P32_013

# P32_013 - 13. An electric ﬁeld with circular ﬁeld lines...

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 13. An electric ﬁeld with circular ﬁeld lines is induced as the magnetic ﬁeld is turned on. Suppose the magnetic ﬁeld increases linearly from zero to B in time t. According to Eq. 31-27, the magnitude of the electric ﬁeld at the orbit is given by E= r 2 dB r = dt 2 B , t where r is the radius of the orbit. The induced electric ﬁeld is tangent to the orbit and changes the speed of the electron, the change in speed being given by ∆v = at = eE t= me e me r 2 B t t= erB . 2m e The average current associated with the circulating electron is i = ev/2πr and the dipole moment is µ = Ai = π r2 ev 2πr = 1 evr . 2 The change in the dipole moment is ∆µ = 1 1 er ∆v = er 2 2 erB 2m e = e2 r 2 B . 4m e ...
View Full Document

Ask a homework question - tutors are online