CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 15 - MCQExams.com

Two infinite linear charge are placed parallel at 0.1 m apart. It has density of 5 $$\mu$$ C/m,then the force per unit length of one of linear charges in N/m is;    
  • 2.5
  • 3.25
  • 4.5
  • 7.5
The electric field in a region is given by $$\vec{E}=a\hat{i}+b\hat{j}$$. Here a and b are constants. Find the net flux passing through a square area of side $$l$$ parallel to y-z plane:
  • $$al^{2}$$
  • $$bl^{2}$$
  • Zero
  • $$(a+b)l^{2}$$
A charge Q is placed at the  centre of cube. The electric flux emerging from any one surface of the cube is .
  • $$\dfrac { Q }{ { \varepsilon }_{ 0 } } $$
  • $$\dfrac { Q }{ 2{ \varepsilon }_{ 0 } } $$
  • $$\dfrac { Q }{ 4{ \varepsilon }_{ 0 } } $$
  • $$\dfrac { Q }{ 6{ \varepsilon }_{ 0 } } $$

Identify the wrong statement in the following. Coulomb's law correctly describes the electric force that 
  • Binds the electrons of an atom to its nucleus
  • Binds the protons and neutrons in the nucleus of an atom
  • Binds atoms together to form molecules
  • Binds atoms and molecules together to form solids
A charge $$Q\mu C$$ is placed at the center of a cube, the flux coming out from three face will be (in coulomb) :
  • $$\dfrac { Q }{ 6{ \varepsilon }_{ 0 } } \times { 10 }^{ -6 }$$
  • $$\dfrac { Q }{ 2{ \varepsilon }_{ 0 } } \times { 10 }^{ -6 }$$
  • $$\dfrac { 3Q }{ { \varepsilon }_{ 0 } } \times { 10 }^{ -6 }$$
  • $$\dfrac { Q }{ 24{ \varepsilon }_{ 0 } } \times { 10 }^{ -6 }$$
A point charge  $$q$$  is placed at a point inside a hollow conducting sphere. Which of the following electric force pattern is correct?
A hemispherical surface (half of a spherical surface) of radius  $$R$$  is located in a uniform electric field  $$E$$  that is parallel to the hemisphere. What is the magnitude of the electric flux through the hemisphere surface ?
1542784_23d419138e2f4c4d88c2734640954853.png
  • $$0$$
  • $$4 \pi R ^ { 2 } E / 3$$
  • $$2 \pi R ^ { 2 } E$$
  • $$ \pi R ^ { 2 } E$$

A dipole of dipole moment $$\overline P  = 2\widehat i - 3\widehat j + 4\widehat k$$ is placed at point $$A\left( {2, - 3,1} \right)$$. The electric potential due to this dipole at the point $$B\left( {4, - 1,0} \right)$$ is equal to ( All the parameters specified here are in S.I. units.)
  • $$2 \times {10^9}\;{\text{Volts}}$$
  • $$ - 2 \times {10^9}\;{\text{Volts}}$$
  • $$3 \times {10^9}\;{\text{Volts}}$$
  • $$ - 3 \times {10^9}\;{\text{Volts}}$$
In the given figure flux through surface  $$S _ { 1 }$$  is  $$\phi _ { 1 }$$   $$\&$$  through  $$S  _ { 2 }$$  is  $$\phi _ { 2 }.$$  Which is correct ?
