-- The two 8-ohm resistors in parallel are equivalent to
a single 4-ohm resistor.
-- The current in the circuit is
(voltage) / (resistance) = (9v) / (4ohms) = 2.25 Amperes
-- If another resistor is added in parallel, then no matter how large
or small it is, the current in the circuit increases.
(When another lane is added to a road, the traffic capacity of the
road increases.)
The circuit is now equivalent to a 12.5-ohm resistor in parallel
with 4-ohms. That's ...
(12.5 x 4) / (12.5 + 4) = 50/16.5 = 3.03 ohms .
-- The new current is (9v) / (3.03 ohms) = 2.97 Amperes
