|Amperes per meter||FREQUENZA|
|ELECTROMAGNETIC ABSORPTION in man||GRANDEZZA VETTORIALE|
|SPECIFIC HEAT||INTENSITA' DI CORRENTE|
|ELECTROMAGNETIC FIELDS BUTTONS||LAVORO ELETTRICO|
|CAMPO MAGNETICO||LUNGHEZZA D'ONDA|
|ELECTRIC CHARGE||ONDA ELETTROMAGNETICA|
|ELECTRICAL CONTINUES ELECTRICITY||PERMEABILITA' MAGNETICA|
|CORRENTE INDOTTA||POTENZIALE ELETTRICO|
|COSTANTE DIELETTRICA||PRODOTTO VETTORIALE|
|DENSITÀ DI CORRENTE||REOSTATO|
|EFFETTO PIEZOELETTRICO||SISTEMA INTERNAZIONALE DI MISURA|
|ELETTROLISI||VALORE QUADRATICO MEDIO|
|ELETTROMAGNETISMO||VOLT per METRO|
|Amperes per meter (A / m): unit of measure in the International System of the intensity of magnetic field (H). 1 A / m corresponds to a magnetic field produced by a current of 1 A linear distance of 1/2p m.|
SCOPE: The width is the value taken from moment to moment components of a wave in the case of electromagnetic wave is the instantaneous value of electric field (measured in V / m) and / or field magnet (measured in A / m). (See ELECTROMAGNETIC WAVE)
ELECTROMAGNETIC ABSORPTION in man: the human body exposed to an electromagnetic field absorbs energy. The extent of absorption of energy depends on the frequency of the electromagnetic incident, as well as the shape and size of the body exposed to the wave front. The absorption has a maximum at a frequency (resonance frequency) that is linked to size of the body. At frequencies below the resonance absorption decreases rapidly, while at frequencies higher than initially decreases and then remains at a nearly constant value. For a man of average size of the resonance frequency is around 70 MHz, while for parts of the body exposed to the smaller size, the frequency of resonance is most high, reaching frequencies of hundreds of MHz, for example, to the retina there is a resonance frequency of about 21 GHz, for the lens around 9 GHz, etc. .. The electromagnetic energy absorbed by a biological tissue is RODUCTION in heat (heat), since the electromagnetic field makes oscillating charges and dipoles in the molecular field, and these fluctuations through the interaction between the molecules are degraded in motion molecular disordered, that is precisely heat. One of the most important molecules nell'assorbimento of electromagnetic energy is water, which is a permanent molecular dipole
(See Electric Dipole). See also ADJUSTMENT MECHANISMS AND DISPERSION OF HEAT.
When varying the current circulating in a conductor, the magnetic field variable resulting invests the same conduit leading to it a difference of potential. This potential difference autoindotta opposes the applied potential difference and tends to limit or reverse the correnteoriginaria. The concept of electric autoinduction is similar to that of mechanical inertia. A coil of arrest tends to soften the current trend of a variable, like a fly sweetens the rotation of an engine. The ability to autoinduction of a coil is quantified dall'induttanza, which is independent of the intensity of current or potential difference and is determined solely by the geometric characteristics of the coil and the magnetic properties of the substance that forms the nucleus.
|SPECIFIC HEAT: heat capacity (View CAPACITY 'TERMICA) of a homogeneous unit
mass, ie the quantity of heat required to raise one degree temperature of a unit mass of a substance. Any material (substance) has a characteristic specific heat that usually depends on the temperature and pressure of the same.
HEAT: energy flowing from one body to another due to the temperature
difference there is between them. Often is measured in calories but in
the International System unit of measurement is the joule (J). (See WORK).
|ELECTROMAGNETIC FIELDS BUTTONS (PEMFA): an electromagnetic field that varies periodically with
a certain period T, whose intensity is greater than a certain value (which may be zero) for a period of time less than T.
