CBSE Questions for Class 12 Medical Physics Moving Charges And Magnetism Quiz 10 - MCQExams.com

The graph gives the magnitude B(t) of a uniform magnetic field that exist throughtout  a conducting loop.  perpendicular to the plane of the graph according to the magnitude of the emf induced in the loop greatest first
1120957_0ce3a3de406c4a0890cfdfe755f1436e.png
  • $$b > (d = \epsilon ) < (a = c )$$.
  • $$b > (d = \epsilon) > (a = c)$$
  • $$b< d< \epsilon < \epsilon < c$$
  • $$b> (a = c) > ( d = \epsilon )$$
$${\vec B_1},{\vec B_2}$$ and $${\vec B_3}$$ are the magnetic field due to $$I_1 , I_2$$ and $$I_3$$. Ampere's circuital law is given by $$\oint {\vec B} .d\vec l = {\mu _0}I$$, here $$\vec B$$ is_____.
1120906_d5e7f440e2cf43fca270d054bfd27122.png
  • $$\vec B = {\vec B_1} - {\vec B_2}$$
  • $$\vec B = {\vec B_1} + {\vec B_2} + {\vec B_3}$$
  • $$\vec B = {\vec B_1} + {\vec B_2} - {\vec B_3}$$
  • $$\vec B = {\vec B_1} - {\vec B_3} $$
A long horizontal wire $$P$$ carries a current $$50\ A$$. It is rigidly fixed. Another line wire $$Q$$ is placed directly above and parallel to $$P$$. The weight of wire $$Q$$ is $$0.075\ Nm^{-1}$$ and caries a current of $$25\ A$$. Find the position of wire $$Q$$ from $$P$$ so that wire to remains suspended due to the magnetic repulsion-
  • $$3.33\ mm$$
  • $$33.3\ mm$$
  • $$334\ mm$$
  • $$333\ mm$$
A particle of mass $$1.6\times 10^{-27}\ kg$$ and charge $$1.60\times 10^{-19}$$ coulomb enters in a uniform magnetic field of $$1$$ Tesla as shown in the fig. the speed of the particle is $$10^{7}\ m/s$$. The distance $$PQ$$ will be-
1081327_4ff17347308d4edab664e93c22d8150d.png
  • $$0.14\ m$$
  • $$0.28\ m$$
  • $$0.4\ m$$
  • $$0.5\ m$$
As shown, a uniform magnetic filed B pointing out of the paper plane is confined in the shaded area of radius r. At a distance R from the center of the shaded area there is a point particle of mass m and carrying charge q. The magnetic filed is then quickly changed to zero.Find the speed of the particle.
1116904_154480f495dd49df9c1326366831b0ba.png
  • $$v=\dfrac{qBr^2}{2mR}$$
  • $$zero$$
  • $$v=\dfrac{qBr^2}{mR}$$
  • $$v=\dfrac{2qBr^2}{mR}$$
A magnetic filed:
  • Always exerts a force on charged particle
  • Never exerts a force on charged particle
  • Exerts a force, if the charged particle is moving across the magnetic field line
  • Exerts a force, if the charged particle is moving along the magnetic field line
An electron has velocity v=$$\left( {2.0\times{{10}^6}\;m/s} \right)\hat{i} + \left( {3.0\times{{10}^{6\;}}m/s} \right)\hat{j}$$, magnetic field present is region is $$B\left( {0.030\;T} \right)\;i - \left( {0.15\;T} \right)j$$. Find the force on electron.
  • $$-6.24\times{10}^{-14} \hat{k}$$
  • $$-0.624\times{10}^{-14} \hat{k}$$
  • $$-62.4\times{10}^{-14} \hat{k}$$
  • $$-624\times{10}^{-14} \hat{k}$$
A long straight wire along the z-axis carries a current I in the negative z direction. The magnetic vector field $$\overline {B}$$ at a point having coordinates (x, y) in the z=0 plane is :
  • $$\dfrac{\mu_0I(y\hat{i} - x \hat{j})}{2\pi (x^2+y^2)}$$
  • $$\dfrac{\mu_0I(x\hat{i} - y \hat{j})}{2\pi (x^2+y^2)}$$
  • $$\dfrac{\mu_0I(x\hat{j} - y \hat{i})}{4\pi (x^2+y^2)}$$
  • $$\dfrac{\mu_0I(x\hat{i} - y \hat{j})}{4\pi (x^2+y^2)}$$
