Ampere’s Law Accessory

SKU: EM-6720 Categories: ,


Students can verify Ampere’s Law experimentally by graphing the magnetic field strength that is tangent to the path taken along a closed path that encloses a current source.

The magnetic field strength is measured with a Wireless Magnetic Field Sensor which rides on a Rotary Motion Sensor. The student pushes the Rotary Motion Sensor, which rolls on its wheel, along a closed path.

If you traverse a path that does not enclose any current source, the area under the curve is zero. The magnetic field of the Earth or any nearby source is measured but they will cancel out in a closed loop that encloses no current.

Ampere’s Law is also available as a complete experiment (EX-5552) that includes the necessary sensors and accessories.

The key to making this work is that the Magnetic Field Sensor element is positioned tangent to the Rotary Motion Sensor’s wheel. This accomplishes the dot product in Ampere’s Law because only the component of the magnetic field that is tangent to the path is recorded

The Ampere’s Law Equation

Ampere's Law equation
The Wireless 3-Axis Magnetic Field and Wireless Rotary Motion sensors allow students to move in any shaped path without wires getting wrapped around the coil. Students can choose any path they want, you don’t have to follow a circular path because the sensors are recording the field tangent to any path.


  • Aluminum Table (46 cm x 46 cm x 11 cm)
  • Sensor Bracket