The sum of voltage drops in a series circuit:

In a series circuit, the sum of the voltage drops across all components equals the total applied voltage. This principle is a direct consequence of Kirchhoff's Voltage Law, which states that the total voltage around any closed circuit must equal zero. In practical terms, when voltage is supplied by a source (such as a battery), it gets divided among all the resistive components in the circuit. Each component has a specific resistance and thus will have a distinct voltage drop according to Ohm's Law (V = IR).

For example, if you have a battery supplying 12V and three resistors in series (with voltage drops of 4V, 3V, and 5V across each), when you sum those voltage drops (4V + 3V + 5V), the total comes to 12V, which matches the voltage supplied by the battery. This demonstrates that the total voltage drop across all components in a series circuit is equal to the applied voltage.