Final answer:
The energy conversion that occurs when the sluice of a dam is opened is the transformation of potential energy to kinetic energy. As the water falls, it picks up speed, which turns potential into kinetic, and in hydroelectric dams, this kinetic energy can then be converted to electrical energy.
Step-by-step explanation:
When the sluice of a dam is opened, the potential energy stored in the water at a higher elevation is converted into kinetic energy as the water falls. This process is analogous to water at the top of a waterfall, where its position grants it potential energy, which is then transformed into kinetic energy due to motion as it descends.
If the falling water flows through generators, the kinetic energy can be harnessed to do work - in the case of a hydroelectric dam, to produce electrical energy. This transition is an excellent example of energy conversion in a real-world scenario. Therefore, based on the conversion processes involved, the correct answer is (a) Potential energy is converted to kinetic energy when the sluice of a dam is opened.