TYPES OF ELECTRICAL HEATING AND APPLICATIONS
INVENTOR OF SKIN EFFECT
JOSEPH STEFAN was born on 24th March 1835 in Austria. He taught physics at the University of Vienna, was Director of the Physical Institute from 1866, Vice-President of the Vienna Academy of Sciences and member of several scientific institutions in Europe. The Stefan hailed from a modest family. His father was a MILLING ASSISTANT and mother served as a MAIDSERVANT. Stefan's father died in 1872 while his mother died almost ten years earlier in 1863.
He published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences, and he is best known for originating a physical power law in 1879 stating that the total radiation from a black body is proportional to the fourth power of its thermodynamic temperature. Very important contributions are also his electromagnetic equations, defined in vector notation, and works in the kinetic theory of heat. He was among the first physicists in Europe who fully understood Maxwell's electromagnetic theory and one of the few outside of England who expanded on it. He calculated inductivity of a coil with a quadratic cross-section, and HE CORRECTED MAXWELL'S MISCALCULATION.
He also researched a phenomenon called the SKIN EFFECT, where high-frequency electric current is greater on the surface of a conductor than in its interior. He died on 7th January 1893.
He lived 57 years in this planet even today he lives in the form of equation, number and constant.
HEAT
The word ‘HEAT’ to mean something that feels warm, but science defines heat as the flow of energy from a warm object to a cooler object. All matter contains heat energy. Heat energy is the result of the movement of tiny particles called atoms, molecules or ions in solids, liquids and gases. Heat energy can be transferred from one object to another, and the transfer or flow due to the difference in temperature between the two objects is called heat.
ALL HEAT ENERGY, INCLUDING HEAT GENERATED BY FIRE, IS TRANSFERRED IN DIFFERENT WAY
RADIATION is the heat we feel coming from a fire. Radiation is the heat that we feel coming from a hot object. It warms the air using heat waves (infrared waves) that radiate out from the hot object in all directions until it is absorbed by other objects.
Transfer of heat by radiation travels at the speed of light and goes great distances.
EMISSIVITY is a measure of the efficiency in which a surface emits thermal energy. It is defined as the fraction of energy being emitted relative to that emitted by a thermally black surface (a black body). A black body is a material that is a perfect emitter of heat energy and has an emissivity value of 1. A material with an emissivity value of 0 would be considered a perfect thermal mirror.
TYPES OF ELECTRIC HEATING – Power frequency heating and High frequency heating.
Electric heating is any process in which electrical energy is converted to heat.
DOMESTIC APPLICATIONS
INDUSTRIAL APPLICATIONS
JOSEPH STEFAN was born on 24th March 1835 in Austria. He taught physics at the University of Vienna, was Director of the Physical Institute from 1866, Vice-President of the Vienna Academy of Sciences and member of several scientific institutions in Europe. The Stefan hailed from a modest family. His father was a MILLING ASSISTANT and mother served as a MAIDSERVANT. Stefan's father died in 1872 while his mother died almost ten years earlier in 1863.
He published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences, and he is best known for originating a physical power law in 1879 stating that the total radiation from a black body is proportional to the fourth power of its thermodynamic temperature. Very important contributions are also his electromagnetic equations, defined in vector notation, and works in the kinetic theory of heat. He was among the first physicists in Europe who fully understood Maxwell's electromagnetic theory and one of the few outside of England who expanded on it. He calculated inductivity of a coil with a quadratic cross-section, and HE CORRECTED MAXWELL'S MISCALCULATION.
He also researched a phenomenon called the SKIN EFFECT, where high-frequency electric current is greater on the surface of a conductor than in its interior. He died on 7th January 1893.
He lived 57 years in this planet even today he lives in the form of equation, number and constant.
HEAT
The word ‘HEAT’ to mean something that feels warm, but science defines heat as the flow of energy from a warm object to a cooler object. All matter contains heat energy. Heat energy is the result of the movement of tiny particles called atoms, molecules or ions in solids, liquids and gases. Heat energy can be transferred from one object to another, and the transfer or flow due to the difference in temperature between the two objects is called heat.
ALL HEAT ENERGY, INCLUDING HEAT GENERATED BY FIRE, IS TRANSFERRED IN DIFFERENT WAY
- Convection spreads heat in a circular motion - Convection transfers heat energy through the air (and liquids). As the air heats up, the particles move further apart and become less dense, which causes the air to rise. Cooler air below moves in and heats up, creating a circular motion. The warm air circles and heats the room.
- Conduction transfers heat through solid materials - Conduction transfers heat energy through one substance to another when they are in direct contact. The moving molecules of a warm material can increase the energy of the molecules in a cooler material. Since particles are closer together, solids conduct heat better than liquids or gases.
RADIATION is the heat we feel coming from a fire. Radiation is the heat that we feel coming from a hot object. It warms the air using heat waves (infrared waves) that radiate out from the hot object in all directions until it is absorbed by other objects.
Transfer of heat by radiation travels at the speed of light and goes great distances.
EMISSIVITY is a measure of the efficiency in which a surface emits thermal energy. It is defined as the fraction of energy being emitted relative to that emitted by a thermally black surface (a black body). A black body is a material that is a perfect emitter of heat energy and has an emissivity value of 1. A material with an emissivity value of 0 would be considered a perfect thermal mirror.
TYPES OF ELECTRIC HEATING – Power frequency heating and High frequency heating.
- RESISTANCE HEATING – When current is passed through a conductor, the conductor becomes hot.
- INDUCTION HEATING – When a magnetic material is subjected brought in the vicinity of an alternating field, heat is produced in the magnetic material.
- DIELECTRIC HEATING – When an electrically insulting material is subjected to electrical stresses, it underwent a temperature rise.
Electric heating is any process in which electrical energy is converted to heat.
DOMESTIC APPLICATIONS
- Hot plates for cooking
- Immersion heater for water heating
- Electric irons
- Electic oven for bakeries
- Room heaters
INDUSTRIAL APPLICATIONS
- Melting of metals
- Heat treatment process
- Moulding of glass
- Baking of insulators
- Enameling of copper wires