Vibrational Direction of Coil of Wire @ Resonance

Thread Starter

ben sorenson

Joined Feb 28, 2022
In the 1st photo is a picture of a horizontal coil of wire loosely wrapped around a steel core.

You can see the reflection of the light shining from the camera onto the coil. In this photo, the coil is not moving, there is no electricity being supplied to the circuit.

The the preceding photos, current flows through the wire and it vibrates at a frequency of 150,000 Hertz.

The light being reflected back from the coil is in a figure 8 pattern, witch would tell me the that the coil is also moving in that direction.

What is causing the pattern? I was under the understanding that a coil of wire facing in a horizontal position would only move to the "left", or to the "right" a speaker when it's diaphragm or cone moves not in a figure 8.




Joined Aug 27, 2009
Horrible pictures that show no detail about the coil shape, windings and mounting.

First have a little backgrounder in:

Then think about how the coil is wound and supported when thinking about the principle of least action .


Joined Mar 24, 2008
Reminds me of something my brother did when he was eight or so, he made a speaker using a tin coffee can wrapped a coil of wire around the nail then fed the coil from a transistor radio, it worked but it was very tinny <insert groan here>.


Joined Jan 27, 2019
The motion of a perfectly regular coil would be strictly like a solenoid. The mechanical properties and arrangement of the practical coil is such that when such a force is applied it moves according to the coil’s constraints and not in a line.

Electrically, there is nothing special about the shape of the motion of that coil, it's just how it is responding to the force.