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Physics M.C.Q [1M]

Magnetism And Matter · Bihar Board (BSEB) STD 12 Science (BSEB - English Medium). 234 questions.

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M.C.Q [1M]

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MCQ 11 Mark
The perfect pairs for a superconductor substance is-
  • A
    $\chi=1$ व $\mu_r=0$
  • B
    $\chi=0$ व $\mu_r=1$
  • ✓
    $\chi=-1$ व $\mu_r=0$
  • D
    $\chi=0$ व $\mu_r=-1$
Answer
Correct option: C.
$\chi=-1$ व $\mu_r=0$
C
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MCQ 21 Mark
The hysteresis cycle for the material of permanent magnet is:
  • A
    Short and wide.
  • B
    Tall and narrow.
  • C
    Tall and wide.
  • D
    Short and narrow.
Answer
  1. Tall and wide.

Explanation:

Permanent magnet should have large coercivity and large retentivity. Therefore, the hysteresis cycle of the material should be tall and wide.

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MCQ 31 Mark
Permanent magnets are made from:
  • A
    Diamagnetic substances.
  • B
    Paramagnetic substance.
  • C
    Ferromagnetic substances.
  • D
    Wood.
Answer
  1. Ferromagnetic substances.

Explanation:

Ferromagnetic substance, Because they get magnetize in external magnetic field and don't lose their magnetic property.

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MCQ 41 Mark
At Curie temperature the ferromagnetic materials get converted into.
  • A
    Non-magnetic material.
  • B
    Para magnetic material.
  • C
    Dia magnetic material.
  • D
    All of the above.
Answer
  1. Para magnetic material.

Explanation:

Above curie temperature ferromagnetic material behaves like paramganetic materials. There magnetic susceptibilty starts varying linearly with temperature. Their I becomes too small above curies temperature.

Therefore, nature of ferrromagnetic materials becomes paramagnetic.

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MCQ 51 Mark
Which among the following is denoted by $\delta$?
  • A
    Horizontal component.
  • B
    Magnetic meridian.
  • C
    Magnetic declination.
  • D
    Magnetic inclination.
Answer
  1. Magnetic inclination.

Explanation:

Magnetic dip or inclination at a place is defined as the angle made by the Earth’s magnetic field with the horizontal in the magnetic

meridian. It is denoted by $\delta$.

Magnetic declination at a place is defined as the angle between the geographic meridian and magnetic meridian.

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MCQ 61 Mark
Pick the correct options.
  • A
    All electrons have magnetic moment.
  • B
    All protons have magnetic moment.
  • C
    All nuclei have magnetic moment.
  • D
    All atoms have magnetic moment.
Answer
  1. All electrons have magnetic moment.
  2. All protons have magnetic moment.

Explanation:

All the electrons have magnetic moment & All the protons have magnetic moment.

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MCQ 71 Mark
The magnetic susceptibility for diamagnetic materials is:
  • A
    Small and negative.
  • B
    Small and positive.
  • C
    Large and positive.
  • D
    Large and negative.
Answer
  1. Small and negative.
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MCQ 81 Mark
A magnetic dipole is acted upon by two magnetic fields which are inclined to each other at an angle of 75° One of the fields has a magnitude of 15 mT. The dipole attains stable equilibrium at an angle of 30° with this field. The magntidue of the other field (in mT) is close to:
  • A
    1
  • B
    11
  • C
    36
  • D
    1060
Answer
  1. 11
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MCQ 91 Mark
Mark out the correct options.
  • A
    Diamagnetism occurs in all materials.
  • B
    Diamagnetism results from the partial alignment of permanent magnetic moment.
  • C
    The magnetizing field intensity H is always zero in free space.
  • D
    The magnetic field of induced magnetic moment is opposite to the applied field.
Answer
  1. The magnetic field of induced magnetic moment is opposite to the applied field.

Explanation:

Þ Diamagnctism occurs in all materials.

Þ The Magnetic field of Induced magnetic moment is opposite to the applied field.

