“Magnetic damping”: Quantitative experiments with MBL sensors

We propose a sequence of experiments with the goal of exploring electromagnetic induction phenomena and “magnetic friction” forces. The experiments have been tested with high school students in the context of a program of cooperation between our Physics Department and the Regional School District. The experiments involve permanent magnets and conductors (a coil of wire or an aluminium plate) in relative motion. Motion and current-voltage online sensors allow real time measurements of position, velocity and induced voltage and provide graphs of these quantities vs time. The role played by the intensity of the induced current in determining the damping of oscillations due to the “magnetic braking” is stressed. To this aim the coil is connected to an external circuit with a variable resistance and students can observe how the damping of the oscillations increases when the circuit resistance decreases and can relate the variation of the mechanical energy of the system to the production of thermal energy in the circuit.