Tiêu đề 5.MAGNETISM AND MATTER - Questions.pdf ✅

5.MAGNETISM AND MATTER (1.)If a magnet of pole strength m is divided into four parts such that the length and width of each part is half that of initial one, then the pole strength of each part will be (a.) m/4 (b.) m/2 (c.) m/8 (d.) 4m (2.)A short bar magnet of magnetic moment 0.4 J T −1 is placed in a uniform magnetic field of 0.16 T. The magnet is in stable equilibrium when the potential energy is (a.) −0.082 J (b.) 0.064 J (c.) −0.064 J (d.) Zero (3.)The magnetic needle of a tangent galvanometer is deflected at angle of 30° due to a current in its coil. The horizontal component of earth’s magnetic field is 0.34 × 10−4 T, then magnetic field at the center of the coil due to current (a.) 1.96 × 10−5 T (b.) 1.96 × 10−4 T (c.) 1.96 × 104 T (d.) 1.96 × 105 T (4.)The given figure represents a material which is (a.) Paramagnetic (b.) Diamagnetic (c.) Ferromagnetic (d.) None of these (5.)The resultant magnetic moment of neon atom will be (a.) Infinity (b.) μB (c.) Zero (d.) μB 2 (6.)A permanent magnet (a.) Attracts all substances (b.) Attracts only magnetic substances (c.) Attracts magnetic substances and repels all non- magnetic substances (d.) Attracts non-magnetic substances and repels magnetic substances (7.)If a magnet is hanged with its magnetic axis then it stops in (a.) Magnetic meridian (b.) Geometric meridian (c.) Angle of dip (d.) None of these (8.)The ultimate individual unit of magnetism is any magnet is called (a.) North pole (b.) South pole (c.) Dipole (d.) Quadrupole (9.)A frog can be levitated in magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as (a.) Paramagnetic (b.) Diamagnetic (c.) Ferromagnetic (d.) Anti-ferromagnetic (10.)A small bar magnet of moment M is placed in a uniform field H. If magnet makes an angle of 30° with field, the torque acting on the magnet is (a.) MH (b.) MH 2 (c.) MH 3 (d.) MH 4 (11.)A magnetic dipole is placed in a uniform magnetic field. The net magnetic force on the dipole (a.) Is always zero (b.) Depends on the orientation of the dipole (c.) Can never be zero (d.) Depends on the strength of the dipole (12.)The magnetic susceptibility does not depend upon the temperature in (a.) Ferrite substances (b.) Ferromagnetic substances (c.) Diamagnetic substances (d.) Paramagnetic substances (13.)A bar magnet is equivalent to (a.) Torroid carrying current (b.) Straight conductor carrying current (c.) Solenoid carrying current (d.) Circular coil carrying current (14.)The material of permanent magnet has (a.) High retentivity, low coercivity (b.) Low retentivity, high coercivity (c.) Low retentivity, low coercivity (d.) High retentivity, high coercivity (15.)A bar magnet has coercivity 4 × 103 Am−1 . It is desired to demagnetise it by inserting it inside a
solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is (a.) 2 A (b.) 4 A (c.) 6 A (d.) 8 A (16.)A magnetic dipole is placed in two perpendicular magnetic fields B⃗ and H⃗ and is in equilibrium taking angle θ with B⃗ . Then (a.) B = H (b.) B cosθ = H sin θ (c.) B sin θ = H cos θ (d.) B = H tan θ (17.)If the angular momentum of an electron is J then the magnitude of the magnetic moment will be (a.) eJ m (b.) eJ 2m (c.) eJ 2m (d.) 2m eJ (18.)A rigid circular loop of radius r and mass m lies in the x − y plane of a flat table and has a current i flowing in it. At this particular place the earth’s magnetic field is B = Bxî+ Bzk̂. The value of i so that the loop start tilting is (a.) mg πr√Bx 2+Bz 2 (b.) mg πrBx (c.) mg πrBz (d.) mg πr√BxBz (19.)Two identical bar magnets with a length 10 cm and weight 50 g-weight are arranged freely with their poles facing in a inverted vertical glass tube. The upper magnet hangs in the air above the lower one so that