The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed from one form to another. In each of these examples, energy undergoes different transformations, such as chemical to thermal to light, electrical to thermal to mechanical, and light to electrical or chemical. These energy transformations play crucial roles in various natural and human-made processes.
1. When the flashlight is turned on, a flow of electrons is created by the batteries. The electricity passes through the incandescent lightbulb, causing the tungsten filament in the lightbulb to heat up. When the metal is hot enough, photons of light are emitted.
The energy transformation in this scenario starts with chemical energy stored in the batteries. When the flashlight is turned on, the chemical reaction inside the batteries generates an electric current, which is the flow of electrons. This electrical energy then passes through the incandescent lightbulb, where it is transformed into thermal energy. The electrical current causes the tungsten filament in the bulb to heat up, reaching a high temperature. Finally, the thermal energy is converted into light energy as the heated filament emits photons, which are packets of light.
2. In a car engine, an electrical spark from the spark plug ignites the fuel-air mixture in the piston. The explosion and heat cause the air in the cylinder to expand, pushing the piston down.
In this case, the energy transformation starts with electrical energy from the spark plug. The spark ignites the fuel-air mixture inside the piston, initiating a chemical reaction that releases thermal energy in the form of an explosion and heat. The heat produced causes the air in the cylinder to rapidly expand, converting the thermal energy into mechanical energy. This mechanical energy is then used to push the piston down, generating the force required for the car engine to function.
3. In the sun, nuclear fusion compresses hydrogen atoms into helium atoms, releasing heat. This heat energizes electrons in the helium and hydrogen atoms, producing light.
The energy transformation in the sun begins with the process of nuclear fusion. The immense gravitational pressure in the sun's core causes hydrogen atoms to combine and form helium atoms, releasing an enormous amount of thermal energy in the process. This heat energizes the electrons in the helium and hydrogen atoms, elevating them to higher energy levels. As the electrons return to their original energy levels, they release excess energy in the form of light, resulting in the emission of photons.
4. A solar panel's photovoltaic cells are made of positive and negative films of silicon under glass. When photons of light hit the silicon, they knock off electrons which flow to the other side of the cell.
In the case of a solar panel, the energy transformation starts with light energy from photons. The photovoltaic cells in the solar panel are made of silicon, which is a semiconductor material. When photons of light strike the silicon, they transfer their energy to the electrons in the silicon atoms, providing enough energy to knock the electrons loose. These freed electrons are then able to flow through the silicon, creating an electric current. This conversion of light energy into electrical energy is the basis of how solar panels generate electricity.
5. When photons of light hit chlorophyll in a green leaf, they excite electrons in chlorophyll molecules, starting a series of chemical reactions.
In the context of photosynthesis, the energy transformation begins with light energy from photons hitting chlorophyll molecules in a green leaf. Chlorophyll is a pigment found in plants that absorbs light energy. When photons interact with the chlorophyll molecules, they transfer their energy to the electrons within the molecules, causing the electrons to become excited and move to higher energy levels. This energy is then used to initiate a series of chemical reactions, leading to the conversion of carbon dioxide and water into glucose and oxygen. The light energy is ultimately transformed into chemical energy stored in glucose molecules, which serve as an energy source for the plant.