question_answer 1) Time period of a freely suspended magnet does not depend upon [NCERT 1980; CPMT 1980; MP PET 1997]
A) Length of the magnet done
clear
B) Pole strength of the magnet done
clear
C) Horizontal component of earth's magnetic field done
clear
D) Length of the suspension thread done
clear
View Solution play_arrow
question_answer 2) Magnetic moments of two bar magnets may be compared with the help of [MP PET/PMT 1988]
A) Deflection magnetometer done
clear
B) Vibration magnetometer done
clear
C) Both of the above done
clear
D) None of the above done
clear
View Solution play_arrow
question_answer 3) The time period of oscillation of a freely suspended bar magnet with usual notations is given by [CPMT 1973, 76, 87; MP PET 1994, 96]
A) \[T=2\pi \sqrt{\frac{I}{M{{B}_{H}}}}\] done
clear
B) \[T=2\pi \sqrt{\frac{M{{B}_{H}}}{I}}\] done
clear
C) \[T=\sqrt{\frac{I}{M{{B}_{H}}}}\] done
clear
D) \[T=2\pi \sqrt{\frac{{{B}_{H}}}{MI}}\] done
clear
View Solution play_arrow
question_answer 4) In sum and difference method in vibration magnetometer, the time period is more if [MP PMT 1989; MP PET/PMT 1988]
A) Similar poles of both magnets are on same sides done
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B) Opposite poles of both magnets are on same sides done
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C) Both magnets are perpendicular to each other done
clear
D) Nothing can be said done
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View Solution play_arrow
question_answer 5) At a certain place a magnet makes 30 oscillations per minute. At another place where the magnetic field is double, its time period will be [MP PMT 1989; MP PET/PMT 1988]
A) 4 sec done
clear
B) 2 sec done
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C) \[\frac{1}{2}\sec \] done
clear
D) \[\sqrt{2}\sec \] done
clear
View Solution play_arrow
question_answer 6) Vibration magnetometer is used for comparing [MP PET/PMT 1988]
A) Magnetic fields done
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B) Earth's field done
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C) Magnetic moments done
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D) All of the above done
clear
View Solution play_arrow
question_answer 7) Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moments is [Bihar PET 1984; MP PET/PMT 1988; MP PET 1992]
A) 4 : 9 done
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B) 9 : 4 done
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C) 2 : 3 done
clear
D) 3 : 2 done
clear
View Solution play_arrow
question_answer 8) Time period for a magnet is T. If it is divided in four equal parts along its axis and perpendicular to its axis as shown then time period for each part will be
A) \[4T\] done
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B) \[T/4\] done
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C) \[T/2\] done
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D) \[T\] done
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View Solution play_arrow
question_answer 9) Keeping dissimilar poles of two magnets of equal pole strength and length same side, their time period will be [DPMT 2001]
A) Zero done
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B) One second done
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C) Infinity done
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D) Any value done
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View Solution play_arrow
question_answer 10) Time period in vibration magnetometer will be infinity at
A) Magnetic equator done
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B) Magnetic poles done
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C) Equator done
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D) At all places done
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View Solution play_arrow
question_answer 11) Twists of suspension fibre should be removed in vibration magnetometer so that
A) Time period be less done
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B) Time period be more done
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C) Magnet may vibrate freely done
clear
D) Cannot be said with certainty done
clear
View Solution play_arrow
question_answer 12) The period of oscillation of a magnet in vibration magnetometer is 2 sec. The period of oscillation of a magnet whose magnetic moment is four times that of the first magnet is [CPMT 1975, 77, 79, 89, 90; MP PMT 1986]
