The purpose of this investigation is for students to learn how to measure current without direct instruction.

For the Preliminary Observations, demonstrate how to measure current in a simple circuit that consists of a power source, a current-measuring device, and one incandescent light bulb. Students will observe that bulb brightness increases as measured current increases.

Students experimentally determine how to use the current probe to accurately measure the current in a circuit with multiple light bulbs. The circuit will contain another current sensor and a “test” light bulb that will aid them in their observations.


  • Understand that ammeters must be connected in series with the circuit element where current is being measured.
  • Begin to develop the concept that “resistance” reduces current, that there is little resistance for current to flow through an ammeter, and that current has a tendency to flow along the path of least resistance.
  • Learn the conventions of “+” and “–” signs of electric current (if desired by the instructor).