A charged particle moving in a magnetic field experience maximum magnetic force when 
  • it moves parallel to the field
  • it moves in opposite direction of the field
  • it moves at right angles to the direction of field
  • it moves at an angle $$45^0$$ to the direction of field
A charged particle moving in a magnetic field experiences, some magnetic force because
  • Moving charged particle produce electric field
  • Moving charged particle produce magnetic field
  • Magnetic field do not allow the charged particle to pass through it.
  • none of these
Motion of charges is noting but :
  • Electric current
  • magnetic effect
  • heating effect
  • all of the above
A particle enters a magnetic field perpendicular and undeviated, (there is no other field present ) then this partical must be
  • $$Electron$$
  • $$Neutron$$
  • $$\alpha-Particle$$
  • $$Proton$$
An electron is executing uniform circular motion in a uniform magnetic field $$\vec{B}$$. If magnetic moment is $$\vec{M}$$. Select incorrect option.
  • $$\vec{M}\times \vec{B}=0$$
  • $$\vec{M}\cdot \vec{B} < 0$$
  • $$\vec{M}\cdot \vec{B} > 0$$
  • Both $$(1)$$ & $$(2)$$
One gram hydrogen has $$6\times 10^{23}$$ atoms. Imagine that all the nuclei are put at the north pole of the earth and the electrons at the south pole of the earth (radius=6400 km). The force between the charges is
  • $$10\times 10^{5}N$$
  • $$5\times 10^{5}N$$
  • $$2.5\times 10^{5}N$$
  • $$2\times 10^{5}N$$
Two identical short bar magnets each of magnetic moment $$10\ Am^{2}$$ are placed at a separation of $$10\ cm$$ between their centres such that their axes are perpendicular to each other. The magnetic field at a point midway between the two magnets is 
  • $$ \sqrt{5} \times 10^{-6}\ T$$
  • $$1.8\times 10^{-2}\ T$$
  • $$4\times 10^{4}\ T$$
  • $$12\times 10^{-4}\ T$$
Three long, straight and parallel wires carrying currents are arranged as shown in the figure. The wire C Wh carries a current of 5.4 is so placed that it experience no force. The distance of wire C from wire D is the 
1243390_55cae671105f43d99e5a981ec6ea8cbe.png
  • 9 cm
  • 7 cm
  • 5 cm
  • 3 cm
If the magnetic  field at P can be written as K $$\left( \tan { \frac { a }{ 2 }  }  \right) $$ then K is 
1191151_a596231ee7bc456c882848a0a36862a2.png
  • $$\dfrac { { \mu }_{ 0 }I }{ 4\pi d } $$
  • $$\dfrac { { \mu }_{ 0 }I }{ 2\pi d } $$
  • $$\dfrac { { \mu }_{ 0 }I }{ \pi d } $$
  • $$\dfrac { {2 \mu }_{ 0 }I }{ \pi d } $$
Fleming's left hand rule is used to find
  • Direction of magnetic field 
  • Direction of current
  • Direction of magnetic force acting on conductor
  • None of these
Three plotting compasses are placed close to a current carrying wire wrapped around an insulator as shown in the figure.
How many compass needles will change direction if the current through the wire is increased? (Ignore the effect of the earth's magnetic field.)
1202493_177ce7c26e1f454282b57edba8f1edee.png
  • 0
  • 1
  • 2
  • 3
The magnetic moment of a current carrying loop is $$2.1\times {10}^{-25}$$ $$amp\times {m}^{2}$$. The magnetic field at a point on its axis at a distance of $$1\ A^o$$ is 
  • $${ 4.2\times 10 }^{ -2 } \ weber/{m}^{2}$$
  • $${ 4.2\times 10 }^{ -3 }\ weber/\ {m}^{2}$$
  • $${ 4.2\times 10 }^{ -4 }\ weber/\ {m}^{2}$$
  • $${ 4.2\times 10 }^{ -5 }\ weber/\ {m}^{2}$$

