Physics Lab Report Name:
Lab 8: Resistance in Electric Circuits and Ohm’s Law*
Intro
In this lab we will use the online PhET simulation to construct a simple direct current (DC)
electric circuit of a known resistance, and to measure the magnitudes of voltage and current.
Upon recording the values of current for varying voltages and graphing the experimental data we
will verify if the Ohm’s law is observed on the instances of two different resistors. The graphical
relationship between voltage and current will be used to determine the experimental value of the
resistance. The slope value found graphically will be compared to the corresponding coefficient
in the trendline equation, and to the original resistance value used in circuit set-up.
Materials required
This lab uses Circuit Construction Kit DC (colorado.edu) simulation from PhET Interactive
Simulations at University of Colorado Boulder.
Excel will be used for graphing and analyzing the data. So, make sure that you have
Microsoft Office package installed on your computer. If you do not have it yet, you may
download Microsoft Office for free through your student account on campus.
Learning objectives
Learning the principles of operation of a simple direct current (DC) electric circuit.
Observing the relationship between three major parameters of a circuit, i.e. Voltage,
Current, and Resistance.
Use measurements and graphing the data to determine if the behavior of a resistor in a
circuit obeys the Ohm’s law.
Obtaining the Resistance value graphically.
Learning how to properly plot the experimental data in Excel and present them in the lab
report.
Theory
General Introduction
Ohm’s Law states that a battery with a resistance R subjected to a voltage V will allow a current
I to flow according to the equation:
*
Credits: This activity was adopted and modified from “Investigating Resistance” distance learning lab by Dr. Dirk
Valk.
, V =IR (1)
This implies that a plot of V as a function of I should be a straight line with a slope of R and
intercept of zero. If the voltage and current are measured, the resistance can be found by
V
R= (2)
I
And, if the voltage and resistance are measured, the current can be found by
V
I= (3)
R
Here the variables are V (voltage, in Volts, V), I (current, in Amperes, A), R (resistance, in
Ohms, Ω).
Simulation review and practicing
Open the resistance simulation. Click the “Intro” button when the simulation starts. Take a
moment to familiarize yourself with the environment. While familiarizing yourself with how this
simulation works, note the following features:
The center of the screen is currently empty.
This is where you will construct your
circuit.
On the left side of the screen are circuit
elements that can be dragged into the circuit
construction area.
Practice dragging elements into the circuit
construction area. Notice that each element
has a dashed circle at each end. When you
drag the end of one element onto the end of
another element and release, the two
elements become electrically connected. If
you click the circle of two joined elements, a scissors icon appears. Clicking on the
scissors will break the connection.
In the top right is a holding area for two measurement tools: a voltmeter and an ammeter.
These will be discussed shortly.
In the bottom right of the screen is a button with a circular arrow. This is a reset button
that will erase your current circuit.
Experimental
Building a circuit
Lab 8: Resistance in Electric Circuits and Ohm’s Law*
Intro
In this lab we will use the online PhET simulation to construct a simple direct current (DC)
electric circuit of a known resistance, and to measure the magnitudes of voltage and current.
Upon recording the values of current for varying voltages and graphing the experimental data we
will verify if the Ohm’s law is observed on the instances of two different resistors. The graphical
relationship between voltage and current will be used to determine the experimental value of the
resistance. The slope value found graphically will be compared to the corresponding coefficient
in the trendline equation, and to the original resistance value used in circuit set-up.
Materials required
This lab uses Circuit Construction Kit DC (colorado.edu) simulation from PhET Interactive
Simulations at University of Colorado Boulder.
Excel will be used for graphing and analyzing the data. So, make sure that you have
Microsoft Office package installed on your computer. If you do not have it yet, you may
download Microsoft Office for free through your student account on campus.
Learning objectives
Learning the principles of operation of a simple direct current (DC) electric circuit.
Observing the relationship between three major parameters of a circuit, i.e. Voltage,
Current, and Resistance.
Use measurements and graphing the data to determine if the behavior of a resistor in a
circuit obeys the Ohm’s law.
Obtaining the Resistance value graphically.
Learning how to properly plot the experimental data in Excel and present them in the lab
report.
Theory
General Introduction
Ohm’s Law states that a battery with a resistance R subjected to a voltage V will allow a current
I to flow according to the equation:
*
Credits: This activity was adopted and modified from “Investigating Resistance” distance learning lab by Dr. Dirk
Valk.
, V =IR (1)
This implies that a plot of V as a function of I should be a straight line with a slope of R and
intercept of zero. If the voltage and current are measured, the resistance can be found by
V
R= (2)
I
And, if the voltage and resistance are measured, the current can be found by
V
I= (3)
R
Here the variables are V (voltage, in Volts, V), I (current, in Amperes, A), R (resistance, in
Ohms, Ω).
Simulation review and practicing
Open the resistance simulation. Click the “Intro” button when the simulation starts. Take a
moment to familiarize yourself with the environment. While familiarizing yourself with how this
simulation works, note the following features:
The center of the screen is currently empty.
This is where you will construct your
circuit.
On the left side of the screen are circuit
elements that can be dragged into the circuit
construction area.
Practice dragging elements into the circuit
construction area. Notice that each element
has a dashed circle at each end. When you
drag the end of one element onto the end of
another element and release, the two
elements become electrically connected. If
you click the circle of two joined elements, a scissors icon appears. Clicking on the
scissors will break the connection.
In the top right is a holding area for two measurement tools: a voltmeter and an ammeter.
These will be discussed shortly.
In the bottom right of the screen is a button with a circular arrow. This is a reset button
that will erase your current circuit.
Experimental
Building a circuit
