Magnetism and Matter Test -12

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Magnetism and Matter Test -12

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Weekly Quiz Competition

Question 1
1 / -0

The field due to a magnet at a distance R from the centre of the magnet is proportional to

A
R²

B
R³

C
1/R²

D
1/R³

Solution

Provided length of magnet is << the distance.
Question 2
1 / -0

Magnetic field intensity is defined as

A
Magnetic moment per unit volume

B
Magnetic induction force acting on a unit magnetic pole

C
Number of lines of force crossing per unit area

D
Number of lines of force crossing per unit volume

Solution

Number of lines of force passing through per unit area normally is intensity of magnetic field.
Question 3
1 / -0

At magnetic poles of earth, angle of dip is

A
Zero

B
45°

C
90°

D
180°

Solution

At magnetic poles of earth, angle of dip is 90°
Question 4
1 / -0

The vertical component of earth's magnetic field is zero at or the earth's magnetic field always has a vertical component except at the

A
Magnetic poles

B
Geographical poles

C
Every place

D
Magnetic equator

Solution

At magnetic equator, the angle of dip is 0°. Hence the vertical component

V = I sinφ = 0
Question 5
1 / -0

A ferromagnetic material is heated above its curie temperature. Which one is a correct statement?

A
Ferromagnetic domains are perfectly arranged

B
Ferromagnetic domains becomes random

C
Ferromagnetic domains are not influenced

D
Ferromagnetic material changes itself into diamagnetic material

Solution

On heating, different domains have net magnetisation in them which are randomly distributed. Thus the net magnetisation of the substance due to various domains decreases to minimum.
Question 6
1 / -0

Two like poles of strength $$m_{1}$$ and $$m_{2}$$ are far distance apart. The energy required to bring them $$r_{0}$$ distance apart is

A
$$\displaystyle \dfrac{\mu _{0}}{4\pi }\frac{m_{1}m_{2}}{r_{0}}$$

B
$$\displaystyle \dfrac{\mu _{0}}{8\pi }\frac{m_{1}m_{2}}{r_{0}}$$

C
$$0$$

D
$$\displaystyle \dfrac{\mu _{0}}{16\pi }\frac{m_{1}m_{2}}{r_{0}^2}$$

Solution

$$V_{1}=\dfrac{\mu _{0}m_{1}}{4\pi \Omega _{0}}$$
$$V_{1}=$$magnetic potential
$$m_{1}=$$pole strength
$$\Omega _{o}$$=distance from $$m_1$$
$$Energy=Vm =\dfrac{\mu _{0}m_{1}m_{2}}{4\pi \Omega _{0}}$$
Question 7
1 / -0

The relative permeability of a material is $$0.9$$. The material is

A
diamagnetic

B
para magnetic

C
ferro magnetic

D
non-magnetic

Solution

diamagnetic material
$$-1\leq \chi < 0$$
0 $$\leq$$ $$\mu$$ < 1
$$\chi$$ $$=$$ Magnetic susceptibility
$$\mu$$ $$=$$ permeability
Question 8
1 / -0

Alnico is used for making permanent magnets because it has

A
High coercivity and high retentivity

B
high coercivity and low retentivity

C
low coercivity and low retentivity

D
low coercivity and high retentivity

Solution

Alnico is used for making permanent magnet because it can be easily magnetised in external magnetic field and It will not lose its magnetic property due to its high coercivity and low retentivity.
Question 9
1 / -0

Liquids and gases never exhibit

A
diamagnetic properties

B
para magnetic properties

C
ferro magnetic properties

D
electro magnetic properties

Solution

Ferromagnetic substances have high susceptibility to magnetisation. Liquid and gases aren't prone to be magnetised.
Question 10
1 / -0

The hysteresis cycle curve for the material of a permanent magnet is :

A
short and wide

B
tall and narrow

C
tall and wide

D
short and narrow

Solution

Hysteresis cycle curve for the material of a permanent magnet is given in the image.
It is clear from the image that hysteresis cycle curve for the material of a permanent magnet is tall and wide.
Question 11
1 / -0

The susceptibility of a diamagnetic substance is

A
$$\infty $$

B
zero

C
small but negative

D
small but positive

Solution

Diamagnetic sultance
-1 $$\leq$$ $$\chi < 0$$
$$\theta =\mu < 1$$
$$\chi =susceptibility$$
Question 12
1 / -0

