CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 3 - MCQExams.com

The charge on an electron was calculated by:
  • Faraday
  • J.J Thompson
  • Millikan
  • Einstein
Torque acting on an electric dipole in a uniform electric field is maximum if the angle between $$\overrightarrow{P}$$; and $$\overrightarrow{E}$$ is:
  • $$180^o$$
  • $$0^o$$
  • $$90^o$$
  • $$45^o$$
Electric lines of force about a positive point charge are:
  • radially outwards
  • circular clockwise
  • radially inwards
  • parallel straight lines
  • circular anti-clockwise
The charge is negative, then the electric lines of forces are 
  • straight lines converging towards the charge
  • concentric circle with charge at the centre
  • Straight lines radiating away from the charge
  • Non of these
The unit of electric dipole moment is:
  • newton
  • coulomb
  • farad
  • debye
Coulomb's law relates two charges and distance between them describing the electric force as being:
  • proportional to the sum of the charges
  • inversely proportional to the distance between charges
  • proportional to the product of the charges and inversely proportional to the distance
  • proportional to the product of the charges and inversely proportional to the square of the distance
If $$\oint _{ s }^{  }{ \overrightarrow { E } .\overrightarrow { d } s } =0$$ over surface, then
  • the electric field inside the surface and on it is zero
  • the electric field inside the surface is necessarily uniform
  • all charges must necessarily be outside the surface
  • all of these
Electric lines of force about negative point charge are
  • Circular, anticlockwise
  • Circular, clockwise
  • Radial, outward
  • Radial, inward
An electric dipole consists of two opposite charges each of magnitude $$1.6 \times 10^-19$$ coulomb at separation $$1\ Armstrong $$. The diploe moment is:
  • $$1.6 \times 10^{-19} c-m$$
  • $$ 1.6 \times 10^{-29} c-m$$
  • $$ 3.2 \times 10^{-29} c-m $$
  • $$3.2 \times 10^{-19} C-m$$
When a glass rod is rubbed with a piece of silk cloth the rod ?
  • And the cloth both acquire positive charge.
  • Becomes positively charged while the cloth has a negative charge.
  • And the cloth both acquire negative charge.
  • Becomes negatively charged while the cloth has a positive charge.
A dipole is placed in a non-uniform field. It will
  • Experience net Force
  • Experience net Moment
  • Experiences both Force and Moment
  • None of the above

A large flat metal surface has uniform charge density $$+\sigma $$. An electron of mass $$m$$ and charge $$e$$ leaves the surface at point A with speed $$v$$, and return to it at point B. The maximum value of AB is:
  • $$\dfrac{vm\epsilon _{0}}{\sigma e}$$
  • $$\dfrac{v^{2}m\epsilon _{0}}{\sigma e}$$
  • $$\dfrac{v^{2}e}{\epsilon _{0}\sigma m}$$
  • $$\dfrac{v^{2}\sigma e}{\epsilon _{0}m}$$

A cube is arranged such that its length, breadth, height are along X,Y and Z directions. One of its corners is situated at the origin. Length of each side of the cube is $$25\ cm$$ . The components of electric field are $$E_{x}=400\sqrt{2}\ N/C,\ E_{y}=0$$ and $$E_{Z}=0$$ respectively. The flux coming out of the cube at one end, whose plane is perpendicular to X axis, will be:
  • $$25\sqrt{2}\ Nm^{2}/C$$
  • $$5\sqrt{2}\ Nm^{2}/C$$
  • $$250\sqrt{2}\ Nm^{2}/C$$
  • $$25\ Nm^{2}/C$$
An electron moves with a velocity $$\vec{v}$$ in an electric field $$\vec{E}$$. If the angle between $$\vec{v}$$ and $$\vec{E}$$ is neither 0 nor $$\pi $$, then the path followed by the electron is a(an):
  • straight line
  • circle
  • ellipse
  • parabola

The electric field in a region of space is given by $$\vec{E}=(\hat{5i}+\hat{2j}  )Nc^{-1}$$ . The electric flux due to this field through an area $$2m^{2}$$ lying in the Y-Z plane in S.I. units is
  • $$10$$
  • $$20$$
  • $$10\sqrt{2}$$
  • $$2\sqrt{29}$$

Drawings I and II show two samples of electric field lines. Then :


6227_6970328d2e4842fbb45a1724f4252598.png
  • the electric fields in both I and II are produced by negative charge located somewhere on the left and positive charges located somewhere on the right
  • in both I and II the electric field is the same everywhere
  • in both cases the field becomes stronger on moving from left to right
  • the electric field in I is the same everywhere, but in II the electric field becomes stronger on moving from left to right
Two thin infinite parallel sheets have uniform surface densities of charge $$+\sigma$$ and $$-\sigma$$. Electric field in the space between the two sheets is:
  • $$\sigma/\epsilon _{0}$$
  • $$\sigma/2\epsilon _{0}$$
  • $$2\sigma/\epsilon _{0}$$
  • zero

