Figure below shows a portion of an electric circuit with the cur ents in ampreres and their directions. The

magnitude and direction of the cur ent in the portion PQ is :

According to kirchhoff's first law (Current Law or Juction Law):

The algebraic sum of currents meeting at a junction is zero.

i.e. In a circuit, at any juction the sum of the currents entering the junction must be equal to the sum of currents leaving the junction.

We will apply Kirchhoff's junction at the junctions L , M, N and O as shown in the figure below:

 

At junction L:

The current would be 2 A + 8A = 10 A towards right

 

At junction M:

The current from junction L (10A) divides into two, one goes upwards towards junction O and other goes downwards towards junction N.

 

At junction N:

 

Its given that at junction N the current splits to 4A and 2 A. So the current entering junction N will be the sum of both 4 A and 2 A. So current entering junction N will be 6 A downwards.

 

At junction O:

 

So the current reaching junction O will be 10 A - 6 A = 4 A upwards.

 

This current entering the junction O gets divided into two: 1 A towards right side and hence towards left it will be 4 A - 1A =3A towards left.

 

At junction Q:

 

So the current entering junction Q will be the sum 3A +3A = 6 A

 

Hence we can say that the current in the portion PQ = 6A towards left.