This is a simulation of the oscillations of current and voltage in an LRC circuit. Users can control all the input parameters: capacitance, inductance, resistance, and initial voltage. The information shown includes the current through the circuit and voltage across the circuit as a function of time, the relative energy in the capacitor, inductor, and dissipated by the resistor as a function of time, and a shematic of the electric and magnetic fields as a function of time.
Type of Material:
Simulation, Java Applet
Recommended Uses:
Lecture/Demo, In-class Exercises
Technical Requirements:
None noted
Identify Major Learning Goals:
Understand the physics behind electromagnetic oscillations and LRC circuits, including the transfer of energy among the various components of the circuit. Compute the relative phases of the voltages and energies in the circuit.
Target Student Population:
Lower level undergrad
Prerequisite Knowledge or Skills:
Introduction to Electric and Magentic fields, field lines, and capcitors, resistors, and inductors. Introduction to AC circuits might also be useful.
Content Quality
Rating:
Strengths:
An excellent demonstration of an LRC circuit. The inclusion of voltage, current, fields, and energy is outstanding. Students struggling with understanding why circuits oscillate will have a number of pictures to help, including the flow of energy in the fields and the flow of charge from high potential to low.
This applet demonstrates why the voltage and current in an LRC circuit are out of phase.
The ability to change parameters in the problem allows the exploration of different physical regimes including undamped, underdamped, and overdamped oscillations.
Concerns:
The output is shown as a function of time, but the quantitative values of voltage, current, and energy are not given. This might be useful for students.
The voltage graph changes as the initial potential is changed, giving an approximate way to determine voltage. The magnitude of the current graph (the height of the first maximum) is unchanged as the resistance is changed. This is not explained.
When displaying the energy bar graph, showing the oscillation of the energy from electric to magentic, the energy lost in the resistor is labelled as "Internal Energy" rather than energy dissipated.
The author does not indicate specifically that the graph of the potential is the potential across the capacitor.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
This applet covers a topic that is very hard for students to understand. This demonstrates the physics in a way that a static set of pictures can not, and a live demonstration would probably not do as well either. Many aspects of the circuit's physics cannot be seen at all in a live demo. The ability for students to picture the changes in the fields during the oscillation is key to them connecting to the concept of energy conservation.
This applet could easily be used in class to stimulate discussion through an interactive quiz. With a little addition material,
it could also be used as an excellent tutorial.
Concerns:
Because there is no indication of the peak current, there is no way to include the relation between peak voltage and current, and the total impedence of the circuit. Numeric displays for voltage and current would better suit this applet for student assignments.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
The applet is very complete, but also rather straight-forward to operate. There are instructions describing the applet and its operation. The graphics are clean and simple and the controls are well laid out.
This is no way to step through the simulation, but the slower time setting makes stopping the simulation at a specific time possible.
Concerns:
There are only two slow-motion rates at which the simulations are run. Changing the rate of the simulations (1/10th real time or 1/100th real time) also changes the rate at which the switch is thrown to start the oscillation (very slow at 1/100th). Students might find this a little odd.
It is not mentioned in the instructions that one needs to press the enter key to change the values of the parameters in the problem.
Creative Commons:
Search by ISBN?
It looks like you have entered an ISBN number. Would you like to search using what you have
entered as an ISBN number?
Searching for Members?
You entered an email address. Would you like to search for members? Click Yes to continue. If no, materials will be displayed first. You can refine your search with the options on the left of the results page.
Searching for Members?
You entered an email address. Would you like to search for members? Click Yes to continue. If no, materials will be displayed first. You can refine your search with the options on the left of the results page.
