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What is back emf ?...

What is back emf ?

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When the armature of a motor rotates in the magnetic field, then due to the change in magnetic flux associated with it, an induced emfis set up in it which is known as back emf.
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BETTER CHOICE PUBLICATION-ELECTROMAGNETIC INDUCTION-NUMERICAL PROBLEMS
  1. What is back emf ?

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  2. A magnetic field of 2xx10^-2T acts at right angles to a coil of area 1...

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  3. A small piece of metal wire is dragged across the gap between this ...

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  4. A copper rod of length 2 m fixed at one end is rotating with an angula...

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  5. A brass rod of length 3.0 m fixed at one end is rotating with angula...

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  6. A silver rod of length one metre fixed at one end is rotating with ang...

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  7. An e.m.f. of 250 muV is induced in a coil, when current in it changes ...

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  8. A wire of length 0.1 m moves with a speed of 10 "m/s" perpendicular to...

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  9. A coil of 100 turns and area 200 "cm"^(2) is placed at right angles to...

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  10. The magnetic flux passing through a coil changes from 6 xx 10^(-3)wb t...

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  11. The magnetic flux passing through a coil changes from 5 xx 10^(-2) w...

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  12. The magnetic flux through a coil changes from 4 xx 10^(-2) wb to 6 xx ...

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  13. A magnetic ifeld 2 xx 10^(-2)"wbm"^(-2) is acting at right angle to a...

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  14. A magnetic field of 4 xx 10^(-4)"wbm"^(-2) is acting at right angle to...

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  15. A magnetic field 5 xx 10^(-4)"wbm"^(-2) is acting at right angle to a...

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  16. A magnetic flux of 5 microweber is linked with a coil when a current o...

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  17. A magnetic flux of 5 microweber is linked with a coil when a current o...

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  18. The magnetic flux threading a coil changes from to 12x10(-3) Wb to 6x1...

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  19. What will be the coefficient of mutual inductance of a pair of coil if...

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  20. A wire is cut across a flux of 0.2x10(-2) weber in 0.12 seconds. What ...

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  21. A railway track running North South has two parallel rails 1.0m apart....

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