Question

Apply the junction rule at point a in Figure 21.52.

Short answer

Using the junction rule on point 'a', we obtained:

${\mathrm{I}}_3={\mathrm{I}}_2+{\mathrm{I}}_1$

Step-by-step solution

Definition of Kirchhoff's law

Kirchhoff's first law defines currents at circuit junctions. It states that the sum of currents flowing into and out of a junction in an electrical circuit equals the sum of currents flowing out of the junction.

Explanation for the junction rule

The sum of currents entering the junction equals the sum of currents leaving the junction, according to the junction rule. An equation may be written for point an in the figure 21.55 using the following rule:

${\mathrm{I}}_3={\mathrm{I}}_2+{\mathrm{I}}_1$

Hence current at location 'a' can be calculated using Kirchhoff's Junction rule as follows:

${\mathrm{I}}_3={\mathrm{I}}_2+{\mathrm{I}}_1$