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CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 9 - MCQExams.com
CBSE
Class 12 Medical Physics
Magnetism And Matter
Quiz 9
Which of the following figures depict non uniform magnetic field?
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Explanation
Uniform magnetic field has a bunch of symmetric lines of forces arranged in a regular fashion. So the correct option is D as lines of forces are not arranged in the regular fashion.
Two short magnets placed along the same axis with their like poles facing each other will repel each other with a force which varies inversely as
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Distance
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Square of distance
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Cube of distance
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Fourth power of distance
Explanation
Hint:- Force between two magnets governs by inverse square law.
Explanation
:-
$$\textbf{Step1: Force between two short magnets}$$
The force of repulsion between two like poles is given by
$$F={\cfrac{\mu_0}{4\pi}}\times{\cfrac{m_1m_2}{r^2}}$$
Where $$m_1$$ and $$m_2$$ are the strengths of the poles, $$r$$ is the distance between the poles and $$\mu_0$$ is the permeability of free space.
We can see that force varies inversely with the square of distance.
Hence option B is correct
The north poles of pole strengths, $$m$$, $$9 m$$ are kept apart by certain distance '$$d$$'. Find distance of null point from larger pole.
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$${2d}/{4}$$
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$${2d}/{3}$$
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$${5d}/{4}$$
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$${3d}/{2}$$
Explanation
Let $$B_1$$ due to large pole and $$B_2$$ due to smaller pole
$$B_1=\dfrac { { \mu }_{ 0 } }{ 4\pi } \dfrac { 2\times 9m }{ x^{ 3 } }$$
$$ B_2=\dfrac { { \mu }_{ 0 } }{ 4\pi } \dfrac { 2\times m }{ { (d-x) }^{ 3 } } $$
if P is null point then,
$$B_1=B_2$$
$$\dfrac { 9 }{ x^{ 3 } } =\dfrac { 1 }{ { (d-x) }^{ 3 } } $$
$$\\ { \left( \dfrac { x }{ d-x } \right) }^{ 3 }=9$$
$$\\ \dfrac { x }{ d-x } =2.08\\ x=\dfrac { 2.08 }{ 3.08 } d$$
The magnetic field lines due to a bar magnet correctly shown are:
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Explanation
As the magnetic field lines are closed curves.
Thus they must pass through the magnets as well and its direction is from south to north for same sense (direction)
Magnetic monopoles are arranged as shown. The resultant magnetic induction at point '$$q$$' is:
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$$\dfrac{{\mu}_{0}}{4 \pi}$$ $$\dfrac{m}{{r}^{2}}$$ $$\dfrac{3}{2}$$
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$$\dfrac{{\mu}_{0}}{4 \pi}$$ $$\dfrac{m}{{r}^{2}}$$ $$\dfrac{1}{4}$$
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$$\dfrac{{\mu}_{0}}{4 \pi}$$ $$\dfrac{m}{{r}^{2}}$$ $$\dfrac{3}{4}$$
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$$\dfrac{{\mu}_{0}}{4 \pi}$$ $$\dfrac{m^2}{{r}^{2}}$$ $$\dfrac{3}{8}$$
Explanation
Magnetic field $$B$$ at point q.
$$B=\dfrac { { \mu }_{ 0 } }{ 4\pi } \dfrac { 2M\quad \quad \dfrac { 3r }{ 2 } }{ { ({ \left( \dfrac { 3r }{ 2 } \right) }^{ 2 }-{ \left( \dfrac { r }{ 2 } \right) }^{ 2 }) }^{ 2 } } $$
$$=\dfrac { { \mu }_{ 0 } }{ 4\pi } (2M)\dfrac { \dfrac { 3r }{ 2 } }{ { \left( \dfrac { 8 }{ 4 } { r }^{ 2 } \right) }^{ 2 } } $$
$$=\dfrac { { \mu }_{ 0 } }{ 4\pi } (2M)\left( \dfrac { \dfrac { 3r }{ 2 } }{ 4{ r }^{ 4 } } \right) $$
$$=\dfrac { { \mu }_{ 0 } }{ 4\pi } (M)\dfrac { 3 }{ 4{ r }^{ 3 } } =\dfrac { { \mu }_{ 0 } }{ 4\pi } \dfrac { M }{ { r }^{ 3 } } \left( \dfrac { 3 }{ 4 } \right) $$
At what temperature $$(^0C)$$, in the case of mercury (Hg) drops abruptly to zero?
