CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 11 - MCQExams.com

The magnetic field of earth at the equator is approximately $$4\times 10^{-5}\ T$$. The radius of earth is $$6.4\times 10^{6}\ m$$. Then the dipole moment of the earth will be near the order of
  • $$10^{23}\ A\ m^{2}$$
  • $$10^{20}\ A\ m^{2}$$
  • $$10^{16}\ A\ m^{2}$$
  • $$10^{10}\ A\ m^{2}$$
The coercivity of a small magnet where the ferromagnet gets demagnetized is $$3\times 10^{3}\ Am^{-1}$$. The current required to be passed in a solenoid of length $$10\ cm$$ and number of turns $$100$$, so that the magnet gets demagnetized when inside the solenoid, is:
  • $$3A$$
  • $$6A$$
  • $$30\ mA$$
  • $$60\ mA$$
A wire of length L metres carrying a current I amperes is bent in the form of circle. The magnitude of its magnetic moment is _________ in MKS units.
  • $$\dfrac{IL^5}{4\pi}$$.
  • $$\dfrac{IL^2}{4\pi}$$.
  • $$\dfrac{IL^3}{4\pi}$$.
  • $$\dfrac{IL^4}{4\pi}$$.
Out of soft iron and steel which has more coercivity, less retentivity.
  • iron
  • steel
  • both are equal
  • can't say
The susceptibility of a diamagnetic substance is
  • $$\infty$$
  • zero
  • Small but negative
  • Small but positive
Some metals get magnetised by orientation of atomic magnetic moments in external magnetic field. What are they called ?
  • just magnets
  • Paramagnetics
  • dimagnetics
  • ferromagnetic
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. 
  • Both I and II are correct
  • Both I and II are incorrect
  • I is correct and II is incorrect.
  • I is incorrect and II is correct
Domain formation is the necessary features of
  • Diamagnetism
  • Paramagnetism
  • Ferromagnetism
  • All of these
Susceptibility is positive and small for 
  • Paramagnetic substances
  • Ferromagnetic substances
  • Non-magnetic substances
  • Diamagnetic substances
The graph of X versus T for a paramagnetic substance will look like 
The relative permeability is represented by $$\mu_r$$ and the susceptibility by $$\chi$$ for a magnetic substance. Then for a paramagnetic substance.
  • $$\mu_r> 1, \chi >0$$
  • $$\mu_r> 1, \chi < 0$$
  • $$\mu_r > 1, \chi >0$$
  • $$\mu_r < 1, \chi < 0$$
Which of the following statements is incorrect about hysteresis?
  • The effect is common to all ferromagnetic substances.
  • The hysteresis loop area is proportional to the thermal energy developed per unit volume of the material.
  • The hysteresis loop area is independent of the thermal energy developed per unit volume of the material.
  • The shape of the hysteresis loop is characteristic of the material.
Time period of a bar magnet oscillating in earth's magnetic field is T. Its magnetic moment is M. Now, a bar magnet of magnetic moment $$2$$M is brought near it. The new time period will. be
  • $$T$$
  • $$\dfrac{T}{\sqrt3}$$
  • $$T\sqrt3$$
  • $$3T$$
The given figure represents a material which is
1025679_89328aa65376430780afd07a0fc24f8c.png
  • Paramagnetic
  • Diamagnetic
  • Ferromagnetic
  • Ferrimagnetic
A frog is levitated in magnetic field produced by current in a vertical solenoid below the frog is:
  • Diamagnetic
  • Paramagnetic
  • Ferromagnetic
  • non-magnetic 
Two small bar magnets are placed in a line at certain distance $$d$$ part. If the length of each magnet is negligible compared to $$d$$, the force between them will be inversely proportional to:
  • $$d$$
  • $${d}^{2}$$
  • $${d}^{3}$$
  • $${d}^{4}$$
The figure shows the various positions (labelled by subscripts) of small magnetised needles P and Q. The arrows show the direction of their magnetic movement.configuration corresponds to the lowest potential energy among all the configurations shown 
1041730_56a67fede37840dda662da2529e69fdf.png
  • $$PQ_3$$
  • $$PQ_4$$
  • $$PQ_5$$
  • $$PQ_6$$
A conductor behave as a super conductor
  • Above critical temperature
  • At critical temperature
  • At $${100}^{o}C$$
  • At boiling point of that metal
Force between two identical bar magnets whose centres are $$r$$ metre apart is $$4.8N$$, when their axes are in the same line. If separation is increased to $$2r$$, the force between them is reduced to.
