Question

1. Find the value of current ‘I’ in Figure 2 given below.
   

2. State the conservation principle on which your calculation is based.

Answer 1

(a) To find the value of I, we use Kirchhoff’s Current Law (KCL), which states that the total current entering a junction must equal the total current leaving it.

Looking at the diagram, we can group the currents:

Currents Entering: 8 A and I

Currents Leaving: 7 A, 5 A and 3 A

Sum of Entering Currents = Sum of Leaving Currents

8 A + I = 7 A + 5 A + 3 A

I + 8 A = 15 A 

I = 15 A − 8 A

= 7 A

(b) The calculation is based on the Law of Conservation of Charge. In a steady-state circuit, charge cannot be created or destroyed. This means that at any junction or node, the rate at which charge enters must be exactly equal to the rate at which it leaves.