JEE Main Physics - Magnetostatics
Exam Duration: 60 Mins Total Questions : 30
Angle of dip is maximum at
- (a)
poles
- (b)
equator
- (c)
latitude 45°
- (d)
latitude 60°
Choose the INCORRECT statement
- (a)
The ratio of magnetic induction to the intensity of the magnetising filed is called permeability
- (b)
The ratio of the intensity of magnetisation to the intensity of the magnetising field is called susceptibility
- (c)
Magnetic elements of the earth are iron, cobalt and nickel
- (d)
A magnet of pole strength 0.2 ampere-metre when cut into two pieces of equal length has the same pole strength
A magnetic dipole in the shape of a sphere placed in a uniform magnetic field of induction \(\overrightarrow { B } \) will, in general
- (a)
be displaced in the direction \(\overrightarrow { B } \)
- (b)
be displaced opposite to the direction of \(\overrightarrow { B } \)
- (c)
remain in equilibrium position after displacement from its initial position
- (d)
execute simple harmonic motion provided the amplitude of motion is small
A magnet is cut into two pieces such that the length of one piece is three times the length of the other. The pole strengthts of these pieces are in the ratio of
- (a)
1:1
- (b)
3:1
- (c)
2:1
- (d)
4:1
Choose the INCORRECT statement
- (a)
The value of dip at the magnetic equator is zero degree.
- (b)
The earth's magnetism is proved by the formation of null points in the field around a bar magnet.
- (c)
Tangent law is applicable to the case of the deflection magnetometer only when the magnetometer is set in tan A and tan B positions.
- (d)
Isoclinic lines are the lines joining places of zero dip.
A magnet gave two null points located on its axis under the influence of the earth's field. In such a case the magnet must have been kept with its axis
- (a)
perpendicular to the meridian North Pole facing North
- (b)
perpendicular to the meridian South Pole facing North
- (c)
in the magnetic meridian South Pole facing North
- (d)
in the magnetic meridian North Pole facing North
At magnetic poles, the angle of dip is
- (a)
45°
- (b)
30°
- (c)
zero
- (d)
90°
A small pellet with a mass of 0.5 mg is fired horizontally from a gun that imparts to it a velocity of 100 ms-1. The pellet carries a charge of \(+5\mu C\). Magnetic field B is required to cancel the Earth's gravitational force on the pellet. The value of B is
- (a)
9.80 mT
- (b)
4.90 mT
- (c)
29.40 mT
- (d)
2.45 mT
In a certain Cartesian frame the velocity of an electron is \(\overrightarrow { \vartheta } =(2.5\hat { k } )\times { 10 }^{ 7 }{ ms }^{ -1 }\) and it experiences a force \(\overrightarrow { F } =(4.0\hat { i } +3.0\hat { j } )\times { 10 }^{ -13 }N\) due to the presence of a uniform magnetic field. When the velocity is redirected and becomes \(\overrightarrow { \vartheta } =(1.5\hat { i } -2.0\hat { j } )\times { 10 }^{ 7 }{ ms }^{ -1 }\), the magnetic force on the electron is zero. The component of magnetic induction vector \(\overrightarrow { B } \) is
- (a)
\(\overrightarrow { B } =(0.100\hat { i } -0.075\hat { j } )T\)
- (b)
\(\overrightarrow { B } =(-0.075\hat { i } +0.100\hat { j } )T\)
- (c)
\(\overrightarrow { B } =(-1.00\hat { i } +0.075\hat { i } )T\)
- (d)
\(\overrightarrow { B } =(0.075\hat { i } -0.100\hat { j } )T\)
A cosmic-ray proton in interstellar space has an energy of 10 MeV and executes a circular orbit with a radius equal to that of Mercury's orbit around the Sun \((5.8\times { 10 }^{ 10 }m)\).The galactic magnetic field in that region of space is
- (a)
\(7.8\times { 10 }^{ -12 }T\)
- (b)
\(15.6\times { 10 }^{ -12 }T\)
- (c)
\(7.8\times { 10 }^{ 12 }T\)
- (d)
\(3.9\times { 10 }^{ -12 }T\)
In order for a material to be suitable for fabricating a good permanent magnet,
- (a)
the remanence of the material must be large but its coercive force must be small
- (b)
its remanence must be small but its coercive force must be large
- (c)
both, its remanence as well as its coercive force must be large
- (d)
its remanence as well as its coercive force must be small
A circular coil of 100 turns has an effective radius of 0.05 and current of 0.1A. How much work is done to turn it through 180° in a uniform field of 1.5W/m2 if the plane of the coil is initially perpendicular to the magnetic field?
