1. What is short circuit? What is the common cause of unintetional short circuits in electrical devices?
A short circuit (sometimes abbreviated to short or s/c) allows a charge to flow along a different path from the one intended.;->is an accidental low-resistance connection between two nodes of an electrical circuit that are meant to be at different voltagesA short circuit happens when a low-resistance conection between two nodes of an electrical circuit that are meant to be at different voltages accidentally breaks which results in an excessive electric current that can cause circuit damage, overheating, fire or explosion. Although usually the result of a fault, there are cases where short circuits are caused intentionally, i.e., for the purpose of volatge-sensing crowbar cicuit protectors.In electrical devices, unintentional short circuits are usually caused when a wire's insulation breaks down, or when another conducting material is introduced, allowing charge to flow along a different path than the one intended.
2. What is a fuse? What happens when you blow a fuse?
Fuse is a piece of metal which has a low meltig point and is enclosed in a fireproof case.It is in series with the line.It is always placed before any of the devices it is to protect.This makes the current pass through the fuse before the current goes to the external circuit.When there is an excessive current because of overloading,the fuse "blows out" and the circuit is broken.Fuses are really just a special type of wire in a self-contained conector. Most automotive fuses today have two blade-connectors and a plastic housing that contains the conductor. The main job of the fuse is to protect the wiring. Fuses should be sized and located to protect the wire they are connected to. If a device like your car suddenly draws enough current to blow the fuse,the radio is probably already toast. The fuse is there to protect the wire, which would be harder to replace than the radio.When a fuse is blown, it must be replaced before the circuit will work. A blown fuse must be replaced with a fuse of the same amperage. The circuit will not work if the fuse within it is damaged because the wire it is connected to is damaged or melted and current cannot pass through.
3-a How do Circuit Breakers work?
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. The circuit breaker's job is to cut off the circuit whenever the current jumps above safe level. The circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. Without circuit breakers (or the alternative, fuses), household electricity would be impractical because of the potential for fires and other mayhem resulting fom simple wiring problems and equipment failures.
3-b when is there an oerload in a circuit?
.An electrical overload is a situation where the wiring to or within a machine or system is subjected to a greater electric current load than it was designed to carry, leading to excessive heating of the wires and a possibility of fire. This excessive current load can be a result of electrical insulation failure (a short circuit) or human error.In an electrical overload, it leads to excessive heating of the wires and a possibility of fire.An electrical overload is a situation where the wiring to or within a machine or system is subjected to a greater electric current load than it was designed to carry, leading to excessive heating of the wires and a possibilty of fire. This excessive current load can be a result of elctrical insulation failure (a short circuit) or human error. A correctly designed electrical system incorporates suitable overload protection devices to prevent damage should such a situation occur. Fuses and circuit breakers are most commonly employed for this purpose.
6. Why will too many electrical devices operating at one time often blow a fuse?
In an electrical overload, it leads to excessive heating of the wires and a possibility of fire.In a short circuit, an accidental low-resistance connection between two nodes of an electrical circuit that are meant to be at different voltages. This results in an excessive electric current limited only by the Thevenin equivalent resistance of the rest of the network and potentially causes circuit damage, overheating, fire or explosion. Although usually the result of a fault, there are cases where short circuits are caused intentionally, for example, for the purpose of voltage-sensing crowbar circuit protectors.Too many electrical devices operating at one time often blow the fuse because the fuse is designed to protect the wire. When there is too much wire to be protected by a fuse, it will most likely blow the fuse. Since there are many appliances working at one time, the fuse will be overloaded and will be the cause for the fuse to blow out.
7. What are the danges of short circuit and overload?
A short circuit-occurs when conductors of opposite polarity are accidentally bridged by a conductive object or bridged to grounded metal. Metal screwdrivers, wrenches, fish tapes, test instruments, etc. have all been found to have made inadvertent contact while persons were working on live equipment. An arcing fault may be established that is limited only by the total impedance of the circuit. The arcing will continue until circuit breaker, fuse, or equipment ground fault protection device on the line side of the fault opens the circuit. Even if the short circuit protective device opens the circuit without any intentional delay, portions of the conductors and other metallic materials in the path of the arc may explode violently, showering the area with hot molten metal that can cause severe burns or death. The flash associated with the arc can also cause permanent eye damage. Finally, a short circuit may expel shrapnel toward the workman, penetrating clothing or the body.Overload-leading to excessive heating of the wires and a possibility of fire. This excessive current load can be a result of electrical insulation failure ( a short circuit) or human error.electricaWhile most electrical appliance manufacturers need convincing that their products can cause fires, the experience of most fire investigators is that electrical appliances frequently do cause fires.One of the most common reasons for appliance fires is through misuse by the owner, however in my experience another prevalent factor is - component fatigue. Design faults are also a common fire cause and this is reflected by the significant number of recall notices issued for television sets, heaters and cooling fans in recent years.
dangers of short circuit.
