Study of electromagnetic damping of an oscillating bar magnet and its energy budget

Abstract The oscillation of a bar magnet along the axis of a closed loop solenoid has been studied quantitatively using an ultrasonic sensor and Arduino microcontroller-based platform. Real-time displacement of the oscillatory magnet with and without the solenoid shows an additional damping effect due to electromagnetic induction in the presence of the closed-loop solenoid. Variation of the induced current in the solenoid circuit has been analyzed over several cycles by simultaneous recording of the voltage developed across two resistors using ‘analogread’ library function. Energy drained from the oscillator due to electromagnetic damping has been compared with the energy lost in Joule heating of the solenoid circuit. A phase plot for the underdamped oscillator was generated using the fitting parameter values of the curve fitted with the position vs. time data points on the plot. This portable and inexpensive microcontroller-based design is well suited for STEM education of high school and for sophomores in an undergraduate physics course.