2015 CAP Congress / Congrès de l'ACP 2015

The Electrodynamometer of the McPherson Collection of Scientific Instruments

16 Jun 2015, 16:45

15m

CCIS 1-160 (University of Alberta)

Oral (Non-Student) / orale (non-étudiant) History of Physics / Histoire de la physique (DHP) T3-8 Advanced Instrumentation at Major Science Facilities: Detectors I (DIMP) / Instrumentation avancée dans des installations scientifiques majeures: détecteurs I (DPIM)

Speaker

Jean Barrette (McGill University)

Description

The Weber electrodynamometer is an instrument used to measure the absolute value of electric power (or current if one knows the voltage). It works by measuring the mechanical torque between two pairs of coils induced by the current in the coils. This is one of the first research instrument bought in 1895 by the newly created McGill Physics Department for 177£. McGill College apparatus originally constructed by Messrs. NALDER from London was intended to be an exact duplicate of the apparatus in the Cavendish Laboratory at Cambridge. When received it did not meet specifications and had to be completely rebuilt by an undergraduate student under the supervision of Prof. Hugh Callendar. After rebuilding it had an absolute precision of the order of one part in a thousand. The repair and operation of the instrument will be described in details.