Every time when you insert the plug of the appliance into the outlet, you snap the electrical network, and it begins to flow electric current.
A simple electric circuit consists of a current source, electricity consumers
the switch and connected the wires.
Consumer electric current converts electrical energy which comes to him in other forms of energy - mechanical (e.g., motors), heat (irons, warmers), lighting (lighting fixtures), etc.
The current in this circuit is equal to
that is, it is directly proportional to voltage and inversely proportional to the resistance that creates the appliance (Ohm's law).
And what happens if the chain will not close as provided by the circuit design and electrical appliance, and directly, bypassing the appliance?
Schematically it looks like this:
In this case, the resistance network collapses, and as a result the current in the circuit increases dramatically. As you know, the amount of heat released at the site of the chain is proportional to the square of the current strength in this area (the Joule-Lenz law). So, if the short circuit current will increase 20 times, the amount of heat produced at the same time, will increase about 400 times! That is why a short-circuit may cause melting wires, ignition isolation and, ultimately, may result in ignition of flammable items around the place of short circuit and fire.
A short circuit occurs and if the load resistance becomes lower than the internal resistance of the power source.
Because of what may be a short circuit? Most often this is caused by the wire insulation failure (due to their wear and tear, incorrect ekspluatacii etc). Also by reason of the short circuit can be mechanical damage in an electrical circuit or electrical device, and network congestion.
How can I prevent a short circuit?
For this purpose, the circuits establish special fuses.
The most simple fuses made of fusible material. In the case of a strong increase in current strength, this material melts or burns and opens the circuit before the circuit will be more serious consequences. Sacrifice a little of the character to replace with a new one.
Automatic fuses arranged so that in the event of a high current short circuit is triggered immediately electromagnetic release, which disconnects the electrical circuit without damage to itself. In order after eliminating a short circuit again to turn on electricity, you just need to press the white button (red serves to switch off or to throw up degraded when the tripping lever.