A text book of physics, for the use of students of science and engineering (1918)
Duncan, John, d. 1941, Starling, Sydney George, 1873- · London Macmillan · leaf 1025
seen (p. 988) that a single coil rotating ina magnetic field gives rise to an alternating electromotive force.To produce a sufficiently highe.m.f. for any useful purpose,the coil would require to havean immense number of turns,or else its rate of rotation wouldhave to In- very high. Also, inusing a… … nator shown in Fig. 942 has II Flit. 042.—Four-pole alternator. four poles and four rin^s. The field magnets in the ease of an alternator must be separately excited by means of a continuous current. In small machines this current ipplied by a battery, bu1 in large machines a separate direct- Lxxvrr…
Physics
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