Accession No

3346

Brief Description

permeability bridge, 1905-1915 (c)

Origin

Maker

Class

electrical; magnetism

Earliest Date

1905

Latest Date

1915

Inscription Date

Material

wood; plastic (ebonite); metal (brass, iron, copper)

Dimensions

length 665mm; breadth 383mm; height 180mm

Special Collection

Provenance

Transferred from Department of Engineering, University of Cambridge, Cambridge, England, 1986.

Inscription

‘EWING’S PATENT
PERMEABILITY BRIDGE’ (on brass plate on top)

Description Notes

Rectangular wooden box; ebonite plate with reversing switch, one three-position, and two eleven-position rotary switches; second ebonite plate with five brass terminals and adjustable brass connecting plate; two solenoids with central holes for standard, and specimen bars; bars joined by soft-iron yokes at the ends, on which two iron horns project upwards, nearly meeting; in the gap between the top ends of the horns a compass needle is pivoted in a brass tube, with a short scale visible at its end; a rod supporting a controlling magnet projects downwards; inside box are lengths of copper wire, providing compensating resistances.

Condition: good; incomplete (pivot for compass needle, and controlling magnet and post missing).

References

Events