Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833- · New York, T. Audel · leaf 58
Fig. 551.—Charge and discharge key, adaptedto condenser testing where the condenser isto be alternately charged and discharged.The insulated handle enables the key to beused without insulating the body. … Fig. 552.—Pohl commutator. This is equiv-alent to a two pole double throw switch.The depressions in the base are filled withmercury into which the contacts dip inclosing the circuit. made as in fig. 550. The known resistance is put in circuit withthe gah^anometer and after noting the deflection,…
Electrical engineering
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