Question

Two identical fuses are rated at 10A. If they are joined
(This question has multiple correct options.)
A. in parallel, the combination acts as a fuse of rating 20A.
B. in parallel, the combination acts as a fuse of rating 5A.
C. in series, the combination acts as a fuse of rating 10A.
D. in series, the combination acts as a fuse of rating 20A.

Answer 1

Find out what is the purpose of fuse in a circuit. Also, we have to understand what is meant by the fuse rating of a fuse. From the unit of fuse rating, we realize that it is related to current. Now, recall how current varies for combination of various elements in series and parallel connections and thus find the answer.

Complete answer:
In the question, we are given two identical fuses each rated at 10A. Now we are given four statements that discuss the situation when the fuses are joined parallel and series. In order for us to answer this question, we have to first understand what are fuses and what is meant by rating of a fuse.
Fuses are actually an electricity safety device that works so as to provide overcurrent protection of an electrical circuit. It has a small metal wire or strip that melts down when current flowing through it is very high and thereby stops the current flow.
Now, what is fuse rating? Fuse rating is the amount of current that is required to break the fuse, or in other words we could say that it is the maximum current that can pass through a fuse. In the question we have two fuses of fuse rating 10A. So, we have to understand that the maximum current that can flow through each fuse is 10A and above that value the fuse blows.
We know that, for a parallel connection the current is split in between the branches. So when the given fuses are connected in parallel, then, a maximum of 10A current can pass through each one which makes the sum total of the current that can pass through the circuit as 20A. Therefore, we found that option A is correct.
Now for series connection, the current remains the same for each element. So when the given fuses are connected in series, we are actually limiting the maximum current flow as 10A. So, the series combination of the given fuses has a fuse rating of 10A and thereby, we see that option C is also true.

Hence, we found that options A and C are the correct options.

Note:
Fuse is actually a self sacrificial device, that is, it blows off when there is too much current in the circuit thereby protecting the circuit by sacrificing itself. However, when this happens it should be replaced soon, for the circuit is vulnerable in the absence of a fuse in it. Fuses normally operate in the case of short circuits, overloading, mismatched loads or device failure.