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3.2 K
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4.2 K
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5.2 K
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6.2 K
Explanation
Mercury becomes a superconductor at $$4.2K$$ and at that temperature its resistance becomes zero.
Answer-(B)
When a superconductor is placed in a weak external magnetic field H, and cooled below its transition temperature,
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the magnetic field is ejected
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the magnetic field get magnetized
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the magnetic field strength increased
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none of the above
Explanation
When a superconductor is placed in a weak external magnetic field $$H$$, and cooled below its transition temperature, the magnetic field is ejected from it and this phenomenon is called effect Meissner effect. The ability of this expulsion effect of the magnetic field is determined by the nature of equilibrium formed by the neutralization within the unit cell of a superconductor.
The critical temperature for superconductors is the temperature at which the electrical resistivity of a metal
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drops to zero
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increase to maximum limit
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decrease to a certain limit
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none of the above
Explanation
The critical temperature is the temperature at which the resistivity of a conductor becomes $$0$$.
Answer-(A)
A straight wire is carrying an electric current :
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There are no magnetic lines of force near the wire
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There are lines of force and they are circular lines encircling the wire
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The lines of force are straight lines parallel to the wire and in the direction opposite to the current
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The lines of force are straight lines parallel to the wire in the direction opposite to the current.
Explanation
The direction of line of forces of magnetic field produced by a current carrying wire can be obtained by using maxwell's right hand thumb .By holding the thumb along the the direction of current then the direction in which your finger encircle the wire will give the direction of magnetic line of forces .
Electricity and magnetism are mutually
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Complementary
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Opposite
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Equal and opposite
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Strongest forces
Explanation
Electricity and magnetism are complementary to each other.
Changing magnetic field produces electric current that is it produces electric field. And moving charges that is changing electric field produces magnetic effect like moving charges produces magnetic field.
Answer-(A)
If the magnetizing field on a ferromagnetic material is increased, its permeability
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Decreased
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Increased
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Is unaffected
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May be increased or decreased
Explanation
The magnetic permeability of a substance is defined as
$$\mu=\dfrac{B}{H}$$
where $$B$$ is the established magnetic field inside the material,
$$H$$ is the applied external magnetic field.
When the external applied magnetic field $$H$$ is increased, the established magnetic field for a ferromagnetic material remains the same. Thus the magnetic permeability decreases.
Curie temperature is defined as the temperature above which.
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A paramagnetic material becomes ferromagnetic
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A ferromagnetic material becomes paramagnetic
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A ferromagnetic material becomes diamagnetic
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A diamagnetic material becomes ferromagnetic
Explanation
The Curie temperature $$T_C$$ is defined as the temperature at which the ferromagnetic material becomes paramagnetic.
Which one of the following statements best describes the nature of the field lines due to a bar magnet?
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Field lines start from the north pole and end on the south pole. Any number of field lines can pass through a point
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Field lines start from the north pole and end on the south pole. Only one field line passes through a point
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Field lines are continuous lines passing inside and outside the magnet. Only one field line passes through a point
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Field lines are continuous lines passing inside and outside the magnet. Any number of field lines can pass through a point
Explanation
The properties of magnetic filed lines are that they start from north pole and end at south pole (outside the magnet). But they flow from south to north pole inside the magnet forming a continuous closed loop. They are very near to each other where the magnetic field is strong whereas they are far away from each other where magnetic field is weak. At poles, magnetic field is the strongest. Thus the magnetic lines of forces are the nearest at the poles. No two magnetic line of forces intersect with each other.
Thus correct answer is option C.
Which of the following statement related to hysteresis loop is incorrect?
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The curve of B against H for a ferromagnetic material is called hysteresis loop
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The area of B-H curve is a measure of power dissipated per cycle per unit area of the specimen
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Coercitivity is a measure of the magnetic field required to destroy the residual magnetism of ferromagnetic material
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The retentivity of a specimen is the measure of magnetic field remaining in the specimen when the magnetising field is removed
Explanation
The hysteresis loop i.e. area of B-H curve is a measure of energy dissipated per cycle per unit volume of the specimen. It depends on the nature of magnetic material.
If a watch-glass containing a small quantity of water is placed on two dissimilar magnetic poles, then water ___________.
