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A 250 V, 10 KW, 1200 rpm dc shunt motor has a full load efficiency of...

A 250 V, 10 KW, 1200 rpm dc shunt motor has a full load efficiency of 80 percent. Its field and armature resistances are 110 ohms and .25 ohm respectively. Calculate the value of the resistance to be inserted in series with the armature and the power lost in the armature circuit to reduce the speed to 80 percent when the load torque is constant regardless of the speed.

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