THE FIELDS OF MOVING CHARGES — Edward Purcell & David Morin
Physics — E&M · unbalanced-current
Problem
Unbalanced current **
As an illustration of the point made in Footnote 13 in Section 4.7, consider a black box that is approximately a 10 cm cube with two binding posts. Each of these terminals is connected by a wire to some external circuits. Otherwise, the box is well insulated from everything. A current of approximately 1 A flows through this circuit element. Suppose now that the current in and the current out differ by one part in a million. About how long would it take, unless something else happens, for the box to rise in potential by 1000 volts?