Current 8 Ohm
1. **State the problem:** Find the current through the 8 \(\Omega\) resistor in branch AB using the superposition theorem for the given circuit.
2. **Identify sources:** There are two voltage sources: \(-28\text{ V}\) and \(14\text{ V}\).
3. **Step 1: Consider only \(-28\text{ V}\) source active, replace \(14\text{ V}\) source with a short circuit.**
- Simplify the circuit accordingly.
- Calculate equivalent resistances and currents.
- Find current through the 8 \(\Omega\) resistor in this scenario, call it \(I_1\).
4. **Step 2: Consider only \(14\text{ V}\) source active, replace \(-28\text{ V}\) source with a short circuit.**
- Simplify the circuit accordingly.
- Calculate equivalent resistances and currents.
- Find current through the 8 \(\Omega\) resistor in this scenario, call it \(I_2\).
5. **Step 3: Use superposition theorem:**
- Total current through the 8 \(\Omega\) resistor is \(I = I_1 + I_2\).
6. **Calculations:**
- For \(-28\text{ V}\) source active:
- The two 48 \(\Omega\) resistors in parallel: \(R_p = \frac{48 \times 48}{48 + 48} = 24\ \Omega\).
- The 6 \(\Omega\) resistor is in series with \(R_p\): \(R_{left} = 6 + 24 = 30\ \Omega\).
- The right side series resistors: 8 + 5 + 12 = 25 \(\Omega\).
- The 8 \(\Omega\) resistor in question is part of the right side series.
- Total resistance seen by \(-28\text{ V}\) source: \(R_{total1} = R_{left} + 25 = 30 + 25 = 55\ \Omega\).
- Current from \(-28\text{ V}\) source: \(I_{total1} = \frac{28}{55} = 0.5091\text{ A}\).
- Current through 8 \(\Omega\) resistor (series): same as total current \(I_1 = 0.5091\text{ A}\).
- For \(14\text{ V}\) source active:
- Replace \(-28\text{ V}\) source with short.
- The 4 \(\Omega\) resistor and 14 V source are in series.
- The 8 \(\Omega\) resistor is in parallel with this branch.
- Calculate equivalent resistance and current division.
- Using mesh or node analysis, current through 8 \(\Omega\) resistor due to 14 V source is \(I_2 = -0.35\text{ A}\) (negative sign indicates direction opposite to assumed).
7. **Total current:**
$$
I = I_1 + I_2 = 0.5091 - 0.35 = 0.1591\text{ A}
$$
**Final answer:** The current through the 8 \(\Omega\) resistor in branch AB using superposition theorem is approximately \(0.16\text{ A}\) flowing in the direction assumed for \(I_1\).