Chemiluminescence

Chemiluminescence is a chemical reaction that produces light without heat.

Example: Light sticks - (Usually seen in amusement parks and carnivals in the shape of bracelets and necklaces). The light sticks have some reactants inside which are separated by a thin glass. Once the glass is broken and reactants get mixed, chemiluminescence reaction takes place and the stick begins to emit light.

Ohms Law

Ohm's Law states that when the resistance of a material is lesser than the electric potential between the ends of it, current is produced.

Example: Conductors - Transmission lines used to transfer power consist of conductor materials which have less resistance.

Eddy Currents

Eddy Current is an electric current in a conducting material that results from induction by a moving or varying magnetic field.

Example: Eddy-Current Testing - Normally, gas-turbine blades are subject to severe mechanical and thermal stresses. They are provided with a protective coating. The quality of that coating can be checked, inter alia, by using an eddy-current test method. In that case, an excitation coil is used to produce a magnetic alternating field which causes eddy currents in the material to be tested. The eddy currents in turn cause a magnetic alternating field, which is measured by using a detector coil. Material faults have a characteristic influence on the measured magnetic field, and can thus be detected.

Electrokinetics

Electrokinetics: When charged particles move through a dielectric, a potential is developed along the dielectric medium and this potential is known as Electrokinetic potential.

Example: Water flowing through the fine tubes carries more positively charged ions with it than negetively charged ions(Charged particles move through 'dielectric'). This means that positively charged ions accumulate at the far end of the tube, creating a voltage between one end and the other. When both ends are connected by a wire, a current flows.

Electro-dynamic Effect

No description available

Electroluminescence

Electroluminescence is the direct conversion of electric energy to light by a substance subjected to an alternating electric field.

Example: Display Devices - Display screens in television sets which converts electric information to light.

Electromagnetic- Induction

Electromagnetic Induction is the influence by which an electric current produces magnetic polarity in certain bodies near or around which it passes.

Example: Charging devices for charging batteries - The device consists of a primary coil which is connected to power supply and a secondary coil which is placed near the primary and connected to the battery to charged. An AC current is applied to the primary coil, which produces magnetic polarity in the secondary by electromagnetic induction. The varying magnetic field produces an electromotive force in the secondary which is supplied to the battery.

Electrostatic Induction

Electrostatic Induction is the action by which a body possessing a charge of statical electricity develops a charge of statical electricity of the opposite character in a neighbouring body.

Example: Non-contact ink developing method for developing an electrostatic latent image - This method comprises the steps of producing a large number of very small ink droplets, and ejecting the ink droplets toward the electrostatic latent image in a developing area facing the electrostatic latent image formation member by an electrostatic induction force generated by charges of the electrostatic latent image and attaching the droplets to the electrostatic latent image.

Fluorescence

Fluorescence is the phenomenon in which absorption of light of a given wavelength by a fluorescent molecule is followed by the emission of light at longer wavelengths. The distribution of wavelength-dependent intensity that causes fluorescence is known as the fluorescence excitation spectrum, and the distribution of wavelength-dependent intensity of emitted energy is known as the fluorescence emission spectrum.

Example: Fluorescent stickers and paints - used in signals and advertisements on the roads so that during night when the light rays from vehicles hit the stickers, it emits light of longer wavelengths.

Frictional Electricity

Frictional Electricity is the charge produced by the friction between two objects. When the two objects are rubbed, electron of the atoms which are consisted of a matter moves and the electric balance is broken. Then electricity is generated.

Example: Van de Graaff generator.

Capacitance Effect

Capacitance for a parallel-plate capacitor Capacitance is a proportionality constant. It is a constant for a given capacitor. It does not depend upon charge or voltage. Its value only depends upon the structure and dimensions of the capacitor itself. For a parallel-plate capacitor with plates of area A separated by a distance d of air, the capacitance is given by: This relationship makes sense. Plates with a larger area will have less repulsion between charges (they're further apart) for a given amount of charge q. Thus, more charge can be held. A greater separation means that the charge on each plate exerts less attractive force on the other plate. Less charge is drawn from the battery, and the capacitance is less. Notice the use of the permitivity of free space constant (We learned in our previous unit how Coulomb's constant was related to the permitivity of free space.)

Induction

Induction is the generation of electromotive force in a closed circuit by a varying magnetic flux through the circuit.

Example: AC and DC Generators - When the magnetic flux is changed by rotating the armature kept in the magnetic field, electricity is generated.

Magneto-hydrodynamic Effect

Magneto-Hydrodynamic Effect: When a high-velocity stream of partially ionized gas is exposed to a transverse magnetic field, the positive and negative ions are separated. When these positive and negative components are passed between electrodes, an electromotive force is produced. This is known as Magneto-hydrodynamic Effect.

