Determination Of Ohm's Law Using Simulated Circuits
Time: 1-2 class periods (45 minutes each)
Regular High School Physics
A basic electric circuit will be simulated, consisting of a power supply, ammeter, resistors, and wiring. Using this circuit simulation, students will do several sets of measurements and plot those data. First, while keeping the resistance constant, voltage will be varied and its effect on electric current measured with an ammeter. Students should collect enough different voltages so they can sketch a graph. The plots will suggest the relationship between current, voltage and resistance, and can be used to justify Ohm’s law.
Students in many science classes do not get many opportunities to use raw data to make plots, fit data, and extract laws or equations from those data. This activity is meant for students to do just that, much as experimentalists do at the professional level.
Students will learn how to make simple circuits, as well as measure the basic quantities associated with electronics.
Students will also learn a useful relationship in Ohm’s law, and be aware of why it is setup the way it is through direct observation and measurement.
Students should be able to make graphs using Excel or other preferred software, and find best-fit equations to data (such as with Excel).
Students should know what a basic circuit consists of, and should be familiar at least with the concepts of what resistance and currents are, so the understand what they are measuring.
This activity can and should be done before students are exposed to basic circuitry principles; the goal is for students to ‘discover’ Ohm’s law.
An electric circuit can be thought of as a racetrack for electrons. In order for the electrons to move through a material, it must get pushed in one direction. This is done with an electric field, which creates forces on electric charges such as electrons.
How do we set up a voltage difference for a circuit? This is what the battery or power supply does. It is commonly called V in textbooks, but in reality this voltage represents the voltage difference between the two terminals of the battery or power supply. When the electric field goes through the wires and components of an electric circuit, the free electrons present in conducting materials feel a force, which pushes all the free electrons in the same general direction. The problem is, those electrons move short distances before they run into atoms and molecules of the material, and bounce around as if they are in a pinball machine. With all those collisions, energy is lost by the electrons and transferred to the lattice of the material. The vibrational energy of the atoms and molecules is felt by us as heat, and those collisions make it tougher for current to flow – this is electrical resistance, measured in ohms (Ω).
Ohm’s law is the relationship between the voltage difference of the battery, V, and the resulting current. The bigger the voltage difference, the stronger the electric field and therefore the larger flow of electrons per unit time, which is electric current, I. Resistance is the constant of proportionality, and therefore Ohm’s law is V = IR.
Computational Thinking in STEM
- Modeling and Simulation Practices
- Using Computational Models to Find and Test Solutions
- Using Computational Models to Understand a Concept
- Data Practices
- Analyzing Data
- Creating Data