Norton's theorem represents a linear electrical network viewed through two terminals by a current source in parallel with a conductance. When the terminal relation has
a well-defined finite short-circuit current 
and conductance 
, it has the affine form
 |
where 
is the current delivered to an external load and 
is the terminal voltage. The source current is the value at
(Massachusetts Institute of Technology
2011).
For finite nonzero 
,
the parallel resistance is 
. The equivalent series-source representation of Thévenin's theorem then has
 |
For a passive resistor network, the resistance is nonnegative. Independent sources may be suppressed
when finding the resistance, but dependent sources must remain active. The case 
is an ideal current source and does
not in general have an equivalent finite series-source representation.