1542916_8c403a9a8c3c4f1ab30c265c92f8595f.png
  • $$\phi _ { 1 } = \phi _ { 2 }$$
  • $$\phi _ { 1 } > \phi _ { 2 }$$
  • $$\phi _ { 1 } < \phi _ { 2 }$$
  • None of these
If $$+ q $$charge is placed inside any spherical surface then total flux coming out from whole surface will be -
  •  $$q\times\epsilon_0$$
  • $$\dfrac{q}{\epsilon_0}$$
  • $$\dfrac{\epsilon_0}{q}$$
  • $$\dfrac{q^2}{\epsilon_0}$$
A charge q is placed at one corner of a cube. The electrons flux through any of the three faces adjacent to the charge is zero. The flux through any one of the other three is
  • $$q/3{ \epsilon }_{ 0 }$$
  • $$q/6{ \epsilon}_{ 0 }$$
  • $$q/12{ \epsilon }_{ 0 }$$
  • $$q/24{ \epsilon}_{ 0 }$$
The surface density of charge on a very large flat metal plate is $$2.25 \times 10^{-9} coul/m^2$$. The intensity of electric field at a point at a distance 20 cm from the middle part of plate is 
  • $$90 \pi N/C$$
  • $$100 \pi N/C$$
  • $$45 \pi N/C$$
  • $$81 \pi N/C$$
A long cylindrical conductor, of radius  $$5\mathrm { mm }$$  and placed in a medium of permittivity  $$55.55\mathrm { pF } / \mathrm { m } ,$$  has surface charge density of  $$2\mu \mathrm { C } / \mathrm { m } ^ { 2 } .$$  The magnitude of the electric intensity at a point  $$2\mathrm { m }$$  from its axis is nearly
  • $$9 \mathrm { N } / \mathrm { C }$$
  • $$90 \mathrm { N } / \mathrm { C }$$
  • $$1.111 \times 10 ^ { 2 } \mathrm { N } / \mathrm { C }$$
  • $$1.111 \times 10 ^ { -2 } \mathrm { N } / \mathrm { C }$$
The electric flux $$ \phi  $$ through a hemisphere surface of radius R, placed in a uniform electric field of intensity E parallel to the axis of its circular plane is:
  • $$ 2 \pi RE $$
  • $$ 2 \pi R^2 E $$
  • $$ \pi R^2 E $$
  • $$ \pi R^3 E $$
When a $$10\mu C$$ charge is enclosed by a closed surface, the flux passing through the surface is $$\phi .$$ Now another $$ - 5\mu C$$ charge is placed inside the same closed surface, then the flux passing through the surface is__________
  • $$2\phi $$
  • $$\phi /2$$
  • $$\phi $$
  • Zero
Given a uniform electric field $$E=5\times 10^3\hat{i} \ N/C$$, find the flux of this field through a square of $$10\ cm$$ on a side whose plane is parallel to the $$y-z$$ plane. What would be the flux through the square if the plane makes $$30^\circ$$ angle with the x-axis.
  • $$23.3N/Cm^2$$
  • $$25N/Cm^2$$
  • $$33.3N/Cm^2$$
  • $$43.3N/Cm^2$$
 A positive charge $$q$$ is enclosed by a Gaussian spherical surface of radius '$$a$$' . If its radius is increased to $$4a$$ then the net outwards flux will
  • Become four time
  • Become two times
  • Become sixten times
  • Remain same
A point charge A of charge $$+4 \mu C $$ and another point charge B of charge $$ -1 \mu C $$ are placed in air at a distance 1 meter apart . then the distance of the point on the line joining the charges and from the charge B , where the resultant electric field is zero , is ( in meter)
  • $$1.5$$
  • $$0.5$$
  • $$1$$
  • $$2$$
A wire of linear charge density  $$\lambda$$  passes through a cuboid of length  $$l ,$$  breadth  $$b$$  and height  $$h$$  in such a manner that flux through the cuboid is maximum. The position of wire is now changed, so that the flux through the cuboid is minimum.  $$l > b > h ,$$  then the ratio of maximum flux to minimum flux will be
  • $$\dfrac { \sqrt { 1 ^ { 2 } + b ^ { 2 } + h ^ { 2 } } } { h }$$
  • $$\dfrac { \sqrt { l ^ { 2 } + b ^ { 2 } } } { h }$$
  • $$\dfrac { h } { \sqrt { l ^ { 2 } + b ^ { 2 } } }$$
  • $$\dfrac { l } { \sqrt { l ^ { 2 } + b ^ { 2 } + h ^ { 2 } } }$$
Two charges $$ +3.2 \times 10^{-19} and -3.2 \times 10^{-19} C$$  placed $$ 2.4 \mathring { A }  $$ apart form an electric dipole.It is placed in a uniform electric field of intensity $$ 4 \times 10^5 V/m $$. The electric dipole moment is
  • $$ 15.36 \times 10^{-29} Cm $$
  • $$ 15.36 \times 10^{-19} Cm $$
  • $$ 7.68 \times 10^{-29} Cm $$
  • $$ 7.68 \times 10^{-19} Cm $$
Two identical metal spheres possess $$+ 60 C$$ and $$- 20 C$$ of charges. They are brought in contact and then separated by $$10 cm$$. The force between them 
  • $$36\times10^{13}N$$
  • $$36\times10^{14}N$$
  • $$36\times 10^{12}N$$
  • $$3.6\times 10^{12}N$$
A current $$I$$ flows through a cylindrical rod of uniform cross-section area $$A$$ and resistivity $$\rho$$. The electric flux through the shaded cross-section of rod as shown in figure is :
1546553_4134cbf4bf5543c88cd718b7a7ac4abf.png
  • $$2 pI$$
  • $$pI$$
  • $$\dfrac { pI }{ A } $$
  • $$\dfrac { pA }{ I } $$
The  electric flux through the  surface 
1605888_a515aef0e0e1451b85295f9477d0fcc3.png
  • in Fig. (iv) is the largest
  • in Fig. (iii) is the least
  • in Fig. (ii) is same as Fig. (iii) but is smaller then Fig (iv)
  • is the same for all the figures
In a region the electric potential is given by $$V = 2x + 2y - 3z$$ obtain the expression for electric field.
