The computer with a circuit simulator applet is a valuable tool which can be used to model a circuit prior to actually building it. You can easily modify the circuit to determine the effects of the modification without buying new, expensive circuit parts. Circuit simulators are invaluable in saving time and money because they allow the circuit designer to narrow his choices to his optimum preference.
- Acircuit containing a battery source, switch, resistor, capacitor, and inductor may appear.
- Modify the circuit to contain one battery, a switch, and one resistor. (Right-click over a circuit component and choose delete, create resistors by right-clicking and choosing “Add Resistor”, then drag a resistor. You can also add wires to replace deleted components in the same manner).
- Edit the value of the resistor to 1 K Ohms. Edit the battery voltage to 9 volts DC. You should have a circuit with a battery, switch, and resistor, all connected by wires.
- Leave the switch Open. How much current flows? (none)
- Close the switch. How much current flows? (9 mA)
- What do the moving dots represent? (Answer: Current flow, or flow of electrons)
- How much power is dissipated? Is it enough to burn you? Let us calculate the power. Power P equals voltage V times current I.
(P=V*I = 9*0.009 = 81 mW. Might get warm but probably will not burn you!
- Diodes, another circuit component, will conduct electricity in only one direction, much like a valve in a water pipe.
- Now, open the switch in the circuit and remove the resistor. Replace the resistor with a light emitting diode (LED). The arrow must point in the same direction that the current is flowing.
- Close the switch. How much current flows? (Answer: large amount of current, should be off the chart! enough to fry the diode!)
- Open the switch.
- Delete a wire between the switch and the LED or between the LED and the battery and add a resistor.
- Change the value to 1K ohms.
- Close the switch. Does the LED (diode) come On? Notice that the current is now limited to a small value with the use of the resistor.
- Use several different values for the resistor and notice the changes in current and in the brightness of the LED.
- Notice that as the resistance increases, the current through the circuit decreases. This is a principle of Ohm's Law.
Virtual models such as this have many benefits: they save time, money/resources, and are easily applicable to real-life scenarios.
Now, let's proceed to building the circuit that we just modeled using real circuit components.