The circuit shown in the figure below, called the Wheatstone
bridge, is used to determine the value of unknown resistor
Xby comparison with three resistors M,
N, and P whose resistances can be varied. For
each setting, the resistance of each resistor is precisely known.
With switches K1 and K2
closed, these resistors are varied until the current in the
galvanometer G is zero; the bridge is then said to be balanced.
(a) Show that under this condition the unknown...