Magnetism and Matter Test -5

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Magnetism and Matter Test -5

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Question 1
1 / -0

Magnetic permeability of the substance μ is

A
μ₀μr

B
μ₀^1.2μr

C
μ₀^1.5μr

D
μ₀^0.8μr

Solution

The releative permeability of a medium is given by permeability of medium divided by permeability of vacuum.Therefore ,

μ=μ₀μr
Question 2
1 / -0

Magnetic material differences are explained by

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

B
atoms contain spinning electrons, and their spin forms microscopic current loops that produce magnetic fields

C
number of neutrons

D
number of protons

Solution

Magnetic field of atoms depends on both orbiting as well as spinning electrons.
Question 3
1 / -0

Diamagnetic substances are

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

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

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

D
those that are uneffected by external magnetic fields

Solution

Dimagnetic substances get feebly magnitized in the direction opposite to that of applied magnetic field, hence they tend to move from region of stronger magnetic field to weaker magnetic field.
Question 4
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For diamagnetic materials

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

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

Solution

Diamagnetic materials get feebly magnetized in the direction opposite to that of applied external magnetic field.
Question 5
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What conclusion is drawn regarding the magnetic field at a point if a compass needle at that point rests in any direction?

A
Magnetic field is non zero.

B
Magnetic field is zero.

C
Magnetic field is more than zero.

D
Magnetic field is less than zero.

Solution

If the compass needle rest in any direction at a certain point it shows that the net magnetic force acting on the point is zero.Hence, the resultant magnetic field is zero.This point is also known as null or neutral point.
Question 6
1 / -0

Iron is ferromagnetic :

A
at all temperatures

B
at NTP only

C
above $${770}^{o}C$$

D
below $${770}^{o}C$$

Solution

Curie temperature for iron is 770 degree centigrade therefore, it behaves as a ferromagnetic material below 770 and above 770 it becomes paramagnetic.
Question 7
1 / -0

Magnetic force required to demagnetize the material

A
retainity

B
coercivity

C
energy loss

D
hysteresis

Solution

For a ferromagnetic substance, coercivity is the intensity of the magnetic field that need to be applied to reduce the magnetization to zero when the sample's magnetization reaches saturation.
It is 'Intensity of the magnetic field' rather than 'Magnetic force'.
Question 8
1 / -0

The B-H curve (i) and (ii) shown in fig., associated with

A
(i) diamagnetic and (ii) paramagnetic substance

B
(i) paramagnetic and (ii) ferromagnetic substance

C
(i) soft iron and (ii) steel respectively

D
(i) steel and (ii) soft iron respectively

Solution

Retentivity of soft iron is more than steel but coercivity of steel is more.
retentivity-the ability of a substance to retain or resist magnetization, frequently measured as the strength of the magnetic field that remains in a sample after removal of an inducing field.
coercivity-the resistance of a magnetic material to changes in magnetization, equivalent to the field intensity necessary to demagnetize the fully magnetized material.
Question 9
1 / -0

How are the field lines in a uniform magnetic field ?

A
curved

B
parallel equidistant straight lines

C
parallel but non-equispaced straight lines

D
nothing can be said.

Solution

A uniform magnetic field is a magnetic field that has the same magnitude and direction throughout the region under consideration, thus the field lines need to be both parallel and spaced out evenly. The density of field lines at a specific point decide the strength of the field at that point, thus a uniform magnetic field or any uniform field for that matter must have the same number of field lines at every point under consideration.
So a uniform magnetic field would look like a bunch of parallel lines spaced out at equal distance from one another.
Question 10
1 / -0

If the field lines in a magnetic field are parallel and equidistant, the magnetic field is __________ .

A
$$uniform$$

B
$$non\ uniform$$

C
$$zero$$

D
can not be determined

Solution

The close continuous curves in a magnetic field are called magnetic lines of force. Curved lines are used to represent a magnetic field, drawn such that the number of lines relates to the magnetic field's strength at a given point and the tangent of any curve at a particular point is along the direction of magnetic force at that point.
The magnetic lines of force are uniform and strong at the center or middle and they diverge as they move towards the ends and the distance between the lines increases. Eventually, the strength of the magnetic field is strong where the lines are closer and they weaken as they closeness decreases. Hence, if the field lines in a magnetic field are parallel and equidistant, the magnetic field is uniform.
Question 11
1 / -0

In the hysteresis cycle, the value of $$H$$ needed to make the intensity of magnetism zero is called

A
Retentivity

B
Coercive force

C
Lorentz force

D
None of the above

Solution

The value of H needed to remove the residual magnetism is coercive force or coercivity.
Question 12
1 / -0

Figure shows the magnetic field lines in a magnetic field. A, B. and C are three points in this field. At what point is the magnetic field strong ?

A
A

B
B

C
C

D
All the above

Solution

The close continuous curves in a magnetic field are called magnetic lines of force. Curved lines are used to represent a magnetic field, drawn such that the number of lines relates to the magnetic field's strength at a given point and the tangent of any curve at a particular point is along the direction of magnetic force at that point.
The magnetic lines of force are uniform and strong at the point C and they diverge as they move towards points A and B and the distance between the lines increases. Eventually, the strength of the magnetic field is strong where the lines are closer and they weaken as the closeness decreases.
Question 13
1 / -0

A curve between magnetic moment and temperature of magnet is :

A

B

C

D

Solution

The magnetic moment varies with temperature as shown in the figure in option C.
The temperature at which the magnetic material loses its magnetism is the Curie's temperature. Hence the point of intersection of curve with the T axis is the Curie's temperature.
Question 14
1 / -0

The magnetic moment of atomic neon is equal to

A
zero

B
$$\cfrac { 1 }{ 2 } { \mu }_{ B }$$

C
$${ \mu }_{ B }$$

D
$$\cfrac { 3 }{ 2 } { \mu }_{ B }$$

Solution

Magnetic moment is cancelled and $${\mu}_{net}=0$$.