Hawkins Electrical Guide v. 01 (of 10) / 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

by N. Hawkins

The voltage of the secondary current is (approximately) to the voltage of the primary current as the number of turns of the secondary winding is to the number of turns of the primary winding.

For instance, if the voltage of the primary current be 5 volts, the primary winding have 10 turns and the secondary 100 turns, then

Secondary voltage: 5 :: 100 : 10 from which

Secondary voltage = 50 volts (approximately)

The watts in each circuit are approximately the same; hence: if, for instance, the current strength in the primary circuit be 5 amperes, the watts in primary circuit are 5 × 5 = 25. Accordingly, for the secondary circuit the current strength is:

25 watts / 50 volts = ¹⁄₂ ampere (approximately)

From this, it is seen that where the voltage is raised in the secondary circuit, the current flow is small as compared to that in the primary circuit; therefore, heavy wire is used in the primary winding and fine wire in the secondary, as indicated in figs. 137 and 143.

For most purposes a very much higher secondary voltage is required than in the example just given.