Cost: Free, with option to upgrade
Strong Points: Large number of interactive tools, each tool includes additional information on the topic.
Weak Points: None.
The Electronics Engineering Toolkit, stylized as EE Toolkit, is an excellent app for anyone who finds themselves tinkering with electronics, either full time or in an attempt to streamline aspects of other experiments. The free version of the app includes a number of useful tools that allow users to enter and calculate values for a number of different applications. For example, the RC Parallel Circuit tool creates a simple circuit and allows users to input the resistance and current values so that the app can calculate the resulting impedance and cut-off frequencies. For beginners, every tool comes with an information page explaining each variable in the equation and the theory behind the math. In addition to basic tools, the app also includes information about commonly used systems, like Arduino and Raspberry Pi. EE Toolkit also has a Pro version that includes even more equations and tools, but the free version alone is worthwhile for anyone working with electronics.