Energy is the capacity to do work or cause change, allowing things to move, heat up, or transform. Energy transfer is the movement of energy from one object or system to another, or its transformation between forms. The law of conservation of energy states that energy can neither be created nor destroyed. Instead, the total amount of energy in an isolated system remains constant, only changing its form or location.
Different Forms of Energy
Energy manifests in various forms, each a distinct way for work to be done or change to occur. Kinetic energy is the energy an object possesses due to its motion. A moving car, a thrown ball, or a person running all demonstrate kinetic energy.
Potential energy is stored within an object or system, ready for conversion into other forms. Gravitational potential energy is stored due to an object’s height or position within a gravitational field, like water held behind a dam. Elastic potential energy is stored when an object is stretched or compressed, like a stretched rubber band or a coiled spring. Chemical energy is stored within the bonds of molecules and is released during chemical reactions, found in food, batteries, or fuel.
Thermal energy relates to the random motion of atoms and molecules within a substance. Examples include warmth radiating from a fire or heat in a cup of hot coffee. Electrical energy is carried by the movement of charged particles, powering devices through wires or appearing as lightning. Radiant energy, also known as light energy, travels in electromagnetic waves and includes sunlight or light emitted from a bulb.
Sound energy is produced by vibrations that travel through a medium, such as music from speakers or the roar of thunder. Nuclear energy is stored within the nucleus of an atom and is released during nuclear reactions, powering nuclear plants or fueling the sun.
Ways Energy Travels
Energy moves between objects and systems through several mechanisms. Conduction is the transfer of thermal energy through direct contact between particles. An example is a metal spoon becoming warm when placed in a hot cup of soup, as heat moves from the liquid to the spoon.
Convection involves the transfer of thermal energy through the movement of fluids, which are liquids or gases. When water boils, warmer, less dense water rises while cooler, denser water sinks, creating a circulating current that distributes heat. Warm air rising from a heater also demonstrates convection.
Radiation is the transfer of energy through electromagnetic waves, and it does not require a medium to travel. The warmth felt from the sun or heat emanating from a campfire are examples of energy transferred by radiation.
Work is a mechanical transfer of energy that occurs when a force causes displacement. Pushing a heavy box or lifting weights are instances where work transfers energy. Electrical current transfers electrical energy through the directed movement of charged particles, enabling appliances to function when plugged into an outlet or charging a phone.
Everyday Energy Transfers
Energy is constantly being transferred and transformed in our daily lives. When a lightbulb illuminates a room, electrical energy is primarily converted into light energy, with some transformed into thermal energy, making the bulb warm.
A car engine is an example of energy conversion. Chemical energy stored in gasoline is released through combustion, becoming thermal energy. This thermal energy is then converted into kinetic energy, propelling the car forward, and also produces sound energy.
Photosynthesis, the process by which plants create their own food, transforms radiant energy from sunlight into chemical energy stored in sugars. This chemical energy supports the plant’s growth and other life processes. The human body similarly converts chemical energy from food into kinetic energy for movement and thermal energy to maintain body temperature.
A common household fan illustrates another energy transfer. Electrical energy is converted into the kinetic energy of moving air, creating a breeze. A small amount is also transformed into sound energy.