[Skip to Content]
[Skip to Content Landing]
Article
December 1940

A METHOD OF ELIMINATING ARCING IN THE FOOT SWITCH OF AN EYE MAGNET

Arch Ophthalmol. 1940;24(6):1255-1256. doi:10.1001/archopht.1940.00870060197013

This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables.

Abstract

In using the old type giant eye magnet for removing intraocular foreign bodies, a disconcerting electric arc and a crackling noise emanate from the foot switch, accompanied by smoke resulting from the burning of the switch contacts. This requires frequent cleaning of the contacts, and at times replacement of the affected parts may be necessitated. A more important consideration is the annoyance to the operator and the frightening effect on the patient.

The physical principles involved in producing these undesirable manifestations are simple, although measurement and calculation are rather complex mathematically. The coil of the magnet is supplied by a direct current, and this creates a powerful magnetic field in the core. When the current is broken, the sudden collapse of this field generates, by self induction, an extremely high voltage, which instantly flows back along the "lead in" wires and jumps the gap which is produced as the

First Page Preview View Large
First page PDF preview
First page PDF preview
×