Lab
Terminal Voltage of a Lantern Battery
Printer Friendly Version
In this lab you will be using resistors, a multimeter, and a circuit board to discover the internal resistance of a 6V lantern battery.
Initially, use the voltmeter to record the emf, in volts, of the battery without any electrical loads.
Next, using collections of 100 and 50ohm resistors, measure and record the voltage lost across 10 different resistance combinations and the current flowing through each one. On your data sheet, neatly draw the circuits for each resistance combination (battery, resistors, voltmeter, ammeter).
Data Table
resistance
voltage
current
trial
(ohms)
(volts)
(amps)
1
2
3
4
5
6
7
8
9
10
Analysis
Once your data has been collected, use EXCEL to graph V vs I.
Theoretically, the voltage lost across each combination of resistors represents the terminal voltage of the battery. This voltage can also be calculated with the equation V =
ε

I
r where r is the internal resistance of your battery.
Rearranging the equation for terminal voltage, V =
ε

I
r, leads to the expression V = 
I
r +
ε
Consequently, your graph of voltage vs current should have a negative slope whose numerical value represents the internal resistance of the battery while the line's yaxis intercept represents the emf of the battery.
What is the filename for your EXCEL graph?
What is the equation of your line?
What is the percent difference between your measured emf (step 1 above) and the yaxis intercept of your line?
Conclusions
Now we will test your equation with a new combination of resistors. Set up an 11
^{th}
combination of resistors and measure the voltage across them and the current following through them.
resistance
voltage
current
trial
(ohms)
(volts)
(amps)
11
Using the equation, V =
ε

I
r, substitute in the internal resistance as the value of the slope of your graph, the emf as the yaxis intercept of your graph, and calculate the voltage that should have theoretically been lost across this final combination of resistors. Give a percent difference between this predicted value and the voltage actually measured.
The theoretical voltage across this new combination should have been
The percent difference between these two voltage values is
Related Documents
Lab:
CP 
Series and Parallel Circuits
Labs 
Parallel and Series Circuits
Labs 
RC Time Constants
Labs 
Resistance and Resistivity
Labs 
Resistance, Gauge, and Resistivity of Copper Wires
Labs 
Telegraph Project
Labs 
Wheatstone Bridge
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: CurrentCarrying Wires
RL 
Meters: CurrentCarrying Coils
RL 
Parallel Plate Capacitors
RL 
RC Time Constants
RL 
Torque on a CurrentCarrying 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 
MultipleBattery Circuits
TB 
Textbook Set #6: Circuits with Multiple Batteries
PhysicsLAB
Copyright © 19972015
Catharine H. Colwell
All rights reserved.
Application Programmer
Mark Acton