How do you add up resistances in series circuits?

To add up resistances in series circuits, simply sum the individual resistances together.

In a series circuit, the total resistance is the sum of all the individual resistances along the path. This is because the current has only one path to follow, and it encounters each resistor one after the other. Imagine you have three resistors with resistances of 2 ohms, 3 ohms, and 5 ohms. To find the total resistance, you just add them up: 2 + 3 + 5 = 10 ohms.

The formula for calculating the total resistance \( R_{\text{total}} \) in a series circuit is:
\[ R_{\text{total}} = R_1 + R_2 + R_3 + \ldots + R_n \]
where \( R_1, R_2, R_3, \ldots, R_n \) are the resistances of the individual resistors.

This principle is crucial because it helps you understand how the overall resistance affects the current flowing through the circuit. According to Ohm's Law, \( V = IR \), where \( V \) is voltage, \( I \) is current, and \( R \) is resistance. In a series circuit, the total resistance determines how much current flows for a given voltage. If you increase the total resistance by adding more resistors, the current decreases.

For example, if you have a battery providing 12 volts and the total resistance in the series circuit is 10 ohms, the current \( I \) can be calculated as:
\[ I = \frac{V}{R_{\text{total}}} = \frac{12 \text{V}}{10 \text{ohms}} = 1.2 \text{A} \]

Understanding how to add resistances in series circuits is fundamental for analysing and designing electrical circuits, ensuring they function correctly and safely.