A current is flowing through a thin cylindrical shell of radius R. If the energy density in the medium, due to the magnetic field, at a distance r from the axis of the shell is equal to U then which of the following graphs is correct?
A conductor of length $$1\ m$$ and carrying current of $$1\ A$$ is placed at an angle $$45 ^ { \circ }$$ to the magnetic field of 1 oersted. The force acting on conductor is 
  • $$\dfrac { 10 ^ { - 4 } } { \sqrt { 2 } } N$$
  • $$\dfrac { 10 ^ { - 4 } } { \sqrt { 3 } } N$$
  • $$\dfrac { 10 ^ { - 2 } } { \sqrt { 3 } } N$$
  • $$\dfrac { 10 ^ { - 2 } } { \sqrt { 2 } } N$$
Two magnetic bars are suspended in horizontal plane and ocillates in earth magnetic field. Their time period of oscillations are $$T_1$$ and $$T_2$$. The ratio of their magnetic dipole moments is : 
  • $$\dfrac{T_1}{T_2}$$
  • $$\dfrac{T_2}{T_1}$$
  • $$\left(\dfrac{T_1}{T_2}\right)^2$$
  • $$\left(\dfrac{T_2}{T_1}\right)^2$$
ON connecting a battery to the two opposite corner of a diagonal of a square wire frame of side 10 cm.The magnetic field at the centre will be (wire is uniform)
  • zero
  • 1 $$\mu{T}$$
  • 2 $$\mu{T}$$
  • 4 $$\mu{T}$$
Two concentric circular coil of radius $$20 cm$$ and $$30 cm$$ carries current $$2A$$ and $$3A$$ respectively in opposite direction then magnetic field at centre will be :-
  • $$4\pi \times 10^{-7}$$
  • $$2\pi \times 10^{-7}$$
  • $$2 \times 10^{-7}$$
  • $$0$$
A wire is bent into three successive quadrants. The quadrant $$ab$$ lies in the $$xy$$ plane. $$b$$ in $$xy$$ plane and $$ca$$ in the $$zx$$ plane. What is the magnetic moment of this system if a current $$I$$ flows through it? Give: $$R=$$radius each quadrant.
1270477_f27b018bf0c1492a80b7b0fea6997a03.png
  • $$\dfrac {\sqrt {3}\pi r^{2}I}{4}$$
  • $$\dfrac {\sqrt {2}\pi r^{2}I}{4}$$
  • $$\dfrac {\pi r^{2}I}{2}$$
  • $$\dfrac {\pi r^{2}I}{4}$$
A charged particle enters in a magnetic field $$H$$ with its initial velocity making an angle of $$45^o$$ with $$H$$. The path of the particle will be 
  • an ellipse
  • straight line
  • a circle
  • a helical
In fig. two long parallel wires carry equal currents in opposite directions. Point O is situated mid way between the wires and X - Y plane contains two wires and +ve Z - axis comes normally out of the plane of paper. The magnetic field B at O is non - zero along
1286521_dc044bb82a5a46819bea0b5f873873d3.png
  • X Y and Z axes
  • X - axis
  • Y - axis
  • Z - axis
If the angular momentum of an electron is $$\overset{\rightarrow}{J}$$ then the magnitude of the magnetic moment will be
  • $$\cfrac{eJ}{m}$$
  • $$\cfrac{2m}{eJ}$$
  • $$eJ2m$$
  • $$\cfrac{eJ}{2m}$$
A conducting rod $$MN$$ of mass $$'m$$ and length $$'\ell '$$ is placed on parallel smooth conducting rails connected to an uncharged capacitor of capacitance $$'C'$$ and a battery of emf $$\varepsilon $$ as shown. A uniform magnetic field $$'B'$$ is existing perpendicular to the plane of the rails.The steady state velocity acquired by the conducting rod $$MN$$ after closing switch $$S$$ is (neglect the resistance of the parallel rails and the conducting rod )
