Loading [MathJax]/jax/output/CommonHTML/jax.js

CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 12 - MCQExams.com

A charge (52+25) coulomb is placed on the axis of an infinite disc at a distance a from the centre of disc. The flux of this charge on the part of the disc having inner and outer radius of a and 2a will be :
  • 32ε0
  • 12ε0
  • 2[5+2]ε0
  • 25+522ε0
Three point charges +q, -2q and +q are placed at point (x =0,y=a, z=0),(x = 0, y=0, z=0) and (x=a, y =0, z =0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are :
  • 2qa along + y direction
  • 2qa along the line joining points

    (x=0,y=0,z=0) and (x=a,y=a,z=0)
  • qa along the line joining points

    (x=0,y=0,z=0) and (x=a,y=a,z=0)
  • 2qa along + x direction
A charged particle 'q' lies at 'P' and the line PC is perpendicular to the surface of ABC (part of disc). Find the flux passing through the surface ABC.
330294.PNG
  • q4ε0
  • q16ε0
  • q32ε0
  • q48ε0
The spatial distribution of the electric field due to two charges (A, B) is shown in figure. Which one of the following statements is correct ? 
431034_325f623ae0f846bcbc1dbdfa65de735b.png
  • A is +ve and B is -ve; |A|>|B|
  • A is -ve and B is +ve; |A|=|B|
  • Both are +ve but A>B
  • Both are -ve but A>B
An electrostatic field line is continuous curve. That is, a field line cannot have sudden breaks. Why not?
  • Electric field vanishes only at the origin
  • Electric field vanishes only at infinity
  • Electric field never vanishes
  • Electric field is imaginary at some points
There exists a non-uniform electric field along x-axis as shown in the figure below. The field increases at a uniform rate along +ve x-axis. A dipole is placed inside the field as shown.Which one of the following is correct for the dipole?
431051_dd76f7e7bc7245c69e581485b48e1abd.png
  • Dipole moves along positive x-axis and undergoes a clockwise rotation
  • Dipole moves along negative x-axis and undergoes a clockwise rotation
  • Dipole moves along positive x-axis and undergoes a anticlockwise rotation
  • Dipole moves along negative x-axis and undergoes a anticlockwise rotation
The diagram shows the cross-section of a sheet that is infinitely long in the x and z directions. The sheet has a height 2D in the y-direction. The charge carried by the sheet is NOT uniform; the charge density varies according to the equation =By2.
Which of the following expressions gives the electric field strength at point P, a point that lies outside the sheet and is located at y=d?
495963_a90f02cff7ea46cd98391eef26a4ae47.png
  • BD44ϵ0
  • Bd33ϵ0
  • BD33ϵ0
  • Bd4ϵ0
  • The electric field is undefined because the sheet carries an infinite amount of charge.
Coaxial cable (typically used for cable and satellite tv) has its signal run on a copper wire surrounded by an insulator which is surrounded by the ground wire, as opposed to the typical side by side configuration.
What is the most logical reason for this?
496030.png
  • The energy held in the electric field between the inside wire and the outside allow for a clearer signal.
  • The outside wire prevents any magnetic field from the inside wire from leaking out of the wire.
  • The outside wire prevents electric fields from interfering with the signal in the inside wire.
  • The overall resistance of the wire is reduced using this configuration.
4 charges are placed at follows:
2q at (a,0)
   q at (0,a)
2q at (a,0)
  3q at (0,a)
The dipole moment of the configuration is 
  • 2qaˆj
  • 3qaˆj
  • 2qa[ˆi+ˆj]
  • None of these
In a region, the intensity of an electric field is given by E=2i+3j+k in NC1. The electric flux through a surface S=10i m2 in the region is:
  • 5 Nm2C1
  • 10 Nm2C1
  • 15 Nm2C1
  • 20 Nm2C1
Consider three charged bodies A, B and C. If A and B repel each other and A attracts C, what is nature of the force between B and C?
  • Attractive
  • Repulsive
  • Zero
  • None of these
The figure shows electric field lines penetrating two surfaces. Then
591887.JPG
  • |Ea|>|Ea|
  • |Ea|=|Ea|
  • |Ea|<|Ea|
  • None of these
Mathematically, electric flux can ϕ be represented as:

E=  electric field
ˆn= surface normal vector
A= surface area
  • ϕ=EˆnA
  • ϕ=E.ˆnA
  • ϕ=E.ˆnA
  • ϕ=EnA
Calculate the flux through the base of the cone of radius r.
592139_926614e2167d48af9ceb14c50bb2c685.png
  • 2πr2E
  • 4πr2E
  • 0.5πr2E
  • πr2E
Electric field lines 
  • can cross each other.
  • can only bisect one another.
  • can only intersect at right angles.
  • should never cross one another.
The density of electric field lines at a specific location in space reveals information about
  • the strength of the field at that location.
  • the strength of the charge at that location.
  • the strength of the potential at that location.
  • All of the above
From the schematic electric field lines, we can infer that
591191_a9db37aed20a46c18e5aef178d7d2238.png
  • the left charge is higher in magnitude than the right one
  • the left charge is lower in magnitude than the right one
  • the left charge is equal in magnitude to the right one
  • None of these
From the schematic electric field lines, we can infer that the
591193_6b860f5932df4e23864857e47cb56e50.png
  • positive charge is higher in magnitude than the negative one
  • positive charge is lower in magnitude than the negative one
  • positive charge is equal in magnitude to the negative one
  • None of these
In the given distribution of electric field lines, it can be ascertained that
591332.JPG
  • Ex<Ey
  • Ex=Ey
  • Ex>Ey
  • Ex.Ey=1
Consider an area element dS at a distance r from a point P. Let ˆr be the unit vector along the outward normal to dS. If α is the angle between ˆr and dS, the element of the solid angle subtended by the area element at P is defined as
  • dΩ=dS sinαr2
  • dΩ=dS tanαr2
  • dΩ=dS cosαr2
  • dΩ=dS αr2
The SI unit of solid angle is
  • radians
  • steradians
  • degrees
  • All of the above
Two charges q1 and q2 are kept on the x-axis and the variation of electric field strength at different points on the x-axis is described in the adjacent figure graphically. Choose correct statement nature are magnitude of q1 and q2.
696524_2c5d9f98f4b746198ddb7a9d48a29ac5.png
  • q1+ve,q2+ve,|q1|>|q2|
  • q1+ve,q2ve,|q1|>|q2|
  • q1+ve,q2ve,|q1|<|q2|
  • q1ve,q2+ve,|q1|<|q2|
Find the charge on an iron particle of mass 2.24mg, if 0.02 % of the electrons are removed from it.
  • 0.01996C
  • 0.01996C
  • 0.00077C
  • 2.0C
Two charges of 2Q and Q are located at points (a,0) and (4a,0) respectively. What is the electric flux through a sphere of radius 3a centred at the origin?
  • Qϵ0 
  • Qϵ0
  • 2Qϵ0
  • 3Qϵ0
Find the charge on the sphere
  • 1.45μC
  • 1.45mC
  • 1.45C
  • 1.45kC
An electric charge qis placed at the centre of a cube of side a The electric flux through one of its faces is
  • q6ϵ0
  • q6ϵ0a2
  • q6πϵ0a2
  • qϵ0
A charge Q is located at the centre of a sphere of radius R. Calculate the flux going out through the surface of the sphere.
  • Q4πϵ0R2
  • Q4πϵ0R
  • Q4πR2
  • Qϵ0
A rod of length l having charge q uniformly distributed moves towards right with constant speed v. At t=0, it enters in an imaginary cube of edge I/2, sketch variation of electric flux passing through the cube with respect to time.
678425_6f8f9797b7a64169a2ab349a17ba97dc.png
The total solid angle subtended by the sphere is
  • 0.25π
  • 0.5π
  • 4π
  • 2π
  • 1π
Which of the following curves shown cannot possibly represent electrostatic field lines?
In a certain region of space,electric  field is along the z-direction throughout. The magnitude of electric field is however not constant, but increases uniformly along the positive z-direction at the rate of 105NC1m1. The force experienced by the system having a total dipole moment equal to 107C m in the negative z-direction is
  • 102N
  • 102N
  • 104N
  • 104N
An electric dipole consists of charges ±2.0×108C separated by a distance of 2.0×103m.It is placed near a long line charge of linear charge density 4.0×104Cm1 as shown in the figure, such that the negative charge is at a distance of 2.0cm from the line charge. The force acting on the dipole will be
941244_8c07253653754cd5a23b3c7864699339.PNG
  • 7.2N towards the line charge
  • 6.6N away from the line charge
  • 0.6N away from the line charge
  • 0.6N towards the line charge
A molecule of a substance has a permanent electric dipole moment of magnitude 1030cm. A mole of this substance is polarised by applying a strong electrostatic field of magnitude 107Vm1. The direction of field is changed by an angle 60o. The heat released by the substance in aligning its dipole along the new direction of the field is
  • 6J
  • 3J
  • 3J
  • 6J
A field of 100Vm1 is directed at 30o to positive x-axis. Find (VAVB) if OA=2m and OB=4m.
790435_b03d710c83cc41e5a606f7a19ce351ac.png
  • 100(32)V
  • 100(2+3)V
  • 100(23)V
  • 200(2+3)V
The electric field at a point 2cm from an infinite line charge of linear charge density 107 Cm1 is?
  • 4.5×104NC1
  • 9×104NC1
  • 9×102NC1
  • 18×104NC1
Two non-conducting plates A and B of radii 2R and 4R respectively are kept at distances x and 2x from the point charge q. A surface cutout of a non conducting shell C is kept such that its centre coincides with the point charge. Each plate and the spherical surface carries a surface charge density σ. If ϕ1 is flux through surface of (B) due to electric field of (A) and ϕ2 be the flux through (A) due to electric field of (B) then:
828615_e8c7adae3f94412fbcfcaed2b7f5bcf1.png
  • ϕ1=ϕ2
  • ϕ1>ϕ2
  • ϕ1<ϕ2
  • It depend and on x and R
The electric flux emerging through the closed surface S1 shown in figure which intersects the spherical conductor S, due to the presence of a positive charge very near to conductor is:
981380_1d9a336e68294d67b88e28c8dc5389b1.png
  • Positive
  • Negative
  • Zero
  • None of the above
A point charge Q(C) is placed at the origin. Find the electric flux of which  an area 4π m2 on a concentric spherical shell of radius R 
  • QR2ϵ0
  • Qϵ0
  • Q4R2ϵ0
  • none of above
A point charge +Q is placed just outside an imaginary hemispherical surface of radius R as shown in the figure.
Which of the following statements is/are correct?