The curie weiss law is obeyed by iron

A
at all temperatures

B
above the curie temperature

C
below the curie temperature

D
at the curie temperature

Solution

Curie - Wiess Law states that all ferromagnetic substances become paramagnteic above the curie temperature.
Question 13
1 / -0

Curie temperature is the temperature above which

A
a paramagnetic material becomes ferromagnetic

B
a ferromagnetic material becomes paramagnetic

C
a paramagnetic material becomes diamagnetic

D
a ferromagnetic material becomes diamagnetic

Solution

Curie temperature is the temperature above which the ferromagnetic material loses the alignment of its atomic magnetic moment and becomes paramagnetic
Question 14
1 / -0

Ferromagnetic materials have their properties due to

A
vacant inner subshells

B
partially filled inner subshells

C
filled inner subshells

D
completely filled outer shells

Solution

Ferromagnetic material have their properties due to partially filled subshells,because the magnetic field of those unpaired electron are responsible for the ferromagnetic property of the material.
Question 15
1 / -0

Domain formation is the necessary feature of

A
ferro magnetism

B
paramagnetism

C
diamagnetism

D
electro magnetism

Solution

This problem is based on Magnetism.

$$\bullet$$ Ferro-magnetism is the property of certain substances due to which they get strongly attracted to a magnet and strongly influenced in a magnetic field.
$$\bullet$$ Certain substances like iron, nickel, cobalt, etc, are ferro-magnetic in nature.
$$\bullet$$ Every atom of such materials, behave like small bar-magnets. The proper word is magnetic dipoles. In ferromagnetic materials, there are small regions known as domains. In each domain, all the atoms are alligned in one direction. All of them have their north-pole facing one side and their south-pole facing the other side. Hence every domain behaves like a dipole.
$$\bullet$$ In the above picture, the arrows indicate the domains, pointing towards their north-poles.
$$\bullet$$ In the absence of any magnetic field, all the domains are alligned randomly and so, the substance doesn't have any magnetic properties.
$$\bullet$$ When the substance is placed in a weak magnetic field, a few domains turn and allign in the direction of the field, some domains which are already in the direction of the field expand slightly, and those alligned in direction opposite to the field, reduce in size. As a result, the entire substance has a mild dipole-like properties.
$$\bullet$$ When the substance is placed in a strong magnetic field, many domains rapidly turn and allign in the direction of the field, the domains which are already in the direction of the field expand tremendously, and those alligned in direction opposite to the field, shrink so much that they almost disappear. As a result, all the domains are parallel to each other and alligned in one direction. The entire substance now becomes a strong bar-magnet.

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Magnetism and Matter Test -12

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Magnetism and Matter Test -12

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Question 1

R2

R3

1/R2

1/R3

Solution

Question 2

Magnetic moment per unit volume

Magnetic induction force acting on a unit magnetic pole

Number of lines of force crossing per unit area

Number of lines of force crossing per unit volume

Solution

Question 3

Zero

45°

90°

180°

Solution

Question 4

Magnetic poles

Geographical poles

Every place

Magnetic equator

Solution

Question 5

Ferromagnetic domains are perfectly arranged

Ferromagnetic domains becomes random

Ferromagnetic domains are not influenced

Ferromagnetic material changes itself into diamagnetic material

Solution

Question 6

$$\displaystyle \dfrac{\mu _{0}}{4\pi }\frac{m_{1}m_{2}}{r_{0}}$$

$$\displaystyle \dfrac{\mu _{0}}{8\pi }\frac{m_{1}m_{2}}{r_{0}}$$

$$0$$

$$\displaystyle \dfrac{\mu _{0}}{16\pi }\frac{m_{1}m_{2}}{r_{0}^2}$$

Solution

Question 7

diamagnetic

para magnetic

ferro magnetic

non-magnetic

Solution

Question 8

High coercivity and high retentivity

high coercivity and low retentivity

low coercivity and low retentivity

low coercivity and high retentivity

Solution

Question 9

diamagnetic properties

para magnetic properties

ferro magnetic properties

electro magnetic properties

Solution

Question 10

short and wide

tall and narrow

tall and wide

short and narrow

Solution

Question 11

$$\infty $$

zero

small but negative

small but positive

Solution

Question 12

at all temperatures

above the curie temperature

below the curie temperature

at the curie temperature

Solution

R²

R³

1/R²

1/R³