Electrical Machines
A 240 V DC series motor takes 40 A when giving its rated output at 1500 rpm. Its resistance is 0.3 ohms. The value of resistance which must be added to obtain rated torque at 1000 rpm is

 1.9 ohms.
 5.7 ohms.
 2.2 ohms.
 6 ohms.

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Electrical Machines
Two dc machines A and B, using the same conductor material, have armature circuit resistances of 0.4 Ω and 1.2 Ω respectively. Of the two machines,

 A is bigger than B for the same current rating
 B is bigger than A for the same current rating
 A is bigger than B for the same voltage rating
 both are of the same size for the same current rating

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