FIGURE 4.6-4 Circuit with a supermesh
that incorporates mesh 1 and mesh 2.
The supermesh is indicated by the dashed line.
A supermesh is one larger mesh created from two meshes that have an independent or
dependent current source in common.
For example, consider the circuit of Figure 4.6-4. The 5-A current source is common to mesh I
and mesh 2. The supermesh consists of the interior of mesh 1 and mesh 2. Writing KVL around the
periphery of the supermesh shown by the dashed lines, we obtain
- 1 0 + l ( i1 - i3 ) + 3( i2 - i3 ) + 2i2 = 0
For mesh 3, we have
1(i3 - l1) + 2 i3 + 3(i3 - i2) = 0
Finally, the equation that relates the current source current to the mesh currents is
i1 - i2 = 5
Then the three equations may be reduced to
supermesh: li1 + 5i2 — 4i3 = 10
mesh 3: — li1— 3i2 + 6i3 = 0
current source: li1 — li2 = 5
Therefore, solving the three equations simultaneously, we find that i2 = 2.5A, i1 = 1.5 A, and
i3 = 2.5A.
The methods of mesh current analysis used when a current source is present are summarized
in Table 4.6-1.