Why are you able to perceive certain electromagnetic fields?

Answer 1

we make use of the observation that a charge (whether magnetic or electric, hence electromagnetic) in a field experiences force. For example, a wire carrying a current builds up a magnetic field around it, and when we place something with a magnetic charge near it (like a compass needle) it pushes the needle to try to line it up with the field (it's definitely not that simple, but it works unless you start doing the calculus and Fourier Transforms). Another neat trick; if we bring a second wire close to the first wire carrying the current, the field pushes on the electrons in the second wire and that tries to make a current in the second wire. This trick works on almost all electromagnetic fields, whether made by current flowing or by something else.