A) 1 sec done
clear
B) 4 sec done
clear
C) 8 sec done
clear
D) 0.5 sec done
clear
View Solution play_arrow
question_answer 13) Moment of inertia of a magnetic needle is 40 gm-cm2 has time period 3 seconds in earth's horizontal field = \[3.6\times {{10}^{-5}}\]weber/m2. Its magnetic moment will be
A) \[0.5\,A\times {{m}^{2}}\] done
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B) \[5\,A\times {{m}^{2}}\] done
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C) \[0.250\,A\times {{m}^{2}}\] done
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D) \[5\times {{10}^{2}}A\times {{m}^{2}}\] done
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View Solution play_arrow
question_answer 14) Vibration magnetometer before use, should be set
A) In magnetic meridian done
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B) In geographical meridian done
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C) Perpendicular to magnetic meridian done
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D) In any position done
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View Solution play_arrow
question_answer 15) If a brass bar is placed on a vibrating magnet, then its time period
A) Decreases done
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B) Increases done
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C) Remains unchanged done
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D) First increases then decreases done
clear
View Solution play_arrow
question_answer 16) A magnetic needle is made to vibrate in uniform field H, then its time period is T. If it vibrates in the field of intensity 4H, its time period will be [MP Board 1988; MP PMT 1992; MH CET (Med.) 1999]
A) \[2T\] done
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B) \[T/2\] done
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C) \[2/T\] done
clear
D) \[T\] done
clear
View Solution play_arrow
question_answer 17) Two bar magnets of the same mass, length and breadth but magnetic moments M and 2M respectively, when placed in same position, time period is 3 sec. What will be the time period when they are placed in different position [NCERT 1977; DPMT 1999]
A) \[\sqrt{3}\sec \] done
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B) \[3\sqrt{3}\sec \] done
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C) \[3\sec \] done
clear
D) \[6\sec \] done
clear
View Solution play_arrow
question_answer 18) To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because
A) Determination of moment of inertia is not needed which minimises the errors done
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B) Less observations are required done
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C) Comparatively less calculations done
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D) All the above done
clear
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question_answer 19) A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a place where dip angle is 30o and 15 oscillations per minute at a place where dip angle is 60o. The ratio of total earth's magnetic field at the two places is [MP PMT 1991; BHU 1997]
A) \[3\sqrt{3}:8\] done
clear
B) \[16:9\sqrt{3}\] done
clear
C) \[4:9\] done
clear
D) \[2\sqrt{3}:9\] done
clear
View Solution play_arrow
question_answer 20) The time period of oscillation of a magnet in a vibration magnetometer is 1.5 seconds. The time period of oscillation of another magnet similar in size, shape and mass but having one-fourth magnetic moment than that of first magnet, oscillating at same place will be [MP PMT 1991; MP PMT 2002]
A) 0.75 sec done
clear
B) 1.5 sec done
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C) 3 sec done
clear
D) 6 sec done
clear
View Solution play_arrow
question_answer 21) A bar magnet A of magnetic moment MA is found to oscillate at a frequency twice that of magnet B of magnetic moment MB when placed in a vibrating magneto-meter. We may say that [MP PMT 1991]
A) \[{{M}_{A}}=2{{M}_{B}}\] done
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B) \[{{M}_{A}}=8{{M}_{B}}\] done
clear
C) \[{{M}_{A}}=4{{M}_{B}}\] done
clear
D) \[{{M}_{B}}=8{{M}_{A}}\] done
clear
View Solution play_arrow