  • $$0.3\ N$$
  • $$0.6\ N$$
  • $$2.4\ N$$
  • $$1.2\ N$$
A small rod of bismuth is suspended freely between the poles of a strong electromagnet. It is found to arrange itself at right angles to the magnetic field. This observation establishes that bismuth is :
  • Diamagnetic
  • Paramagnetic
  • Ferro-magnetic
  • Antiferro-magnetic
As a result of a change in the magnetic flux linked to the closed loop shown in the figure, an e.m.f. . V volt is induced in the loop. The work done(joules) in taking a charge Q coulomb once along the loop is:
1096348_90a81975f74047e09f6924bb2c4aff66.png
  • QV
  • Zero
  • $$2$$QV
  • QV$$/2$$
The wing span of an aeroplane is 20 meter. it is flying in a field.where the vertical component of magnetic field of earth is $$ 5 \times 10^-5 $$ tesla with velocity $$ 360mh^1 $$. The potential difference product between the blades is:
  • 0.15 V
  • 0.16 V
  • 0.20 V
  • 0.30 V
A magnetising force of $$360 Am^{-1}$$ produces a magnetic flux density of $$0.6 T$$ in a ferromagnetic material. The susceptibility of the material is: 
  • $$1625$$
  • $$1329$$
  • $$2105$$
  • $$1914$$
The force between two magnetic poles is $$F$$ in air. If the pole is doubled that second pole is tripled and the distance between the poles is halved the force between the poles becomes and increase by
  • $$24\ F$$ and $$2300\%$$
  • $$24\ F$$ and $$2400\%$$
  • $$\dfrac {3}{2}\ F$$ and $$150\%$$
  • $$2\ F$$ and $$100\%$$
Temperature of a conductor increases by $$5^\circ C$$ on passing electric current for some time. The increases inits temperature when double current is passed through the same conductor for the same time is _______ $$^\circ C$$.
  • $$10$$
  • $$12$$
  • $$18$$
  • $$20$$
The armature of dc motor has 20Ω resistance .It draws current of 1.5 ampere when run by 220 volts dc supply. The value of back e.m.f. induced in it will be
  • 190 V
  • 150 V
  • 170 V
  • 120 V
When a diamagnetic substance is placed near a magnet then it is
  • Attracted
  • Repelled
  • No effect
  • None of these
The force between two poles is reduced to P newton. when their separation in increased to x times, it is increased to Q newton, when their separation is made 1/xth of their original value.
  • $$Q=XP$$
  • $${ Q=X }^{ 2 }P$$
  • $${ Q=X }^{ 3 }P4$$
  • $${ Q=X }^{ 4 }P$$
Copper is :
  • Paramagnetic
  • Diamagnetic
  • Ferromagnetic
  • None of these
Which of the followings is not property of magnetic lines of force.
  • The tangent at any point on the magnetic lines of pole given the direction of the magnetic field at that point.
  • No two magnetic lines of pole can intersect each other.
  • Magnetic lines of force are crowded where the magnetic field is strong and far from each other where field is weak.
  • They are closed continuous curves. They start from south pole and end on north pole.
a force acting on a magnetic pole of $$0.07 A m$$ is $$31.5 N$$. the magnetic field at that point is
  • $$450$$
  • $$400$$
  • $$350$$
  • $$300$$
The magnetic dipole moment of a small bar magnet is $$1.6 Am^{2}$$. It is placed in magnetic meridian with its north pole pointing toward geographic south of the earth. If the neutral point is obtained at $$20$$ cm from the centre of the magnet then, the horizontal component of earth's magnetic field is:
  • $$10^{-5}T$$
  • $$4\times 10^{-5}T$$
  • $$4\times 10^{+5}T$$
  • $$4\times 10^{-7}T$$
Magnetic field at point 'P'due to following current distribution is 
1242248_7c62f77934b74320bbb66f1a15c41ff6.png
  • $$\dfrac { \mu _ { 0 } I } { \pi r ^ { 2 } } \sqrt { r ^ { 2 } - a ^ { 2 } }$$
  • $$\dfrac{{{\mu _0}i}}{{2\pi a}}$$
  • $$\dfrac { \mu _ { 0 } I } { 2 \pi r ^ { 2 } } \sqrt { r ^ { 2 } - a ^ { 2 } }$$
  • $$\dfrac { \mu _ { 0 } l a } { 2 \pi r ^ { 2 } }$$
For protecting a sensitive equipment from the external magnetic  field, it should be 
  • Placed inside an aluminium cane
  • Placed inside an iron cane
  • Wrapped with insulation around it when passing current through it
  • Surrounded with fine copper sheet
Atomic number of an element is $$26$$. The element shows:
  • Ferromagnetism
  • Diamagnetism
  • Paramagnetism
  • None of these
The variation of magnetic susceptibility (x) with temperature for a diamagnetic substance is best represented by 
If a solution of ferromagnetic material is poured into a U-tube and one arm of this is placed between the poles of a strong magnet with the meniscus in line with the field, then the level of the solution will:
  • Rise
  • Fall
  • Rise till the liquid comes out
  • Remain unchanged
The basic magnetization curve for a ferromagnetic material is shown in figure. Then,the value of relative permeability is highest for the point
1259453_a1bf0bfb2811445696ca267cb5e65fc3.PNG
  • P
  • Q
  • R
  • S
 In the given figure, the electron enters into the magnetic field. It deflects in  x direction .
