Answer to Question 3

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A motor has an armature of 200 turns of rectangular form 4 cm 5 cm.  The armature is placed in a magnetic field of flux density 0.15 T and a current of 1.5 A is flowing through it.  The motor is turning at 2400 rpm.  Calculate the power.

P = BANIw

f = 2400 60 = 40 Hz.

w = 2p 40 Hz = 251 rad s-1

A = 0.040 0.050 = 2.0 10-3 m2

P = 0.15 T 2.0 10-3 m2 200 1.5 A 251 rad s-1 = 23 W