Current Magnitude Direction
1. **State the problem:** Given the currents $I_1=10$ A, $I_2=12$ A, and $I_5=8$ A, find the magnitude and direction of currents $I_3$, $I_4$, $I_6$, and $I_7$ in the diamond-shaped network using Kirchhoff’s Current Law (KCL).
2. **Label nodes and incoming/outgoing currents:**
- Node $a$: currents $I_1$ entering
- Node $b$: currents $I_2$ entering
- Node $c$: currents $I_3$, $I_6$ (unknown directions)
- Node $d$: currents $I_4$, $I_5$, $I_7$ (unknowns involve $I_4$, $I_7$)
3. **Apply KCL at node $a$:**
Current entering = current leaving
$$I_1 = I_3 + I_4$$
So,
$$I_4 = I_1 - I_3 = 10 - I_3$$
4. **Apply KCL at node $b$:**
Similar relation gives
$$I_2 = I_4 + I_7$$
So,
$$I_7 = I_2 - I_4 = 12 - I_4$$
5. **Apply KCL at node $c$:**
Currents entering = currents leaving
$$I_3 + I_6 = I_1$$
But we need direction info; instead, more direct is to write KCL at $c$:
$$I_3 = I_6 + I_5$$
Given $I_5=8$ A,
$$I_3 = I_6 + 8$$
6. **Apply KCL at node $d$:**
Currents entering = currents leaving
$$I_6 + I_4 = I_5 + I_7$$
Rearranged,
$$I_7 = I_6 + I_4 - I_5$$
7. **Substitute $I_4$ from step 3:**
$$I_7 = I_6 + (10 - I_3) - 8 = I_6 + 2 - I_3$$
8. **From step 4, $I_7 = 12 - I_4 = 12 - (10 - I_3) = 2 + I_3$**
9. **Equate the two expressions for $I_7$:**
$$2 + I_3 = I_6 + 2 - I_3$$
Simplify:
$$I_3 = I_6 - I_3$$
$$2I_3 = I_6$$
So,
$$I_6 = 2I_3$$
10. **From step 5, $I_3 = I_6 + 8$, substitute $I_6$:**
$$I_3 = 2I_3 + 8$$
$$-I_3 = 8$$
$$I_3 = -8$$ A (negative means opposite direction)
11. **Calculate other currents:**
$$I_6 = 2 imes (-8) = -16$$ A (opposite direction)
$$I_4 = 10 - I_3 = 10 - (-8) = 18$$ A
$$I_7 = 2 + I_3 = 2 - 8 = -6$$ A (opposite direction)
**Final answers:**
- $I_3 = 8$ A opposite assumed direction
- $I_4 = 18$ A
- $I_6 = 16$ A opposite assumed direction
- $I_7 = 6$ A opposite assumed direction
These signs indicate their actual directions are opposite to the initially assumed ones in the figure.