Circuit Construction Kit 

Circuit Construction Kit (DC only) is an electric simulation model. It allows you to create circuits on your screen. You can add wires, resistors, batteries, light bulbs, and switches. It allows you to make very basic circuits. Bear in mind that this is a simulation that illustrates some of the principles of basic direct current circuitry. I don't think the tool is suitable for circuit testing. It was more likely intended to teach the basics of making circuits.

To create a working circuit, you need to add a power source. In this case you can drag a battery to the screen. Then, you connect it to some wiring to both negative and positive ends. The wires will hopefully go to a light bulb. If you don't add resistors to the circuit, you will fry the light bulb. When the circuit is completed, the light bulb will light up. You can also add a switch to control the circuit. At the top of the screen there is a button Grab Bag. Inside this imaginary bag, there are a few objects that you can use with your circuit: a dog, a hand, a penny, a pencil, etc.

There are also a few tools that you can use to measure your circuit current. There is a voltmeter, an ammeter, and a non-contact ammeter. Those can be added to the screen, and you need to drag and drop them to contact points for them to work.

In short, this application proves to be a very fun way of learning the basics of circuitry making.