MEDIUM
JEE Main
IMPORTANT
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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:
(a)
(b)
(c)
(d)

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Important Questions on Magnetic Effects of Current and Magnetism
HARD
JEE Main
IMPORTANT
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:

HARD
JEE Main
IMPORTANT
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
JEE Main
IMPORTANT
A magnetic compass needle oscillates times per minute at a place where the dip is and times per minute where the dip is . If and are the net magnetic fields due to the earth at the two places respectively, then the ratio is approximately equal to

HARD
JEE Main
IMPORTANT
A galvanometer of resistance has divisions on its scale and has sensitivity of . It is to be converted to voltmeter with three ranges, of and The appropriate circuit to do so is:

MEDIUM
JEE Main
IMPORTANT
A thin ring of radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of about its axis, perpendicular to its plane. Is the magnetic field its centre is , then the charge carried by the ring is close to

MEDIUM
JEE Main
IMPORTANT
An electron, moving along the axis with an initial energy of enters a region of magnetic field at S (see figure). The field extends between and The electron is detected at the point on a screen placed away from the point The distance d between and (on the screen) is:
(electron’s charge , mass of electron )


HARD
JEE Main
IMPORTANT
A moving coil galvanometer, having a resistance produces full scale deflection when a current flows through it. This galvanometer can be converted into (i) an ammeter of range 0 to by connecting a shunt resistance to it and (ii) into a voltmeter of range 0 to by connecting a series resistance to it. Then,

MEDIUM
JEE Main
IMPORTANT
Find the magnetic field at point due to a straight line segment of length carrying a current of (See figure)
