12. (a) The force due to the electric field (FqE=GG) is distinguished from that associated with the magnetic field (vB=×GGG) in that the latter vanishes at the speed is zero and the former is independent of speed. The graph (Fig.28-36) shows that the force (y-component) is negative at v= 0 (specifically, its value is –2.0×10–19 N there) which (because q = –e) implies that the electric field points in the +ydirection. Its magnitude is 19net,192.0 10N1.25 N/C 1.25 V/m||1.6 10 CyFEq−−×====×. (b) We are told that the xand zcomponents of the force remain zero throughout the motion, implying that the electron continues to move along the xaxis, even though magnetic forces generally cause the paths of charged particles to curve (Fig. 28-11).
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This note was uploaded on 06/03/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.