2 An electron is accelerated through $V = 2400\U{V}$ from rest and then
3 enters a uniform $B = 1.70\U{T}$ magnetic field. What are \Part{a}
4 the maximum and \Part{b} the minimum values of the magnetic force this
6 \end{problem*} % problem 22.4
9 First we compute the electron's velocity $v$ upon entering the field.
12 qV &= \frac{1}{2} m v^2 \\
13 v &= \sqrt{\frac{2qV}{m}}
17 The magnetic force is given by $\vect{F} = q\vect{v}\times\vect{B}$,
18 so it is maximized when \vect{B} is perpendicular to \vect{v}, at
21 F = qvB = \ans{7.90\U{pN}}
23 The force is minimized then \vect{B} is parallel (or anti-parallel) to
24 \vect{v}, at which point $\ans{F = 0}$.