# How to calculate voltage across a resistor

When working with electrical circuits, it is essential to understand how to calculate the voltage across various components, such as resistors. In this article, we will explore the methods for calculating the voltage across a resistor. By understanding these techniques, you can work efficiently with electrical circuits and troubleshoot any problems that may arise.

**The Ohm’s Law:**

One fundamental principle used when calculating voltage across a resistor is Ohm’s Law. Ohm’s Law states that the voltage (V) across a resistor is equal to the current (I) passing through it, multiplied by its resistance (R). Symbolically, it can be expressed as:

**V = I * R**

To use Ohm’s Law for calculating voltage, you need first to determine the resistance of the resistor and the current passing through it.

**1.Identify the resistor’s resistance:**

Resistors come in various color codes denoting their resistance values. These color codes consist of colored bands that represent different digit values and a multiplier. To determine the resistance value of a resistor, observe these color bands, consult a reference chart or use an online calculator.

**2.Determine the current passing through the circuit:**

To calculate current, you can either measure it with an ammeter or calculate it if you know the total circuit voltage and resistance using Kirchhoff’s current law. You can also rely on Ohm’s Law for finding current by dividing total circuit voltage by total resistance if there is only one path for current flow.

**3.Calculate the voltage across the resistor:**

Once you have determined both the resistance of the resistor and the current passing through it, use Ohm’s Law (V = I * R) to calculate the voltage across the resistor.

**Example:**

Suppose you have a 10 kΩ (10,000 Ω) resistor with a current of 2 mA (0.002 A) flowing through it. Using Ohm’s Law:

V = I * R

V = 0.002 A * 10,000 Ω

V = 20 V

In this example, the voltage across the resistor would be 20 volts.

**The Voltage Divider Rule:**

Another useful technique for calculating voltage across a resistor is the Voltage Divider Rule. This rule is applicable when dealing with series circuits where resistors are connected in a single line.

The Voltage Divider Rule states that the voltage across a resistor in a series circuit is directly proportional to its resistance and inversely proportional to the total circuit resistance.

Mathematically, it can be expressed as:

**Vx = (Rx / (R1 + R2 + … + Rn)) * Vtotal**

Where Vx is the voltage across the resistor of interest (Rx), and Vtotal is the total voltage supplied to the series circuit.

By using either Ohm’s Law or the Voltage Divider Rule, you can accurately calculate the voltage across resistors in electrical circuits. Understanding these methods will enhance your ability to work with electronic components and troubleshoot any issues that may arise.