|ELECTRIC FIELD: you can define an electric field region of the space in which an electrical charge (or electrically charged body) is subjected to a force proportional to the position itself. To describe the field using the vector electric field, which indicates that E is the electrical force that acting on the charge. In the International System unit of electric field is the newton / coulomb (N / C) or volt / m (V / m), or their multiples (eg kV / m). The electric field is generated by electric charges or magnetic field from a variable duration (see LAW OF FARADAY). When the electric charges which generate an electric field is fixed in space the field Electricity has a constant value at any point and is called the electrostatic field.|
|Electromagnetic fields: a magnetic field variable frequency f, produces near a variable electric field, also at frequency f, which is still held close to a magnetic field variable ... and so on. Magnetic and electric fields rapidly varying do not remain separate from them: one creates the other and both coexist in an inseparable which is called electromagnetic field. As a result of processes of mutual generation, under appropriate conditions, the electromagnetic field propagates, ie moves away from its source, with a characteristic speed, which in vacuum coincides with the speed of light (c 3108 m / s) generating the so called electromagnetic waves.|
FIELD The magnetic field is generated by moving charges, ie
current electrical, and in turn acts on currents or moving
charges. The magnetic field can be created by an electric
field varies in time (see FOR MAXWELL EQUATIONS). The magnets
Permanent (magnets) generate a magnetic field caused by the presence of
currents, these currents atom, due to the motion of electrons
(spin). The magnetic field is represented by a
Carrier said magnetic induction B or H the magnetic field strength. The relationship between H and B is the
follows: H = B / mem = magnetic permeability of the medium considered. Graphically the magnetic field is
often represented by lines of force that are at every point tangent to the direction of the vector magnetic field (either B or H), in agreement with Farady, the number of lines of force crossing perpendicular to the unit area is proportional to the carrier. See also FLOW MAGNETIC.
|ELECTRICAL LOAD: the electric charge should be considered a fundamental property of matter.
There are two types of electric charge, one positive and one negative. Two electric charges of the same type repel each, two opposite charges attract each type. The unit of charge in the International System is the coulomb (C) which is defined as the amount of charge flowing in a second when you have a current stable of 1 amps. Exists in nature a small electric charge elementary, which corresponds to that of electronics (e = 1.6 × 10-19 coulomb) and any other charge is always a multiple of this.
ELECTRIC CHARGE (Q) For the physical current (Note: there are those who deny it) is a property of matter. The charge can be positive or negative. Its unit is the Coulomb (C).
The smallest charge exists in nature, the elementary charge, is that electronics (negative), exactly (we think) the same as the proton (positive). It is true 1.602 * 10-19C. The proton has a
mass equal to 1840 times the mass of electronics.
Any pair of conductors (armature) separated by an insulator (dielectric), are a
If you apply a voltage between the armor, separate electric charges, and in the dielectric, is formed an electric field. The armature is connected to the highest potential is positively charged, negatively the other. The positive and negative charges are equal and their absolute value is the charge Q of the capacitor. The charge is proportional to the applied voltage and the proportionality constant is a characteristic of that particular capacitor which is called capacity. Is measured in farad [F] = [C] [V] -1 <
The ability of a plane condenser (flat armature and parallel) is proportional to the ratio between the area (A) one of the armors and their distance (d). The constant of proportionality (and) is a characteristic dell'isolante to come and is called absolute dielectric constant and is measured in farad / m [F] [M]
The dielectric constant of the vacuum that is absolute and 0 = 8.85 * 10-12 F / m. The relationship between the absolute dielectric constant of an insulating dielectric constant and the absolute vacuum is a pure number called the relative dielectric constant (er = e / e 0).
