Chemical current sources (batteries and accumulators) is so firmly established in our lives, becoming something familiar and naturally, that many owners do not read what is written on their packages and packaging.And it is in vain, because there is a very curious warning - "Do not close."Who are the least familiar with the basics of electrical engineering, he is well aware that such a short-circuit current, and why we can not make contact.
Any current source always has two poles: positive and negative (+ and -) DC, as well as the phase and the ground (zero mass, sometimes the other phase) for the variable.The movement of charged particles is only possible if these poles are connected with a conductive material.If the rupture of a conductor to connect the appliance, the current flowing on the circuits of the device will perform certain work.The main feature - the specified appliance chain does not allow electrons to pass through it freely, so we can always assume that there is a resistance (load), which limits the maximum flow of particles (short circuit current).
To facilitate understanding give an example of the water flowing through the channel (conductor).Start flow - is one pole, and its end - the second pole.In the middle of the channel arranged blades watermill (load), the rotating movement of water (current).Obviously, the rate of flow is always limited by the resistance of the blades.But what happens when the mill will disappear?Water does not experience resistance, rush through the channel with a top speed that can provide a source (short circuit).It is very likely damage to rapid flow as a source and channel.The intensity of the electricity flow - is the power of short-circuit current.
The same goes for electricity.If for any reason the resistance of the circuit begins to go to zero, there is a short circuit current.Explorer is being heated, and the power supply is damaged.This mode of operation is the electrical emergency and requires immediate removal.Usually installed in the circuit breaker, tearing the loop if they fixed the fault current.By analogy with the water: the flow channel is blocked and disappears.When the energy source stopped determine whether a short circuit on any circuit section can be quite simple.For this purpose a special device (multimeter) measure the resistance value between the points of application probes.The indirect method is based on the use of the indicator or continuity: if you know that on the scanned area of direct contact between the poles should not be, then a check of this condition.The security apparatus is more efficient than resistance measurement precision multimeter.
By the way, that's why you can not lock the battery poles.Although their power is not enough to significantly damage the conductor, but inside the chemical components of a short-circuit rapidly degraded, reducing the overall life of the source.
When studying electrical often used the term "short-circuit current."It determines the highest current value appears as a result of a short circuit.In AC circuits, its maximum value is reached after halftime (from 0.01 to 50 Hz).
should be noted that there are special electrical devices, for which the short-circuit is not an emergency, as normal.A striking example - welding machines, in which the visible arc is just a short-circuit current.