question_answer 22) Two magnets A and B are identical in mass, length and breadth but have different magnetic moments. In a vibration magnetometer, if the time period of B is twice the time period of A. The ratio of the magnetic moments \[{{M}_{A}}/{{M}_{B}}\] of the magnets will be [MP PET 1990; MP PMT 1990]
A) \[1/2\] done
clear
B) \[2\] done
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C) \[4\] done
clear
D) \[1/4\] done
clear
View Solution play_arrow
question_answer 23) A magnet of magnetic moment M oscillating freely in earth's horizontal magnetic field makes n oscillations per minute. If the magnetic moment is quadrupled and the earth's field is doubled, the number of oscillations made per minute would be [MP PET 1991]
A) \[\frac{n}{2\sqrt{2}}\] done
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B) \[\frac{n}{\sqrt{2}}\] done
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C) \[2\sqrt{2}n\] done
clear
D) \[\sqrt{2}n\] done
clear
View Solution play_arrow
question_answer 24) A magnetic needle suspended horizontally by an unspun silk fibre, oscillates in the horizontal plane because of the restoring force originating mainly from [CPMT 1980, 89]
A) The torsion of the silk fibre done
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B) The force of gravity done
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C) The horizontal component of earth's magnetic field done
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D) All the above factors done
clear
View Solution play_arrow
question_answer 25) At two places A and B using vibration magnetometer, a magnet vibrates in a horizontal plane and its respective periodic time are 2 sec and 3 sec and at these places the earth's horizontal components are HA and HB respectively. Then the ratio between HA and HB will be [MP PMT 1985, 89]
A) 9 : 4 done
clear
B) 3 : 2 done
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C) 4 : 9 done
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D) 2 : 3 done
clear
View Solution play_arrow
question_answer 26) The time period of a bar magnet suspended horizontally in the earth's magnetic field and allowed to oscillate [MP PET 1992]
A) Is directly proportional to the square root of its mass done
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B) Is directly proportional to its pole strength done
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C) Is inversely proportional to its magnetic moment done
clear
D) Decreases if the length increases but pole strength remains same done
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View Solution play_arrow
question_answer 27) Magnets A and B are geometrically similar but the magnetic moment of A is twice that of B. If T1 and T2 be the time periods of the oscillation when their like poles and unlike poles are kept together respectively, then \[\frac{{{T}_{1}}}{{{T}_{2}}}\]will be [SCRA 1998]
A) \[\frac{1}{3}\] done
clear
B) \[\frac{1}{2}\] done
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C) \[\frac{1}{\sqrt{3}}\] done
clear
D) \[\sqrt{3}\] done
clear
View Solution play_arrow
question_answer 28) A small bar magnet A oscillates in a horizontal plane with a period T at a place where the angle of dip is 60o. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be [MP PMT 1992]
A) \[\frac{T}{\sqrt{2}}\] done
clear
B) \[T\] done
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C) \[\sqrt{2}T\] done
clear
D) \[2T\] done
clear
View Solution play_arrow
question_answer 29) Vibration magnetometer works on the principle of [MP PET 1993]
A) Torque acting on the bar magnet done
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B) Force acting on the bar magnet done
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C) Both the force and the torque acting on the bar magnet done
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D) None of these done
clear
View Solution play_arrow
question_answer 30) Tangent galvanometer is used to measure [MP PET 1993]
A) Steady currents done
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B) Current impulses done
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C) Magnetic moments of bar magnets done
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D) Earth's magnetic field done
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View Solution play_arrow
