I got a question from my exam. We are given the name of three fields; electric field, magnetic field and gravitational field. A charged particle is placed in a field, but no force will act on it if it's stationary or moving in any direction. What field is the particle placed in?
I'm sorry that I have no pic, but please bear with my description.
The circuit diagram is made up of 3 horizontal lines. On the top line, there's battery A, (-) on the left, (+) on the right, and an arrow going to the right (>) to show direction of current.