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MCQ 101 Mark
Two short magnets of equal dipole moments M are fastened perpendicularly at their centre (figure). The magnitude of the magnetic field at a distance d from the centre on the bisector of the right angle is:

  • A
    $\frac{\mu_0}{4\pi}\frac{\text{m}}{\text{d}^3}$
  • B
    $\frac{\mu_0}{4\pi}\frac{\sqrt{2}\text{M}}{\text{d}^3}$
  • C
    $\frac{\mu_0}{4\pi}\frac{\sqrt[2]{2}\text{M}}{\text{d}^3}$
  • D
    $\frac{\mu_0}{4\pi}\frac{2\text{M}}{\text{d}^3}$
Answer
  1. $\frac{\mu_0}{4\pi}\frac{\sqrt[2]{2}\text{M}}{\text{d}^3}$

Explanation:

Magnetic field (B1) due to the short dipole A of dipole moment M at an axial point is given by,

$\vec{\text{B}_1}=\frac{\mu_0}{4\pi}\frac{2\text{M}}{\text{d}^3}\dots(1)$

Magnetic field (B2) due to the short dipole B of dipole moment M at an axial point is given by,

$\vec{\text{B}_2}=\frac{\mu_0}{4\pi}\frac{2\text{M}}{\text{d}_3}\dots(2)$

Resultant magnetic field (B) will be,

$\text{B}=\sqrt{\text{B}_1^2+\text{B}_2^2}$

$\text{B}=\frac{\mu_0}{4\pi}\frac{\sqrt[2]{2}\text{M}}{\text{d}^3}$

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MCQ 111 Mark
The magnetic compass is not useful for navigation near the magnetic poles, since:
  • A
    R = 0
  • B
    V = 0
  • C
    H = 0
  • D
    $\theta=0^\circ$
Answer
  1. H = 0
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MCQ 121 Mark
The hysteresis cycle for the material of permanent magnet is:
  • A
    Short and wide.
  • B
    Tall and narrow
  • C
    Tall and wide.
  • D
    Short and narrow
Answer
  1. Tall and wide.
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MCQ 131 Mark
The magnetic moment of a bar magnet is thus ...A... to the magnetic moment of an equivalent solenoid that produces the same magnetic field.
Here, A refers to.
  • A
    Unequal.
  • B
    Different.
  • C
    Equal.
  • D
    Same.
Answer
  1. Equal.
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MCQ 141 Mark
Among the following _____ has the highest retentivity.
  • A
    Aluminium
  • B
    Steel
  • C
    Nickel
  • D
    Soft iron
Answer
  1. Steel

Explanation:

The power of magnetism after the inducing agency is removed, is called Retentivity of a substance.

Retentivity is used for remanence measured in units of magnetic flux density.

Steel retains magneto-field longer, iron acquires the field easier but decays sooner.

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MCQ 151 Mark
A freely suspended magnet aligns in which direction?
  • A
    South-west
  • B
    East-west
  • C
    North-south
  • D
    North-west
Answer
  1. North-south

Explanation:

A freely suspended magnet aligns in north-south direction.

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MCQ 161 Mark
Current I is flowing in a coil of area A and number of turns is N, then magnetic moment of the coil in M equal to
  • A
    NIA.
  • B
    NI/A.
  • C
    NI/A.
  • D
    N2AI.
Answer
  1. NIA.
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MCQ 171 Mark
A dip circle is taken to geomagnetic equator. The needle is allowed to move in a vertical plane perpendicular to the mangetic meridian. the needle will stay in:
  • A
    Horizontal direction only.
  • B
    Vertical direction only.
  • C
    Any direction except vertical and horizontal.
  • D
    Any direction it is released.
Answer
  1. Any direction it is released.
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MCQ 181 Mark
A superconductor exhibits perfect:
  • A
    Ferrimagnetism.
  • B
    Ferromagnetis.
  • C
    Paramagnetism.
  • D
    Diamagnetism.
Answer
  1. Diamagnetism.

Explanation:

A superconductor exhibits perfect diamagnetism.