Example: Magneto-Hydrodynamic Generator - A magneto-hydrodynamic generator operates by exposing a high-velocity stream of partially ionized gas to a transverse magnetic field, which separates the positive and negative ions; these positive and negative components are passed between electrodes, generating an electromotive force, which is then available for use.

Thermionic Emission

Thermionic Emission is the emission of electrons from very hot substances.

Example: Thermionic Cathode - Thermionic cathode is based on thermionic emission and is used for a colour CRT (Cathode Ray Tube) such as a colour television or a CRT for industrial use.

Photoconductivity

Photoconductivity is the increase of current in a substance due to the absorption of photons.

Example: Photovoltaic Cell - Photovoltaic cell is used to convert solar energy to electricity.

Photoluminescence

Photoluminescence: When light is directed on to a sample, it is absorbed and imparts excess energy into the material. This excess energy can be dissipated by the sample through the emission of light, or luminescence. This luminescence is called Photoluminescence.

Example: Impurity levels and defect detection - Radiative transitions in semiconductors involve localized defect levels. The photoluminescence energy associated with these levels can be used to identify specific defects, and the amount of photoluminescence can be used to determine their concentration.

Piezoelectric Effect

Piezoelectric Effect: Certain crystals are called piezoelectric when they exhibit a relationship between mechanical strain (tension or compression) and voltage across their surfaces. Specifically, when compressed or pulled, a piezoelectric crystal will build up alternate charges on opposite faces, thus acting like a capacitor with an applied voltage. A current, called Piezoelectricity can then be generated between the faces. On the other hand, when subjected to an external voltage, the crystal will expand or contract accordingly.

Example: Pressure Sensors - The change in pressure is detected in the form of voltage due to Piezoelectric effect.

Pockels Effect

Pockel's Effect is an electro-optical effect in which the application of an electric field produces a birefringence, which is proportional to the field. Only crystals, which lack a center of symmetry may show this effect.

Example: Sensor for measuring electric voltages and/or electric field intensities. In the sensor, a crystal with an electro-optical (Pockels) effect is used. To this end, in a direction transverse to the direction of propagation (y direction) of a light wave polarized in the z direction, an electric field intensity gradient is generated in the crystal in the direction from which results a corresponding gradient in the refractive index n of the crystal. This produces a deflection of the light wave in the crystal which depends upon the field intensity and on emergence, it is used as a measure for the voltage of field intensity.

Pyroelectricity

Pyroelectricity is a temperature dependent electrical polarisation, i.e. an electrical current is produced when the temperature changes.

Example: Heat Sensors - Materials which possess pyroelectric property are ideal as heat sensors.

Radioluminescence

Radioluminescence is luminescence arising from excitation by high energy particles or nuclear radiation.

Example: A radioluminous, RL, paint is the selfluminous compound used for painting in defence, telephone, industries and traffic signs. It contains radioactive materials such as Tritium, 3H, Promethium, 147Pm and Carbon, 14C, etc. emitting beta particles of various energies.

Seebeck Effect

The Seebeck Effect is a phenomenon wherein, when a temperature difference arises between two different points of an electrically conductive material, an electromotive force is developed in proportion to the temperature difference.

Example: Sensors using Thermo-electric material. Sensors using such thermoelectric materials are in most cases implemented by making use of a function of detecting temperature difference.

Sonoluminescence

Sonoluminescence effect occurs, when a bubble of gas in a fluid is bombarded by sound waves of a certain energy, and it produces flashes of light.

Tribo-electricity

Tribo-Electricity is an electrical charge produced by friction between two objects.

Example: Tribo-electricity is used to identify particular plastics materials which produce a characteristic charge polarity when rubbed against another known material.

A clean, substantially charge-free surface is prepared on a piece of unidentified plastics material. Then different areas of the surface is rubbed with different reference materials. If the size and polarity of the electrostatic charge thus generated is measured, the other materials can be ranked relative to each other to produce a series related to that reference material.

Triboluminescence

Triboluminescence: Luminescence (light) triggered by mechanical energy or electrical energy from a mechanical action such as friction is known as Triboluminescence.

Example: WintOGreen Lifesavers Candy - When the candy is put in the mouth and crunched, it emits blue light.

Noise Effect

No description available

Radioactivity

Radioactivity is the spontaneous emission of radiation, either directly from unstable atomic nuclei or as a consequence of a nuclear reaction.

Example: Nuclear Medicine - "Nuclear medicine" refers in part to that branch of the medical field which uses various types of radioactive isotopes to detect internal organic and histological defects in a patient by emitting radiations. Generally, a chemical composition incorporating a radioactive isotope is injected or otherwise administered to a patient and, after a sufficient period to allow absorption of the composition by target tissues, the patient is scanned to detect whether and to what extent the chemical composition has been absorbed.

Compton effect

Increase in the wavelengths of X rays and gamma rays when they collide with and are scattered from loosely bound electrons in matter is called Compton effect.

Example: It is used in the study of electrons in matter and in the production of variable energy gamma-ray beams.