A cylinder of radius R and length L is placed in the uniform electric field E parallel to the cylinder axis. The total flux from the curved surface of the cylinder is given by :
  • $$2\pi R^{2}E$$
  • $$\dfrac{\pi R^{2}}{E}$$
  • $$\dfrac{\pi R^{2}-\pi R}{E}$$
  • $$zero$$
A hemisphere of radius r is placed in a uniform electric field of strength E. The electric flux through the hemisphere is :
142433_bce57a5901da4e188efdbed53fb70f8b.png
  • $$2E\pi r^{2}$$
  • $$-E\pi r^{2}$$
  • $$-2E\pi r^{2}$$
  • zero

A particle that carries a charge $$-q$$ is placed at rest in uniform electric field $$10\ N/C$$. It experiences a force and moves in a certain time t, it is observed to acquire a velocity $$10\vec{i}-10\vec{j}$$ m/s. The given electric field intersects a surface of area $$A$$ $$m^{2}$$in the X -Z plane. Electric flux through surface is:
  • $$5\sqrt{2}A\ Nm^{2}/C$$
  • $$5A\ Nm^{2}/C$$
  • $$\sqrt{2}A\ Nm^{2}/C$$
  • $$2\sqrt{5}A\ Nm^{2}/C$$

The electric dipole moment is:
  • $$15.36 \times 10^{-29}C-m$$
  • $$15.36 \times 10^{-19}C-m$$
  • $$7.68 \times 10^{-29}C-m$$
  • $$7.68 \times 10^{-19}C-m$$

Two charges when kept at a distance of $$1m$$ apart in vacuum have some force of repulsion. If the force of repulsion between these two charges be same, when placed in an oil of dielectric constant $$4$$, the distance of separation is :
  • $$0.25m$$
  • $$0.4m$$
  • $$0.5m$$
  • $$0.6m$$

An electric dipole is placed in a non uniform electric field increasing along the $$+ve$$ direction of X - axis. The dipole moves along $$\underline{\hspace{0.5in}}$$ and rotates $$\underline{\hspace{0.5in}}$$


7109.JPG
  • $$+ ve$$ direction of X - axis, clockwise
  • $$- ve$$ direction of X - axis, clockwise
  • $$+ ve$$ direction of X - axis, anti clockwise
  • $$- ve$$ direction of X - axis, anti clockwise
A small electric dipole is placed at origin with its dipole moment directed along positive x -axis. The direction of electric field at point $$\left ( 2,2\sqrt{2},0 \right )$$is:
  • along z-axis
  • along y-axis
  • along negative y-axis
  • along negative z-axis

Two electric dipoles each of dipole moment $$p=6.2\times 10^{^{-30}}C-m$$ are placed with their axis along the same line and their centres at a distance d $$=10^{-8}cm$$. The force of attraction between dipoles is:
  • $$2.1\times 10^{-16}N$$
  • $$2.1\times 10^{-12}N$$
  • $$2.1\times 10^{-10}N$$
  • $$2.1\times 10^{-8}N$$
A metallic shell has a point charge q kept inside its cavity. Which one of the following diagrams correctly represents the electric lines of forces?
A dipole of moment p is placed in uniform electric field E then torque acting on it is given by : -
  • $$\vec\tau=\vec P\cdot \vec E$$
  • $$\vec\tau=\vec P\times \vec E$$
  • $$\vec\tau=\vec P+ \vec E$$
  • $$\vec\tau=\vec P-\vec E$$
A hollow cylinder has a charge q coulomb distributed uniformly within it. If $$\phi$$ is the electric flux in units of voltmeter associated with the curved surface $$B$$, the flux linked with the plane surface $$A$$ in units of voltmeter will be

70032_98dc7a38c4b448159789c6b7bb9d9e1d.png
  • $$\dfrac{q}{\epsilon _{0}}-\phi $$
  • $$\dfrac{1}{2}\left ( \frac{q}{\epsilon _{0}}-\phi \right )$$
  • $$\dfrac{q}{2\epsilon _{0}}$$
  • $$\dfrac{\phi }{3}$$

The dipolemoment of the given system is:


