» Compass Galvanometer (0318)
Immagini
DESCRIPTION
Exhibit 318 is a galvanometer derived from a tangent compass. It consists of a coil of N turns mounted on a vertical circle that can be rotated within a horizontal circle until the coil is aligned with the horizontal component of the earth's magnetic field as indicated by a magnetic needle free to rotate on a pivet located in the center of the coil. When an known current I circulates in the coil of N turns and radius R the needle assumes a new equilibrium position determined by the magnetic field due to the superposition of the field due to the coil
![Formula: [{\rm H^{'} = 2\pi\frac{NI}{R}}]](/foto/equaz/318_fr01.png "Formula: [{\rm H^{'} = 2\pi\frac{NI}{R}}]")
.
and that due to the earth's magnetic field at an angle
α such that ![Formula: [{\rm H}^{'} \cos(\alpha) = {\rm H}\sin(\alpha)]](/foto/equaz/318_fr02.png "Formula: [{\rm H}^{'} \cos(\alpha) = {\rm H}\sin(\alpha)]")
.
Knowing R, N, and the value of the earth's magnetic field, and measuring the angle α on the graduated horizontal circle, one derives
![Equazione: [{\rm I = \frac{HR\tan(\alpha)}{2\pi\, N}}]](/foto/equaz/318_eq01.png "Equazione: [{\rm I = \frac{HR\tan(\alpha)}{2\pi\, N}}]")
The instrument is conserved in a wood chest which contains also a spare magnetic needle, spare pivot and a small coil with four terminals.
ISCRIZIONI
- Sul quadrante di ottone è inciso il nome del costruttora (Siemens - Halske). Più sotto "Berlin" e "N.1473"
Dati Catalografici
| Data di costruzione: | --- |
|---|---|
| Data di carico: | 1894-01-15 |
| Nr. Inventario: | Cons. 151 (Consorzio Univ. di Torino) |
| Costruttore: | Siemens & Halske |
| Materiale: | acciaio, ferro, ottone, vetro, legno |
| Dimensioni: | Misure della cassetta: 25,3 cm x 25,3 cm x 18,5 cm Diametro del galvanometro: 20 cm |
| Conservazione: | buono (Le parti in acciaio sono macchiate ma il goniometro è ancora leggibile) |