Energy Forms and Conversion Flashcards

A student uses a battery-powered flashlight to see in a dark room. Which of the following describes the primary energy conversions that take place?

Answer: Chemical energy to electrical energy to light and thermal energy

The batteries in a flashlight store chemical potential energy. When the flashlight is turned on, this chemical energy is converted into electrical energy, which flows through the circuit. The bulb then converts the electrical energy into radiant (light) energy and thermal (heat) energy.

In a hydroelectric power plant, a dam holds back a large volume of water in a reservoir. When the water is released, it flows through a turbine, which spins a generator to produce electricity. What is the correct sequence of energy transformations in this process?

Answer: Potential energy → Kinetic energy → Electrical energy

The water held in the reservoir at a high elevation possesses gravitational potential energy. When released, this potential energy is converted into kinetic energy as the water flows downwards. The moving water spins a turbine (mechanical energy), which powers a generator that converts this motion into electrical energy.

A student drops a rubber ball from a height of one meter. The ball bounces back up, but not to its original height. According to the Law of Conservation of Energy, what best explains why the ball does not reach its starting height?

Answer: Some mechanical energy was converted into thermal and sound energy.

The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed. When the ball hits the floor, some of its kinetic energy is converted into other forms, primarily thermal energy (heat) due to friction and the deformation of the ball, and sound energy. This loss of mechanical energy prevents it from returning to its original height.

Photosynthesis is the process plants use to make their own food. What is the fundamental energy conversion that occurs during photosynthesis?

Answer: Radiant energy is converted into chemical energy.

During photosynthesis, plants capture radiant energy (light energy) from the sun. They use this energy to convert carbon dioxide and water into glucose (a sugar), which stores the energy in its chemical bonds. This process is a direct conversion of radiant energy into stored chemical energy.

Which of the following scenarios is the best example of elastic potential energy being converted into kinetic energy?

Answer: A stretched rubber band being released to fly across a room

Elastic potential energy is the energy stored in an object when it is stretched or compressed. A stretched rubber band has stored elastic potential energy. When it is released, this stored energy is converted into kinetic energy, the energy of motion, causing the rubber band to move.

A student pushes a heavy box across a rough floor. After the student stops pushing, the box slides for a short distance and then stops. The student observes that the bottom of the box and the floor feel slightly warmer. This is because the box's kinetic energy was converted primarily into:

Answer: thermal energy.

Friction is a force that opposes motion. As the box slides across the rough floor, friction does work on the box, converting its kinetic energy (energy of motion) into thermal energy (heat). This is why both the box and the floor feel warmer after the interaction.