### Paramagnetic material - class-XII

 Description: paramagnetic material Number of Questions: 26 Created by: Gagan Singh Tags: magnetism magnetism and matter magnetic effects of current and magnetism physics
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A substance is placed in a non uniform magnetic field. It experiences weak force towards the strong field. The substance is _________ type.

1. Ferromagnetic

2. Diamagnetic

3. Paramagnetic

4. None of these

Correct Option: C
Explanation:

Paramagnetic substance has the property that when they are placed in an external magnetic field, they get weakly magnetised in the same direction as that of external magnetic field and are weakly attracted by the external magnetic field.
So, correct answer is option C.

Liquid oxygen remains suspended between two pole forces of a magnet because it is:

1. diamagnetic

2. paramagnetic

3. ferromagnetic

4. antiferromagnetic

Correct Option: B
Explanation:

Oxygen is paramagnetic in nature. So if it will be attracted both by North pole or South pole. When it is placed exactly between two magnetic poles, the forces acting on it due to magnetic poles will be equal & opposite. Hence it will remain suspended between them.

When the atomic magnetic moments are randomly oriented in a solid its magnetic behavior is termed as

1. semi-magnetic.

2. anti-ferromagnetic.

3. paramagnetic.

4. poly crystalline.

Correct Option: C
Explanation:

When the atomic magnetic moments are randomly oriented in a solid its magnetic behavior is termed as paramagnetic.in paramagnetism electrons are unpaired.

A paramagnetic substance when placed in an externally applied non-uniform magnetic field tends to ___________.

1. increase the applied field

2. decrease the applied field

3. vary the applied field

4. change the applied field

Correct Option: A
Explanation:

Paramagnetic substances are the substances which are feebly attracted by a magnet. When a non-uniform external magnetic field is applied to a paramagnetic substance the magnetic field tries to aligned the magnetic moment in the direction of the field

Completely alignment is however not possible, on account of thermal vibration. A better allingement can be achieved by increasing the strength of the applied magnetic field.

An atom is paramagnetic if it has :

1. an electric dipole moment

2. no magnetic moment

3. a magnetic moment

4. no electric dipole moment

Correct Option: A

Substances in which the magnetic moment of a

single atom is not-zero

1. diamagnetic

2. ferromagnetic

3. paramagnetic

4. electromagnetic

Correct Option: C

Which of the following is paramagnetic  in nature ?

1. $N _{2}$

2. $C _{2}$

3. $B _{2}$

4. $O _{2}^{2+}$

Correct Option: A

According to  molecular orbital theory, the paramagnetism of $O _{2}$  molecule is due to presence of

1. Unpaired electrons in the bonding $\sigma$ molecular orbital

2. Unpaired electrons in the anti- bonding $\sigma$ molecular orbital

3. Unpaired electron in the bonding $\pi$ molecular orbital

4. Unpaired electrons in the anti - bonding $\pi$ molecular obrital

Correct Option: A

Consider the following statements and select the select option which correctly identifies true (T) and false (F).

1. Iron loses its magnetism easily.

2. Steel is a hard magnetic material.

3. Soft iron is used to make permanent magnet.

4. non of these

Correct Option: A

Atomic number of an element is $26$. The element shows

1. Ferromagnetism

2. Diamagnetism

3. Paramagnetism

4. None of these

Correct Option: B

The relative permeability is represented by $\mu _r$ and the susceptibility by $\chi$ for a magnetic substance. Then, for a paramagnetic substance. Then, for a paramagnetic substance

1. $\mu _r> 1, \chi >0$

2. $\mu _r> 1, \chi < 0$

3. $\mu _r > 1, \chi >0$

4. $\mu _r < 1, \chi < 0$

Correct Option: A
Explanation:

Susceptence $(\chi) = \dfrac{B-B _0}{B _0}$

Where $B _0$ is external applied magnetic field and $B$ is magnetic field in presence of paramagnetic substance.
Since dipoles in paramagnetic substance align in direction of applied magnetic filed, therefore $B > B _0$

And $B$ is bit more than $B _0$
$\Rightarrow \chi > 0$

And also $\mu _r = \chi + 1$
$\Rightarrow \mu _r > 0 + 1$
$\Rightarrow \mu _r > 1$
Therefore option A is correct.

Some metals get magnetised by orientation of atomic magnetic moments in external magnetic field. What are they called ?

1. just magnets

2. Paramagnetics

3. dimagnetics

4. ferromagnetic

Correct Option: B

How will you quantize the relative permeability of a paramagnetic substance ?

1. Much more than one

2. Slightly more than one

3. Less than one but greater than zero

4. Zero

Correct Option: B
Explanation:

Paramagnetic substances are those which are attracted slightly in the direction of the magnetic field. As such, the magnetic permeability of these materials is slightly greater than $1$.
Similarly, diamagnetic materials are those which are repelled slightly away from the direction of magnetic field. These materials have their permeability slightly less than $1$.
And ferromagnetic materials are those which are attracted very strongly and their permeabilities are much higher than $1$.

What is not true about paramagnetic substances?

1. When freely suspended in a uniform magnetic field, they align themselves parallel to the magnetic field

2. The magnetic susceptibility of paramagnetic substances has a small negative value

3. Para-magnetism is temperature dependent

4. They are feebly attracted by a magnet

Correct Option: B

Magnetic permeability of paramagnetic substances is?

