Answer by Egirl Team
That is a question that can’t be answered in just a few lines. There is quite a lot to it. If you are really interested in the subject you might consider studying online. Here is one resource that might get you started: http://www.electronicstheory.com/COURSES/ELECTRONICS/e101-1.htm
The 2017 EngineerGirl Essay Contest is now open! Students (both boys and girls) in grades 3-12 can submit an essay with their engineering ideas for helping vulnerable and endangered animals.