The goal of this activity is for students to explore the magnetic field strength of a long, straight current-carrying wire. Students may relate current and field, or they may relate distance and field for a constant current.

In the Preliminary Observation, students observe a compass needle in the presence and absence of current in a wire. During the subsequent inquiry process, students will investigate the mathematical relationship between the magnetic field strength and either the distance from the wire or the current.

The magnetic field strength can be measured using a magnetic field sensor or with a magnetic compass and ruler.


  • Identify variables, design and perform the investigations, collect data, analyze data, draw a conclusion, and formulate a model based on data from the investigation
  • Create graphical representations of magnetic field in the vicinity of a current-carrying wire
  • Create a mathematical model of magnetic field strength with respect to distance from a long, straight, current-carrying wire