A laboratory manual in physics, to accompany Black and Davis' "Practical physics for secondary schools," (1913)
Black, Newton Henry, 1874- [from old catalog] · New York, The Macmillan company · leaf 96
Fig. 49 EFFICIENCY OF AN ELECTRIC MOTOR 81 tension on the brake cord so as to slow down themotor a little. Keeping this pull steady, we getthe speed of the motor and at the same time readthe spring balances, ammeter and voltmeter. Thenrepeat this experiment, putting more load on themotor by pulling… … Fig. 50 First Trial Second Trial Third Trial Voltmeter reading Ammeter reading Watts put in motor Number of revolutions per minute .Distance meters per minute . . .Balance A reading (kg.) ....Balance B reading (kg.) .... Friction (A - B) (kg.) ....Work got out of motor (watts) . .Efficiency % It…
Physics
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