Mathematically summarizing what was said:
Q = C * U (defining capacity of a condenser)
C and re 0A = / d (condenser capacity plan)
K = U / d (electric field in the dielectric of a condenser piano)
|CONDUCTOR OR ELECTRIC CONDUCTOR: any body or medium capable of conducting current electricity.|
|ALTERNATING ELECTRICITY: Electrical current is called alternating current, whose intensity sinusoidal varies as a function of time. For the distribution of electricity generally is usedan alternating current frequency of 50 Hz (in Europe) or 60 Hz (in USA).|
|ELECTRICAL CONTINUES ELECTRICITY: an electric current is called continuous if its intensity and its direction (conventionally understood as the direction of the virtual displacement of positive charges), do not vary over time.|
|ELECTRICITY: Electrical current is called every motion of electric charges ordered. The intensity power is expressed by the amount of charge (in coulombs, C) through a certain section in the unit of time (seconds, s). The intensity of the current international system, as has Unit measuring the amps (A). 1 amps corresponds to 1 coulomb / s.|
|POWER LED: the induced current is a current that occurs in a conductor when it is placed in a region of space where a magnetic field variable in time. In accordance with Faraday's law (one of the four Maxwell equations) the current is maintained as long as there is a change in the flow of the magnetic field and is greater the more rapid is the change. On the law of Faraday are based applications, such as alternators and generator, which, in power stations to generate electricity from mechanical energy (the rotation produced by a heat engine or the drop of water).|
|Dielectric constant: see dielectric constant e. ABSOLUTE|
ABSOLUTE dielectric constant (or dielectric constant) and is a parameter characteristic of a material and represents the effect that the barrier material itself produces when two charges immersed in it interact: the strength of interaction (Coulomb force) is reduced by a factor and . Represents the
characteristic of the insulation material. The dielectric constant e0 absolute vacuum that is the International System 8.85 × 10-12 (C2 / N) m2. Typically a substance has a dielectric constant and greater than 0; The e/e0 = er is the so-called relative dielectric constant. er depends on the frequency and the applied field strength: this dependence is the frequency
so-called dielectric dispersion.
|Dielectric constant er ON: see dielectric constant e. ABSOLUTE|
|POWER DENSITY: the current density at a point is defined by the relationship between the intensity of current through an element of the surface (perpendicular to the current direction) and the surface of the same. The current density is a vector and indicates with J. It is shown that the intensity of current can be represented as the flow of the carrier through the J section of the conductor. The current density in the International System, is measured in ampère/metro2 (A/m2). You often use the sub: milliampère/metro2 (mA/m2), microampère/metro2 (mA/m2) or microampère/centimetro2 (mA/cm2), sometimes also uses the nanoampère/metro2 (nA/m2).|
|Dielectric is a non-conducting material or insulating. In these substances do not have offices
free electricity, that is, the electrons are tightly bound to atoms and can not be removed from their home by an ordinary electric field.
Piezoelectric effect: it consists in the appearance of electric charges of opposite sign on the faces of some crystals subjected to mechanical deformation along certain directions, and vice versa (dual effect): the polarization of a material by an electric field it produces a mechanical deformation. This effect is of great practical importance, for example, is used in the construction of oscillators that cause the ultrasound, or to convert mechanical oscillations into electrical oscillations. Some biological tissues such as bones have piezoelectric properties.
|Electricity from the greek = ELEKTRON AMBRA|
|Electricity term introduced in 1694 by R.Boyle in scientific terminology.|
|Electrolysis chemical decomposition by electric current, a term coined by Faraday|
|Electromagnetism term coined by Oersted|
|Electronvolt (eV): unit of measure for the energy used in physics to measure energy scale Atomic Energy. A electronvolt (eV) represents the energy gained by an electron passing through apotential difference of one volt. As in the International System charge of electronics and = = 1.6x10-19 C then follows that 1 eV = 1.6x10-19x1V = 1.6x10-19 J.|
|ENERGY: Energy can be defined as the ability of a body to do work, and the extent of this work is also measure of energy. There are different forms of energy: a body that moves with the kinetic energy. Even a strong body can have energy, due to its position that potential energy. In addition, any body has an energy-related internal energy of its atomic components. Still, the law of Einstein E = mc2 (where m = mass c = speed of light = 3x108m / s) provides that at each mass is associated with an energy and, virtually, vice versa. Although we are used to thinking of energy as an attribute of a body, it can exist even without the presence of a body of material (ie with mass). For example, an electromagnetic field has energy, called electromagnetic energy, even where there is no issue. Energy is a size and scale as the unit of measurement in the International System joule (symbol J).|
|MAGNETIC FLUX: number of lines of force passing through a given surface perpendicular. Dividing the number of lines of force to the surface is obtained by the density of magnetic flux.|
|Electromotive STRONG (E) The energy that the generator actually supplies all' unit of positive charge. It corresponds to the voltage present at terminals of the generator when it delivers current (no-load operation, open circuit). Is measured in volts.|
|FREQUENCY: the number of times a periodic phenomenon occurs in the unit of time or number of oscillations in time. Typically the frequency is measured in hertz (Hz) or in an equivalent manner, in seconds-1 (s-1), which represents the number of oscillations (or cycles) per second.|
ELECTRIC GENERATOR A machine using a different form of energy (thermal, mechanical, chemical, solar, etc..) Transforms it into electricity, creating a separation of charges (excess of electrons at the negative pole, the lack of positive electrons).