question_answer 31) A tangent galvanometer has a coil with 50 turns and radius equal to 4 cm. A current of 0.1 A is passing through it. The plane of the coil is set parallel to the earth's magnetic meridian. If the value of the earth's horizontal component of the magnetic field is \[7\times {{10}^{-5}}\]tesla and\[{{\mu }_{0}}=4\pi \times {{10}^{-7}}weber/amp\times m\], then the deflection in the galvanometer needle will be [MP PMT 1993]
A) 45o done
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B) 48.2o done
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C) 50.7o done
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D) 52.7o done
clear
View Solution play_arrow
question_answer 32) A bar magnet has a magnetic moment equal to\[5\times {{10}^{-5}}weber\times m.\] It is suspended in a magnetic field which has a magnetic induction equal to \[8\pi \times {{10}^{-4}}tesla.\] The magnet vibrates with a period of vibration equal to 15 sec. The moment of inertia of the magnet is [MP PMT 1993; CBSE PMT 2001]
A) \[22.5kg\times {{m}^{2}}\] done
clear
B) \[11.25\times kg\times {{m}^{2}}\] done
clear
C) \[5.62\times kg\times {{m}^{2}}\] done
clear
D) \[7.16\times {{10}^{-7}}kg-{{m}^{2}}\] done
clear
View Solution play_arrow
question_answer 33) The time period of a freely suspended magnet is 4 seconds. If it is broken in length into two equal parts and one part is suspended in the same way, then its time period will be [NCERT 1984; CPMT 1991; MP PMT 1994; MH CET 2004]
A) 4 sec done
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B) 2 sec done
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C) 0.5 sec done
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D) 0.25 sec done
clear
View Solution play_arrow
question_answer 34) Which of the following statement is true about magnetic moments of atoms of different elements [CPMT 1977]
A) All have a magnetic moment done
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B) None has a magnetic moment done
clear
C) All acquire a magnetic moment under external magnetic field and in same direction as the field done
clear
D) None of the above statements are accurate done
clear
View Solution play_arrow
question_answer 35) The number of turns and radius of cross-section of the coil of a tangent galvanometer are doubled. The reduction factor K will be [NCERT 1983; MP PMT 2002]
A) K done
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B) 2K done
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C) 4K done
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D) K/4 done
clear
View Solution play_arrow
question_answer 36) A magnetic needle suspended by a silk thread is vibrating in the earth's magnetic field. If the temperature of the needle is increased by 500?C, then [MNR 1994]
A) The time period decreases done
clear
B) The time period remains unchanged done
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C) The time period increases done
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D) The needle stops vibrating done
clear
View Solution play_arrow
question_answer 37) The sensitivity of a tangent galvanometer is increased if [AFMC 1995]
A) Number of turn decreases done
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B) Number of turn increases done
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C) Field increases done
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D) None of the above done
clear
View Solution play_arrow
question_answer 38) Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of 60? and 45? respectively. The ratio of the number of turns in the coils is [MP PET 1995; MP PMT 1999]
A) 4/3 done
clear
B) \[(\sqrt{3}+1)/1\] done
clear
C) \[(\sqrt{3}+1)/(\sqrt{3}-1)\] done
clear
D) \[\sqrt{3}/1\] done
clear
View Solution play_arrow
question_answer 39) Using a bar magnet P, a vibration magnetometer has time period 2seconds. When a bar Q (identical to P in mass and size) is placed on top of P, the time period is unchanged. Which of the following statements is true [MP PMT 1995]
A) Q is of non-magnetic material done
clear
B) Q is a bar magnet identical to P, and its north pole placed on top of P's north pole done
clear
C) Q is of unmagnetized ferromagnetic material done
clear
D) Nothing can be said about Q's properties done
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View Solution play_arrow
question_answer 40) The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become [Haryana CEE 1996]
A) Twice its original value done
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B) Four times its original value done