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Shows a depression in the middle
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Shows an elevation in the middle
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Surface remains horizontal
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Evaporates immediately
Explanation
Water is a diamagnetic material and hence it has a property, when placed in non uniform magnetic field it tends to move from stronger to weaker regions of magnetic field. Therefore,
when water in a watch glass is placed on two pole pieces lying close to each other, we observe a depression in the middle and when the pole pieces are placed sufficiently apart, then we observe depressions at the sides .
Consider the regular array of vertical identical current carrying wires (with direction of current flow as indicated in the figure) protruding through a horizontal table. If we scatter some diamagnetic particles on the table, they are likely to accumulate.
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Around regions such as A
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Around regions such as B
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In circular regions around individual wires such as C
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Uniformly everywhere
Explanation
As diamagnetic particles move from strong to weak magnetic field, therefore they will accumulate around regions such as A.
State whether true or false.
A cylindrical magnet has only one pole.
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True
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False
Explanation
A cylindrical magnet has only two pole.A cylindrical shape enables the magnets to produce high levels of magnetism from a relatively small surface pole area
A diamagnmetic material in a magnetic field moves :
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Perpendicular to the field.
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From weaker to the stronger parts of the field.
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From stronger to the weaker parts of the field.
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In none of the above directions.
Explanation
When a diamagnetic material is placed in an external magnetic field the spin motion of electrons is so modified that the electrons which produce the moments in the direction of external field show down while the electrons which produce magnetic moments in opposite direction get accelerated.
Thus, a net magnetic moment is induced in the opposite direction of applied magnetic field. Hence the substance is magnetized opposite of the external field. Thus, it moves from stronger. Weaker parts of the magnetic.
A hydrogen atom is paramagnetic. A hydrogen molecule is :
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Diamagnetic
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Paramagnetic
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Ferromagnetic
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Antiferromagnetic
Explanation
Hydrogen molecule behaves as diamagnetic as no net magnetic moment is associated with it.
Permanent magnet has properties retentivity and coercivity respectively as:
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high-high
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low-low
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low-high
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high-low
Explanation
The material for a permanent magnet should have high retentivity (so that magnet is strong) and high coercivity (so that magnetism is not wiped out by strong magnetic fields).
If $$\chi $$stands for the magnetic susceptibility of a substance, $$\mu$$ for its magnetic permeability and $${ \mu }_{ 0 }$$ for the permeability of free space, then
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For a paramagnetic substance: $$\chi >0,\mu >0$$
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For a paramagnetic substance: $$\quad \chi >0,\quad \mu >{ \mu }_{ 0 }$$
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For a diamagnetic substance: $$\chi <0,\mu <0$$
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For a ferromagnetic substance: $$\quad \chi >1,\mu >>{ \mu }_{ 0 }$$
Explanation
$$\chi ={ \mu }_{ r }-1,{ \mu }_{ r }=\cfrac { \mu }{ { \mu }_{ 0 } } $$
For paramagnetic $$\chi >0$$ $$\therefore$$ $${\mu}_{r}> 1$$ $$\therefore$$ $$\mu> {\mu}_{0}$$
For diamagnetic $$\chi < 0$$ $$\therefore$$ $${\mu}_{r}< 1$$ $$\therefore$$ $$\mu< {\mu}_{0}$$
for ferro magnetic $$\chi >>1$$ $$\mu >> {\mu}_{0}$$
Magnetic susceptibility of diamagnetic materials is of the order of (SI units) :
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$$+ 10^{5}$$
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$$+10^{-4}$$ to $$+10^{-2}$$
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$$+10^{-5}$$
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$$-10^{-5}$$
Explanation
Magnetic susceptibility of diamagnetic substance is negative and close to zero. So, from the given option (d) is correct.
A. Ferromagnetic materials will lose their magnetism if heated above a point known as the Curie temperature.
B. You would have to re-magnetize the magnet again, either in a solenoid or with another permanent magnet, in order to restore the magnetism.
C. If you heat a magnet up a little bit, it will lose some of its magnetism, but on returning to room temperature full magnetism can be restored.
Which among the following is/are true?
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Only A
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Both A and B
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Only C
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All A, B and C
Explanation
All the three statements are true that the ferromagnetic materials lose their magnetism on heating above the Curie temperature,
The magnet has to re-magnetized with another magnet or solenoid to restore its magnetism and the magnetism of the magnet is fully recovered when it is kept at room temperature after heating.
