NEET
Practice Test 5
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DIRECTION: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following-

Statement-1 : Electromagnetic are made of soft iron.

Statement-2 : Coercivity of soft iron is small.

 

  • Solution

    (b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

    Electromagnets are magnets, which can be turnd on and off by switching the current on and off.As the material in electromagnets is subjected to cyclic changes (magnification and demangetisation), the hysteresis loss of the material must be small. The material should attain high value of I and B with low value of magnetising field intensity H. As soft iron has small coercivity, so it is a best choice for this purpose.

DIRECTION: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following-

 

Statement-1: A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled.

Statement-2 : The magnetisation does not depend ontemperature.

  • Solution

    (d)Statement -1 is true, Statement-2 is false

    A paramagnetic sampled is play greater magnetisation when cooled, this is because at lower temperature, the tendency to disrupt the alignment of dipoles (due to magnetising field) decreases on account of reduced random thermal motion.

DIRECTION: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following-

Statement-1 : The ferromagnetic substance do not obey Curie’s law.

Statement-2 : At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.

 

  • Solution

    (b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

    A magnetic field is produced by the motion of electric charge. Since motion is relative, the magnetic field is also relative.

DIRECTION: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following-

Statement-1 : The ferromagnetic substance do not obey Curie’s law.

Statement-2 :At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.

  • Solution

    (c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

    The susceptibility of ferromagnetic substance decreases with the rise of temperature in a complicated manner. After Curies point in the susceptibility of ferromagnetic substance varies in versely with its absolute tempearture. Ferromagnetic substance obey’s Curie’s law only above its Curie point.

A bar magnet of length ‘l’ and magnetic dipole moment ‘M’is bent in the form of an arc as shown in figure.The new magnetic dipole moment will be

  • Solution

Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at Pin between the gap of the two magnets at a distance D from the centre O as shown in the figure.

The force on the charge Q is

  • Solution

    Force on a charged particle is given by F= qvB. Here v= 0 and also resultant B is zero.

    ∴ Force =0

A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2 sec in earth’s horizontal magnetic field of 24 microtesla. When a horizontal field of 18 microtesla is produced opposite to the earth’s field by placing a current carrying wire, the new time period of magnet will be

  • Solution

If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by μd, μp and μf respectively, then

  • Solution

    The magnetic dipole moment of diamagnetic material is zero as each of its pair of electrons have opposite spins,i.e., μd= 0.

    Para magnetic substances have dipole moment > 0,i.e. μp ≠ 0, because of excess of electrons in its molecules spinning in the same direction.

    Ferro-magnetic substances are very strong magnets and they also have permanent magnetic moment,i.e.μf ≠ 0.

A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that \(\overrightarrow{B}\) is in plane of the coil. If due to a current i in the triangle a torque τ acts on it, the side l of the triangle is

  • Solution


Two magnets of magnetic moments M and 2M are placed in a vibration magnetometer, with the identical poles in the same direction. The time period of vibration is T1. If the magnets are placed with opposite poles together and vibrate with time period T2, then

  • Solution

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