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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=ϵ)<(a=c).
  • b>(d=ϵ)>(a=c)
  • b<d<ϵ<ϵ<c
  • b>(a=c)>(d=ϵ)
B1,B2 and B3 are the magnetic field due to I1,I2 and I3. Ampere's circuital law is given by B.dl=μ0I, here B is_____.
1120906_d5e7f440e2cf43fca270d054bfd27122.png
  • B=B1B2
  • B=B1+B2+B3
  • B=B1+B2B3
  • B=B1B3
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 Nm1 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 1.6×1027 kg and charge 1.60×1019 coulomb enters in a uniform magnetic field of 1 Tesla as shown in the fig. the speed of the particle is 107 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=qBr22mR
  • zero
  • v=qBr2mR
  • v=2qBr2mR
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=(2.0×106m/s)ˆi+(3.0×106m/s)ˆj, magnetic field present is region is B(0.030T)i(0.15T)j. Find the force on electron.
  • 6.24×1014ˆk
  • 0.624×1014ˆk
  • 62.4×1014ˆk
  • 624×1014ˆk
A long straight wire along the z-axis carries a current I in the negative z direction. The magnetic vector field ¯B at a point having coordinates (x, y) in the z=0 plane is :
  • μ0I(yˆixˆj)2π(x2+y2)
  • μ0I(xˆiyˆj)2π(x2+y2)
  • μ0I(xˆjyˆi)4π(x2+y2)
  • μ0I(xˆiyˆj)4π(x2+y2)
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 450 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
  • αParticle
  • Proton
An electron is executing uniform circular motion in a uniform magnetic field B. If magnetic moment is M. Select incorrect option.
  • M×B=0
  • MB<0
  • MB>0
  • Both (1) & (2)
One gram hydrogen has 6×1023 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
  • 10×105N
  • 5×105N
  • 2.5×105N
  • 2×105N
Two identical short bar magnets each of magnetic moment 10 Am2 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 
  • 5×106 T
  • 1.8×102 T
  • 4×104 T
  • 12×104 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 (tana2) then K is 
1191151_a596231ee7bc456c882848a0a36862a2.png
  • μ0I4πd
  • μ0I2πd
  • μ0Iπd
  • 2μ0Iπd
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 2.1×1025 amp×m2. The magnetic field at a point on its axis at a distance of 1 Ao is 
  • 4.2×102 weber/m2
  • 4.2×103 weber/ m2
  • 4.2×104 weber/ m2
  • 4.2×105 weber/ m2

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 to the magnetic field of 1 oersted. The force acting on conductor is 
  • 1042N
  • 1043N
  • 1023N
  • 1022N
Two magnetic bars are suspended in horizontal plane and ocillates in earth magnetic field. Their time period of oscillations are T1 and T2. The ratio of their magnetic dipole moments is : 
  • T1T2
  • T2T1
  • (T1T2)2
  • (T2T1)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 μT
  • 2 μT
  • 4 μT
Two concentric circular coil of radius 20cm and 30cm carries current 2A and 3A respectively in opposite direction then magnetic field at centre will be :-
  • 4π×107
  • 2π×107
  • 2×107
  • 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
  • 3πr2I4
  • 2πr2I4
  • πr2I2
  • πr2I4
A charged particle enters in a magnetic field H with its initial velocity making an angle of 45o 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 J then the magnitude of the magnetic moment will be
  • eJm
  • 2meJ
  • eJ2m
  • eJ2m
A conducting rod MN of mass m and length is placed on parallel smooth conducting rails connected to an uncharged capacitor of capacitance C and a battery of emf ε 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
  • 2CBε(m+CB22)
  • CBε(m+CB22)
  • CBε2(m+CB22)
  • CBε4(m+CB22)
Two point dipoles of dipole moment P1andP2 are at a distance x from each other and P1P2 The force between the dipoles is:
  • 14πe04p1p2x4
  • 14πe03p1p2x3
  • 14πe06p1p2x4
  • 14πe08p1p2x4
A magnetised wire of moment 3.14 Am2 is bent in the form of a semi-circle ; then the new magnetic moment will be:-
  • 3.14 Am2
  • 2 Am2
  • 6.28 Am2
  • 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/m3 and induced magnetic field in iron is 8 x105 A/m then find magnetic dipole moment of each iron atom is (nearly)

  • 6×10 ^{-24} Am ^{2} $$
  • 9×10 ^{-22} Am ^{2} $$
  • 1023Am2
  • 4×10 ^{-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 σ>0 per unit area. The disk rotates about axis with a uniform angular speed ω. The magnetic moment of the disk is:
  • 2πR4σω
  • πR4σω
  • πR42σw
  • πR44σω
Two particles having same charge and KE enter at right angles into the same magnetic field and travel in circular paths of radil 2cm and 3cm respectively. The ratio of their masses is.
  • 2:3
  • 3:2
  • 4:9
  • 9:4
A fixed horizontal wire carries a current of 200A. Another wire having a mass per unit length 103kg/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 v=3ˆi+4ˆj and a=2ˆi+xˆj. 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
  • θ
  • 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 5×102 T. If a current of 0.1 A is passed through the coil, what is the couple acting
  • 53×107 N-m
  • 53×1010 N-m
  • 35×107 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
  • 2Mπ
  • Mπ
  • Mπ
The Biot-Savart's law in vector from is:
  • dB=μo4πdi(l×r)r2
  • dB=μo4πi(dl×r)r2
  • dB=μo4πi(r×dl)r2
  • dB=μo4πi(dl×r)r3
A circular loop of area 1 cm2, 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
  • 104 N-m
  • 102 N-m
  • 1 N-m
Two similar bar magnets P and Q, each of magnetic moment 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 M4
  • magnetic moment 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(V×B)
  • qE
  • q{E+(v×B)}
  • q{B+(v×E)}
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 rp, re and rHe be their respectively radii, then ,
  • re>rp>rHe
  • re<rp<rHe
  • re<rp=rHe
  • re>rp=rHe
0:0:2


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