Kirchhoff’s second law

The sum of all the voltages, as you go around a circuit from some fixed point and return there from the opposite direction, and taking polarity into account, is always zero. This might sound strange. Surely there is voltage in your electric hair dryer, or radio, or computer. Yes, there is, between different points. But no point can have an EMF with respect to itself. This is so simple that it’s almost laughable. A point in a circuit is always shorted out to itself.
What Kirchhoff really was saying, when he wrote his second law, is a more general version of the second and third points previously mentioned. He reasoned that voltage cannot appear out of nowhere, nor can it vanish. All the potential differences must balance out in any circuit, no matter how complicated and no matter how many branches there are.
This is Kirchhoff’s Second Law. An alternative name might be the law of conservation of voltage.
Consider the rule you’ve already learned about series circuits: The voltages across all the individual resistors add up to the supply voltage. Yes, they do, but the polarities of the EMFs across the resistors are opposite to that of the battery. This is shown in Fig. 1. It’s a subtle thing. But it becomes clear when a series circuit is drawn with all the components, including the battery or other EMF source, in line with each other, as in Fig. 1.

Fig. 1: Kirchhoff’s Second Law. The sum of the voltages across the resistors is equal to, but has opposite polarity from, the supply voltage E. Thus E + E1 + E2 + E3 + E4 = 0.