1277078_0ad826838d304ed382cdf89e50bbc375.JPG
  • $$\frac{{2CB\ell \varepsilon }}{{\left( {m + C{B^2}{\ell ^2}} \right)}}$$
  • $$\frac{{CB\ell \varepsilon }}{{\left( {m + C{B^2}{\ell ^2}} \right)}}$$
  • $$\frac{{CB\ell \varepsilon }}{{2\left( {m + C{B^2}{\ell ^2}} \right)}}$$
  • $$\frac{{CB\ell \varepsilon }}{{4\left( {m + C{B^2}{\ell ^2}} \right)}}$$
Two point dipoles of dipole moment $$ \xrightarrow [ P_ 1 ]{  } \quad and\quad \xrightarrow [ P_ 2 ]{  }  $$ are at a distance x from each other and $$ \xrightarrow [ P_ 1 ]{  } \parallel \xrightarrow [ P_ 2 ]{  }  $$ The force between the dipoles is:
  • $$ \dfrac { 1 }{ 4\pi e_ 0 } \dfrac { 4p_ 1p_ 2 }{ x^ 4 } $$
  • $$ \dfrac { 1 }{ 4\pi e_ 0 } \dfrac { 3p_ 1p_ 2 }{ x^ 3 } $$
  • $$ \dfrac { 1 }{ 4\pi e_ 0 } \dfrac { 6p_ 1p_ 2 }{ x^ 4 } $$
  • $$ \dfrac { 1 }{ 4\pi e_ 0 } \dfrac { 8p_ 1p_ 2 }{ x^ 4 } $$
A magnetised wire of moment $$3.14\ A-m^{2}$$ is bent in the form of a semi-circle ; then the new magnetic moment will be:-
  • $$3.14\ A-m^{2}$$
  • $$2\ A-m^{2}$$
  • $$6.28\ A-m^{2}$$
  • $$Noone\ of\ these$$
Two long parallel wires are at a distance 2d apart. They carry steady equal currents flowing out of the plane of the paper, as shown in figure. The variation of the magnetic field B along the line XX' is given by :-
The intensity of magnetic field is H and moment of magnet is M. The maximum potential energy is
  • MH
  • 2 MH
  • 3 MH
  • 4 MH
Density of iron is 7800 kg/m$$ ^{3} $$ and induced magnetic field in iron is 8 x10$$ ^{5} $$ A/m then find magnetic dipole moment of each iron atom is (nearly)
  • $$6\times10$$ ^{-24} $$Am$$ ^{2} $$
  • $$9\times10$$ ^{-22} $$Am$$ ^{2} $$
  • 10$$ ^{-23} $$Am$$ ^{2} $$
  • $$4\times10$$ ^{-24} $$Am$$ ^{2} $$
If two streams of electrons move parallel to each other in same direction then they.
  • attract each other
  • repel each other
  • do not exert any force on one other
  • Get rotated perpendicular to each other
An infinitely straight conductor $$AB$$ is fixed and a current is passed through it  Another  movable straight wire $$CD$$ of finite length and carrying current is held perpendicular to it and released. Neglect weight of the wire
1456866_090602930c7945148c750fc1187fb708.png
  • The rod $$CD$$ will move upwards parallel to itself
  • The rod $$CD$$ will move downward parallel to itself
  • The rod $$CD$$ will move upward and turn clockwise at the same time
  • The rod $$CD$$ will move upward and turn anticlockwise at the same time
A thin circular disk of radius R is uniformly charged with density $$  \sigma>0  $$ per unit area. The disk rotates about axis with a uniform angular speed $$  \omega  $$. The magnetic moment of the disk is:
  • $$

