Abstract: In university physics experiment of tuning fork forced vibration and resonance, the amplitude-frequency response curve measured by the electromagnetic coil should be the velocity resonance curve in theory, according to the existing textbooks and literature. However, there exists discrepancy between the characteristics of the measured amplitude-frequency response curve and the ideal velocity resonance curve. In this work, the reason for the discrepancy between the measured amplitude-frequency response curve and the ideal velocity resonance curve is theoretically analyzed and experimentally verified. The results reveal that the measured amplitude-frequency response curve is the superimposing of the velocity resonance curve the displacement resonance curve, where the characteristics of the displacement resonance curve is manifested as follows. The resonant frequency of the tuning fork resonance experimental system decreases with the increasing damping. Besides, the closer initial distance between the receiving coil and the tuning fork arm can induce the greater contribution of displacement resonance to the induced voltage, resulting in the larger the slope of the resonant frequency changing with the damping. The results are of great significance to understand the physical laws involved in the tuning fork forced vibration and resonance experiments, and are also helpful to improve the forced vibration and resonance experiments in college physics experimental textbooks.

Key words: tuning fork, forced vibration, speed resonance, displacement resonance