A closed surface $$S$$ encloses a magnet of magnetic moment $$2\ ml$$. The magnetic flux emerging from the surface is :
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$$\mu_{0}m$$
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Zero
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$$2\mu_{0}m$$
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$$2m/\mu_{0}$$
Explanation
According to Gauss's law in magnetism, net magnetic flux through any closed surface is always zero, ie,
$$\oint B\cdot ds = 0$$.
Curie-Weiss law is obeyed by iron.
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At curie temperature only
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At all temperatures
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Below curie temperature
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Above curie temperature
Explanation
$$\textbf{Hint:}$$ Below curie temperature ferromagnetic substance behave as paramagnetic .
$$\textbf{Step 1-Curie -Weiss law}$$
The Curie-Weiss Law relates the susceptibility of ferromagnets like iron to their temperature.
$$\chi=\dfrac{C}{T-T_c}$$
Here
C
C
is the Curie constant and dependent only on the material.
and $$T_c$$ is Curie temperature.
$$\textbf{Step 2-Behaviour of iron}$$
Iron is a ferromagnetic material so it obeys curie-weiss law above curie temperature.
Below curie temperature ferromagnetic material changes to paramagnetic material and then it obeys curie law.
Resultant force acting on a diamagnetic material in a magnetic field is in direction.
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From stronger to the weaker part of the magnetic field
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From weaker to the stronger part of the magnetic field
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Perpendicular to the magnetic field
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In the direction making $$60^o$$ to the magnetic field
Explanation
Resultant force acting on a diamagnetic material in a magnetic field is in
direction
from stronger to the weaker part of the magnetic field.
The magnetic lines of force inside a bar magnet.
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Are from S-pole to N-pole
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Are from N-pole to S-pole
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Depends on teh cross-sectional area of magnet
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Do not exist
Two magnetic poles of the same length attract each other with a force of $$2$$N when placed on the two corners of an equilateral triangle. If a south pole of the same strength is placed at the third vertex, it experiences a force of magnitude.
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$$4$$N
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$$3$$N
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$$2$$N
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$$1$$N
Explanation
As the magnetic poles A and B attract each other, so they are of opposite polarity, when a third pole of same strength is placed at C then it experiences a force as shown in the figure.
The net force acting on C is
$$F_1=\sqrt{F^2_1+F^2_2+2F_1F_2\cos 120^o}$$
$$=\sqrt{\displaystyle 2^2+2^2+2\times 2\times 2\left(-\displaystyle\frac{1}{2}\right)}=2$$N.
A ferromagnetic material heated above its curie temperature. Which one is a correct statement?
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Ferromagnetic domains are perfectly arranged
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Ferromagnetic domains become random
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Ferromagnetic domains are not influenced
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Ferromagnetic material changes into diamagnetic material
Explanation
Beyond curie temperature, ferromagnetic material turns into paramagnetic material, as if ferromagnetic domains become random.
Horizontal component of the earth's field is $$3 \times 10^{-5} \, T$$ and of dip is $$53^o$$. Magnetic field of the earth at that place is
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$$25 \times 10^{-5} \, T$$
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$$5 \times 10^{-5} \, T$$
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$$85 \times 10^{10} \, T$$
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$$9.9 \times 10^{-8} \, T$$
Explanation
Horizontal component of the earths magnetic fields is given by
$$B_H=B \, cos \delta $$
$$\Rightarrow B=\frac {B_H}{cos\,\delta }=\frac {3\times 10^{-5}}{cos\, 53^o}$$
$$ = 5 \times 10^{-5}\, T$$
The earth's magnetic field at some place on magnetic equator of the earth is $$0.5\times { 10 }^{ -4 }T$$. Consider the radius of the earth at that place as $$6400 km$$. Then, magnetic dipole moment of the earth is ___________ $${ Am }^{ 2 }$$. $$\left( { \mu }_{ 0 }=4\pi \times { 10 }^{ -7 }Tm{ A }^{ -1 } \right) $$
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$$1.31\times { 10 }^{ 23 }$$
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$$1.05\times { 10 }^{ 23 }$$
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$$1.15\times { 10 }^{ 23 }$$
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$$1.62\times { 10 }^{ 23 }$$
Explanation
Given,
$${ R }_{ e }=6400 km=6.4\times { 10 }^{ +6 }m$$
$${ B }_{ e }=0.5\times { 10 }^{ -4 }T$$
$${ \mu }_{ 0 }=4\pi \times { 10 }^{ -7 }Tm{ A }^{ -1 }$$
$$M=$$?
