The Toroid Illustration (Fig. 8.26)

Fig. 8.26. A nerve cell preparation is threaded through the magnetic toroid to measure the magnetic field. The changing magnetic flux in the toroid induces an electromotive force in the winding. Any external current that flows through the hole in the toroid diminishes the magnetic field.

In Chapter 8 ( Biomagnetism) of Intermediate Physics for Medicine and Biology, Russ Hobbie and I show an illustration of a nerve axon threaded through a magnetic toroid to measure its magnetic field (Fig. 8.26).

While this figure is clear and correct, I wonder if we could do better? I started with a figure of a toroidal coil from a paper I published with my PhD advisor John Wikswo and his postdoc Frans Gielen.

Gielen FLH, Roth BJ, Wikswo JP Jr (1986) Capabilities of a Toroid-Amplifier System for Magnetic Measurements of Current in Biological Tissue. IEEE Trans. Biomed. Eng. 33:910–921.

Starting with Figure 1 from that paper (you can find a copy of that figure in a previous post), I modified it to resemble Fig. 8.26, but with a three-dimensional appearance. I also added color. The result is shown below.

An axon (purple) is threaded through a toroid to measure the magnetic field. The toroid has a ferrite core (green) that is wound with insulated copper wire (blue). It is then sealed in a coating of epoxy (pink). The entire preparation is submerged in a saline bath. The changing magnetic flux in the ferrite induces an electromotive force in the winding. Any current in the bath that flows through the hole in the toroid diminishes the magnetic field.

Do you like it?

To learn more about how I wound the wire and applied the epoxy coating, see my earlier post about The Magnetic Field of a Single Axon. The part about “any current in the bath that flows through the hole in the toroid diminishes the magnetic field” is described in more detail in my post about the Bubble Experiment.

Originally published at http://hobbieroth.blogspot.com.

--

--

--

Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

Love podcasts or audiobooks? Learn on the go with our new app.

Recommended from Medium

Role of Subnuclear NSrp70 in Immunity-Studied at Gwangju Institute of Science & Technology

Alternative-splicing regulator NSrp70 influences immune T cell development

“Quantum Computing” Science-Research, October 2021, Week 1 — summary from Arxiv and Astrophysics…

“Carbon Capture” Science-Research, April 2022 — summary from DOE Pages and OSTI GOV

Physics of Life

Yes, Yes, More Testing!

“Cancer Cell” Science-Research, September 2021, Week 4 — summary from DOAJ, Springer Nature, Wiley…

What do objects really look like when we perceive them

Qiskit Summer School 2020

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Brad Roth

Brad Roth

Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

More from Medium

Sociophysics

Origin of Universe

Aquaporins and Peter Agre

beaty of heavens (the rocket equation)