# Entry Test MCQ :: Electromagnetic Induction

21.  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

22.  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

23.  A coil of wire is arranged with its plan perpendicular to a uniform magnetic field o flux density B. when the radius of the coil increases from r1 to r2 in time ?t then what is the emf induced in the coil?
 A. ?B/r22-r12/?t B. ?B(r2-r1)2/?t C. ?B(r22-r12)/?t D. ?B(r22+r12)/?t

24.  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

25.  The self-inductance of a solenoid is increased when a soft iron core is inserted into it. This is because the soft iron core
 A. Decreases the resistance of the solenoid B. Reduces the effect of eddy current C. Improves the flux linkage between the turns of the coil D. Increases the mutual inductance between the solenoid and the core

26.  A small coil lies inside a large coil. The two coils are horizontal concentric and carry currents in opposite directions. The large coil will experience
 A. A torque about horizontal axis B. A torque about vertical axis C. An upward force along the axis D. No resultant force

27.  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 = 4x10-5T). 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

28.  A.C can not be used for
 A. producing heat B. producing light C. Magnetizing iron D. Producing magnetic field

29.  Non inductive resistances are used in decreasing
 A. Mutual inductance B. Self inductance C. Magnetic fields D. Heating effect

30.  Magnetic compass needle will be deflecting if it is kept near
 A. Static charge B. Soft iron C. Semi-conductor D. Accelerating charge