
Electricity and Magnetism Background
Kirchhoff's Laws: Analyzing Circuits with Two or More Batteries
Kirchhoff's Laws: Analyzing DC Circuits with Capacitors
Magnetic Field Along the Axis of a Current Loop
Magnetism: Current-Carrying Wires
Meters: Current-Carrying Coils
Parallel Plate Capacitors
RC Time Constants
Torque on a Current-Carrying Loop
The Circuit Rider
The Cycle Shop
RIVP Charts #1
RIVP Charts #2
Light and Heat
Capacitors - Connected/Disconnected Batteries
Combinations of Capacitors
Introduction to R | I | V | P Charts
Kirchhoff's Laws: DC Circuits with Capacitors
Kirchhoff's Laws: Sample Circuit
Resistance, Wattage, and Brightness
34A: Electric Current
35A: Series and Parallel
Basic DC Circuits
Textbook Set #6: Circuits with Multiple Batteries
Copyright © 1997-2017
Catharine H. Colwell
All rights reserved.