A capacitor is kept connected to the battery and a dielectric slab is ...
When you connect a capacitor to a battery the primary goal is that "the potential difference between the plates of the capacitor is constant". Say a capacitor is connected to the battery. When you insert a dielectric slab inside it, the capacitance of the capacitor increases. But as the potential must remain constant the charge from the plates of the capacitor flows. This flown charge when reaches the battery will do work against it and there will be some loss in energy. So, I think the correct answer must be (c).
A capacitor is kept connected to the battery and a dielectric slab is ...
Explanation:
When a dielectric slab is inserted between the plates of a capacitor that is already connected to a battery, there is a change in the electric field between the plates. This change leads to a change in the potential energy of the system.
The question asks whether work is done during this process and if so, who or what is providing the energy for this work.
No work is done
If the battery is ideal and has no internal resistance, then no work is done when the dielectric slab is inserted. This is because the battery maintains a constant potential difference across the plates of the capacitor, and the energy stored in the capacitor before the slab is inserted is equal to the energy stored after the slab is inserted. Therefore, no work is done.
Work is done at the cost of the energy stored in the capacitor
If the battery has internal resistance and some energy is dissipated in the resistance, then work is done at the cost of the energy stored in the capacitor before the slab is inserted. This is because the energy stored in the capacitor before the slab is inserted is used to overcome the resistance of the battery, and to establish the new electric field with the dielectric slab in place.
Work is done at the cost of the battery
If the battery is not ideal and has a finite internal resistance, then work is done at the cost of the battery. This is because some energy is dissipated in the battery due to its internal resistance, and the battery must supply additional energy to maintain a constant potential difference across the plates of the capacitor.
The work is done at the cost of both the capacitor and battery
In reality, the work done when a dielectric slab is inserted is likely to come at the cost of both the capacitor and battery. This is because both the capacitor and battery have internal resistance, and some energy will be dissipated as heat in both components during the process.
Conclusion:
To summarise, the work done when a dielectric slab is inserted between the plates of a capacitor connected to a battery depends on the properties of the battery and the capacitor. If the battery is ideal with no internal resistance, no work is done. If the battery has internal resistance, work is done at the cost of the energy stored in the capacitor or the battery. In reality, both the capacitor and battery are likely to contribute to the work done, and some energy will be dissipated as heat in both components.