1011049_e65a0acaa573434485b347dba18b0621.png
  • The electric flux passing through the curved surface of the hemisphere is Q2ε0(112)
  • Total flux through the curved and the flat surface is Qε0
  • The component of the electric field normal to the flat surface is constant over the surface
  • The circumference of the flat surface is an equipotential
Two large metal sheets having surface charge density +σ and σ are kept parallel to each other at a small separation distance d. The electric field at any point in the region between the plates is
  • σϵ0
  • σ2ϵ0
  • 2σϵ0
  • σ4ϵ0
Three infinitely charged sheets are kept parallel to xy plane having charge densities as shown. Then the  value of electric field at P is:
1010582_6f444ffa730343e78a0ef7374aabc012.png
  • 4σ0ˆk
  • 4σ0ˆk
  • 2σ0ˆk
  • 2σ0ˆk
Two infinite uniform sheet of charge  each with surface charge density σ  are located at x = a and x = a. Which of the following  is correct?
  • E = σϵ0i ; For x<a
  • E = 0 ; For a<x<a
  • E = σϵ0i ; For x>a
  • E = 2σϵ0i ; For a<x<a
Consider a triangular surface whose vertices are three points having co-ordinate A ( 2a, 0, 0 ), B(0, a, 0), C(0, 0, a). If there is a uniform electric field E0ˆi+2E0ˆj+3E0ˆk then flux linled to triangular surface ABC is:
  • 7E0a22
  • 3E0a2
  • 11E0a22
  • Zero
A uniformly charged rod of length 4 cm and linear charge density λ=30μC/m is placed as shown in figure. Calculate the x-component of electric field at point P
1084716_850d66f6ab354db6bc9661dd871a23a1.JPG
  • 36×105N/C
  • 9×105N/C
  • 1.8×105N/C
  • 27×105N/C
Two non-conducting spheres of radii R1 and R2 and carrying uniform volume charge densities +ρ and ρ, respectively, are placed such that they partially overlap, as shown in the figure. At all points in the overlapping region,
1011064_73676efb41074d3a96dd2e88c92227bf.png
  • the electrostatic field is zero
  • the electrostatic potential is constant
  • the electrostatic field is constant in magnitude
  • the electrostatic field has different  direction
The flux of the electric field due to charges distributed in a sphere of radius 5 cm is 10 Vm. What will be the electric flux, through a concentric sphere of radius 10 cm ?
  • 20 Vm
  • 30 Vm
  • 5 Vm
  • 10 Vm
Which of the following statement(s) is/are correct?
  • If the electric field due to a point charge varies as r2.5 instead r2, then the Gauss law will still be valid.
  • The Gauss law can be used to calculate the field distribution around an electric dipole.
  • If the electric field between two point charges is zero somewhere, then the sign of the two charges is the same.
  • The work done by the external force in moving a unit positive charge from point A at potential VA to point B at potential VB is (VBVA).
A positively charged thin metal ring of radius R is fixed in the xyplane with its centre at the origin O. A negatively charge particle  P is released from rest from the point (0,0,Z0) where Z0>0. Then the motion of P is
  • Periodic, for all values of Z0 satisfying 0<z0<
  • simple harmonic, for all values of 0<z0R
  • approximately simple harmonic, provided z0R
  • such that P crosses O and continues to move along negative zaxis towards z=
A number of spherical conductors of different radii are changed to same potential. The surface charge density of each conductor is related with its radius as
  • σ1R2
  • σ1R
  • σR
  • None of these
An insulated conductor initially free from charge is charged by repeated contacts with a plate which after each contact is replenished to a charge Q from an electrophorus. If q is the charge on the conductor after the first operation,  The maximum charge which can be given to the conductor in this way is Qq/(Qq).
  • True
  • False
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Class 12 Medical Physics Quiz Questions and Answers