If the poles of the generator are connected to each other, is established in the circuit an electric current to the conventional bead positive pole of the generator. Inside the generator, the conventional current flows from negative to positive (the charges buy energy) outside the positive pole to the negative (the charges lose energy).
|IDEAL GENERATOR VOLTAGE (U = E for each I).
A generator that keeps the voltage between its terminals regardless of the value of the intensity of current that goes through it.
|IDEAL POWER GENERATOR (I = I0 per U). |
A generator that maintains the constant current output regardless of the value of the voltage to its terminals.
|GENERATOR REAL LINEAR VOLTAGE (UAB-Ri = E * I) |
It 'an electric generator in which the voltage at the terminals decreases in proportion to the intensity of current which is crossed. E 'shown by an ideal voltage generator in series with a resistor Ri, the internal resistance of the generator.
The electromotive force of the generator voltage is ideal voltage vacuum.
The maximum current that the generator can deliver, you have in a short circuit, because
voltage at the terminals is cleared through a resistance of zero. This current is called
Short circuit current of the generator and applies Icc = E / Ri. The product of internal resistance to current is the internal voltage drop.
| LINEAR GENERATOR REAL POWER (I = I0-UAB/Ri) |
It 'an electric generator in which the output current decreases in proportion to the voltage present at its terminals. Is shown with an ideal current generator, whose value, I0, is the maximum current supplied by the generator (which is in short circuit) in parallel with a resistance that internal resistance Ri. If the terminals of the generator is a voltage equal to Ri * I0 current output is nothing (the generator is operating under vacuum)
|SIZE SCALE (or Scala): greatness that is completely determined by the number that the measures at a certain scale. E 'a number which expresses the relationship between size and another magnitude of the same type used as a unit. For example, the length, time, temperature values arescalars, which may be defined by a number which expresses the measure.|
|Vector (or vector) size determined by a module (or intensity), which represents the numerical value in accordance with a scale set arbitrarily, and its direction. Graphically a vector is represented by an oriented segment whose length is' intensity of the carrier. Carriers are often marked with bold letters or letters with the above by an arrow (for example, or). A carrier may be added or subtracted from other carriers and can also be multiplied for a scale size is another vector: vector nell'algebra us are two possible types of multiplication: the product and the scalar vector product (or product andouter product).|
E 'a component that produces a magnetic field. From this point of view, any path from the current conductor is an inductor. Call but preferably the inductor component which was specially built to produce a magnetic field of given value. The parameter that characterizes the rate of autoinduction L which is defined as the ratio of the magnetic flux concatenated with the conductor and the intensity of current which produces it. Hence
L = Fc / I
The unit of measurement is called the henry (H) and corresponds to the ratio of weber and amps, as the weber, unit of measure of magnetic flux, is the product of volt * second, the henry is the product of ohm per second.
[H] = [W] [s]
The coefficient of autoinduction depends on the geometric characteristics of the conductor, appearing as the number of turns N (number of laps completed by the angles conductor), and the size and physical properties of the medium in which the conductor develops its magnetic field. To fix ideas we consider a solenoid (coil) consists of N straight circular coils of diameter D, uniformly distributed over a length l. We have:
L = N2/Ri
where Ril = (1 / m) * l / A is called reluctance. A = PD2 / 4, is the surface area bounded by a flat coil, m is the absolute magnetic permeability of the medium in which the field is formed. Since N is a pure number, the unit of measure of the reluctance is the inverse dell'henry [H] -1. The magnetic permeability is, theoretically, the coefficient that characterizes autoinduction by a particular circuit configuration: that for which N2 * A / l = 1. Therefore be measured in meters divided henry [H] [M] -1, units that do not have a proper name.