The magnetic field at the equator
$$B=\dfrac { { \mu }_{ 0 } }{ 4\pi } \cdot \dfrac { i }{ { R }_{ e } }$$
and $$M=iA$$
$$M=\dfrac { 4\pi { R }_{ e }\cdot B }{ { \mu }_{ 0 } } \times \pi { R }_{ e }^{ 2 }$$
$$=\dfrac { 4\pi \times 64\times { 10 }^{ 5 }\times 5\times { 10 }^{ -5 }\times 3.14\times 4096\times { 10 }^{ 10 } }{ 4\pi \times { 10 }^{ -7 } }$$
$$=130\times { 10 }^{ 7 }\times 3.14\times 4096\times { 10 }^{ 10 }$$
$$=1673508.57\times { 10 }^{ 17 }$$
$$=1.67\times { 10 }^{ 23 }{ Am }^{ 2 }$$
At a place of Earth, the vertical component of Earth's magnetic field is $$\sqrt {3}$$ times its horizontal component. The angle of dip at this place is _____.
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$$60^{\circ}$$
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$$30^{\circ}$$
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$$45^{\circ}$$
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$$0^{\circ}$$
Explanation
As, vertical component of Earth's magnetic field,
$$B_{V} = \sqrt {3}B_{H}$$
Angle of dip at any place is given by
$$\tan \delta = \dfrac {B_{V}}{B_{H}} = \dfrac {\sqrt {3}B_{H}}{B_{H}} = \sqrt {3}$$
$$\Rightarrow \delta = \tan^{-1}(\sqrt {3}) = 60^{\circ}$$.
A material is placed in a magnetic field and it is thrown out of it. Then the material is
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paramagnetic
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diamagnetic
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ferromagnetic
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non-magnetic
Explanation
Diamagnetic materials are repelled by the magnetic field, thus the above material must be diamagnetic.
Relative permittivity and permeability of a material are $$\varepsilon_r$$ and $$\mu_r$$, respectively. Which of the following values of these quantities are allowed for a diamagnetic material?
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$$\varepsilon_r=1.5, \mu_r=1.5$$
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$$\varepsilon_r=0.5, \mu_r=1.5$$
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$$\varepsilon_r=1.5, \mu_r=0.5$$
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$$\varepsilon_r=0.5, \mu_r=0.5$$
Explanation
The values of relative permeability of diamagnetic materials are slightly less than $$1$$ and $$\varepsilon_r$$ is quite high. According to the table given, one takes $$\varepsilon_r=1.5$$ and $$\mu_r=0.5$$. Then the choice (c) is correct.
A magnetic dipole is placed in a uniform magnetic fields, B, the potential energy is minimum when dipole is
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Parallel to $$B$$
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Perpendicular to $$B$$
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Inclined at an angle of $$45^{\circ}$$ to $$B$$
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Anti-parallel to $$B$$
Explanation
Potential energy is given by
$$U=M.B = -MB cos\, \theta$$
Thus, potential energy is minimum when dipole is parallel to B.
Which of these devices uses a magnet or electromagnet to make it work?
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An electric bell
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A compact disc
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A microchip
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All of these
Explanation
An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound. Electric bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, doorbells, and alarms in industrial plants, since the late 1800s, but they are now being widely replaced with electronic sounders. It consists of coils of insulated wire wound round iron rods. When an electric current flows through the coils, the rods became magnetic and attract a piece of iron attached to a clapper. The clapper hits the bell and makes it ring.
The main advantage of a permanent magnet over an electromagnet is that a permanent magnet does not require a continuous supply of electrical energy to maintain its magnetic field.
State whether the above statement is true or false?
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True
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False
Explanation
The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.
An electromagnets magnetic field can be rapidly manipulated over a wide range by controlling the amount of electric current supplied to the electromagnet.
State whether the above statement is true or not?
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True
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False
Explanation
A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. ... The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding.
What advantage does an electromagnet have over a permanent magnet?
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An electromagnet can be used for picking up more metals.
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An electromagnet can be switched off.
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An electromagnet is lighter.
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All of these
Explanation
The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.An electromagnet can be switched off.
How can an electromagnet be made stronger?
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Add more coils of wire.
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Add an iron core.
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Increase the voltage.
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All of these answers are correct.
Explanation
We can make an electromagnet stronger by doing these things,
wrapping the,coil around an iron core.
,adding more turns to the coil.
,increasing the current flowing through the coil.