 Two parallel beams of electrons moving in the same direction produce a mutual force 

1185594_21546ce257a1415f9cfe95fa5a5122c1.png
  • + ve X direction
  • - ve X direction
  • + ve Y direction
  • - ve Y direction
A charge particle of charge q = 2 C has velocity $$v=100{ ms }^{ -1 }$$. When it passes point A adn has velocity in the direction shown. The strength of magnetic field at the point B due to this moving charge is (r = 2m)
1280769_24689dcbae234ff8b787bf63185eaebe.png
  • $$2.5\mu T$$
  • $$5.0\mu T$$
  • $$2.0\mu T$$
  • None of these
A wire carrying $$I$$ is shaped as shown. Section $$AB$$ is a quarter circle of radius $$r$$. The magnetic field at $$C$$ is directed:
1275283_8eacb916f803453b95d199b27e2b9fdc.png
  • Along the bisector of the angle $$ACB$$, away from $$AB$$
  • Along the bisector of the angle $$ACB$$, towards $$AB$$
  • Perpendicular to the plane of the paper directed into the paper
  • At an angle $$\pi /4$$ to the plane of the paper
A coil of surface area $$100{cm}^{2}$$ having $$50$$ turns is held perpendiculars to the magnetic field intensity $$0.02Wb{m}^{-2}$$. The resistance of the coil is $$2\Omega$$. If it is removed from the magnetic field in $$1s$$, the induced charge in the coil is ______
  • $$5C$$
  • $$0.5C$$
  • $$0.05C$$
  • $$0.005C$$
A thin straight vertical conductor has $$10amp$$ current flows vertically upwards. It is present at a place where $${B}_{H}=4\times {10}^{-6}T$$. At which point magnetic feild will be maximum
  • $$0.5m$$ on south of conductor
  • $$0.5m$$ on west of conductor
  • $$0.5m$$ on east of conductor
  • $$0.5m$$ on north-east of conductor
The magnetic susceptibility is negative for
  • Paramagnetic materials only
  • Diamagnetic material only
  • Ferromagnetic materials only
  • paramagnetic and ferromagnetic materials
A compass needle made of pure iron (with density $$8000 kg/m^3$$) has a length 5 cm, width 1.0 mm and thickness $$0.50$$ mm. The magnitude of magnetic dipole moment of an iron is $$\mu Fe = 2\times 10^{-23}$$ JiT, If magnetisation of needle is equivalent to the alignment of 10% of the atoms in the needle, what is the magnitude of the needle's magnetic dipole moment $$\overrightarrow { \mu  } $$? (mass of iron per mole $$= 0.05 kg/mole, N_A = 6 x 10^{23}$$) 
  • $$2.4 \times 10^{-3} J/T$$
  • $$4.8 \times 10^{-3} J/T$$
  • $$7.2 \times 10^{-3} J/T$$
  • $$9.6 \times 10^{-3} J/T$$
Temperature above which a ferromagnetic substance becomes paramagnetic is called    
  • Critical temperature
  • Boyle's temperature
  • Debye's temperature
  • Curie temperature
The mass of a specimen of a ferromagnetic material is $$0.6kg$$ and its density is $$7.8\times{10}^{3}kg/{m}^{3}$$. If the area of hysteresis loop of alternating magnetising field of frequency $$50Hz$$ is $$0.722MKS$$ units  then the hysteresis loss per second will be-
  • $$277.7\times{10}^{-5}$$ Joule
  • $$277.7\times{10}^{-6}$$ Joule
  • $$277.7\times{10}^{-4}$$ Joule
  • $$277.7\times{10}^{-7}$$ Joule
The susceptibility of a paramagnetic substance was found for different temperatures and a graph of $$\chi $$ against $$\frac{1}{T}$$ was plotted. From the graph, it was found that what $$\chi =0.5, \frac{1}{T}=5 \times 10^{-3}/K$$. What is the curie constant for the substance ?
  • 50 K
  • 75 K
  • 100 K
  • 125 K
Magnetic field is not associated with
  • a change in uniform motion.
  • an accelerated charge.
  • a deaccelerated charge.
  • a stationary charge.
Magnetic dipole moment is a:
  • Scalar quantity
  • Vector quantity
  • Constant quantity
  • None of these
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