    2 \pi R^{4} \sigma \omega

    $$
  • $$

    \pi R^{4} \sigma \omega

    $$
  • $$

    \dfrac{\pi R^{4}}{2} \sigma w

    $$
  • $$

    \dfrac{\pi R^{4}}{4} \sigma \omega

    $$
Two particles having same charge and KE enter at right angles into the same magnetic field and travel in circular paths of radil $$2  \mathrm{cm}  $$ and $$3  \mathrm{cm}  $$ respectively. The ratio of their masses is.
  • $$ 2 : 3 $$
  • $$ 3 : 2 $$
  • $$ 4 : 9 $$
  • $$ 9 : 4 $$
A fixed horizontal wire carries a current of $$200 A.$$ Another wire having a mass per unit length $$10^{3} kg/m$$ is placed below the first wire at a distance of 2 cm and parallel to it How much current must be passed through the second wire if it floats in air without any support? What should be the direction of current in it
  • 25A (direction of current is same to first wire)
  • 25A (direction of current is opposite to first wire)
  • 49A (direction of current is same to first wire)
  • 49A (direction of current is opposite to first wire)
Velocity and acceleration vectors of a charged particle moving in a magnetic field at some instant are $$\vec{v}=3\hat{i}+4\hat{j}$$ and $$\vec{a}=2\hat{i}+x\hat{j}$$. Select the correct alternative(s) :
  • $$x = 1.5$$
  • $$ x = 3$$
  • magnetic field is along z-direction
  • kinetic energy of the particle is constant
A charge particle of mass m and charge q is projected with velocity v along plane at a distance a from a long staright current carrying conductor as shown in figure. the radius of curvature of the path traced by the particle at the given position does not depend on
1563662_a953fa1830914d149f6c120077f74c47.png
  • $$ \theta $$
  • q
  • i
  • m
A coil in the shape of an equilateral triangle of side 0.02 m is suspended from its vertex such that it is hanging in a vertical plane between the poles pieces of permanent magnet producing a uniform field of $$5 \times 10^{-2}$$ T. If a current of 0.1 A is passed through the coil, what is the couple acting
  • $$5\sqrt{3} \times 10^{-7}$$ N-m
  • $$5\sqrt{3} \times 10^{-10}$$ N-m
  • $$\dfrac{\sqrt{3}}{5} \times 10^{-7}$$ N-m
  • None of these
An iron rod of length L and magnetic moment M is bent in form of a semicircular.Now its magnetic moment will be.
  • M
  • $$ \frac {2M}{\pi} $$
  • $$ \frac {M}{\pi} $$
  • $$ M \pi $$
The Biot-Savart's law in vector from is:
  • $$ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { di\left( \overrightarrow { l } \times \overrightarrow { r } \right) }{ r^ 2 } $$
  • $$ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { dl } \times \overrightarrow { r } \right) }{ r^ 2 } $$
  • $$ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { r } \times \overrightarrow { dl } \right) }{ r^ 2 } $$
  • $$ d\overrightarrow { B } =\dfrac { \mu _ o }{ 4\pi } \dfrac { i\left( \overrightarrow { dl } \times \overrightarrow { r } \right) }{ r^ 3 } $$
A circular loop of area $$1\ cm^2$$, carrying a currrent of $$10$$ A, is placed in a magnetic field of $$0.1$$ T perpendicular to the plane of the loop. The torque on the loop due to the magnetic field is
  • zero
  • $$10^{-4}\ \hbox{N-m}$$
  • $$10^{-2}\ \hbox{N-m}$$
  • $$1\ \hbox{N-m}$$
Two similar bar magnets P and Q, each of magnetic moment $$ \mathrm{M} $$, are taken. If P is cut along its axial line and Q is cut along its equatorial line, All the four pieces obtained have
  • equal pole strength
  • magnetic moment $$\dfrac M4$$
  • magnetic moment $$\dfrac M2$$
  • magnetic moment $$M$$

Two infinitely long parallel wires carry equal current in same direction. The magnetic field at a mid point in between the two wires is 
  • Twice the magnetic field produced due to each of the wires
  • Half of the magnetic field produced due to each of the wires
  • Square of the magnetic field produced due to each of the wires
  • Zero
A charge $$'q'$$ moves in a region where electric field $$'E'$$ nd magnetic filed $$'B'$$ both exist, then force on it is :-
  • $$q(\vec{V}\times \vec{B})$$
  • $$q\vec{E}$$
  • $$q\left\{\vec{E}+(\vec{v}\times \vec{B}) \right\} $$
  • $$q\left\{\vec{B}+(\vec{v}\times \vec{E}) \right\} $$
A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicular to the plane. let $$r_p$$, $$r_e$$ and $$r_{He}$$ be their respectively radii, then ,
  • $$r_e > r_p > r_{He}$$
  • $$r_e < r_p < r_{He}$$
  • $$r_e < r_p = r_{He}$$
  • $$r_e > r_p = r_{He}$$
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Medical Physics Quiz Questions and Answers