I'm interested in the definition of the voltage drop and the potential difference. In a circuit, between two points 1 and 2 , which equation is true (in general case) :
U= φ1-φ2+ε12 ... (1) - This is defined as the ratio of the net work done by electrostatic and extraneous force ,
U= φ1-φ2 ... (2) - This is defined as the ratio of the work done by electrostatic force.
In some books I found this to be same, but in others I don't , so I'm really confused now if anybody knows please answer :)