At the instant the valve (R) is opened, the pressure in the tank (C) is 100 lbs. and the pressure at the valve (R) is

100 lbs. The source of pressure is the water in the tank (C), and this same pressure is developed at the valve (R)).

In the RC circuit (fig. 9D), at the instant C starts to discharge, the voltage (pressure) on C is 100 volts and the

voltage across R (valve) is 100 volts.

The source of voltage (pressure) is the voltage on C, and this same voltage (pressure) is developed across R.

In .1 RC time, C discharges 10%, or 10 volts, which leaves 90 volts on C. THIS SAME 90 VOLTS IS ALSO

THE VOLTAGE ACROSS R (fig. 9E).

This compares with draining 10 lbs. of water pressure from the tank (fig. 9F), which leaves 90 lbs. of

pressure in the tank. This same 90 lbs. of pressure is felt at the valve (R).

In 1 RC time, C discharges 63% or 63 volts, which leaves 37 volts on C. THIS 37 VOLTS IS ALSO THE

VOLTAGE ACROSS R (fig. 9G).

This compares with the draining 63 lbs. of water from the tank (fig. 9H) which leaves 37 lbs. of pressure in the

tank (C). This 37 lbs. of pressure is felt at the valve (R).