1. $0$

2. $> 1$

3. $< 1$

4. $1$

Correct Option: B
Explanation:

Paramagnetic substances are substances which are weakly attracted by the magnetic field when they are placed in an external magnetic field. Magnetic permeability of paramagnetic substances is slightly greater than one whereas that of diamagnetic materials is slightly less than one.

Magnetically aligned atoms in a magnetic material forms a cluster. The cluster is called a:

1. Domain

2. Molecule

3. Pole

4. Charge

5. Electron cloud

Correct Option: A
Explanation:

Each atom has its own magnetic field, and if a group of atoms can align their magnetic fields, this group or cluster of atoms is called a magnetic domain.

A bar magnet has been cut equally lengthwise and widthwise to give four equal pieces. The pole strength of each piece as compared to the pole strength of original bar magnet is :

1. Same

2. $\displaystyle \frac{1}{8}$

3. $\displaystyle \frac{1}{4}$

4. $\displaystyle \frac{1}{2}$

Correct Option: D

The purpose of soft iron cylinder between the pole pieces of the horse-shoe magnet in a moving coil galvanometer is

1. to increase the magnetic induction in the polar

gap

2. to evenly distribute the magnetic lines of force

3. to provide a radial magnetic field

4. to reduce the magnetic flux leakage in the polar

gap

Correct Option: A
Explanation:

Soft iron cylinder is placed between the pole pieces of the horse-shoe magnet in a moving coil galvanometer to increase the magnetic induction in the polar gap. Soft iron is paramagnetic which increases magnetic induction when placed in field because atoms in soft iron align in such manner that it increases field.

Metals getting magnetised by orientation of atomic magnetic moments in external magnetic field are called

1. diamagnetics

2. paramagnetics

3. ferromagnetics

4. antimagnetics

Correct Option: B
Explanation:

In paramagnetic metals, magnetism is acquired by orientation of atomic magnetic  dipoles.

The meniscus of a liquid contained in one of the limbs of a narrow U-tube is held electromagnet with the meniscus in line with the field. The liquid is seen to rise. This indicates that the liquid is

1. anti-ferromagnetic

2. paramagnetic

3. diamagnetic

4. non-magnetic

Correct Option: B
Explanation:

Paramagnetic liquid tends to flow from region of weaker magnetic fields to stronger magnetic fields..

Assertion(A) : Earth's magnetic field inside a closed iron box is less as compared to the outside.
Reason(R) : The magnetic permeability of iron is low.

1. Both A, R are true and R is the correct explanation of A

2. Both A, R are true and R is not correct explanation of A

3. A is true R is false

4. A is false R is true

Correct Option: C

Consider the following statements I and II.
(I) Paramagnetism is explained by domain theory
(II) Susceptibility of a diamagnetic substance is independent of temperature.
Identify the correct choice from the following.

1. Both I and II are correct

2. Both I and II are incorrect

3. I is correct and II is incorrect.

4. I is incorrect and II is correct

Correct Option: D

Assertion : Paramagnetic substances get weakly attracted to a magnet.
Reason : They have tendency to move from a region of strong magnetic field to weak magnetic field

1. If both assertion and reason are true and reason is the correct explanation of assertion.

2. If both assertion and reason are true and reason is not the correct explanation of assertion.

3. If assertion is true but reason is false.

4. If both assertion and reason are false

Correct Option: C
Explanation:

Paramagnetic substances have tendency to move from a region of weak magnetic field to strong magnetic field i.e., they get weakly attracted to a magnet.

The magnetic susceptibility of a paramagnetic material at $-73^0$ is $0.0075$, its value at $-173^0$C will be

1. $0.0045$

2. $0.0030$

3. $0.015$

4. $0.0075$

Correct Option: C
Explanation:
Given,
$X=0.0075 \,\,at\,\,\, T=-73^{\circ}$
Curie's law, $X=\cfrac{C}{T}$
$X _{1} \propto \cfrac{1}{T _{1}}$
$\therefore \cfrac{X _{1}}{X _{2}}=\cfrac{T _{2}}{T _{1}}$
$X _{2}=X _{1}\times \cfrac{T _{1}}{T _{2}}=0.0075\times \cfrac{273-73}{2.73-173}=0.015$

A paramagnetic liquid is taken in a U-tube and arranged so that one of its limbs is kept between pole pieces of the magnet. The liquid level in the limb is

1. goes down

2. rises up

3. remains same

4. first goes down and then rise

Correct Option: B
Explanation:

When a paramagnetic liquid is taken in U-tube and one arm is placed between the poles of strong magnet, the liquid is feebly attracted by the magnet. Therefore, the level of the solution in the arm rises.

Out of given paramagnetic substance (Calcium, Chromium, Oxygen and Tungsten) which substance has maximum susceptibility?

1. Calcium

2. Chromium

3. Oxygen

4. Tungsten

Correct Option: B
Explanation:

Susceptibility at the standard temperature, $T=300K$

Calcium $\rightarrow 1.9\times 10^{-5}$
Chromium $\rightarrow 2.7\times 10^{-4}$
Oxygen $\rightarrow 2.1\times 10^{-6}$
Tungsten $\rightarrow 6.8\times 10^{-5}$
Chromium have maximum susceptibility.
The correct option is B.

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