The power output function is
.
Where
is electromotive force
volts.
is resistance
ohms.
So
.
When
then
.
When
then
.
To find the maximum output power , derivative the power function and equate to zero.
\
Apply derivative with respect to
.

Equate it to zero .
\
Critical number is
.
When
then
.
When
then
.
So the maximum out power occurs when
.
The maximum out power lies in the interval
(
amp fuse ).
The power output will not increase by replacing the
amp fuse with
amp fuse.
Because the output power decreases for
.
The maximum out power is
.