- (a)
0.5523 J
- (b)
0.3255 J
- (c)
0.2355 J
- (d)
0.5235 J
A magnet is suspended in a vertical plane which makes an angle of 30º with the magnetic meridian. In equilibrium, the axis of the magnet makes an angle of 45º with horizontal. What is the real value of dip at the place?
- (a)
4º
- (b)
40.9º
- (c)
45º
- (d)
NONE OF THESE
Unit of pole strength is
- (a)
Am
- (b)
Am-2
- (c)
Am-1
- (d)
Am2
A magnet oscillates in the earth's field with a time period T. It its mass is quadrupled, then its new time period will be
- (a)
4T
- (b)
2T
- (c)
T/2
- (d)
unaffected but motion is not SHM
A magnet of the magnetic moment M is rotated through \(360º\) in a magnetic field H; the work done will be
- (a)
MH
- (b)
2MH
- (c)
4MH
- (d)
Zero
The force between two short bar magnets with magnetic moments M1 and M2 whose centres are r metres apart is 8.0 N when their axes are in the same line. If the separation is increased to 2r, then force between them is reduced to
- (a)
4.0 N
- (b)
2.0 N
- (c)
1.0 N
- (d)
0.5 N
Which of the following substances has negative permeability and very large value of susceptibility?
- (a)
Ferromagnetic
- (b)
Paramagnetic
- (c)
Diamagnetic
- (d)
NONE OF THE ABOVE
A dip circle is so set that its needle moves freely in the magnetic meridian. In this position, the angle of dip is \(40º\). Now the dip circle is rotated so that the plane in which the needle moves makes an angle of \(30º\) with the magnetic meridian. In this position, the needle will dip by an angle
- (a)
\(40º\)
- (b)
\(30º\)
- (c)
more than \(40º\)
- (d)
less than \(40º\)
Susceptibility is positive and large for a
- (a)
paramagnetic substance
- (b)
ferromagnetic substance
- (c)
diamagnetic substance
- (d)
non-magnetic substance
A certain amount of current when flowing in a properly set tangent galvanometer produces a deflection of \(45º\). If the current be reduced by a factor of \(\sqrt { 3 } \), the deflection would
- (a)
decrease by \(30º\)
- (b)
decrease by \(15º\)
- (c)
increase by \(15º\)
- (d)
increase by \(30º\)
Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of \(60º\) and \(45º\) respectively. The ratio of the number of turns in the coils is
- (a)
4/3
- (b)
\((\sqrt { 3 } +1)/1\)
- (c)
\((\sqrt { 3 } +1)/(\sqrt { 3 } -1)\)
- (d)
\(\sqrt { 3 } /1\)
A circular loop of radius 0.0157 m carries a current of 2.0 A. The magnetic field at the centre of the loop is \(\left[ { \mu }_{ 0 }=4\pi \times { 10 }^{ -7 }\quad weber/amp-m \right] \)
- (a)
\(1.57\times { 10 }^{ -5 }weber/{ m }^{ 2 }\)
- (b)
\(8.0\times { 10 }^{ -5 }weber/{ m }^{ 2 }\)
- (c)
\(2.0\times { 10 }^{ -5 }weber/{ m }^{ 2 }\)
- (d)
\(3.14\times { 10 }^{ -5 }weber/{ m }^{ 2 }\)
Two identical magnetic dipoles of magnetic moments 1.0 Am2 each, placed at a separation of 2 m with their axes perpendicular to each other. The resultant magnetic field at a point midway between the dipole is
- (a)
\(5\times { 10 }^{ -7 }T\)
- (b)
\(\sqrt { 5 } \times { 10 }^{ -7 }T\)
- (c)
\({ 10 }^{ -7 }T\)
- (d)
\(2\times { 10 }^{ -7 }T\)
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
A ferromagnetic material is heated above its Curie temperature. Which one is a correct statement?
- (a)
Ferromagnetic domains are perfectly arranged
- (b)
Ferromagnetic domains become random
- (c)
Ferromagnetic material changes into diamagnetic material
- (d)
Ferromagnetic domains are not affected
A vibration magnetometer is placed at the south pole, then the time period will be
- (a)
zero
- (b)
infinity
- (c)
same as at equator
- (d)
same as at any other place on the earth