Physics – 1.7.1 Energy | e-Consult

Energy can be transferred between stores in various ways. The most common forms of energy stores are potential energy (stored due to position or configuration), kinetic energy (stored due to motion), thermal energy (stored as heat), and chemical energy (stored in chemical bonds). Energy transfer involves a change in the amount of energy in one store and a corresponding change in another.

Mechanical work done involves the transfer of energy through forces acting over a distance. For example, when lifting an object, we do work on it, increasing its potential energy. The work done is equal to the force applied multiplied by the distance moved. Similarly, a car engine converts chemical energy into kinetic energy through mechanical work done by the pistons. A hydraulic press uses mechanical work to amplify force and transfer energy to compress materials.

Electrical work done involves the transfer of energy through electrical currents. When a current flows through a resistor, electrical energy is converted into thermal energy (Joule heating). This is the principle behind electric heaters and incandescent light bulbs. A battery provides electrical energy that is then transferred to a circuit, powering devices like lamps and motors. The electrical work done is equal to the voltage multiplied by the current and the time.

Heating is a common method of energy transfer. Conduction transfers heat through materials by the vibration of particles. Convection transfers heat through the movement of fluids (liquids and gases). Radiation transfers heat through electromagnetic waves. A radiator uses radiation to transfer thermal energy to a room. A kettle uses thermal energy to heat water. A furnace uses radiation and convection to heat a space.

Electromagnetic waves transfer energy through space. Examples include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Solar panels convert light energy (photons) into electrical energy. Microwaves in a microwave oven transfer energy to water molecules, causing them to vibrate and heat up food. Radio waves transmit information wirelessly.

Sound waves transfer energy through a medium (solid, liquid, or gas) by causing vibrations. A loudspeaker converts electrical energy into sound energy by vibrating a cone. The vibrations propagate through the air as sound waves, which are then detected by our ears. The amplitude of the sound wave determines the loudness, and the frequency determines the pitch.

Other forms of energy transfer include nuclear reactions (e.g., in nuclear power plants, where nuclear energy is converted to thermal energy and then to electrical energy) and the transfer of energy through chemical reactions (e.g., burning fuel, where chemical energy is converted to thermal and light energy).