Physlet Physics by Christian and Belloni: Illustration 31.1

Illustration 31.1: Circuit Builder

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Circuit Builder can be used to build and analyze DC and AC electrical circuits. Circuit Builder was written by Toon Van Hoecke at the Universiteit Gent.

If you want to change the size of the circuit grid, change the number of rows and columns and then press the "Set grid" button. Be aware that all components on the screen will disappear. The "Show ->" button is used to visualize arrows representing the chosen current direction. New components for the circuit are entered by a drag-and-drop method. Press the button of the component you want to add, hold the mouse button, and release it on the position where you want to put this component. Once you drop the component on the circuit grid, a box will appear that will allow you to change the parameters of the component. Any horizontal or vertical position between two black dots can be taken.

The following direction-independent (no positive or negative side) components can be added:

Resistor: value entered in ohms.
Capacitor: value entered in farads.
Inductor: value entered in henries.
Lightbulb: characterized by voltage (in V) and power (in W). The color varies from black (no current) to white (maximum current).
Wire: used to close connections.
Switch: can be opened and closed.

Some components are polarized and thus have a positive and a negative side. The direction can be set by choosing "+ down/right" or "+ up/left" on the Direction list item. The following direction-dependent components can be added:

Battery: value entered in V.
General Voltage source: Its function prescription (in V) can be entered next to the source button and its default value is sin(t*2*pi*f). Use t as the time variable, f as the frequency variable, and "p" as the period variable.
Current Source: value entered in A.
Oscilloscope: simulation of a one-beam oscilloscope. A window with the view on the particular oscilloscope can be opened by selecting the "Display Oscilloscope" option on the popup menu that appears when you click the right mouse button on the oscilloscope icon in the circuit.
Voltmeter: simulation of a digital voltmeter. Use the "Display Voltmeter" option on the right-mouse-button popup menu.
Ampèremeter: simulation of a digital ampèremeter. Use the "Display Ampèremeter" option on the right-mouse-button popup menu.

The "Calculate" button is used for recalculating data. A number of Step # data points is calculated iteratively with a step size of Step (s). The step size is entered in seconds (default is 1e-6 s).

The "Start/Pause" button and the "Reset" button are used when a real-time clock is necessary. This is in situations with slow varying sources or the displaying of voltage or current graphs. The number of frames per second is 1/(10*step size). This is in real time up to step sizes of 0.01 s.

You can move a component to another position by using drag and drop. Other actions are available as options on the popup menu that appears when you click the right mouse button on the component's icon in the circuit. The possible options are only enabled if they are relevant:

Delete Component: deletes the selected component.
Change Value: changes the value or function of the selected component.
Display Value Knob: pops up a little window with a scroll bar to change the value dynamically (linear steps or logarithmic steps).
Display Frequency Knob: pops up a little window with a scroll bar to change the frequency of an AC source dynamically. This only works when the f variable is present in the function prescription.
Show/Hide Value or Function: concerns the display on the circuit grid.
Set Label: gives a name to the selected component.
Display Oscilloscope: pops up the oscilloscope window of the selected oscilloscope.
Display Voltmeter: pops up the digital voltmeter window of the selected voltmeter. The mode can be switched between DC and AC (rms value).
Display Ampèremeter: pops up the digital ampèremeter window of the selected ampèremeter. The mode can be switched between DC and AC (rms value).
Display Voltage Graph: pops up a voltage graph for the selected component (use "Start" button).
Display Current Graph: pops up a voltage graph for the selected component (use "Start" button).
Change Switch: changes the status of the selected switch, open or closed.
Change Polarity: switches the + and - signs of components that are polarized.

Illustration authored by Toon Van Hoecke.
Applet authored by Toon Van Hoecke.
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