Helmholtz coil

例句：

1. 1. The scientist used a Helmholtz coil to detect the magnetic field.
   科学家使用亥姆霍兹线圈来探测磁场。
2. 2. The experiment was designed to test the theory of electromagnetism with a Helmholtz coil.
   实验设计用来测试电磁理论的亥姆霍兹线圈。
3. 3. The coil's design is based on the principles of electromagnetic induction, which explains why it can be used to create a magnetic field.
   线圈的设计基于电磁感应的原理，这就是为什么它可以用来产生磁场的原因。