What is that occurs when uncontrolled electricity flows from the hot line to the neutral line or from the hot line to ground?

Answer 1

A short circuit, or "short", occurs when uncontrolled electricity flows from the hot line to the neutral line or from the hot line to the ground.

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An unbroken short circuit is one of the causes of house fires if an electrical cable catches on fire because its circuit breaker has failed to trip.

Some reasons for this happening include:

• a breaker wrongly specified with an amperage that is too high for the circuit it is protecting;
• a faulty breaker;
• someone illegally replaced a breaker or a fuse with a length of heavy gauge wire.

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  Your question is asking specifically what happens when a hot conductor makes contact with a ground or neutral conductor. To be frank, what happens is really no different from what happens when electricity flows through a device or appliance - an electrical circuit is created and electrical current flows around it.

  The only bits of information you really need to know are that A) current is created by the flow of charged particles (typically electrons) through a conductor and measured in amps, B) the potential for this flow is a separation of opposite charges, typically called electrical potential and measured in Volts (V), C) almost all conductors and circuit elements have resistance, measured in Ohms, which opposes the flow of charge. A light bulb has much more resistance than a wire.

  Finally, putting it all together, the relationship between current, potential, and resistance in a circuit is I = V/R. In other words, current equals voltage divided by resistance.

  So let's take the example of a light bulb connected by wires to a power source. The wires have negligible resistance compared to the bulb. A typical household incandescent light bulb has a resistance of around 200 Ohms. The voltage supplied to most US household outlets is about 120 Volts. So 120 Volts divided by 200 Ohms gives us the current, which is less than 1 Amp.

  Now, let's take the light bulb out of the mix and simply cross the two wires. The only resistance we can take into account is the very small resistance of the wires. At the most, this is only a few Ohms. If the wires are only a few feet long, the total resistance may be less than 1 Ohm. 120 Volts divided by .5 Ohm equals 240 Amps, which is a lot of charge flow.

  This results in a few things. First, you see a big spark when you connect the wires. The wire heats up due to power being dissipated, which can also be calculated by squaring the current and multiplying by the resistance. For the light bulb, a current of .5 Amp and a resistance of 200 Ohms would give 50 Watts of power dissipation, which sounds like a reasonable light bulb. When the wires are simply crossed, squaring 120 Amps and multiplying by .5 Ohm gives 7200 Watts of power, which can toast a 16-gauge copper wire pretty quickly. Hopefully your circuit is protected by a 15- or 20-Amp fuse or circuit breaker, which will trip when current in the circuit rises above the breaker current rating.