63. (a) We are given ~ B = B x ˆ i=6 × 10 − 5 ˆ iT ,sothat ~v × ~ B = − v y B x ˆ kwhere v y =4 × 10 4 m/s. We note that the magnetic force on the electron is ( − e )( − v y B x ˆ k) and therefore points in the + ˆ k direction, at the instant the electron enters the Feld-Flled region. In these terms, Eq. 29-16 becomes r = m e v y eB x =0 . 0038 m . (b) One revolution takes T =2 πr/v y =0 . 60 µ s, and during that time the “drift” of the electron in the x direction (which is the pitch of the helix) is ∆ x = v x T =0 .
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.