Lab
Wheatstone Bridge
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The
purpose
of this lab is to use a Wheatstone Bridge to investigate the resistance of resistors wired in series and in parallel.
Equipment
slide-wire Wheatstone bridge
3 100-W resistors
1 500-W resistor (to be used as R
_{1}
)
2 50-W resistors
2 uncovered alligator clips
1 galvanometer
1 DC 6V power supply
leads and test probe
Procedure
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.
Combinations
Data Table:
Equilibrium
Position
Left Length
R
_{2}
Right Length
R
_{3}
Experimental
R
_{x}
Theoretical
R
_{x}
Percent
Error
A
B
C
D
E
F
Conclusions:
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?"
Related Documents
Lab:
CP -
Series and Parallel Circuits
Labs -
Parallel and Series Circuits
Labs -
RC Time Constants
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Resistance, Gauge, and Resistivity of Copper Wires
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Resource Lesson:
RL -
A Comparison of RC and RL Circuits
RL -
Ampere's Law
RL -
An Introduction to DC Circuits
RL -
Capacitors and Dielectrics
RL -
Dielectrics: Beyond the Fundamentals
RL -
Electricity and Magnetism Background
RL -
Filaments
RL -
Kirchhoff's Laws: Analyzing Circuits with Two or More Batteries
RL -
Kirchhoff's Laws: Analyzing DC Circuits with Capacitors
RL -
Magnetic Field Along the Axis of a Current Loop
RL -
Magnetism: Current-Carrying Wires
RL -
Meters: Current-Carrying Coils
RL -
Parallel Plate Capacitors
RL -
RC Time Constants
RL -
Torque on a Current-Carrying Loop
Worksheet:
APP -
The Circuit Rider
APP -
The Cycle Shop
CP -
DC Currents
CP -
Electric Power
CP -
Ohm's Law
CP -
Parallel Circuits
CP -
Power Production
CP -
Power Transmission
CP -
RIVP Charts #1
CP -
RIVP Charts #2
CP -
Series Circuits
NT -
Brightness
NT -
Light and Heat
NT -
Parallel Circuit
NT -
Series Circuits
NT -
Shock!
WS -
Capacitors - Connected/Disconnected Batteries
WS -
Combinations of Capacitors
WS -
Introduction to R | I | V | P Charts
WS -
Kirchhoff's Laws: DC Circuits with Capacitors
WS -
Kirchhoff's Laws: Sample Circuit
WS -
Resistance, Wattage, and Brightness
TB -
34A: Electric Current
TB -
35A: Series and Parallel
TB -
Advanced Capacitors
TB -
Basic Capacitors
TB -
Basic DC Circuits
TB -
Multiple-Battery Circuits
TB -
Textbook Set #6: Circuits with Multiple Batteries
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