Magnetic-Effect-Of-Current-And-Magnetism-Quiz-10

Magnetic Effect Of Current And Magnetism Quiz-10

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Q91. When a magnet is placed vertically on horizontal board, number of neutral points obtained on the board is

•  Four
•  Three
•  Two
•  One

Solution
At one point only, vertical component of earth’s magnetic field may balance the field due to vertical magnet (which is vertical being along the axis of the magnet).

Q92.Two similar bar magnets P and Q, each of magnetic moment M, are taken, If P is cut along it axial line and Q is cut along its equatorial line, all the four pieces obtained have

•  Equal pole strength
•  Magnetic moment M/4
•  Magnetic moment
•  Magnetic moment M

Solution
               

Q93.  When a piece of a ferromagnetic substance is put in a uniform magnetic field, the flux density inside it is four times the flux density away from the piece. The magnetic permeability of the material(in N/A²) is

•   1
•  2
•  3
•  4

Solution
                     

Q94. At a certain place, a magnet makes 30 oscillations per min. At another place where the magnetic field is double, its time period will be

•  4 s
•  2 s
•  1/2 s
•  2 s

Solution
                        

Q95.Substances in which the magnetic moment of a single atom is not zero, is known as

•  Diamagnetism
•  Ferromagnetism
•  Ferromagnetism
•  Ferrimagnetism

Solution
  The property of paramagnetism is found in these substances whose atoms have an excess of electrons spinning in the same direction. Hence atoms of paramagnetic substances have a net non-zero magnetic moment of their own

Q96. A bar magnet has a magnetic moment equal to 5×10^-5 Wb-m. It is suspended in a magnetic field which has a magnetic induction B equal to 8π×10^-4 T. The magnet vibrates with a period of vibration equal to 15 s. The moment of inertia of magnet is

•  4.54×10⁴ kg-m²
• 4.54 ×10^-5 kg-m²
•  4.54 ×10^-4 kg-m²
•  4.54 ×10⁵ kg-m²

Solution
                     

Q97.AWhat happens to the force between magnetic poles when their pole strength and the distance between them are both doubled

•  Force increases to two times the previous value
•  No change
•  Force decreases to half the previous value
•  Force increases to four times the previous value

Solution
                   

Q98.The vertical component of earth’s magnetic field is zero at or The earth’s magnetic field always has a vertical component except at the

•  Magnetic poles
•  Geographical poles
•  Every place
•  Magnetic equator

Solution
At magnetic equator, the angle of dip is 0°. Hence the vertical component V=I sin⁡ϕ=0

Q99.A bar magnet is held at right angles to a uniform magnetic field. The couple acting on the magnet is to be halved by rotation it from this position. The angle of rotation is

•  60°
•  45°
•  30°
•  75°

Solution
                

Q100. Two bar magnets with magnetic moments 2 M and M are fastened together at right angles to each other at their centres to form a crossed system, which can rotate freely about a vertical axis through the centre. The crossed system sets in earth’s magnetic field with magnet having magnetic moment 2M making an angle θ with the magnetic meridian such that

•  The horizontal component of the earth’s magnetic field
•  The location of the geographic meridian
• The vertical component of the earth’s field
•  The direction of the earth’s magnetic field

Solution
The direction of the earth’s magnetic field