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C) Half its original value done
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D) One-fourth its original value done
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View Solution play_arrow
question_answer 41) A certain amount of current when flowing in a properly set tangent galvanometer, produces a deflection of 45?. If the current be reduced by a factor of \[\sqrt{3}\], the deflection would [MP PMT 1996; DPMT 2005]
A) Decrease by 30? done
clear
B) Decrease by 15? done
clear
C) Increase by 15? done
clear
D) Increase by 30? done
clear
View Solution play_arrow
question_answer 42) Two normal uniform magnetic field contain a magnetic needle making an angle 60? with F. Then the ratio of \[\frac{F}{H}\] is [CPMT 1987; DPMT 2001]
A) 1 : 2 done
clear
B) 2 : 1 done
clear
C) \[\sqrt{3}:1\] done
clear
D) \[1:\sqrt{3}\] done
clear
View Solution play_arrow
question_answer 43) A short magnetic needle is pivoted in a uniform magnetic field of strength 1 T. When another magnetic field of strength \[\sqrt{3}\,T\] is applied to the needle in a perpendicular direction, the needle deflects through an angle q, where q is [KCET 1999]
A) 30o done
clear
B) 45o done
clear
C) 90o done
clear
D) 60o done
clear
View Solution play_arrow
question_answer 44) Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth's magnetic field with like poles together, 12 oscillations per minute are made but for unlike poles together only 4 oscillations per minute are executed. The ratio of their magnetic moments is [MP PMT 1996; CPMT 2002]
A) 3 : 1 done
clear
B) 1 : 3 done
clear
C) 3 : 5 done
clear
D) 5 : 4 done
clear
View Solution play_arrow
question_answer 45) To measure which of the following, is a tangent galvanometer used [MP PET 1997; CBSE PMT 2001]
A) Charge done
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B) Angle done
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C) Current done
clear
D) Magnetic intensity done
clear
View Solution play_arrow
question_answer 46) When \[\sqrt{3}\]ampere current is passed in a tangent galvanometer, there is a deflection of 30? in it. The deflection obtained when 3 amperes current is passed, is [MP PMT 1997]
A) 30? done
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B) 45? done
clear
C) 60? done
clear
D) 75? done
clear
View Solution play_arrow
question_answer 47) The period of oscillations of a magnetic needle in a magnetic field is 1.0 sec. If the length of the needle is halved by cutting it, the time period will be [MP PMT/PET 1998]
A) 1.0 sec done
clear
B) 0.5 sec done
clear
C) 0.25 sec done
clear
D) 2.0 sec done
clear
View Solution play_arrow
question_answer 48) The time period of a freely suspended magnet is 2 sec. If it is broken in length into two equal parts and one part is suspended in the same way, then its time period will be [MP PMT 1999]
A) 4 sec done
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B) 2 sec done
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C) \[\sqrt{2}\sec \] done
clear
D) 1 sec done
clear
View Solution play_arrow
question_answer 49) The bob of a simple pendulum is replaced by a magnet. The oscillations are set along the length of the magnet. A copper coil is added so that one pole of the magnet passes in and out of the coil. The coil is short-circuited. Then which one of the following happens [KCET 1994]
A) Period decreases done
clear
B) Period does not change done
clear
C) Oscillations are damped done
clear
D) Amplitude increases done
clear
View Solution play_arrow
question_answer 50) The period of oscillation of a vibration magnetometer depends on which of the following factors [KCET 1994]
A) I and M only done
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B) M and H only done
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C) I and H only done
clear
D) I, M and H only where I is the moment of inertia of the magnet about the axis of suspension, M is the magnetic moment of the magnet and H is the external magnetic field done
clear
View Solution play_arrow
question_answer 51) The time period of oscillation of a bar magnet suspended horizontally along the magnetic meridian is T0. If this magnet is replaced by another magnet of the same size and pole strength but with double the mass, the new time period will be [SCRA 1994; JIPMER 2001, 02]