10211_7241f921e95e4443ae9f99cd6e32ad91.png
  • $$\sqrt{3}$$ $$ql$$  along perpendicular bisector of $$q - q$$ line
  • $$2\ ql$$ along perpendicular bisector of $$q - q$$ line
  • $$ql$$ $$\sqrt{2}$$ along perpendicular bisector of $$q - q$$ line
  • $$0$$
A square surface of side L metres is in the plane of the paper. A uniform electric field $$\underset{E}{\rightarrow}$$(volt/m),also in the plane of the paper, is limited only to the lower half of the square surface, (see figure).The electric flux in SI units associated with the surface is:-
70968_6edf56ad80d34172a5cd94047ca7e1ef.png
  • $$EL^{2}$$/$$\left (2\varepsilon_{0} \right )$$
  • $$EL^{2}$$/2
  • Zero
  • $$EL^{2}$$
Fill in the blank :
The mutual electrostatic force between two point charges $$q_{1}$$ and $$q_{2}$$ is _____ to the product of charges $$q_1$$ and $$q_{2}$$.
  • inversely proportional
  • directly proportional
  • square proportional
  • inversely square proportional
The force of interaction between any two point charges is proportional to :
  • $$q_{1}q_{2}$$
  • $$r^{2}$$
  • $$r^{-2}$$
  • $$q_1/q_2$$
The formation of a dipole is due to two equal and unlike point charges placed at a :
  • short distance
  • long distance
  • both (a) and (b)
  • None of these
The ratio of electric force between two electrons to that between two protons separated by the same distance in air is :
  • $$10^{0}$$
  • $$10^{6}$$
  • $$10^{4}$$
  • None of the above
Electric lines of force are:
  • Exist everywhere
  • Exist only in the immediate vicinity of electric charges
  • Exist only when both positive and negative charges are near one another
  • Are imaginary
A charge $$q$$ is enclosed in a cube. What is the electric flux associated with one of the faces of cube ?
  • $$q/ \varepsilon _{0}$$
  • $$ \varepsilon /q$$
  • $$6q/ \varepsilon _{0}$$
  • $$q/ 6\varepsilon _{0}$$
The value of $$\dfrac {1}{4\pi \epsilon_0}$$ is _________  $$m^{-3} \ kg^{-1} \ s^4 \ A^2$$
  • $$8.854\times 10^{-12}$$
  • $$4\pi \times 10^{-7}$$
  • $$6.25\times 10^{12}$$
  • $$9\times 10^9$$
Two charges are placed a certain distance apart in air. If a glass slab is introduced between them, the force between them will:
  • increase
  • decrease
  • remains the same
  • be zero
Electric flux at a point in an electric field is
  • positive
  • negative
  • zero
  • None of these
SI unit of permittivity is:
  • $$F m^{-1}$$
  • $$N m^2C^{-2}$$
  • $$N m^{-2}C^{-1}$$
  • $$Am^{-1}$$
Choose the correct statement from the following:
  • Electric lines of force never cross each other
  • Electric lines of force end at a positive charge
  • The electric field lines inside a conductor are infinity
  • Lines of electric field point towards regions of lower potential.
A charge Q is placed at the corner of a cube. The electric flux through all the faces of the cube is
  • $$Q/ \varepsilon _{0}$$
  • $$Q/6 \varepsilon _{0}$$
  • $$Q/8 \varepsilon _{0}$$
  • $$Q/ 3\varepsilon _{0}$$
A point charge $$+10\mu C$$ is at a distance $$5\ cm$$ directly above the centre of a square of side $$10\ cm$$, as shown in the figure. What is the magnitude of the electric flux through the square?
112106.jpg
  • $$1.2\times 10^5 Nm^2/C$$
  • $$1.9\times 10^5 Nm^2/C$$
  • $$3.2\times 10^5 Nm^2/C$$
  • $$4.2\times 10^5 Nm^2/C$$
A positively charged body has deficiency of ______.
  • Electrons
  • Protons
  • Neutrons
  • None of the above
$$4$$ charges are placed each at a distance 'a' from origin. The dipole moment of configuration is :
120581_4a47ee3dea8e47b898262e987c608ce2.png
  • $$2qa\widehat{j}$$
  • $$3qa\widehat{j}$$
  • $$2aq[\widehat{i}+\widehat{j}]$$
  • none
$$96,000\  C$$ deposit on 1 gm atom of mono-valent silver. The positive charge on a silver ion is equal in magnitude to that of an electron and Avogadro's number is $$6 \times { 10 }^{ 23 }$$. Electronic charge will be:
  • $$-1.6\times { 10 }^{ -19 }\ C$$
  • $$5.76\times { 10 }^{ 28 }\ C$$
  • $$-6.2\times { 10 }^{ 18 }\ C$$
  • $$- 160\ C$$
In Coulomb's law, the constant of proportionality K has the units
  • $$N$$
  • $$Nm^2$$
  • $$NC^2/m^2$$
  • $$Nm^2/C^2$$
The electrostatic force between two point charges $$q_{1}$$ and $$q_{2}$$ at separation 'r' is given by $$F = \dfrac {Kq_{1}q_{2}}{r^{2}}$$. The constant K:
  • Depends on the system of units only
  • Depends on the medium between the charges only
  • Depends on both the system of units and the medium between the charges
  • Is independent of both the system of units and the medium between the charges
The dipole moment of a system of charge $$+q$$ distributed uniformly on an arc of radius $$R$$ subtending an angle $$\pi{/2}$$ at its centre where another charge $$-q$$ is placed is :
  • $$\displaystyle \frac{2\sqrt{2}qR}{\pi}$$
  • $$\displaystyle \frac{\sqrt{2}qR}{\pi}$$
  • $$\displaystyle \frac{qR}{\pi}$$
  • $$\displaystyle \frac{2qR}{\pi}$$
Select the correct statement : (Only force on a particle is due to electric field)
  • A charged particle always moves along the electric line of force
  • A charged particle may move along the line of force
  • A charge particle never along the line of force
  • A charged particle moves along the line of force only if released from rest
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