What Is Electric Energy Into Heat Energy Called?

Electric energy refers to energy that comes from electric currents and is distributed through wires and cables. It is often generated at power plants using methods like combustion, nuclear fission, or renewable sources. Heat energy, also known as thermal energy, is the internal energy within a system that makes atoms and molecules move faster and spread apart. When electric energy is converted into heat, it involves the electric current overcoming resistance in a conductor and releasing energy in the form of heat. This conversion process is known by several names:

Joule Heating

Joule heating, also known as resistive or Ohmic heating, refers to the process by which the passage of an electric current through a conductor converts electrical energy into heat. It was named after James Prescott Joule, a physicist who studied this phenomenon in the 19th century.

When an electric current passes through a conductor, it encounters resistance. The collisions between the moving electrons and the conductor’s ions convert the ordered kinetic energy of the electrons into random thermal motion. The resistance to electron flow causes the conductor’s temperature to rise.

The amount of heat (Q) generated is proportional to the square of the current (I), the resistance (R) of the conductor, and the time (t) the current flows through it. This relationship is described by Joule’s first law:

Q = I² x R x t

Joule heating occurs in all conductors to some extent when a current passes through them. It is utilized in many electrical heating devices like space heaters, stoves, toasters, and electric kettles. The conductor is designed to offer the desired resistance to generate the required heat for the application.

Resistive Heating

Resistive heating works by passing an electric current through a conductive material that has electrical resistance. As the current passes through, the resistance of the material converts the electric energy into heat energy according to Joule’s first law. The higher the resistance, the more heat that is generated.

Some common examples of resistive heating devices include:

• Electric stoves
• Electric heaters
• Hair dryers
• Toasters
• Coffee makers
• Electric blankets
• Clothes irons

In these devices, heat is generated in the resistive wiring or heating elements. This allows the electrical energy to be efficiently converted into usable heat for cooking, space heating, blow drying hair, etc.

Induction Heating

Induction heating is a process that uses electromagnetic induction to convert electrical energy into heat. It involves passing an alternating current through a coil to generate a fluctuating electromagnetic field, which then induces eddy currents within a conductive material placed nearby. The eddy currents flowing through the resistance of the material generate heat via the Joule effect.

Induction heating has a variety of industrial and commercial applications. It is often used to heat metals and other electrically conductive materials. Some examples include:

• Hardening, tempering, and annealing of metals in heat treatment applications
• Melting and preheating of metals prior to processing
• Brazing and soldering of metal components
• Curing of glues, inks, and coatings
• Cooking and heating of conductive foods and liquids
• Sealing and shrinking of plastic films and packaging

The rapid, non-contact heating provided by induction makes it valuable for industrial manufacturing. It provides efficient targeted heating without direct contact between the coil and workpiece. This helps prevent contamination while offering precise control and consistency.

Dielectric Heating

Dielectric heating, also known as radio frequency heating, is a process that converts electric energy into heat through the interaction of radio frequency electromagnetic fields with dielectric materials such as plastics, ceramics, paper, and wood. Dielectric heating works by applying an alternating electric field to a dielectric material which forces its molecules to rotate back and forth rapidly. The molecular friction from this rapid oscillation generates thermal energy which heats up the material.

In dielectric heating, a high-frequency alternating current is passed between two metal electrodes which have the material to be heated placed between them. The rapidly oscillating electric field applied to the material causes its molecules to rotate continuously in an attempt to align themselves with the alternating field. However, the molecules are unable to rotate fast enough to keep up with the changes in direction of the electric field, resulting in molecular friction and heating.

The amount of heat generated depends on the frequency of the alternating field, the strength of the electric field, and the properties of the dielectric material itself. Materials with a high dielectric constant such as water can be heated more effectively than low dielectric constant materials like air. Dielectric heating is useful for industrial applications like drying wood, plastic welding, food processing, and semiconductor fabrication where materials need to be heated quickly and uniformly.

Microwave Heating

Microwave heating refers to the process of using microwave radiation, usually at a frequency of 2.45 GHz, to generate heat in materials that absorb microwave energy. When irradiated with microwaves, polar molecules such as water align themselves with the rapidly changing electric field. The internal friction generated by this molecular movement causes rapid heating throughout the material.

