Single-stringed, no-touch instrument demonstrates physics for students

During the COVID-19 pandemic, students around the world struggled with their studies. To help combat this disinterest, a team of physics professors in China developed a fun learning project that combined music and physics.

The outcome of their work, presented by Wei et al., is a demonstration of a single-stringed musical instrument that can be played without touching it. Typically, when a single string is strung, it plays a single note. But by leveraging the Lorentz force, the string can be made to play entire melodies.

“Music is one of the best examples of merging science and art through physics,” said author Junqing Li. “We wanted to introduce some physical phenomena related to musical acoustics into students’ learning projects because we know that music can affect people’s spiritual well-being and bring happiness.”

The instrument consists of a taut guitar string placed near a permanent magnet. When an AC current is fed to the string near the magnet, the string resonates at the same frequency as the current due to the Lorentz force. By adjusting the AC current frequency, a full octave scale can be played using the eighth to sixteenth harmonics of the string’s fundamental frequency.

“Very innovatively, we’ve built scales using integer ratios among musical components,” Li said. “By compiling the current with unique timbre, we played melodic music, such as Ode to Joy, and successfully achieved chord playing on a single string that usually needs several strings.”

The authors hope their work can be used as a demonstration or laboratory activity for physics students around the world.

Source: “Playing melodies on a single string by exciting harmonics using the Lorentz force,” by Yukai Wei, Hao Zhu, Haotian Jiang, Quanxin Luo, Shan Lin, Junqing Li, Yu Zhang, and Bibo Zhao, American Journal of Physics (2023). The article can be accessed at https://doi.org/10.1119/5.0152828 .