KNOW PHYSICS

MAGNETIC FIELD Today we are going to talk about magnetic fields .   (Suggest more topics in the comment section) The fundamental problem electrodynamics hopes to solve is this(figure): We have some electric charges, q1,q2,q3,...........(call them source charges); what force do they exert on another charge, Q (call it test charge)? The position of the source charges are given (as functions of time); the trajectory of the test particle is to be calculated. Source charge and test charge According to the principle of superposition , it is sufficient to find the force of a single source  charge- the total is then the vector sum of all the individual forces. In the simplest case, electrostatics, the source charge is at rest(though the test charge need not be). We will consider the forces between charges in motion. To give you some sense of what is in store, imagine that I set up the following demonstration:  Two wires hang from the ceiling, a few centimetres apart; when I turn on a current,