The magnetic flux through the sides of the cone illustrated in figure 16.13 is zero. The magnetic field may be assumed to be approximately normal to the ends of the cone and the magnetic flux into the left end is . The areas of the left and right ends of the cone are and . Converging magnetic field passing through a closed surface. In the lab frame a wire has negative charge with linear charge density moving at speed corresponding to a current as shown in figure 16.14 .
Positive charge is stationary, and has charge density , so the net charge is zero.
A horizontal wire with current viewed in two different reference frames. The Lorentz contraction must be taken into account here. Explain why the net force on a separate charged particle some distance from the wire and stationary in the lab frame is zero in both reference frames. A emitting a real photon, turning into a possibly different real particle B after the emission. If particle A and particle B have the same mass, show that this process is energetically impossible.