An engineer is testing an electromagnetic energy harvester. A magnetic carriage consisting of a strong bar magnet is mounted on a low-friction horizontal track. The carriage is connected to two identical tension springs anchored to the ends of the track, allowing it to oscillate horizontally. Positioned at the exact center of the track is a multi-turn induction coil. As the carriage oscillates back and forth, the magnet passes through the center of this coil, which is connected to an oscilloscope.
The carriage is pulled to one side and released from rest so that it oscillates back and forth through the induction coil.
Explain why the oscilloscope records an induced electromotive force (emf) that periodically changes polarity.
State which feature of the oscilloscope trace indicates that the induced emf is alternating.
Explain why the peak emf of each successive cycle decreases over time.
The engineer repeats the experiment, but replaces the induction coil with one that has three times the number of turns. All other physical parameters of the springs, track, and magnet remain unchanged. The period of the carriage's horizontal oscillation is unaffected.
Describe three key features of the new voltage-time trace compared to the original one shown on the oscilloscope screen.