A) \[\frac{{{T}_{0}}}{2}\] done
clear
B) \[\frac{{{T}_{0}}}{\sqrt{2}}\] done
clear
C) \[\sqrt{2}{{T}_{0}}\] done
clear
D) \[2{{T}_{0}}\] done
clear
View Solution play_arrow
question_answer 52) Two short magnets having magnetic moments in the ratio 27 : 8, when placed on opposite sides of a deflection magnetometer, produce no deflection. If the distance of the weaker magnet is 0.12 m from the centre of deflection magnetometer, the distance of the stronger magnet from the centre is [EAMCET (Med.) 2000]
A) 0.06 m done
clear
B) 0.08 m done
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C) 0.12 m done
clear
D) 0.18 m done
clear
View Solution play_arrow
question_answer 53) The magnet of a vibration magnetometer is heated so as to reduce its magnetic moment by 19%. By doing this the periodic time of the magnetometer will [MP PMT 2000, 01]
A) Increase by 19% done
clear
B) Decrease by 19% done
clear
C) Increase by 11% done
clear
D) Decrease by 21% done
clear
View Solution play_arrow
question_answer 54) A magnet makes 40 oscillations per minute at a place having magnetic field intensity of 0.1 ? 10?5 T. At another place, it takes 2.5 sec to complete one vibration. The value of earth?s horizontal field at that place is [AIIMS 2000; CPMT 2000; Pb PET 2002]
A) 0.25 ? 10?6 T done
clear
B) 0.36 ? 10?6 T done
clear
C) 0.66 ? 10?8 T done
clear
D) 1.2 ? 10?6 T done
clear
View Solution play_arrow
question_answer 55) A tangent galvanometer has a coil of 25 turns and radius of 15 cm. The horizontal component of the earth?s magnetic field is 3 ? 10?5 T. The current required to produce a deflection of 45o in it, is [MP PMT 2000]
A) 0.29 A done
clear
B) 1.2 A done
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C) 3.6 ? 10?5 A done
clear
D) 0.14 A done
clear
View Solution play_arrow
question_answer 56) The time period of a vibration magnetometer is T0. Its magnet is replaced by another magnet whose moment of inertia is 3 times and magnetic moment is 1/3 of the initial magnet. The time period now will be [MP PMT 2000]
A) 3T0 done
clear
B) T0 done
clear
C) \[{{T}_{0}}/\sqrt{3}\] done
clear
D) T0/3 done
clear
View Solution play_arrow
question_answer 57) The error in measuring the current with a tangent galvanometer is minimum when the deflection is about [MP PET 2001]
A) 0o done
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B) 30o done
clear
C) 45o done
clear
D) 60o done
clear
View Solution play_arrow
question_answer 58) Before using the tangent galvanometer, its coil is set in [MP PMT 2001; CPMT 2005]
A) Magnetic meridian (or vertically north south) done
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B) Perpendicular to magnetic meridian done
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C) At angle of 45o to magnetic meridian done
clear
D) It does not require any setting done
clear
View Solution play_arrow
question_answer 59) The time period of a thin bar magnet in earth?s magnetic field is T. If the magnet is cut into two equal parts perpendicular to its length, the time period of each part in the same field will be [MP PET 2001]
A) \[\frac{T}{2}\] done
clear
B) T done
clear
C) \[\sqrt{2}\,T\] done
clear
D) 2T done
clear
View Solution play_arrow
question_answer 60) A magnet freely suspended in a vibration magnetometer makes 10 oscillations per minute at a place A and 20 oscillations per minute at a place B. If the horizontal component of earth?s magnetic field at A is \[36\times {{10}^{-6}}T,\] then its value at B is [EAMCET (Med.) 2001]
A) 36 ? 10?6 T done
clear
B) 72 ? 10?6 T done
clear
C) 144 ? 10?6 T done
clear
D) 288 ? 10?6 T done
clear
View Solution play_arrow
question_answer 61) When 2 amperes current is passed through a tangent galvanometer, it gives a deflection of 30o. For 60o deflection, the current must be [MP PMT 2001]
A) 1 amp done
clear
B) \[2\sqrt{3}\,amp\] done
clear
C) 4 amp done
clear
D) 6 amp done
clear
View Solution play_arrow
question_answer 62) Which of the following statement is not the true [KCET (Engg./Med.) 2001]
A) While taking reading of tangent galvanometer, the plane of the coil must be set at right angles to the earth?s magnetic meridian done
clear
B) A short magnet is used in a tangent galvanometer since a long magnet would be heavy and may not easily move done
clear
C) Measurements with the tangent galvanometer will be more accurate when the deflection is around 45o done
clear