Most important is the magnetic permeability of the void: m0 = 4 * p * 10-7 H / m
Magnetic permeability is defined on half of the physical relationship between its permeability and absolute permeability of vuotomr = m/m0. E 'a pure number.
MAGNETIC INDUCTION DENSITY or 'magnetic flux in each point in space where you resent a magnetic field is called magnetic induction vector B, whose width is given by the full force that is exercised on the current divided by explorer the product of current and for the length of the item. This vector characterizes in full all of the properties of the magnetic field and is measured in the International System, in tesla (symbol T) by the name the Croatian physicist Nicola Tesla. It is sometimes also used an old unit of measurement called gauss (G symbol, 1G = 10-4T). See also MAGNETIC FLUX.
|INTENSITY OF POWER (or DC), which defines the current intensity through the surface S amount of charge that passes in time through the surface. It is a size scale and its units, in the International System, the amps (A). A = 1 coulomb / s, where coulomb (C) indicates the unit of charge.|
|ELECTRICAL INSULATING OR INSULATING: device high electrical resistance used to support or separate conductors to prevent flow of unwanted current between the conductors and other objects.|
|ELECTRICAL WORK: Work done by an electric field to move an electrical charge from a point A to point B. The electrical work is given by the following expression: L = q (VA-VB) where VA and VB are the electric potential of A and B respectively.|
|WORK: When a force acting on a body, moving it to a certain distance it is said that the force is making a job. Work is defined as the scalar product between the vector representing the intensity of force and the displacement vector. The unit of measurement of work in the International System, is the joule (J). 1J = 1N × m.|
|VISIBLE LIGHT: non-ionizing radiation with frequencies between 385 MHz and 106 × 750 × 106 MHz and wavelength of between 0.4 and 0.8 mm. (See ELECTROMAGNETIC SPECTRUM)|
WAVE LENGTH: represents the maximum distance between two (or two minima) of a sine wave. The wavelength is indicated with the letter l and its measurement unit meter (m).
|ELECTROMAGNETIC WAVE: electromagnetic waves are called electromagnetic fields that propagate in space, even in the absence of matter. The electromagnetic waves are transverse, the electric field vector E and the vector magnetic field H are mutually perpendicular and lie on a plane perpendicular to vector v, the wave propagation speed. The relationship between E and H, in an electromagnetic wave is determined by Maxwell equations. Like any type of wave, electromagnetic waves can transport energy from one point to another and can be characterized by its frequency (or the wavelength) and its width.|
|Ohm Unit of measure of resistance that has the same name of its discoverer Ohm|
PERIOD: The smallest interval of time after which a periodic motion summarizes the same physical characteristics (amplitude and its derivative). The period is indicated by the symbol T and its units to the second (s).
Permeability 'MAGNETIC m is a parameter characteristic of the material and represents the ability to leave this to permeate from magnetic fields. The magnetic permeability of vacuum m0 namely, in the International System, 4p10-7 H / m. The report m/m0 = mr is the so-called relative magnetic permeability (to empty). mr is used to distinguish between substances diamagnetic (mr <1) and paramagnetic substances (mr> 1).
|POWER: is the ability to produce work per unit of time. Also represents the energy
produced or dissipated per unit of time. In the International System unit of power is J / s, said Watt
ELECTRIC POTENTIAL: Is the work to be done against the forces of the field to bring
a unit charge from a reference point in question, the reference point is at infinity or, for convenience, on the surface of the earth or some other major tenant. The electric potential is a scalar magnitude and in the International System is measured in volts, the symbol V (1V = 1J / C). The electrical potential can be considered as an intensive quantity like the pressure, or level in a fluid. A difference of potential can bring a positive charge from one point to greater potential to one with less potential, similar to what the water that falls from a higher level to a
|INTENSITY 'POWER. (I = Q / t) |
It defines the intensity of the current amount of charge that passes through a section of a tenant in the unit of time. The name of the unit of measure is the 'Ampere (A) which corresponds to 1 Coulomb per second. Is taken as to the conventional argument that the current move the posts positive. In metallic conductors the offices that are moving electrons, those of value, also responsible for chemical reactions.
