The figure below shows a part of an electric circuit. The current marked \( I_A \) is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1.3 A
By Kirchhoff's junction rule, the total current entering a junction equals the total current leaving it.
Readings from the figure:
\( \mathrm{Into\ A:}\ 0.2\,\mathrm{A},\ 0.2\,\mathrm{A},\ I_A \)
\( \mathrm{Out\ of\ A:}\ I_{AB}\ \mathrm{(towards\ B)} \)
\( \mathrm{Out\ of\ B:}\ 1.2\,\mathrm{A},\ 0.5\,\mathrm{A} \)
At junction B, all the current coming from A leaves through the two branches:
\( \displaystyle I_{AB} = 1.2 + 0.5 = 1.7\,\mathrm{A} \)
At junction A:
\( \displaystyle 0.2 + 0.2 + I_A = 1.7 \;\Rightarrow\; I_A = 1.7 - 0.4 = 1.3\,\mathrm{A} \)