Final answer:
The voltage across the capacitor will decrease to zero when the switch is moved from point b to point a as the capacitor discharges. Due to the relationship between current and voltage in a capacitor, the current will become negative as the capacitor discharges until the voltage reaches zero.
Step-by-step explanation:
When the switch is disconnected from point b and connected to point a, the voltage across the capacitor will eventually become zero. Initially, the capacitor has a maximum voltage across it, with no current as it is fully charged. Once the switch moves from point b to point a, the capacitor starts discharging and the voltage across the capacitor decreases.
The relationship between voltage and current in a capacitor is such that as the capacitor discharges, the voltage decreases and the current changes direction. Furthermore, the current through the capacitor becomes negative as it moves charge away from the capacitor. This continues until the capacitor is fully discharged at point a, where the voltage is zero.
After the capacitor reaches zero voltage at point a, if the circuit allows, the current may continue in the same direction depending on the configuration, leading to a reverse voltage across the capacitor. However, in many practical circuits, the configuration might change or include other components that impact the capacitor's behavior post-discharge.