EASY
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The magnetic field on the axis at a distance from the centre of the bar magnet would be?
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Important Questions on Matter and Magnetism
HARD
A hoop and a solid cylinder of same mass and radius are made of a permanent magnetic material with their respective axes. But the magnetic moment of hoop is twice of solid cylinder. They are placed in a uniform magnetic field in such a manner that their magnetic moments make a small angle with the field. If the oscillation periods of hoop and cylinder are and respectively, then:
MEDIUM
A -Turn rectangular coil of length and width carries a current of and subjected to a magnetic field of strength Work done for rotating the coil by against the torque is:
MEDIUM
The magnetic field of earth at the equator is approximately . The radius of earth is . Then the dipole moment of the earth will be nearly of the order of :
HARD
At some location the horizontal component of earth's magnetic field is At this location, magnetic needle of length and pole strength is suspended from its mid-point using a thread, it makes angles with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is:
MEDIUM
A magnetic needle of magnetic moment and moment of inertia is performing simple harmonic oscillations in a magnetic field of . Time taken for complete oscillations is:
EASY
A circular coil having turns and radius carries a current It is held in the plane in a magnetic field . The torque on the coil due to the magnetic field is:
MEDIUM
The mid points of two small magnetic dipoles of length in end-on positions, are separated by a distance . The magnitude of force between them is proportional to where is :
MEDIUM
A thin rod of length is magnetized and has magnetic moment . The rod is then bent in a semicircular arc. The magnetic moment in the new shape is
HARD
The magnetic flux near the axis and inside the air-core solenoid of length carrying current is Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length, SI units)
MEDIUM
Two identical bar magnets are held perpendicular to each other with a certain separation, as shown below. The area around the magnets is divided into four zones.
Given that there is a neutral point it is located in,
EASY
The magnetic dipole moment of a short magnetic dipole at a distant point along the equator of magnet has a magnitude of in SI units. If the distance between point and the magnet is halved then the magnitude of dipole moment will be
HARD
Two short bar magnets of length each have magnetic moments and respectively. They are placed on a horizontal table parallel to each other with their poles pointing towards the south. They have a common magnetic equator and are separated by a distance of . The value of the resultant horizontal magnetic induction at the mid-point of the line joining their centres is close to
( Horizontal component of earth's magnetic induction is )
HARD
An electron gun is placed inside a long solenoid of radius on its axis. The solenoid has turns/length and carries a current The electron gun shoots an electron along the radius of the solenoid with speed If the electron does not hit the surface of the solenoid, maximum possible value of is (all symbols have their standard meaning):
MEDIUM
A rectangular coil (Dimension ) with turns, carrying a current of in the clock-wise direction, is kept centered at the origin and in the plane. A magnetic field of is applied along . If the coil is tilted through about , then the torque on the coil is:
EASY
A small bar magnet is placed with its axis at with an external magnetic field of experiences a torque of . The minimum work required to rotate it from its stable to unstable equilibrium position is:
HARD
Two short bar magnets and (having magnetic moments and respectively) are kept one above the other with their magnetic axis perpendicular to each other. If their resultant at a point on the axis of magnet is inclined at with the axis of magnet then the ratio of magnetic moments is
EASY
A magnetic needle kept in a non-uniform magnetic field, can experiences
HARD
A uniform magnetic field of is along the positive -direction. A rectangular loop () of sides carries a current of . Out of the following different orientations which one corresponds to stable equilibrium?
MEDIUM
A short bar magnet is placed in the magnetic meridian of the earth with North Pole pointing north. Neutral points are found at a distance of from the magnet on the East-West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in is close to:
(Given in SI units and Horizontal component of earth's magnetic field Tesla.)
MEDIUM
An insulating thin rod of length has a linear charge density on it. The rod is rotated about an axis passing through the origin and perpendicular to the rod. If the rod makes rotations per second, then the time averaged magnetic moment of the rod is:
