Norton Theorem

Norton’s theorem bears a close resemblance to Thevenin’s theorem.

The Norton equivalent of a linear network is the Norton current source i_sc in parallel with the Thevenin resistance R_th. Thus, we see that in fact it is possible to obtain the Norton equivalent of a network by performing a source transformation on the Thevenin equivalent. This result in a direct relationship between V_oc, i_sc and R_th.
V_oc = R_thi_sc

Procedure to Calculate Norton’s Current

To find the Norton current I_N, first of all short circuit the load and measure the short circuit current as per prescribed direction as shown in fig. (c).

Note:

If a circuit contains dependent sources only, i.e. there is no independent source present in the network then its short-circuit current or Norton current will simply be zero.

Norton’s Resistance

Norton resistance is the input or equivalent resistance seen at the load terminals when all independent source are set to zero (voltage sources replaced by short-circuits and current sources replaced by open-circuits) i.e. Norton resistance is same as Thevenin’s resistance R_N = R_Th

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