ELECTROMOTIVE FORCE AND CIRCUITS
conductor to have a steady current, it must be part of a path that forms a closed It circuit. Here’s why. If you establish an electric field EI inside an with resistivity p that is not part of a complete circuit, a current begins ith current density 1-E/p (Fig. 26-9a). As a result a net positive charge at one end of the conductor, and a net negative charge accumulates end (Fig. 26-9b). These charges themselves produce an electric field E2 in on opposite to EI’ causing the total electric field and hence the current to a very small fraction of a second, enough charge builds up on the ends that the total electric field E – EI + E2 – 0 inside the conductor. Then 11.and the current stops altogether. So there can be no steady motion of charge incomplete circuit.
How to maintain a steady current in a complete circuit, we recall a basic fact potential energy: If a charge q goes around a complete Circuit and returns II) point, the potential energy must be the same at the end of the round trip as g. A described in Section 26-4, there is always a decrease in potential charges move through an ordinary conducting material with resistance. So me part of the circuit in which the potential energy increases. is analogous to an ornamental water fountain that recycles its water. out of openings at the top, cascades down over the terraces and spouts direction of decreasing gravitational potential energy), and collects in , A pump then lifts it back to the top (increasing the potential energy) the pump, the water would just fall to the bottom and stay there.