Download Voltage, Resistance, and Current Lab Instructions

ELE 100 Introduction to Engineering
Voltage, Resistance, and Current Laboratory Guidelines
The objectives of the laboratory are:
 Become familiar with the instrumentation
 Measure resistance, voltage, and current
 Draw circuit diagrams
 Determine the relationship between voltage, resistance and current for a single
resistance and for multiple resistances in series
 Learn something about a battery as a voltage source.
A. Relationship among voltage, resistance, and current
Using the ohmmeter, measure and record the resistances of the three resistors you have
been given.
Construct a circuit as shown in the diagram and the photograph. Use a 10 ohm resistor.
Set the power supply voltage to 0 volts. Set the current coarse knob to ¾ i.e. “east”.
Ammeter
Power
Supply
R
Voltmeter
For the following supply voltages, measure and record: power supply voltage, current
through the resistor, and voltage across the resistor: 0.0, 2.0, 3.0, and 4.0 volts.
Disconnect the supply from the circuit.
What is the relationship among the current through the resistor, the resistance, and the
voltage across the resistor?
Repeat for the 5 ohm resistance and the 2 ohm resistance. When 4 volts is applied to the 2
ohm resistance, carefully feel the resistors with your fingers. What do you observe?
Each person, using a spreadsheet, plot for one resistance the relationship between the
voltage across the resistance (on the vertical axis) and the current through the resistance
(on the horizontal axis). What is the shape of the line? What is the equation describing
the line? What is the slope of the line? Repeat for the remaining two resistances. Plot all
three curves on the same set of axes. Everyone on the team should have an electronic
copy of the spreadsheets.
B. Resistance, current and voltage in a single loop with two resistors
Using the 2 ohm resistance and the 5 ohm resistance in series construct a circuit as shown
in the diagram, but do not yet connect the positive terminal of the power supply to the
circuit.
Ammeter
Supply
2 ohms
5 ohms
Voltmeter
Set the voltage to 4.0 volts. Connect the supply to the circuit.
Measure and record: supply voltage, current, and voltage across the ammeter and across
each resistor. The diagram shows voltage being measured across the 5 ohm resistor.
What is the relationship between the voltage across each resistor and the current through
that resistor? How do the individually measured voltages relate to the supply voltage?
Calculate the resistance of the ammeter.
C. Battery Supply and Resistances
This experiment repeats the experiment in Part A but uses an AAA battery as the power
supply, and we will use Ohm’s Law to calculate the current. Using the 10 ohm resistor,
construct the circuit but do not yet connect the red wire from the battery to the
resistor. Draw the circuit diagram.
Measure the battery voltage. Connect the red wire to the resistor, quickly measure the
voltage across the resistor, then disconnect the red wire from the resistor. Repeat using
the 5 ohm and the 2 ohm resistors. Why is the voltage less when the battery is connected
to the resistor?
Following the lecture, describe the principles you have learned in this class session.
Include any formulas and calculations. Create an electronic file that includes your
description and the spreadsheets. Later, this file will be uploaded to the server and
become part of your electronic course portfolio.