Correction to HRW CHAPTER 28, #33.

    EMF2 in the figure for that problem should be drawn from
    the negative side of the battery to the positive side.
    Battery EMF's always go from negative to positive.

Problems from Fishbane, Gasiorowicz, and Thornton
(2nd edition) Chapter 28

57.  Find a differential equation which can be solved
     for Q(t), the charge as a function of time, on a
     discharging capacitor.  The figure for this problem
     is Fig. 28-13, with an initial charge of Q_0 on
     capacitor C when the switch is moved to position
     b at t = 0.  Let positive current represent a
     charging capacitor, i.e. i = (dQ/dt).  Show by
     direct substitution that Q(t) = (Q_0)e^(-t/RC) is
     a solution of this differential equation.