The intensity of current is taken as a sample of units of measurement. It defines ABSOLUTE AMPERE the intensity of the current one which, along two parallel wires of negligible section and infinite length, placed in a vacuum at a distance of one meter means that they attract (current agreement) or reject (current disagreement) with a force equal to 2 * 10-7 N per meter length of wire.
|PRODUCT Vector between two vectors a and b that are inclined at an angle q is written as: ax bed is defined as a vector which has the form given by ab × senq direction perpendicular to the plane containing AEBE given to the direction of advancement of a lives destrogira ordered perpendicular to the plane containing the two carriers, which go on to b through the angle smaller.|
Rheostat term coined by C. Wheatstone esistor variable resistance
|ELECTRICAL RESISTANCE (R = U / I) - Read Ohm.
And 'the relationship between the voltage at the head of a tenant and the stream that runs. It remains almost constant if the temperature of the conductor does not undergo major changes. E 'therefore a property of the respective conduit which depends on the material of which it is composed and is proportional to the length of the conductor divided by its cross section.
Is measured in ohms 1 Ohm is the resistance of a conductor subjected to voltage of 1 volt is
crossed by the current of 1 Ampere.
The direction of current through a conventional resistance goes from a higher potential to the potential to lower.
Resonance: the phenomenon on a physical system with a characteristic frequency (free oscillations), which occurs every time a system to oscillate is subject to a periodic series of pulses of frequency equal or near to one of the frequencies of oscillation of the system. When these conditions are met the state of the system oscillates with an amplitude that increases until it reaches a maximum value at which the energy absorbed by the matched pulses is dissipated fromby the forces of friction.
|INTERNATIONAL MEASUREMENT SYSTEM: A system of physical units in which the fundamental are the length, time, mass, electric current, temperature, light intensity and amount of substance, and the corresponding units of measurement are the meter, second, kilogram, the amps, the kelvin, the candela and the mole.|
|THEOREM OF EQUIVALENT GENERATOR VOLTAGE (Thevenin)
Each bipolar produced by a complex network, however, composed of ideal voltage generator and / or current and bipolar linear passive (resistance, impedance AC) is always a schematization generator real linear voltage generator Thevenin said. The electromotive force of generator Thevenin (Eth) is equal to the no-load voltage measured between the terminals of bipolar (Eth = (UAB) I = 0). Its internal resistance (rth) is obtained:
1.dal relationship between the electromotive force and current short-circuit that is obtained when
connecting the terminals of a bipolar with no resistance wire
2.determinando the equivalent resistance of bipolar which is obtained by annulling the action of all generators (thus opening the branches with the ideals of current generators (I0 = 0), and short-circuit generators ideal voltage (U = 0)).
|THEOREM OF EQUIVALENT POWER GENERATOR (NORTON)
Each bipolar produced by a complex network, however, composed of ideal voltage generator and / or current and bipolar linear passive (resistance, impedance AC) is always a schematization generator real power linear generator Norton said. The intensity of the current ideal of the generator current (Ino, current Norton) is the current one has short-circuit the terminals of the bipolar. Its internal resistance (RNO) is obtained:
1.dal relationship between the no-load voltage and current of Norton.
2.determinando the equivalent resistance of bipolar which is obtained by annulling the action of all generators (thus opening the branches with the ideals of current generators (I0 = 0), and short-circuit generators ideal voltage (U = 0)). So RNO = rth
TESLA: units of measurement in the International System magnetic induction B (symbol T).
|Transducer goes to a device that performs one to another of the ways in which energy is manifested
(electrical, mechanical sound, heat, light).
EFFECTIVE VALUE OF A SIZE: See root mean square value.
mean square value (RMS) is the square root of the average of the
squares of a size periodically. For example, for a sinusoidal signal,
the mean square value scale is the maximum scale value divided by
square root of two: Aeffe AM = /. The root mean square value is
used to simplify some formulas, for example, when you want to derive the average power dissipated by un'induttanza, and / or capacity, and / or resistance in a circuit path from AC power.
|Volts per meter (V / m): unit of measure in the International System the intensity of electric field (E). 1 V / m is the electric field between two points separated by a distance of one meter between which there is a potential difference of 1 volt.|