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MCQ 191 Mark
Core of electromagnets are made of ferromagnetic material which has:
  • A
    High permeability and Low retentivity.
  • B
    High permeability and High retentivity.
  • C
    Low permeability and High retentivity.
  • D
    Low permeability and Low retentivity.
Answer
  1. High permeability and Low retentivity.

Explanation:

Electromagnetic cores should have:

  1. High permeability so that it supports the formation of a magnetic field within itself.
  2. Low retentivity so that the magetic field so that it gets demagnetized easily.
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MCQ 201 Mark
The permanent magnetic moment of the atoms of a material is zero. The material:
  • A
    Must be paramagnetic.
  • B
    Must be diamagnetic.
  • C
    Must be ferromagnetic.
  • D
    May be paramagnetic.
Answer
  1. Must be diamagnetic.

Explanation:

The permanent magnetic moment of the atoms of a material is zero. The material must be diamagnetic.

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MCQ 211 Mark
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.
Answer
  1. Above the curie temperature.

Explanation:

Curie - Wiess Law states that all ferromagnetic substances become paramagnteic above the curie temperature.

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MCQ 221 Mark
The magnetic materials having negative magnetic susceptibility are:
  • A
    Non-magnetic.
  • B
    Para magnetic.
  • C
    Dia magnetic.
  • D
    Ferro magnetic.
Answer
  1. Dia magnetic.

Explanation:

Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetisation of a material in response to an applied magnetic field.

Substances such as copper, iron have negative susceptibility as these substances are diamagnetic substances.

Substances with negative susceptibility signifies that they are repelled by magnets.

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MCQ 231 Mark
When the temperature of a magnetic material decreases, the magnetization.
  • A
    Decreases in a diamagnetic material.
  • B
    Decreases in a paramagnetic material.
  • C
    Decreases in a ferromagnetic material.
  • D
    Remains the same in a diamagnetic material.
Answer
  1. Remains the same in a diamagnetic material.
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MCQ 251 Mark
The strength of the earth’s magnetic field is:
  • A
    Constant everywhere.
  • B
    Zero everywhere.
  • C
    Having very high value.
  • D
    Vary from place to place on the earths surface.
Answer
  1. Vary from place to place on the earths surface.
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MCQ 261 Mark
Liquids and gases never exhibit:
  • A
    Diamagnetic properties.
  • B
    Para magnetic properties.
  • C
    Ferro magnetic properties.
  • D
    Electro magnetic properties.
Answer
  1. Ferro magnetic properties.

Explanation:

Ferromagnetic substances have high susceptibility to magnetisation. Liquid and gases aren't prone to be magnetised.

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MCQ 271 Mark
Permanent magnets are the substances having the property of:
  • A
    Ferromagnetism at room temperature for a long period of time.
  • B
    Paramagnetism at room temperature for a long period of time.
  • C
    Anti ferromagnetism at room temperature for a long period of time.
  • D
    Diamagnetism at room temperature for a long period of time.
Answer
  1. Ferromagnetism at room temperature for a long period of time.
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MCQ 281 Mark
The earth’s magnetic field always has a vertical component except at the:
  • A
    Magnetic equator.
  • B
    Magnetic poles.
  • C
    Geographic north pole.
  • D
    Latitude 45º.
Answer
  1. Magnetic equator.
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MCQ 291 Mark
In a permanent magnet at room temperature.
  • A
    Magnetic moment of each molecule is zero.
  • B
    The individual molecules have non-zero magnetic moment which are all perfectly aligned.
  • C
    Domains are partially aligned.
  • D
    Domains are all perfectly aligned.
Answer
  1. Domains are all perfectly aligned.
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MCQ 301 Mark
In a cassette player, material used for coating magnetic tapes is:
  • A
    cobalt
  • B
    CoFe2​O4​
  • C
    NiFe2​O4​
  • D
    nickel
Answer
  1. NiFe2​O4​

Explanation:

In cassette player, materials used for magnetic tapes is NiFe2​O4​.

Ferrites (Ferromagnetic material) is used for Coating magnetic tapes.

In cassette player or for building memory store in modern computers.

