Having trouble visualizing how current flows in a circuit? A great way to get a feel for how a circuit works is to use a circuit simulator, however most are either expensive or require a fair bit of electronics knowledge to use. If you are just wondering how a common circuit works, then you might want to check out this Java-based Circuit Simulator. It’s got a large library of parts and pre-built circuits that you can simulate and modify to get the feel for how they work. Though it may not be a full substitute for more traditional full-featured simulators such as LTSpice or Qucs, it is free, runs in your browser, and is actually pretty fun to play around with. [via Stephen Hobley]