the distance between the nearest pole of the magnet is 3mm. Pole strength of the poles of each magnet will be (a.) 6.64 amp × m (b.) 2 amp × m (c.) 10.25 amp × m (d.) None of these (20.)At a certain place, horizontal component is√3 times the vertical component. The angle of dip at this place is (a.) Zero (b.) π/3 (c.) π/6 (d.) None of these (21.)Two identical short bar magnets, each having magnetic moment M, are placed a distance of 2d apart with axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is (a.) μ0 4π (√2) M d3 (b.) μ0 4π (√3) M d3 (c.) ( 2μ0 π ) M d3 (d.) μ0 4π (√5) M d3 (22.)A copper rod is suspended a non homogenous magnetic field region. The rod when in equilibrium will align itself (a.) In the region where magnetic field is strongest (b.) In the region where magnetic field is weakest and parallel to direction of magnetic field there (c.) In the direction in which it was originally suspended (d.) In the region where magnetic field is weakest and perpendicular to the direction of magnetic field there (23.)A magnet of length 14 cm and magnetic moment M is broken into two parts of length 6 cm and 8 cm. They are put at a right angle to each other with opposite poles together. The magnetic moment of the combination is (a.) M/10 (b.) M (c.) M/1.4 (d.) 2.8 M (24.)A uniform magnetic field parallel to the plane of paper, existed in space initially directed from left to right. When a bar of soft iron is placed I the field parallel to it, the lines of force passing through it will be represented by figure. (a.) (b.) (c.) (d.) N S S N
(25.)Two magnets of equal mass are joined at 90° each other as shown in figure. Magnet N1 S1 has a magnetic moment √3 times that of N2 S2. The arrangement is pivoted so that it is free to rotate in horizontal plane. When in equilibrium, what angle should N1 S1 make with magnetic meridian? (a.) 75° (b.) 60° (c.) 30° (d.) 45° (26.)The deflection magnetometer is most sensitive when deflection θ is (a.) Nearly zero (b.) Nearly 30° (c.) Nearly 45° (d.) Nearly 90° (27.)Isogonic lines on magnetic map will have (a.) Zero angle of dip (b.) Zero angle of declination (c.) Same angle of declination (d.) Same angle of dip (28.)A magnet makes 5 oscillations per min in B = 0.3 × 10−4 T. By what amount should the field be increased so that number of oscillations is 10 in the same time? (a.) 0.3 × 10−4 T (b.) 0.6 × 10−4 T (c.) 0.9 × 10−4 T (d.) 1.2 × 10−4 T (29.)When a ferromagnetic material is heated to temperature above its curie point, the material (a.) Is permanently magnetized (b.) Remains ferromagnetic (c.) Behaves like a diamagnetic material (d.) Behaves like a paramagnetic material (30.)When a magnetic substance is heated, then it (a.) Becomes a strong magnet (b.) Losses its magnetism (c.) Does not effect the magnetism (d.) Either (a) or (c) (31.)At a point on the right bisector of a magnetic dipole magnetic (a.) Potential varies as 1 r 2 (b.) Potential is zero at all points on the right bisector (c.) Field varies as r 2 (d.) Field is perpendicular to the axis of dipole (32.)The magnetized wire of moment M and length l is bent in the form of semicircle of radius r. Then its magnetic moment is (a.) 2M π (b.) 2 M (c.) M π (d.) Zero (33.)Due to a small magnet, intensity at a distance x in the end on position is 9 gauss. What will be the intensity at a distance x 2 on broad side on position (a.) 9 gauss (b.) 4 gauss (c.) 36 gauss (d.) 4.5 gauss (34.)A short bar magnet has a length 2l and a magnetic moment 10 Am2 . Find the magnetic field at a distance of z = 0.1 m from its centre on the axial line. Here, l is negligible as compared to z. (a.) 2 × 10−3 T (b.) 3 × 10−3 T (c.) 1 × 10−3 T (d.) 4 × 10−3 T (35.)A small bar magnet has a magnetic moment 1.2 A-m2 . The magnetic