The areas under the I-H hysteresis loop and B-H hysteresis loop are denoted by $$A_1$$ and $$A_2$$, then the ratio of $$\frac{A_2}{A_2}$$ is given by
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$$\mu_0$$
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$$\dfrac {1}{\mu_0}$$
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$$1$$
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$$\sqrt{\mu_0}$$
Explanation
The relation between B and H is given by
$$B= \mu_0 (H+I)$$
$$db=\mu_0 dH+\mu_0 dl$$
$$\oint H\cdot dB=\mu _0\oint H\cdot dH +\mu _0\oint H\cdot dl$$
Also $$\oint H\cdot dH=0$$
$$\oint H\cdot dB=\mu _0\oint H\cdot dl$$
Area of B-H loop $$=\mu_0 \times area \, of \, l-H \, loop$$
$$A_2 =\mu_0 A_1$$
$$\Rightarrow \frac {A_1}{A_2} =\mu_0$$
When an iron cylinder of diameter $$0.20cm$$ and length $$30cm$$ is kept parallel to a magnetic field of intensity $$4800A/m$$ the cylinder acquires a pole strength of $$9Am$$. Find the permeability of the material of the rod?
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$$0.075222\times {10}^{-4}H/m$$
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$$9.522\times {10}^{-4}H/m$$
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$$75.22\times {10}^{-4}H/m$$
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$$7.522\times {10}^{-4}H/m$$
Explanation
Pole Strength = m=9A*m
B =
Therefore,
=
Hence, Option D is correct.
In the given diagrams, compasses are used to plot the magnetic field around a bar magnetic field around a bar magnet with poles marked N (North) and S (South). Which of the following diagrams correctly shows the expected field pattern?
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Explanation
The magnetic field line is directed from the North pole to the South Pole outside the magnet. The arrowhead of the needle of the compass points toward the direction of the field.
So option (D) is correct.
Which of the following is not true about the advantages of electromagnet over permanent magnet?
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Small electromagnets are used in electronic lock
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Scrapyard cranes have powerful electromagnets that lift metal car bodies with ease.
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Magnetic Resonance Imaging machines use very powerful electromagnets to produce highly detailed images of the human body.
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None of the above
Explanation
Magnets come in two main types: permanent magnets and electromagnets. As its name suggests, a permanent magnet is always magnetized -- think of a kitchen magnet that stays stuck to a refrigerator door for years. An electromagnet is different; its magnetism works only when powered by electricity. Although an electromagnet is more complicated than a permanent magnet, it has useful and important advantages. An electromagnet can be made very strong by increasing the number of turns in the coil, and by increasing the current passing through the coil. On the other hand, a permanent magnet cannot be made so strong.
State whether true or false :
An electromagnet can produce very strong magnetic force as compared to permanent magnet.
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True
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False
Explanation
A simple electromagnet consisting of a coil of wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created. The strength of magnetic field generated is proportional to the amount of current through the winding.An electromagnet can produce very strong magnetic force as compared to permanent magnet.
State whether true or false :
An electromagnet requires a continuous supply of current to maintain the magnetic field.
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True
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False
Explanation
The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.
Magnetic permeability of paramagnetic substances is?
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$$0$$
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$$> 1$$
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$$< 1$$
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$$1$$
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.
Which of the following statement is correct?
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Both dynamo and electric motor converts mechanical energy into electrical energy
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Dynamo converts electrical energy into light energy and electric motor converts mechanical energy into electrical energy
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Dynamo converts mechanical energy into electrical energy and electric motor converts electrical energy into mechanical energy
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Both dynamo and electric motor converts electric energy into mechanical energy
Explanation
Dynamo is used to convert mechanical energy into electric energy while
the electric motor is used to convert electrical energy into mechanical energy.
Hence option 'C' is correct.
Here, in the shown figure :
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Dot represents into the paper, while cross represent out of the paper
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Cross represents into the paper, while dot represent out of the paper
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Dot and cross, both represent into the paper
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Dot and cross, both represent out of the paper
Magnetic susceptibility for a paramagnetic and diamagnetic materials is respectively
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small, positive and small, positive
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large, positive and small, negative
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small, positive and small, negative
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large, negative and large, positive
Explanation
Magnetic susceptibility of paramagnetic materials is small and positive.
And, magnetic susceptibility of diamagnetic materials is small and negative.
Hence, answer is option-(C).
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Practice Class 12 Medical Physics Quiz Questions and Answers
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