PhET, from the University of Colorado provides FREE top quality interactive simulations on a variety of subjects. Recently PhET released Capacitor Lab Basics, and Circuit Construction Kit: DC virtual lab. If you have not taken a look at PhET interactive simulations it is worth taking time out to do so. You can sort by grade level, topic and yes even device. Their SIMS have been converted to HTML 5 so they can be used on any platform, even the iPad!