A lot of times we hear the phrase that there has been a short circuit once the lights go out and sometimes there is even a sudden blackout. We ourselves commonly use this phrase a lot but few amongst us actually realize what actually happens. This is something technical but obviously not rocket science! The physicians amongst us can easily tell what a short circuit is. Even students who have had physics in high school will be able to at least describe what happens to cause a short circuit. What is actually interesting is what makes the two types of short circuit, the one in a series circuit and the one in a parallel circuit different.
Let us first see what are parallel and series circuits. There are basically two ways of arranging the components of an electric circuit; in series and in parallel. As the name suggests, a series circuit merely consist of electrical components arranged in a series or along a single path. Therefore, the same current passes through all the components. This is not the case for a parallel circuit. The electrical components are arranged in parallel or in sections so that the same current does not flow to all the components. To understand this, consider the main wire carrying current and dividing into two parts (so the current is divided), both parts taking a fraction of the current along its own path. The voltage remains undivided in a parallel circuit unlike a series circuit. The primary reason that a short circuit is different in these two types of circuit is the arrangement and that is why it was important to first explain the different arrangements in the two types of circuits.
A short circuit occurs if current travels along a path it is not supposed to. Usually the path is such where there is very low impedance. This is the only case whereby a short circuit occurs and it is wrong to describe any electrical fault as a short circuit as is commonly the case. If the resistance is very low; to a point where a lot of current is able to flow, such that it may destroy the circuit components, then a short circuit has occurred. About a decade or two ago, short circuits had different effects in the two types of circuits. If there was a short circuit in a series circuit, then one of the components would blow out and the entire circuit, that is, all the components would stop working. Therefore all the lights would go out. That would explain a blackout even if there was a short circuit of one component. In parallel, however, if there is a short circuit, all the components in that path would stop working but the other paths would work fine. Only one part would be affected.
As is the case nowadays, a circuit breaker or a fuse is used in wiring. The fuse can blow or the circuit breaker can trip if there is a short circuit and that will cut off the current supply to all the components irrespective of a series or a parallel arrangement. This measure is usually taken as too much current flowing through the unaffected path can be dangerous and can cause a series of short circuits in a parallel circuit. This would make the series and parallel circuit both stop working in the case of a short circuit.
Summary of differences expressed in points
1. Different arrangements in series and parallel circuit account for different effects when a short circuit occurs; series- electrical components arranged in a series or along a single path; parallel- main wire carrying current and dividing into two parts (so the current is divided), both parts taking a fraction of the current along its own path, electrical components are arranged in parallel or in sections
2. In most circuits; short circuits-cause all components to stop working in a series arrangement; not so for parallel, only one path affected, rest work fine
3. Circuit breakers or fuses used in some cases; can stop all the current from flowing if there is a short circuit; effect becomes same in parallel and series arrangement