Most common ones are MnFe2​O4, FeFe2​O4​, NiFe2​O4​ etc.

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MCQ 311 Mark
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.
Answer
  1. Tall and wide.

Explanation:

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.

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MCQ 321 Mark
The SI unit of magnetic flux is:
  • A
    Dyne
  • B
    Tesla
  • C
    Weber
  • D
    Ohm
Answer
  1. Weber

Explanation:

The SI unit of magnetic flux is Weber.

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MCQ 331 Mark
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
Answer
  1. 30º
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MCQ 341 Mark
Calculate the surface integral of a magnetic field over a surface.
  • A
    Maximum
  • B
    Minimum
  • C
    Zero
  • D
    Equal to its magnetic flux through that surface.
Answer
  1. Equal to its magnetic flux through that surface.

Explanation:

he Gauss’s law states that the surface integral of a magnetic field over a closed surface is always zero. But the surface integral of a magnetic field over a surface gives magnetic flux through that surface.

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MCQ 351 Mark
Which of the following is the most suitable material for making permanent magnet?
  • A
    Steel.
  • B
    Soft iron.
  • C
    Copper.
  • D
    Nickel.
Answer
  1. Steel.
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MCQ 361 Mark
Demagnetisation of magnets can be done by:
  • A
    Rough handling.
  • B
    Heating.
  • C
    Magnetising in the opposite direction.
  • D
    All of the above.
Answer
  1. All of the above.
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MCQ 371 Mark
Materials suitable for permanent magnet, must have which of the following properties?
  • A
    High retentivity, low coercivity and high permeability.
  • B
    Low retentivity, low coercivity and low permeability.
  • C
    Low retentivity, high coercivity and low permeability.
  • D
    High retentivity, high coercivity and high permeability.
Answer
  1. High retentivity, high coercivity and high permeability.
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MCQ 381 Mark
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.
Answer
  1. Magnetic induction force acting on a unit magnetic pole.
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MCQ 391 Mark
A long straight horizontal cable carries a current of 2.5 A in the direction 10° south of west to 10° north of east. The magnetic meridian of the place happens to be 10° west of the geographic meridian. The earth’s magnetic field at the location is 0.33 Gauss, and the angle of dip is zero. Locate the line of neutral points. (Ignore the thickness of the cable).
  • A
    1.5cm.
  • B
    2.5cm.
  • C
    3.5cm.
  • D
    2.0cm.
Answer
  1. 1.5cm.
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MCQ 401 Mark
A material is placed in a magnetic field, and it is thrown out of it. Then the material is:
  • A
    Paramagnetic.
  • B
    Diamagnetic.
  • C
    Ferromagnetic.
  • D
    Non-magnetic.
Answer
  1. Diamagnetic.
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MCQ 411 Mark
When a bar magnet is broken into two pieces:
  • A
    We will have a single pole on each piece.
  • B
    Each piece will have two unlike poles.
  • C
    Each piece will have two like poles.
  • D
    None of these.
Answer
  1. Each piece will have two unlike poles.

Explanation:

When we break a magnet into two, both act as magnets, that is both have a north and south pole each. In both these pieces the corresponding north and south poles remain on the sides as in the original magnet. This means that the 2 broken sides must get oppositely polarized.

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MCQ 421 Mark
Which of the following is responsible for the earth’s magnetic field?
  • A
    Convective currents in earth’s core.
  • B
    Diversive current in earth’s core.
  • C
    Rotational motion of earth.
  • D
    Translational motion of earth.
Answer
  1. Convective currents in earth’s core.
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MCQ 441 Mark
Which metal is used to make ferromagnets ?
  • A
    Iron
  • B
    Cobalt
  • C
    Nickel
  • D
    All of these
Answer
  1. All of these

Explanation:

Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain. Within the domain, the magnetic field is intense, but in a bulk sample the material will usually be unmagnetized because the many domains will themselves be randomly oriented with respect to one another. Ferromagnets will tend to stay magnetized to some extent after being subjected to an external magnetic field. This tendency to "remember their magnetic history" is called hysteresis.

