The figure shows currents in a part of electric circuit. Then current $I$ is
The figure shows currents in a part of electric circuit. Then current $I$ is
3.5 A
4 A
1.5 A
2.5 A
Solution
According to Kirchhoff's first law,
At junction $\mathrm{A}, \mathrm{I}_{\mathrm{A}}=1+4=5 \mathrm{~A}$
At junction $\mathrm{B}, \mathrm{I}_{\mathrm{A}}=\mathrm{I}_{\mathrm{BC}}+0.5 \Rightarrow \mathrm{I}_{\mathrm{BC}}=4.5 \mathrm{~A}$
At junction $\mathrm{C}, \mathrm{I}=\mathrm{I}_{\mathrm{BC}}-1=4.5-1=3.5 \mathrm{~A}$
