DC Motors
The value of back emf in dc motor is maximum at

Full load
No load
None of the listed here
Half full load

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DC Motors
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor

Of higher H.P. should be selected
Of lower H.P. should be selected
Is to be de-rated by a factor recommended by manufacturer and select the next higher H.P. motor
Can be used for 50°C ambient temperature also

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DC Motors
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit

A resistance is connected parallel to the armature
A high value resistor is connected across the field winding
A resistance is connected in series with armature
Armature is temporarily open circuited

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