Without an understanding of what the current, related to the study of the physics of electricity section impossible.The concept of the current is the basis on which, like a house on a solid foundation, line circuits, and further calculations are more and more determination.The strength of the current is one of the values of the international SI system, so a universal unit of measurement is Ampere (A).
physical meaning of the unit explain as follows: the current in amperes occurs when one movement have charge of particles of two conductors of infinite length, between which the gap of one meter.This occurs at every meter stretch of wire interaction force is numerically equal to 2 x 10 to the power of -7 Newton.Generally added that the conductors are arranged in a vacuum (which can neutralize the influence of the intervening medium), and their cross-section tends to zero (this maximum conductivity).
However, as is usually the case, the classical definition understandable only to specialists, which, in fact, is no longer interested in the basics.But people unfamiliar with electricity "entangled" even more.Therefore, let us explain what the current, literally "on his fingers."Imagine an ordinary battery, from the poles to the bulb which are two insulated wires.The rupture of one wire connected switch.As is known from the initial course of physics, electrical current - a movement of particles with their own electrical charge.Typically, they assumed the electrons (in fact, it is a single electron has a negative charge), although it is actually a little more complicated.These particles are characterized by the conductive materials (metals), but in atmospheres further transfer charge ions (remember the term "ionization" and "breakdown of the air gap");conduction in semiconductors not only electronic but also the hole (positive charge);in electrolytic conductivity of pure ionic solutions (eg car batteries).But let's return to our example.It forms the current movement is free electrons.While the switch is on, the circuit is broken, the particles move nowhere, therefore, the current is zero.But it is necessary "to collect the scheme" as electrons rush from the negative to the positive pole of the battery, passing through the bulb and causing it to glow.Strength, forcing them to move, comes from the electric field generated by a battery (EMF - field - current).
Current - is the ratio of the charge at the time.That is, in fact, we are talking about the amount of electricity flowing through a wire of a conventional unit of time.One can make an analogy with the water: the more open valve, the greater the volume of water has passed through the pipeline.But if the water is measured in liters (cubic meters), the current - or a number of carriers that is also true of amperes.That is so simple.It is not difficult to understand that to increase the strength of the current in two ways: by removing the bulb from the circuit (resistance, prevents movement), as well as increasing the electric field generated by the battery.
Actually, we came to that in the general case, the calculation of the current strength.There are many formulas for example, to complete the circuit, considering the influence of the characteristics of the power supply;for AC and DC currents;for multiphase systems and so forth. However, they all share a single rule - the famous Ohm's law.So give it a common (universal) view:
I = U / R,
where I - current in amperes;U - voltage across the terminals of the power supply, in volts;R - resistance of the circuit or the site in ohms.This relationship only confirms all of the above: current increase can be achieved in two ways, through the resistance (our light) and voltage (parameter source).
