By Timothy Banas, Updated Aug 30, 2022

In 1827, German physicist Georg Ohm formalized the relationship between current, voltage, and resistance, giving us Ohm’s Law: Voltage = Current × Resistance. This foundational principle allows engineers and hobbyists alike to determine the voltage drop across any resistor in a circuit.

Step 1 – Identify the Resistor

Start by selecting the resistor whose voltage you want to measure. For illustration, let’s use a 4 Ω resistor.

Step 2 – Measure the Current

Using a calibrated multimeter or ammeter, place the device in series with the resistor. To do this, cut the circuit wire immediately after the resistor, then connect the cut ends to the meter’s electrodes. Suppose the meter reads 0.5 A.

Step 3 – Apply Ohm’s Law

Insert the measured values into the equation: Voltage = 0.5 A × 4 Ω = 2 V. Thus, the voltage drop across the resistor is 2 volts.

Repeat these steps for any resistor in your circuit to quickly determine voltage drops and verify circuit performance.