field at a distance 0.1 m on it axis will be: (μ0 = 4π × 10−7 -m/A) (a.) 1.2 × 10−4T (b.) 2.4 × 10−4T (c.) 2.4 × 104T (d.) 1.2 × 104T (36.)The direction of the null points is on the equatorial line of a bar magnet, when the north pole of the magnet is pointing (a.) North (b.) South (c.) East (d.) West (37.)A magnetic needle is made to vibrate in uniform field H, then it time period is T. If it vibrates in the field of intensity 4H, its time period will be (a.) 2T (b.) T/2 (c.) 2/T (d.) T (38.)On applying an external magnetic field, to a ferromagnetic substance domains (a.) Align in the direction of magnetic field (b.) Align in the direction opposite to magnetic field (c.) Remain unaffected (d.) None of the above (39.)The angle of dip at the magnetic equator is (a.) 0° (b.) 45°
(c.) 30° (d.) 90° (40.)The magnetic susceptibility is negative for (a.) Paramagnetic materials (b.) Diamagnetic materials (c.) Ferromagnetic materials (d.) Paramagnetic and ferromagnetic materials (41.)There are four light-weight-rod samples, A, B, C,D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted (i) A is feebly repelled (ii) B is feebly attracted (iii) C is strongly attracted (iv) D remains unaffected Which one of the following is true (a.) A is of a non-magnetic material (b.) B is of a paramagnetic material (c.) C is of a diamagnetic material (d.) D is of a ferromagnetic material (42.)In which direction, the magnetic field on the axis at a distance z from the centre of the bar magnet would be? (a.) In the perpendicular direction of the magnetic moment (M) of the magnet (b.) In the direction of the magnetic dipole moment (M) of the magnet (c.) Its direction depends on the magnitude of the magnetic moment (M) of the magnet (d.) In the opposite direction of the magnetic dipole moment(M) of the magnet (43.)If the magnetic is cut into four equal parts such that their lengths and breadths are equal. Pole strength of each part is (a.) m (b.) m/2 (c.) m/4 (d.) m/8 (44.)The relative permeability (μr) of a ferromagnetic substance varies with temperature (T) according to the curve (a.) A (b.) B (c.) C (d.) D (45.)If a diamagnetic solution is poured into a U- tube and one arm of this U-tube is placed between the poles of a strong magnet, with the meniscus in line with the field, then the level of solution will (a.) Rise (b.) Fall (c.) Oscillate slowly (d.) Remain as such (46.)If magnetic lines of force are drawn by keeping magnet vertical, then number of neutral points will be (a.) One (b.) Two (c.) Four (d.) Five (47.)What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled (a.) Force increases to two times the previous value (b.) No change (c.) Force decreases to half the previous value (d.) Force increases to four times the previous value (48.)A paramagnetic substance of susceptibility 3 × 10−4 is placed in a magnetic field of 4 × 10−4 Am−1 . Then the intensity of magnetization in the units of Am−1 is (a.) 1.33 × 108 (b.) 0.75 × 10−8 (c.) 12 × 10−8 (d.) 14 × 10−8 (49.)The relative magnetic permeability of ferromagnetic materials is of the order of (a.) 10 (b.) 100 (c.) 1000 (d.) 10000 (50.)Choose the correct statement (a.) A paramagnetic material tends to move from a strong magnetic field to weak magnetic field (b.) A magnetic material is in the paramagnetic phase below its Curie temperature (c.) The resultant magnetic moment in an atom of a diamagnetic substance is zero (d.) Typical domain size of a ferromagnetic material is 1 nm (51.)Water is (a.) Diamagnetic (b.) Paramagnetic (c.) Ferromagnetic (d.) None of these (52.)The time period of a freely suspended magnet does not depend upon (a.) Length of magnet (b.) Pole strength of magnet (c.) Horizontal component of earth’s field A B D Tc T 1.0 10 100 0.1 r C