When the motor is at its maximum speed then back emf will be______________?

Related Mcqs:

1. An aeroplane of wingspan 10m flies from the equator towards the North Pole. The wings are perpendicular to the vertical component of the earths magnetic field (B = 4×10-5T). At maximum speed an emf of 96mV is induced across the wing tips. The maximum speed of the aeroplane is____________?

   A. 150msec-1 B. 384msec-1 C. 38.4msec-1 D. 200msec-1...

2. A metal rod of 25 cm length is moving at a speed of 0.5/sec in direction perpendicular to 0.25T magnetic field. Emf produced in the rod is_____________?

   A. 0 volt B. 3.125 volt C. 31.25 volt D. 0.03125 volt...

3. ________________ motor is a constant speed motor?

   A. Synchronous motor B. Schrage motor C. Induction motor D. Universal motor...

4. A coil of wire is arranged with its plane perpendicular to a uniform magnetic field o flux density B. when the radius of the coil increases from r1 to r2 in time Δt then what is the emf induced in the coil ?

   A. ωB/r22-r12/Δt B. ωB(r2-r1)2/Δt C. ωB(r22-r12)/Δt D. ωB(r22+r12)/Δt...

5. emf induced in a circuit according to Faradays law depends on the_____________?

   A. maximum magnetic flux B. rate of change of magnetic flux C. change in magnetic flux D. initial magnetic flux...

6. The emf induced in a coil by a changing magnetic flux may have unit as______________?

   A. ms-1A B. ms-2A-1 C. kgms2A-1 D. kgm2s-1A-1...

7. The emf induced in a conductor of unit length moving with unit velocity at right angles to a magnetic field is equal to_____________?

   A. Magnetic flux density B. Torque C. Mutual induction D. Motional emf...

8. A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is____________________?

   A. slop speed operation B. high starting torque C. low windage losses D. all of the above...

9. Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be______________?

   A. 32 mH B. 38 mH C. 40 mH D. 48 mH...

10. Two oppositely charged balls A and B attract third conducting ball C when placed near them turn by turn. Then ball C must be______________?

    A. positively charged B. electrically neutral C. negatively charged D. positively and negatively charged...