Step 1: Understanding the given data
We are given the following information:
- Switch \( S \) is at position \( P \), and after a long time, the potential difference across the capacitor branch is:
\[
\frac{4 \times 1}{3} = \frac{4}{3} \, \text{V}
\]
- The charge on the capacitor is denoted as \( q_1 \) in microcoulombs (\( \mu C \)).
Step 2: Applying the formula for charge on the capacitor
The charge \( q_1 \) on a capacitor is related to the potential difference across the capacitor and its capacitance \( C \) by the equation:
\[
q = C \times V
\]
where \( V \) is the potential difference and \( C \) is the capacitance.
In this case, the potential difference is given as \( \frac{4}{3} \) V, and from the information provided, we can deduce that the charge on the capacitor \( q_1 \) is also \( \frac{4}{3} \) microcoulombs, as it is related to the potential difference.
Step 3: Conclusion
Therefore, the charge on the capacitor is:
\[
q_1 = \frac{4}{3} \, \mu C = 1.33 \, \mu C
\]