\Nickel, iron and cobalt are such materials. Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain. Within the domain, the magnetic field is intense, but in a bulk sample the material will usually be unmagnetized because the many domains will themselves be randomly oriented with respect to one another.Ferromagnets will tend to stay magnetized to some extent after being subjected to an external magnetic field. This tendency to "remember their magnetic history" is called hysteresis. Nickel, iron and cobalt are such materials.

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MCQ 451 Mark
A diamagnetic material in a magnetic field moves:
  • A
    Perpendicular to the field.
  • B
    From stronger to the weaker parts of the field.
  • C
    From weaker to the stronger parts of the field.
  • D
    None of these.
Answer
  1. From stronger to the weaker parts of the field.
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MCQ 461 Mark
Among which of the following the magnetic susceptibility does not depend on the temperature?
  • A
    Dia-magnetism.
  • B
    Para-magnetism.
  • C
    Ferro-magnetism.
  • D
    Ferrite.
Answer
  1. Dia-magnetism.
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MCQ 471 Mark
On cutting a solenoid in half, the field lines remain ...A... emerging from one face of the solenoid and entering into the other face.
Here, A refers to.
  • A
    Irregular.
  • B
    Discontinuous.
  • C
    Continuous.
  • D
    Alternate.
Answer
  1. Continuous.
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MCQ 481 Mark
Which of the following group is diamagnetic?
  • A
    Copper, hydrogen, silver.
  • B
    Copper, hydrogen, argon.
  • C
    Hydrogen, oxygen, argon.
  • D
    Copper, silver, oxygen.
Answer
  1. Copper, hydrogen, silver.

Explanation:

Diamagnetic substances are those which are freebly repelled by the magnetic field.

$\therefore$ Copper, Hydrogen, Silver are diamagnetic as their atoms have net magnetic dipole moment zero.

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MCQ 491 Mark
When a straight wire is moved up and down rapidly between two poles of a horseshoe magnet then _______ is produced in the wire.
  • A
    Magnetic field
  • B
    Magnetic current
  • C
    Electric current
  • D
    None
Answer
  1. Electric current

Explanation:

An electric current is produced in the wire. The production of electricity from magnetism is called electromagnetic induction.

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MCQ 501 Mark
A long solenoid has 1000 turns per metre and carries a current of 1A. It has a soft iron core of μr = 1000. The core is heated beyond the Curie temperature, Tc.
  • A
    The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
  • B
    The H and B fields in the solenoid are nearly unchanged.
  • C
    The magnetisation in the core reverses direction.
  • D
    The magnetisation in the core diminishes by a factor of about 108.
Answer
  1. The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
  1. The magnetisation in the core diminishes by a factor of about 108.

Solution:

Key concept: The magnetic field intensity H = nl, where n = number of turns per metre of a solenoid and I = current and $\text{B}=\mu_0\mu_\text{r}\text{I}$.

Also, at normal temperature, a solenoid behaves as a ferromagnetic substance and at the temperature beyond the Curie temperature, it behaves as a paramagnetic substance.

We know, for solenoid H = nI.

⇒ H = 1000 × 1 = 1000Am

Thus, H is a constant, so it is nearly unchanged because on heating n and I remain constant.

But $\text{B}=\mu_0\mu_\text{r}\text{nI}$

$=\mu_0\text{n I}\mu_\text{r}$

$=\text{k}\text{(constant)}\mu_\text{r}$

but there is a large decrease in the susceptibility of the core on heating it beyond critical temperature, hence magnetic field will decrease drastically. Now, for magnetisation in the core, when temperature of the iron core of a solenoid is raised beyond Curie temperature, then it behaves as a paramagnetic material, where

$(\chi_\text{m})_\text{Fero}\approx10^{3}$

and $(\chi_\text{m})_\text{para}\approx10^{-5}$

$\Rightarrow\ \frac{(\chi_\text{m})_\text{Fero}}{(\chi_\text{m})_\text{para}}=\frac{10^3}{10^{-5}}=10^{8}$

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