software - Free circuit simulator for educational purposes

I am looking for a free circuit simulator for educational purposes. My requirements are:

1. Visual ("draw a circuit diagram, click simulate")



2. 
   

   It should contain light bulbs as circuit components such that

   
   

   2.1. They become (visually) brighter if you apply more power

   
   

   2.2. You can change the manufacturer specs for example "3.5V,0,2A"

   
   


3. 
   

   It should contain swiches, npn-transistors, diodes and LEDs as well (the LEDs should react to interactive changes in the simulation)

   
   

Any recommodations for this? It would be nice if the simulator runs under Linux, but that's not a strict requirement.

Answer

I often use the falstad simulator: http://www.falstad.com/circuit

It's a Java applet, so will work on pretty much any operating system. The interface does take a bit of getting used to, and there are problems saving in Linux (it gives you a link to copy and paste, and copy and paste in Java doesn't work too well in Linux).

Other than that it ticks all your boxes. It also has some good sample circuits. A Windows version (circuitmod) is based on this.