American engineer Norton explained his theorem in 1926 after 43 years publishing Thevenin’s theorem. Norton’s theorem is similar to Thevenin’s theorem.

Nortons theorem states that **“a linear two terminal circuit can be replaced by an equivalent current source I _{N} in parallel with a resistance R_{N} where R_{N} is the input or equivalent resistance at the terminals and I_{N} is the short circuit current through the terminals when all the independent sources are turned off”.**