Home
Class 12
PHYSICS
Assertion : An electric motor will have ...

Assertion : An electric motor will have maximum efficiency when back emf becomes equal to half of applied emf.
Reason : Efficiency of electric motor depends only on magnitude of back emf.

A

If both assertion and reason are t rue and the reason is the correct explanation of the assertion.

B

If both assertion and reason are true but reason is not the correct explanation of the assertion

C

If assertion is true but reason is false.

D

If the assertion and reason both are fal se.

Text Solution

Verified by Experts

The correct Answer is:
D
Promotional Banner

Topper's Solved these Questions

  • ELECTRO MAGNETIC INDUCTION

    ERRORLESS |Exercise OT|3 Videos

  • ELECTRO MAGNETIC INDUCTION

    ERRORLESS |Exercise Motional EMI|1 Videos

  • CURRENT ELECTRICITY

    ERRORLESS |Exercise Self Evaluation Test -19|23 Videos

  • ELECTRON, PHOTON, PHOTOELECTRIC EFFECT AND X-RAYS

    ERRORLESS |Exercise Self Evaluation Test|3 Videos

Similar Questions

Explore conceptually related problems

Assertoion : An electric motor will have maximum efficiency when back emf becomes equal of half of applied emf. Reason. Power factor of series R_L circuit is given by cos theta = (2R)/(sqrt(R^(2) + omega^(2) L^(2)))

In a dc motor, induced e.m.f. will be maximum

In the above question, show that power output of electri motor is maximum when the back emf is one-half of the sourece emf, provided the resistance of the winding of the motor is negligible .

(a) An electric motor runs on a d.c. source of emf e and internal resistance r. show that the power output of the source is maximum when the current drawns by the motor is epsilon//2r . (b) Show that power output of electric motor is maximum when the back emf is one-half the source emf provided the resistance of the windings of the motor is negligible. (c) Compare and contrast carefully the situation in this excercise with that in Example 43 above.

(a) An electric motor runs on a d.c. source of emf e and internal resistance r. show that the power output of the source is maximum when the current drawns by the motor is epsilon//2r . (b) Show that power output of electric motor is maximum when the back emf is one-half the source emf provided the resistance of the windings of the motor is negligible. (c) Compare and contrast carefully the situation in this excercise with that in Example 43 above.

An electric motor operates with an efficiency of 90% . A pump operated by the motor has an efficiency of 80% . The overall efficiency of the system is

Assertion : An electric motor converts electical energy to mechanical energy. Reason : The working of the motor is based on mutualn induction.

ERRORLESS -ELECTRO MAGNETIC INDUCTION-SET
  1. Assertion : An electric motor will have maximum efficiency when back e...

    Text Solution

    |

  2. The figure shows four wire loops, with edge length of either L or 2L. ...

    Text Solution

    |

  3. A circular coil and a bar magnet placed nearby are made to move in the...

    Text Solution

    |

  4. A square coil ABCD lying in x-y plane with its centre at origin. A lon...

    Text Solution

    |

  5. A short magnet is allowed to fall from rest along the axis of a horizo...

    Text Solution

    |

  6. The horizontal component of the earth's magnetic field at a place is 3...

    Text Solution

    |

  7. A copper disc of radius 0.1 m rotates about its centre with 10 revolut...

    Text Solution

    |

  8. A coil of Cu wire (radius r, self-inductance L) is bent in two concen...

    Text Solution

    |

  9. In which of the following circuits is the current maximum just after t...

    Text Solution

    |

  10. A small coil is introduced between the poles of an electromagnet so th...

    Text Solution

    |

  11. Two circular coils A and B are facing each other as shown in figure. T...

    Text Solution

    |

  12. A conductuing loop having a capacitor is moving outward from the magne...

    Text Solution

    |

  13. A straight wire of length L is bent into a semicircle. It is moved in ...

    Text Solution

    |

  14. If in a coil rate of change of area is (5meter^(2))/(milli second)and ...

    Text Solution

    |

  15. In series with 20 ohm resitor a 5 henry inductor is placed. To the com...

    Text Solution

    |

  16. Two circular coils P & Q are coaxially & carry currents I1 and I2 resp...

    Text Solution

    |

  17. The phase difference between the flux linkage and the induced e.m.f. i...

    Text Solution

    |

  18. A pair of parallel conducting rails lie at right angle to a uniform ma...

    Text Solution

    |

  19. The magnetic field in the cylindrical region shown in figure increase ...

    Text Solution

    |

  20. An aircraft with a wingspan of 40 m flies a speed of 1080 km hr(1) in ...

    Text Solution

    |

  21. A hundred turns of insulated copper wire are wrapped around an iron cy...

    Text Solution

    |