Microwaves penetrate efficiently into most materials, so microwave heating can be utilized to efficiently heat food, dry substances, cure polymers, and perform many other important heating processes. It has advantages over conventional heating methods in terms of speed and uniformity of heating.

Some common examples and applications of microwave heating include:

• Heating, cooking, and defrosting food in microwave ovens
• Drying paper, wood, textiles, yarn, leather, and other materials
• Curing adhesives, seals, and molded rubber and plastic products
• Sintering ceramic and plastic materials
• Pasteurizing and sterilizing pharmaceutical and medical products

Microwave heating is widely used across industries because it often allows faster, more uniform, and more energy-efficient heating than conventional thermal processing.

Infrared Heating

Infrared heating involves using infrared radiation to transfer heat. Infrared radiation is part of the electromagnetic spectrum that is longer in wavelength than visible light, but shorter than microwaves. When infrared radiation is absorbed by an object, the radiation turns into heat. Many materials, including most non-metals, efficiently absorb infrared radiation.

Some examples of infrared heating uses include:

• Infrared heaters that warm people, surfaces, and spaces
• Drying and curing coatings on products
• Cooking and heating food using infrared heating elements
• Melting and forming glass, plastics, and other substances in manufacturing
• Shrink fitting of metal parts using infrared lamps
• Treating for pain, injury, and various conditions in therapy
• Sanitizing objects like medical tools using infrared waves

Arc Heating

Arc heating is a process that uses electric arcs to heat materiels. An electric arc is formed when a high amperage current passes through a gap between two conductors, resulting in bright, sustained electrical discharge.

The high temperature of the electric arc (which can be up to several thousand degrees Celsius) generates heat that is transferred to the material being processed. The heated material melts or vaporizes, allowing materials to be cut or welded.

Some common arc heating application include:

• Arc welding – Joining metals by melting them with an electric arc and adding a filler material
• Plasma arc cutting – High-power electric arc cutting of metals
• Arc furnaces – Melting metals and alloys with electric arcs

Laser Heating

Laser heating converts electric energy into heat energy through a process called laser ablation. A high power laser beam is focused on the material, hitting the surface with extremely high levels of energy density in a very small area. This intense energy causes the material surface to rapidly heat up, melt, and vaporize, creating a plasma plume. The surrounding material is also heated by conduction as the heat dissipates into the target.

Laser heating is used for a variety of industrial processes that require extremely precise, localized heating including:

• Welding and micro-welding of metals
• Drilling small, high-precision holes
• Cutting intricate patterns and profiles in sheet metal
• Heat treatment to selectively harden, temper or anneal small areas of metals and alloys
• Printed circuit board machining
• Surface texturing
• Marking parts with insignia, serial numbers, barcodes

The rapid, precise heating provided by lasers allows for better control, less thermal distortion, and lower heat input compared to other heating methods. As laser technology continues advancing, so too will laser heating applications across many industries.

Conclusion

In summary, there are several key types of electric energy to heat energy conversions, including:

• Resistive heating – where heat is generated by an electric current moving through a resistive material.
• Induction heating – where heat is generated in a conductor by an electric current induced by an alternating magnetic field.
• Dielectric heating – where heat is generated by applying electromagnetic waves to a dielectric material.
• Microwave heating – a dielectric heating technique applied specifically to microwave frequencies.
• Infrared heating – where infrared radiation (or light) is used to heat an object.
• Arc heating – generating high levels of heat at the site of an electric arc (discharge).
• Laser heating – where heat is generated by focusing a laser beam on a material surface.

The common term used to describe converting electric energy into thermal energy through these processes is Joule heating. This refers to heat produced by the passage of current through a resistive material, causing vibrations in the material’s molecules and atoms. Joule heating power is mathematically defined by Joule’s first law as being proportional to the square of the electric current, times the resistance of the conductor. Many of the processes above employ the principles of Joule heating at their core to enable electric to thermal energy conversion.