D) A tangent galvanometer cannot be used in the polar region done
clear
View Solution play_arrow
question_answer 63) The period of oscillations of a magnet is 2 sec. When it is remagnetised so that the pole strength is 4 times its period will be [Kerala PMT 2002]
A) 4 sec done
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B) 2 sec done
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C) 1 sec done
clear
D) 1/2 sec done
clear
View Solution play_arrow
question_answer 64) When two magnetic moments are compared using equal distance method the deflections produced are 45o and 30o. If the length of magnets are in the ratio 1 : 2, the ratio of their pole strengths is [JIPMER 2002]
A) 3 : 1 done
clear
B) 3 : 2 done
clear
C) \[\sqrt{3}:1\] done
clear
D) \[2\sqrt{3}:1\] done
clear
View Solution play_arrow
question_answer 65) The magnetic needle of a tangent galvanometer is deflected at an angle 30o due to a magnet. The horizontal component of earth?s magnetic field 0.34 ? 10?4 T is along the plane of the coil. The magnetic intensity is [AIIMS 2000, 2002; BHU 2000; AFMC 2000; KCET (Engg./Med.) 1999]
A) 1.96 ? 10?4 T done
clear
B) 1.96 ? 10?5 T done
clear
C) 1.96 ? 104 T done
clear
D) 1.96 ? 105 T done
clear
View Solution play_arrow
question_answer 66) In a tangent galvanometer a current of 0.1 A produces a deflection of 30o. The current required to produce a deflection of 60o is [MP PET 2003]
A) 0.2 A done
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B) 0.3 A done
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C) 0.4 A done
clear
D) 0.5 A done
clear
View Solution play_arrow
question_answer 67) A bar magnet is oscillating in the Earth?s magnetic field with a period T. What happens to its period and motion if its mass is quadrupled [CBSE PMT 2003]
A) Motion remains S.H.M. with time period = 2T done
clear
B) Motion remains S.H.M. with time period = 4T done
clear
C) Motion remains S.H.M. and period remains nearly constant done
clear
D) Motion remains S.H.M. with time period \[=\frac{T}{2}\] done
clear
View Solution play_arrow
question_answer 68) A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T ?, then ratio \[\frac{{{T}'}}{T}\]is [AIEEE 2003]
A) \[\frac{1}{4}\] done
clear
B) \[\frac{1}{2\sqrt{2}}\] done
clear
C) \[\frac{1}{2}\] done
clear
D) 2 done
clear
View Solution play_arrow
question_answer 69) A bar magnet is oscillating in the earth's magnetic field with time period T. If its mass is increased four times then its time period will be [J & K CET 2004]
A) 4 T done
clear
B) 2 T done
clear
C) T done
clear
D) T/2 done
clear
View Solution play_arrow
question_answer 70) The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. The time period of this combination will be [AIEEE 2004]
A) 2 s done
clear
B) 2/3 s done
clear
C) \[2\sqrt{3}\,s\] done
clear
D) \[2/\sqrt{3}\,s\] done
clear
View Solution play_arrow
question_answer 71) A magnet oscillating in a horizontal plane has a time period of 2 second at a place where the angle of dip is 30o and 3 seconds at another place where the angle of dip is 60o. The ratio of resultant magnetic fields at the two places is [Pb. PET 2001]
A) \[\frac{4\sqrt{3}}{7}\] done
clear
B) \[\frac{4}{9\sqrt{3}}\] done
clear
C) \[\frac{9}{4\sqrt{3}}\] done
clear
D) \[\frac{9}{\sqrt{3}}\] done
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question_answer 72) Two identical bar magnets are placed on above the other such that they are mutually perpendicular and bisect each other. The time period of this combination in a horizontal magnetic field is T. The time period of each magnet in the same field is [CPMT 2005]
A) \[\sqrt{2}\,T\] done
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B) \[{{2}^{\frac{1}{4}}}T\] done
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C) \[{{2}^{-\frac{1}{4}}}T\] done
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D) \[{{2}^{-\frac{1}{2}}}T\] done
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question_answer 73) The radius of the coil of a Tangent galvanometer. which has 10 turns is 0.1m. The current required to produce a deflection of 60? \[({{B}_{H}}=4\times {{10}^{-5}}T)\] is [MP PET 2005]
A) 3 A done
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B) 1.1 A done
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C) 2.1 A done
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D) 1.5 A done
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