Apply Kirchhoff's law to find the current I in the part of the following circuit.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 8 A
By Kirchhoff’s junction rule, at every junction the total current entering equals the total current leaving. Apply it to the three junctions one after the other, reading the currents from the figure.
First junction: 10 A and 4 A enter, so the wire to the right carries
\( 10 + 4 = 14\,\mathrm{A} \)
Second junction: 14 A and 1 A enter, 2 A leaves.
\( 14 + 1 - 2 = 13\,\mathrm{A} \) goes on to the third junction
Third junction: 13 A enters, and 3 A, 2 A and I leave.
\( 13 = 3 + 2 + I \Rightarrow I = 8\,\mathrm{A} \)