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. See more about the contest! Also, come see us at this year's Invent It Build It Expo on October 29th in Philadelphia!