JEE Questions for Physics Magnetism And Matter Quiz 3

If two identical bar magnets, each of length l, pole strength m and magnetic moment M are placed perpendicular to each other with their unlike poles in contact, the magnetic moment of the combination is

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A magnet of length 14 cm and magnetic moment M is broken into two parts of lengths 6 cm and 8 cm. They are put at right angle to each other with opposite poles together. The magnetic moment of the combination is

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M/10
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M
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M/1.4
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2.8M

A vibration magnetometer consists of two identical bar magnets placed one over the other such that they are mutually perpendicular and bisect each other. The time period of combination is 4 s. If one of the magnets is removed, find the period of other

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5 s
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3.36 s
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4.36 s
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5.36 s

A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60°. The torque required to keep the needle in this position will be

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Two identical magnetic dipoles of magnetic moment 2 Am² are placed at a separation of 2 m with their axis perpendicular to each other in air. The resultant magnetic field at a mid point between the dipoles is

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A bar magnet is placed in the position of stable equilibrium in a uniform magnetic field of induction B. If it is rotated through an angle 180°, then the work done is (M= Magnetic dipole moment of bar magnet)

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MB
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2MB
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MB / 2
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zero

A magnetic dipole is placed in a uniform magnetic field. The net magnetic force on the dipole

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is always zero
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depends on the orientation of the dipole
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can never be zero
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depends on the strength of the dipole

A short bar magnet has a length 2l and a magnetic moment 10 Am² . Find the magnetic field at a distance of r = 0.1m from its centre on the axial line. Here, l is negligible as compared to r .

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2 × 10 -3 T
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3 × 10 -3 T
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1 × 10 -3 T
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4 × 10 -3 T

A short bar magnet experiences a torque of magnitude 0.64 J. When it is placed in a uniform magnetic field of 0.32 T, taking an angle of 30° with the direction of the field. The magnetic moment of the magnet is

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1 Am2
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4 Am2
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6 Am2
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None of these

The magnetic field of a small bar magnet varies in the following manner by the influence of a magnet placed at a large distance d .

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An electron of charge e moves in a circular orbit of radius r around the nucleus at a frequency v. The magnetic moment associated with the orbital motion of the electron is

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A bar magnet when placed at an angle of 30° to the direction of magnetic field induction of 5 × 10^-2 T, experiences a moment of couple 25 × 10 ^-6 Nm. If the length of the magnet is 5 cm, then its pole strength is

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2 × 10-2 Am
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5 × 10-2 Am
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2 Am
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5 Am

A magnet of magnetic moment 20 CGS units is freely suspended in a uniform magnetic field of intensity 0.3 CGS units. The amount of work done in deflecting it by an angle of 30° in CGS units is

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6
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3

At a point on the right bisector of a magnetic dipole the magnetic

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potential varies as
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potential is zero at all points on the right bisector
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field varies as r2
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field is perpendicular to the axis of dipole

The magnetic lines of force inside a bar magnet

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are from North-pole to South-pole of the magnet
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do not exist
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depend upon the area of cross-section of the bar magnet
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are from South-pole to North-pole of the magnet

The effect due to uniform magnetic field on a freely suspended magnetic needle is as follows

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both torque and net force are present
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torque is present but no net force
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both torque and net force are absent
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net force is present but not torque

The intensity of magnetic field due to an isolated pole of strength m at a point distant r from it will be

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If the B–H curves of two samples of P and Q of iron are as shown below, then which one of the following statements is correct?
Physics-Magnetism and Matter-77899.png

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Both P and Q are suitable for making permanent magnet
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P is suitable for making permanent magnet and Q for making electromagnet
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P is suitable for making electromagnet and Q is suitable for permanent magnet
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Both P and Q are suitable for making electromagnets

Needles N₁ , N₂ and N₃ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will

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attract N1 and N2 strongly but repel N3
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attract N1 strongly, N2 weakly and repel N3 weakly
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attract N1, strongly, but repel N2 and N3 weakly
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attract all three of them

The magnetic needle has magnetic moment 8.7 × 10^-2 Am² and moment of inertia 11.5 × 10^-6 kg m². It performs 10 complete oscillations in 6.70 s, what is the magnitude of the magnetic field?

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0.012 T
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0.120 T
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1.200 T
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2.10 T

A dip circle is so that its needle moves freely in the magnetic meridian. In this position, the angle of dip is 40°. Now the dip circle is rotated so that the plane in which the needle moves makes an angle of 30° with the magnetic meridian. In this position, the needle will dip by an angle

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40°
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30°
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more than 40°
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less than 40°

Two tangent galvanometers A and B have coils of radii 8 cm and 16 cm respectively and resistance 8 Ω each. They are connected in parallel with a cell of emf 4 V and negligible internal resistance. The deflections produced in the tangent galvanometers A and B are 30° and 60° respectively. If A has 2 turn, then B must have

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18 turn
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12 turn
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6 turn
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2 turn

A deflection magnetometer is adjusted in the usual way. When a magnet is introduced, the deflection observed is θ, and the period of oscillation of the needle in the magnetometer is T . When the magnet is removed, the period of oscillation is T ₀ . The relation between T and T ₀ is

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With a standard rectangular bar magnet the time period of a vibration magnetometer is 4 s. The bar magnet is cut parallel to its length into four equal pieces The time period of vibration magnetometer when one piece is used (in second) (bar magnet breadth is small). is

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16
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8
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4
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2

The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2s. 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

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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', the ratio T'/ T is

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2
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The coil in a tangent galvanometer is 16 cm in radius. If a current of 20 mA is to produce a deflection of 45°, then the number of turns wound on it, is (take horizontal component of the earth's magnetic field = 0.36 × 10^-4 T and μ₀ = 4π × 10^-7 WbA ^-1 m ^-1 )

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229
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458
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689
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916

A bar magnet of magnetic moment M and moment of inertia I is freely suspended such that the magnetic axial line is in the direction of magnetic meridian. If the magnet is displaced by a very small angle (θ), the angular acceleration is (magnetic induction of the earth's horizontal field = B_H )