Magnetism and Matter Test 3

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Question 1
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Which of the following statements about earth's magnetism is correct

A
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south-west to the north-east.

B
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south-east to the north-west.

C
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic east to the west.

D
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south to the north.

Question 2
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magnetic permeability of the substance μ is

A
μ₀μ^r

B
μ₀^0.8μ_r

C
μ₀^1.2μ_r

D
μ₀^1.5μ_r

Question 3
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A toroid wound with 60.0 turns/m of wire carries a current of 5.00 A. The torus is iron, which has a magnetic permeability of μm=5000μ0 under the given conditions. H and B inside the iron are

A
340AT/m,2.88T

B
340AT/m,1.88T

C
380AT/m,1.98T

D
300AT/m,1.88T

Question 4
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A bar magnet of magnetic moment 1.5 J/T lies aligned with the direction of a uniform magnetic field of 0.22 T. What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment opposite to the field direction?

A
0.66J

B
0.76J nC

C
0.86J

D
0.56J

Question 5
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In the magnetic meridian of a certain place, the horizontal component of the earth’s magnetic field is 0.26G and the dip angle is 60^o. What is the magnetic field of the earth at this location

A
0.65G

B
0.62G

C
0.58G

D
0.52G

Question 6
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Which of the following statements about bar magnets is correct ?

A
We can isolate the north and south pole of a bar magnet.

B
North Pole atrracts North Pole.

C
South Pole atrracts South Pole.

D
We cannot isolate the north and south pole of a bar magnet.

Question 7
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Magnetic material differences are explained by

A
atoms contain moving electrons, and these electrons form microscopic current loops that produce magnetic fields of their own.

B
number of neutrons

C
number of protonsatoms contain spinning electrons, and their spin forms microscopic current loops that produce magnetic

D
fields

Question 8
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A cube-shaped permanent magnet is made of a ferromagnetic material with a magnetization 500M of about The side length is 20 cm. Magnetic dipole moment of the magnet is.

A
5Am²

B
3Am²

C
4Am²

D
6Am²

Question 9
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A bar magnet of magnetic moment 1.5 J/T lies perpendicular to the direction of a uniform magnetic field of 0.22 T. What is the torque acting on it?

A
0.23J

B
0.38J

C
0.43J

D
0.33J

Question 10
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A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at 14 cm from the centre of the magnet. The earth’s magnetic field at the place is 0.36 G and the angle of dip is zero. What is the total magnetic field on the normal bisector of the magnet at the same distance as the null–point (i.e., 14 cm) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth’s magnetic field.)

A
0.64 G in the direction of earth’s field.

B
0.62 G in the direction of earth’s field.

C
0.54 G in the direction of earth’s field.

D
0.58 G in the direction of earth’s field.

Question 11
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When iron filings are sprinkled on a sheet of glass placed over a short bar magnet then,

A
The iron filings form a pattern of suggesting that the magnet has north pole similar to the positive charge

B
The iron filings form a random pattern of suggesting that the magnet has random pole

C
The iron filings form a pattern suggesting that the magnet has two poles similar to the positive and negative charge of an electric dipole

D
The iron filings form a pattern of suggesting that the magnet has south pole similar to the negative charge

Question 12
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Diamagnetic substances are

A
those which have tendency to move from stronger to the weaker part of the external magnetic field

B
those that are uneffected by external magnetic fields

C
those that develop a net magnetic moment in direction of applied field

D
those which have tendency to move from weaker to the stronger part of the external magnetic field

Question 13
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A cube-shaped permanent magnet is made of a ferromagnetic material with a magnetization 8 * 10⁵ M of about The side length is 2 cm. Magnetic field due to the magnet at a point 10 cm from the magnet along its axis is

A
0.003 T

B
0.002 T

C
0.004 T

D
0.001 T

Question 14
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A bar magnet of magnetic moment 1.5 J/T lies parallel to the direction of a uniform magnetic field of 0.22 T. What is the torque acting on it?

A
-0.3J

B
0.0J

C
0.23J

D
0.3J

Question 15
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A short bar magnet of magnetic moment 5.25×10⁻²JT⁻¹ is placed with its axis perpendicular to the earth’s field direction. At what distance from the centre of the magnet, the resultant field is inclined at 45 with earth’s field on its normal bisector . Magnitude of the earth’s field at the place is given to be 0.42 G. Ignore the length of the magnet in comparison to the distances involved.

A
5.5 cm

B
7.0 cm

C
6.0 cm

D
5 cm

Question 16
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Which of the following statements about magnetic field lines true?

A
The magnetic field lines of a magnet (or a solenoid) form continuous closed loops

B
The smaller the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field B.

C
The perpendicular to the field line at a given point gives direction of magnetic field

D
The larger the number of field lines crossing per unit area, the weaker is the magnitude of the magnetic field B.

Question 17
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For diamagnetic materials

A
additional field caused by atoms is always parallel in direction to that of the external field

B
additional field caused by atoms is always perpendicular in direction to that of the external field

C
additional field caused by atoms is always in same direction as that of the external field

D
additional field caused by atoms is always opposite in direction to that of the external field

Question 18
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permeability of a paramagnetic material is expected to decrease with increasing temperature because

A
random thermal motion increases magnetic moment alignment

B
electrons stop moving

C
electrons go into forbidden gap

D
random thermal motion reduces magnetic moment alignment

Question 19
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A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at 220 with the horizontal. The horizontal component of the earth’s magnetic field at the place is known to be 0.35 G. Determine the magnitude of the earth’s magnetic field at the place.

