Energy exists in different forms including light, thermal, sound, electricity, gravitational potential, and kinetic. Kinetic energy is the energy of moving objects and can be converted to electricity through wind and water turbines. Gravitational potential energy is stored energy that exists from height and springs and can be converted to kinetic energy. The principle of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. Work is the transfer of energy done by a force over distance, and power is the rate of work done or energy converted per unit time.