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NOTE This session was thrown together to replace the GNUCAP session due to problems with getting GCompris installed. I got a bit carried away with Ohms law and prefixes, lost the class, and went to plan B: bring up interesting circuits (high-voltage transmission, spark-gap, 2-way light switch) and talk about them.

Click to open the circuit simulator (if that fails, try the local copy).

Note that your browser must have JavaScript and Java enabled.


You should see the opening screen of the Java-based circuit simulator:

Screenshot-Circuit Simulator v1.5n.png

Ohm's Law

This circuit is a little advanced, so let's start with something simpler.

Open the Circuits menu, select the Basics sub-menu and the Ohm's Law circuit:

Screenshot-Circuit Simulator v1.5n-1.png

You should see a simple circuit demonstrasting one of the fundamental laws of Electronics:

Screenshot-Circuit Simulator v1.5n-2.png

[Ohm's Law], V = I x R

V stands for the voltage across a component. Think of it like the pressure in a water-hose

I stands for the electric current through a comonent. It's like the flow-rate of water through a hose.

R stands for the resistance of a component, something that impedes flow. Think of a kink in a water-hose slowing down the flow.

Hover the mouse over the left-hand resistor and note the details:

I 10mA
Vd 5V
R 500 Ohm
P 50 mW

Check the math (remember that m is a [prefix] for milli meaning one-thousanths):

I x R = 50mA * 100 Ohm
      = (50 / 1000) * 100 * A * Ohm
      = 5V

Double-check with the right-hand resistor (remember that k is a [prefix] for kilo meaning thousand).

Now adjust the Voltage across the resistors with the slider-bar:

Screenshot-Circuit Simulator v1.5n-9.png

You can also adjust the value of the resistors. Right-click on one of them and select Edit:

Screenshot-Circuit Simulator v1.5n-6.png

Now enter a new value and press OK:

Screenshot-Circuit Simulator v1.5n-7.png

And check the results again:

Screenshot-Circuit Simulator v1.5n-8.png

Joule's first Law

Note the P in the last row. That stands for Power:

[Joule's first Law], P = V x I

P stands for the Power dissipated by the component.

Circuits -> Other Passive Circuits -> Transformers -> Long-Distance Power Transmission Screenshot-Circuit Simulator v1.5n-3.png Circuits -> Transistors -> Switch Screenshot-Circuit Simulator v1.5n-4.png Screenshot-Circuit Simulator v1.5n-5.png