  • $$-2\hat {i} - 2\hat {j} + 3\hat {k}$$
  • $$3\hat {i} + 4\hat {j} - 2\hat {k}$$
  • $$2\hat {i} - 2\hat {j} - 3\hat {k}$$
  • None of these
The force of intraction of two dipoles, if the two dipole moments are parallel to each other and placed at a distance $$x$$ apart.
1704370_4fef066af5d041d7ae9dc2e6f3ac4d85.png
  • $$\dfrac {3p_{1}p_{2}}{4\pi \epsilon_{0}x^{4}}$$
  • $$\dfrac {p_{1}p_{2}}{4\pi \epsilon_{0}x^{4}}$$
  • $$\dfrac {p_{1}p_{2}}{4\pi \epsilon_{0}x^{4}}$$
  • $$\dfrac {p_{1}p_{2}}{3\pi \epsilon_{0}x^{4}}$$
Mark correct option:
Electrostatic experiment is
  • Affected on the humid day
  • Not affected on humid day
  • Independent of medium
  • None of the above
A long thread carrying a uniform charge $$\lambda$$ per unit length has the configuration shown in the figure. An element of charge $$q$$ is cut from the thread. The cutting portion is shown as small gap $$(AB)$$. The electric field at the point $$O$$ is
1704042_00bdb1e87e1f468d8acc71f98bbc3501.png
  • Zero
  • $$\dfrac {q}{4\pi \varepsilon_{0}R^{2}}$$
  • $$\dfrac {q}{2\pi \varepsilon_{0}R^{2}}$$
  • None of these
The electric lines of force are represented by the equation $$x^2+y^2=1$$. A unit positive charge initially at rest at point $$(1,0)$$ will move.
  • along the circular line of force
  • at right angles to circular line of force
  • along equidistant parallel lines of force
  • at right angles to equidistant parallel lines of force
A charged particle $$q$$ is placed at the centre $$O$$ of a cube of length $$L(A\ B\ C\ D\ E\ F\ G\ H)$$. Another same charge $$q$$ is placed at a distance $$L$$ from $$O$$. Then the electric flux through $$ABCD$$.
1592051_37d59cae2a744c72aaa289ff377fb2d7.png
  • $$q/6\pi \epsilon_{0}L$$
  • Zero
  • $$q/2\pi \epsilon_{0}L$$
  • $$q/3\pi \epsilon_{0}L$$
In a region, an electric field $$\vec {E} = E_{0}\hat {i}$$ is present. The potential of points $$A(a, 0, 0), B(0, b, 0), C(0, 0, c)$$ and $$D(-a, 0, 0)$$ and $$V_{A}, V_{B}, V_{C}$$ and $$V_{D}$$ respectively, then
  • $$V_{A} = V_{B} = V_{C} = V_{D}$$
  • $$V_{B} = V_{C}$$
  • $$V_{D} < V_{B} < V_{A}$$
  • None of these
Electric field in a plane varies like $$(2x\hat {i} + 2y\hat {j})N/C$$. If potential at infinity is taken as zero, potential at $$x = 2m, y = 2m$$ is
  • $$8\ V$$
  • $$-8\ V$$
  • Zero
  • Infinity
Six negative equal charges are placed at the vertices of a regular hexagon. $$6q$$ charge is placed at the centre of the hexagon. The electric dipole moment of the system is
1704373_ba4e84f5a6fd4ddf8fee52fe9a15626b.png
  • Zero
  • $$6qa$$
  • $$3qa$$
  • None of the above
Electric dipole moment of combination shown in the figure, is
1704372_97273cb55953432b8e1c140cf0642690.PNG
  • $$qa + qa\sqrt {2} + qa$$
  • $$2\sqrt {2}qa$$
  • $$\sqrt {2}qa$$
  • $$(\sqrt {2} + 1)qa$$
Each of the following figures shows electric field vectors at two points A and Bin an electric field. In which figure or figures can the illustrated field be created by a single point charge?
Electric charges $$ q , q , - 2q $$ are placed at the corners of an equilateral triangle ABC of sides l . The magnitude of electric dipole moment of the system is 
  • $$ql$$
  • $$ 2 ql $$
  • $$ \sqrt{3} ql $$
  • $$ 4 ql $$
0:0:1


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