Current Through Series Resistances:

Have you ever use those tiny holiday lights which come in strings? When one bulb burns out, the entire set of bulbs goes dark. Then you have to discover which bulb is bad and substitute it to acquire the lights working again. Each bulb works with somewhat like 10 V, and there are around a dozen bulbs in the string. You plug the entire bunch, and the 120-V utility mains drive just the right quantity of current through each bulb.

In a series circuit like a string of light bulbs, the current at any given point is similar as the current at any other point. Ammeter can be connected in series at any point in the circuit, and it will always show similar reading. This is true in any series dc circuit, no matter what the components really are and regardless of whether or not they all have similar resistance.

When the bulbs in a string are of various resistances, some of them will consume more power than others. In situation one of the bulbs burns out and its socket is shorted out rather than filled with a replacement bulb, the current through the entire chain will rise since the overall resistance of the string will go down. And this will force each of the remaining bulbs to carry so much current. The other bulb will burn out before long as an outcome of this excess current. If it, too, is substituted by a short circuit, the current will be raised still further. A third bulb will blow out nearly right away. At this point it would be intelligent to buy some new bulbs!