A
0.48G

B
0.28G

C
0.58G

D
0.38G

Question 20
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A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of 12 A ?

A
4.48 T

B
5.48 T

C
44.8 T

D
48 T

Question 21
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In which case of comparing solenoid and bar magnet there is no exact similarity?

A
There is a current entering and a current leaving a solenoid

B
soenoid can be broken into two weaker solenoids

C
flux lines enter one end of a solenoid

D
moving a small compass needle in the neighbourhood of a solenoid enables tracing the flux lines

Question 22
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For paramagnetic materials

A
orbital and spin magnetic moments of the electrons are of the order of bohr magneton

B
orbital magnetic moments of the electrons are zero

C
orbital and spin magnetic moments of the electrons are less than zero

D
spin magnetic moments of the electrons are zero

Question 23
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If a magnet is suspended over a container of liquid air, it attracts droplets to its poles. The droplets contain only liquid oxygen and no nitrogen because

A
oxygen is ferromagnetic whereas nitrogen is diamagnetic

B
oxygen is ferrimagnetic whereas nitrogen is diamagnetic

C
oxygen is diamagnetic whereas nitrogen is paramagnetic

D
oxygen is paramagnetic whereas nitrogen is diamagnetic

Question 24
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A short bar magnet has a magnetic moment of 0.48 J/T .Magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on the axis has a direction and magnitude of .

A
1.06 G along S-N direction.

B
0.96 G along S-N direction.

C
0.86 G along S-N direction.

D
0.76 G along S-N direction.

Question 25
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A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of 45⁰ with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. Determine the horizontal component of the earth’s magnetic field at the location

A
0.34G

B
0.49G

C
0.29G

D
0.39G

Question 26
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Far axial magnetic field of a solenoid as well as bar magnet vary

A
directly as R squared R = axial distance to the magnet/solenoid

B
inversely as R squared R = axial distance to the magnet/solenoid

C
directly as R cubed R = axial distance to the magnet/solenoid

D
inversely as R cubed R = axial distance to the magnet/solenoid

Question 27
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In Ferromagnetic materials

A
atomic magnetic moments are random in strong external fields

B
strong interactions between atomic magnetic moments cause them to line up anti parallel to each other in external field

C
weak interactions between atomic magnetic moments cause them to line up anti parallel to each other in external field

D
strong interactions between atomic magnetic moments cause them to line up parallel to each other in regions called magnetic domains even if there is no external field

Question 28
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which of the following features of atomic structure determine whether an element is diamagnetic or paramagnetic

A
orbital angular momentum ,spin angular momentum

B
atomic weight

C
number of electrons

D
principal quantum number

Question 29
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A toroidal solenoid with 500 turns is wound on a ring with a mean radius of 2.90 cm. Find the current in the winding that is required to set up a magnetic field of 0.350 T in the ring if the ring is made of annealed iron Km=1400

A
82.5mA

B
72.5mA

C
79.5mA

D
69.5mA

Question 30
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Correct unit of Bohr magneton is

A
T

B
T/J

C
J/T

D
J

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Magnetism and M...

Question 1

The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south-west to the north-east.

The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south-east to the north-west.

The earth behaves as a magnet with the magnetic field pointing approximately from the geographic east to the west.

The earth behaves as a magnet with the magnetic field pointing approximately from the geographic south to the north.

Question 2

μ0μr

μ00.8μr

μ01.2μr

μ01.5μr

Question 3

340AT/m,2.88T

340AT/m,1.88T

380AT/m,1.98T

300AT/m,1.88T

Question 4

0.66J

0.76J nC

0.86J

0.56J

Question 5

0.65G

0.62G

0.58G

0.52G

Question 6

We can isolate the north and south pole of a bar magnet.

North Pole atrracts North Pole.

South Pole atrracts South Pole.

We cannot isolate the north and south pole of a bar magnet.

Question 7

atoms contain moving electrons, and these electrons form microscopic current loops that produce magnetic fields of their own.

number of neutrons

number of protonsatoms contain spinning electrons, and their spin forms microscopic current loops that produce magnetic

fields

Question 8

5Am2

3Am2

4Am2

6Am2

Question 9

0.23J

0.38J

0.43J

0.33J

Question 10

0.64 G in the direction of earth’s field.

0.62 G in the direction of earth’s field.

0.54 G in the direction of earth’s field.

0.58 G in the direction of earth’s field.

Question 11

The iron filings form a pattern of suggesting that the magnet has north pole similar to the positive charge

The iron filings form a random pattern of suggesting that the magnet has random pole

The iron filings form a pattern suggesting that the magnet has two poles similar to the positive and negative charge of an electric dipole

The iron filings form a pattern of suggesting that the magnet has south pole similar to the negative charge

Question 12

those which have tendency to move from stronger to the weaker part of the external magnetic field

those that are uneffected by external magnetic fields

those that develop a net magnetic moment in direction of applied field

those which have tendency to move from weaker to the stronger part of the external magnetic field

Question 13

0.003 T

0.002 T

0.004 T

0.001 T

Question 14

-0.3J

0.0J

0.23J

0.3J

Question 15

5.5 cm

7.0 cm

6.0 cm

5 cm

Question 16

The magnetic field lines of a magnet (or a solenoid) form continuous closed loops

The smaller the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field B.

The perpendicular to the field line at a given point gives direction of magnetic field

μ₀μ^r

μ₀^0.8μ_r

μ₀^1.2μ_r

μ₀^1.5μ_r

5Am²

3Am²

4Am²

6Am²