1. **Problem Statement:** Calculate the current flowing through resistor $R_3$ in the given circuit with two loops and two voltage sources $V_1=12$ V and $V_2=9$ V.
2. **Identify the loops and currents:** Let $I_1$ be the current in the left loop and $I_2$ be the current in the right loop. The resistor $R_3$ is shared between the two loops, so the current through $R_3$ is $I_1 - I_2$ (assuming directions as shown).
3. **Write Kirchhoff's Voltage Law (KVL) equations:**
- Left loop (with $V_1$, $R_1$, $R_2$, and $R_3$):
$$12 - 10I_1 - 2I_1 - 6(I_1 - I_2) = 0$$
- Right loop (with $V_2$, $R_3$, and $R_4$):
$$9 - 22I_2 - 6(I_2 - I_1) = 0$$
4. **Simplify the equations:**
Left loop:
$$12 - 12I_1 - 6I_1 + 6I_2 = 0$$
$$12 - 18I_1 + 6I_2 = 0$$
Right loop:
$$9 - 22I_2 - 6I_2 + 6I_1 = 0$$
$$9 - 28I_2 + 6I_1 = 0$$
5. **Rewrite as system of linear equations:**
$$\begin{cases}
-18I_1 + 6I_2 = -12 \\
6I_1 - 28I_2 = -9
\end{cases}$$
6. **Divide first equation by 6:**
$$-3I_1 + I_2 = -2$$
7. **Divide second equation by 2:**
$$3I_1 - 14I_2 = -4.5$$
8. **Solve the system:**
From first equation:
$$I_2 = -2 + 3I_1$$
Substitute into second:
$$3I_1 - 14(-2 + 3I_1) = -4.5$$
$$3I_1 + 28 - 42I_1 = -4.5$$
$$-39I_1 = -32.5$$
$$I_1 = \frac{32.5}{39} \approx 0.8333\, \text{A}$$
9. **Find $I_2$:**
$$I_2 = -2 + 3(0.8333) = -2 + 2.5 = 0.5\, \text{A}$$
10. **Calculate current through $R_3$:**
$$I_{R_3} = I_1 - I_2 = 0.8333 - 0.5 = 0.3333\, \text{A}$$
**Final answer:** The current flowing through resistor $R_3$ is approximately $0.33$ A.
Current R3 B7864D
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