Electrophorus Electric Bell

[pomodoro]

The cap is like an empty gas cylinder getting pressurized by pump, which is the battery. The resistor is like a restricting gas valve. The volume of the gas cylinder is the capacitance, the pressure of the pump is the voltage and the orifice size of the valve is the resistance (1/R) to be correct.
So you can see that work energy is required to fill up the cylinder. Not only that but you can also see that charging the cap with the fixed battery voltage is quite inefficient because it is like compressing a gas irreversibly .If you look up reversible vs irreversible compression you will understand why that is. The cap needs to be charged from a voltage that changes with the rate of change of the cap voltage itself for high efficiency.