Circuit voltage is measured using a voltmeter, an electrical device with two metal probes and either a needle or digital readout. The probes are placed on either side of the resistor that you want to measure, and the needle moves across a scale to the appropriate value, or the digital screen shows the numerical value of the voltage.

Try building your own circuit in the activity below:

Click to Run

Source: circuit construction kit (DC only), University of Colorado – Physics

In the tools box, select "Voltmeter." Then, drag the circuit elements into the blue screen area to make the following series circuit:

Change the resistance by right-clicking on the resistor. Set the three resistors to 2 Ω, 3 Ω, and 4 Ω, and then use the voltmeter to measure the voltage drop across each. To measure a voltage, drag the red and black probes to either side of a resistor.

Interactive popup. Assistance may be required.

Check Your Answer

2 Ω → 2 V
3 Ω → 3 V
4 Ω → 4 V

Analyzing Electric Potential Difference in Series and Parallel Circuits

Electric potential difference behaves differently in parallel and series circuits. View the following video; it shares a lab demonstration exploring the relationship between the type of circuit and electric potential difference. After the video screen, there are guiding questions. First, copy the questions into your notes, and then answer the questions as you step through the video lab.

Guiding Questions

Series Circuits

1. What is a series circuit? Interactive button. Assistance may be required.

   _______________________________

   a circuit in which all of the components line up in a single path

2. In a series circuit, current rate Interactive button. Assistance may be required. ______________ stays constant from one side to the other.
3. Voltage drop or change is also Interactive button. Assistance may be required. ________ _________ __________ electric potential difference .
4. In a series circuit, large resistors drop Interactive button. Assistance may be required. ______ large voltage and small resistors drop Interactive button. Assistance may be required. _____ small voltage. They are Interactive button. Assistance may be required. ________ _____________ directly proportional .

Parallel Circuits

1. What is a parallel circuit? Interactive button. Assistance may be required.

   _______________________________

   a circuit where there is more than one path for current to flow

2. The voltage drop for both large and small resistors will be the Interactive button. Assistance may be required. ____ same .
3. The voltage drop in a parallel circuit will be Interactive button. Assistance may be required. _____ equal to the battery voltage.
4. In a parallel circuit, current will be Interactive button. Assistance may be required. _______ largest through the Interactive button. Assistance may be required. ________ smallest resistor and Interactive button. Assistance may be required. ________ smallest through the Interactive button. Assistance may be required. _______ largest resistor.

You may check your answers by clicking on the blanks above.