lengthening coil

例句：

1. 1. The lengthening coil is used to adjust the tension in a wire.
   拉长线圈用于调整电线的张力。
2. 2.In this experiment, we need to use the lengthening coil to control the speed of the motor.
   在这个实验中，我们需要使用拉长线圈来控制电机的速度。
3. 3. The lengthening coil was designed to improve the performance of the machine.
   拉长线圈被设计用来提高机器的性能。