A load is a device that uses electricity to do work when connected to a circuit. A light bulb is an example of a load. If a light bulb is connected to a solar panel, the electricity produced by the panel can do the work of lighting the light bulb.

The load connected to a solar panel affects the amount of power that is produced by the panel. There is an optimum, or best, level of load that will make the panel produce the most amount of power.

One way to create the optimum load for the solar panel is to connect multiple light bulbs to the solar panel. While this would work, it is not very practical to always carry a bunch of light bulbs around with you!

Instead of using light bulbs, in this experiment, you will use a device called a resistor to add load to the circuit. Resistors affect the flow of electrons in a circuit. They are rated based on how much resistance they add to the circuit. Resistance is measured in units of ohms.

In this experiment, you will find the optimum resistance for three solar panels connected in series.


  • Measure current, potential difference (voltage), and power output of three solar panels with a Vernier Energy Sensor.
  • Explore how current, potential difference (voltage), and power output vary depending on the resistance (load) in the circuit.
  • Investigate the relationship between resistance and maximum power output.