The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be

• A.  48.0%.
• B.  57.1%.
• C.  59.2%.
• D.  88.8%.

Answer: (A)