 Welcome to Voltage Drops in a Series Circuit. As an electronics technician, you may be expected to determine the voltage drop of a particular element in a series. This activity will show you how to calculate voltage drops in a series circuit. In a series resistive circuit, as shown, the voltage drop across each resistor is proportional to the resistor value. In this example, R2 is twice as large as R1, so the voltage drop across R2 is double the value across R1. A concept that can be applied to series circuits is, whatever the percentage is of an individual resistor to the total resistance, the voltage drop across it is the same percentage of the applied voltage. Let's use the series resistive circuit to show what the statement means. We'll use some fundamental math operations to prove it. First, determine the total resistance by adding the sum of the individual resistors. Next, find the percentage of a resistor value to the total resistance. This is done by using the formula percentage equals individual resistor value divided by total resistance multiplied by 100. Let's take R2 as an example. Divide 30 ohms by 100 ohms to get 0.30 or 30% of total resistance. Calculate the percentage of R2 to the total resistance and then multiply that percentage by the applied voltage to obtain the voltage across R2. Now it's time for you to check your knowledge. Select the correct answers for the next questions. Using this technique, you can determine if the measured voltage drop across a heating element wired in series is correct. You have completed this learning activity. Voltage drops in a series circuit.