Jun 13 – 19, 2015
University of Alberta
America/Edmonton timezone
Welcome to the 2015 CAP Congress! / Bienvenue au congrès de l'ACP 2015!

The Electrodynamometer of the McPherson Collection of Scientific Instruments

Jun 16, 2015, 4:45 PM
CCIS 1-160 (University of Alberta)

CCIS 1-160

University of Alberta


Jean Barrette (McGill University)


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.

Primary author

Jean Barrette (McGill University)

Presentation materials

There are no materials yet.