1. **State the problem:**
We need to find the branch currents $I_1$, $I_2$, $I_3$, and $I_4$ in the given circuit using Kirchhoff's Current Law (KCL).
2. **Recall KCL:**
KCL states that the algebraic sum of currents entering a node is zero. In other words, the sum of currents entering a junction equals the sum of currents leaving it.
3. **Identify nodes and currents:**
- Given currents: $I_1 = 1A$ downward, $I_2 = 7A$ downward, $I_4 = 4A$ downward, and a horizontal current of $2A$ rightward at the top.
- Also given: a $3A$ current downward in the middle vertical segment (likely $I_3$ or part of it).
4. **Apply KCL at the top node (junction of $I_1$, $I_2$, and horizontal $2A$):**
$$I_1 + I_2 = 2A + I_x$$
where $I_x$ is the current continuing downward or to the next branch.
5. **Apply KCL at the bottom node (junction of $I_3$, $I_4$, and horizontal $2A$):**
$$I_3 + I_4 = 2A + I_y$$
where $I_y$ is the current entering or leaving the node.
6. **Use given values and directions:**
- $I_1 = 1A$
- $I_2 = 7A$
- $I_4 = 4A$
- $I_3$ is unknown.
7. **Sum currents at the top node:**
$$1A + 7A = 8A$$
The horizontal current is $2A$ rightward, so the remaining current downward is:
$$I_3 = 8A - 2A = 6A$$
8. **Check currents at the bottom node:**
Given $I_3 = 6A$ downward and $I_4 = 4A$ downward, total downward current is:
$$6A + 4A = 10A$$
The horizontal current is $2A$ rightward, so the current entering the node from the left must be:
$$10A - 2A = 8A$$
9. **Final branch currents:**
$$I_1 = 1A, \quad I_2 = 7A, \quad I_3 = 6A, \quad I_4 = 4A$$
These satisfy KCL at all nodes.
Branch Currents Ea9685
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.