CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 10 - MCQExams.com

Which charge is not possible
  • $$4.8\times 10^{-16}C$$
  • $$8.0\times 10^{-17}C$$
  • $$11.2\times 10^{-17}C$$
  • $$12.0\times 10^{-20}C$$
A point charge $$Q$$ is placed at the centre of a circular wire of radius $$R$$ having charge $$q$$. The force of electrostatic interaction between point charge and the wire is:
1311019_b26f7a3bf6644b7a8d61aba941a10efd.png
  • $$\cfrac{qQ}{4\pi\varepsilon_oR^2}$$
  • $$\cfrac{q}{4\pi\varepsilon_oR}$$
  • Zero
  • none of these
The tangent at any point of  field line gives the direction of
  • Electric field at that point
  • Electric force on positive charge at that point
  • Both $$(1)$$ & $$(2)$$
  • Rotation of charge
Under the influence of the Coulomb field of charge $$+Q$$, a charge $$-q$$ is moving around it in an elliptical orbit. Find out the correct statements.
  • The angular momentum of the charge $$-q$$ is constant.
  • The linear momentum of the charge $$-q$$ is constant.
  • The angular velocity of the charge $$-q$$ is constant.
  • The linear speed of the charge $$-q$$ is constant.
Five positively charged particles are kept fixed on the x-axis at point $$(1\, m ,0) (2 \,m, 0), (3 \,m  0) (4\, m 0)$$ and $$(5 \, m 0)$$. The magnitude of charges kept at these points are $$1\, \mu C, 4\, \mu C, 9\, \mu C, 16\, \mu C,$$ and $$25 \, \mu C$$ respectively. The magnitude of net electric force on charge $$1 \,\mu C$$ placed at origin is  
  • $$4.5 \times 10^3 N$$
  • $$4.5 \times 10^2 N$$
  • $$4.5 \times 10^{-2} N$$
  • $$4.5 \times 10^{-4} N$$
A charge Q is placed a the corner of a cube. The electric flux through all the six faces of the tube is 
  • $$\frac{Q}{{{\varepsilon _0}}}$$
  • $$\frac{Q}{{{6\varepsilon _0}}}$$
  • $$\frac{Q}{{{8\varepsilon _0}}}$$
  • $$\frac{Q}{{{3\varepsilon _0}}}$$
The SI unit of electric flux is 
  • Voltmetre
  • Joule/Metre
  • Newton
  • None
A hollow cylinder has a charge q coulomb within it. If f the electric flux in units of volmeter associated with the curved surface B , the flx linked with the plane surface A in units of V-m will be :

1340015_ed82ace225f84713846ee366cd22759d.png
  • $$\dfrac { q }{ 2{ \varepsilon }_{ 0 } } $$
  • $$\dfrac { \Phi }{ 3 } $$
  • $$\dfrac {q}{\varepsilon _0}$$
  • $$\dfrac {4q}{\varepsilon_0}$$
In the hydrogen atom the electron moves around the proton with a speed of $$2.0 \times 10 ^ { 6 } \mathrm { ms } ^ { - 1 }$$ in a circular orbit of radius $$5.0 \times 10 ^ { - 11 }$$ What is the equivalent dipole moment ?
  • $$2 \times 10 ^ { - 24 } \mathrm { Am } ^ { 2 }$$
  • $$4 \times 10 ^ { - 24 } \mathrm { Am } ^ { 2 }$$
  • $$8 \times 10 ^ { - 24 } \mathrm { Am } ^ { 2 }$$
  • $$16 \times 10 ^ { - 24 } \mathrm { Am } ^ { 2 }$$
A and B are two points on the axis and the perpendicular bisector respectively of an electric dipole. A and B are far away from the dipole and at equal distances from its centre. The fields at A and B i.e. $$\overrightarrow { { E }_{ A } } \quad and\overrightarrow { { E }_{ B } } $$ are respectively such that
  • $$\overrightarrow { { E }_{ A } } =\overrightarrow { { E }_{ B } } $$
  • $$\overrightarrow { { E }_{ A } } =2\overrightarrow { { E }_{ B } } $$
  • $$\overrightarrow { { E }_{ A } } =-2\overrightarrow { { E }_{ B } } $$
  • $$\overrightarrow { { E }_{ A } } =\frac { 1 }{ 2 } \overrightarrow { { E }_{ B } } $$
Figure shows two equipotential surface $$V_1$$ and $$V_2$$ . The component of electric field in $$x$$ and $$y$$ direction will be


1392881_bb66f16e63ca4c58b53bd0fcc4a0357e.png
  • $$E _ { x }i$$ and $$E _ { x } j$$
  • $$-E _ { x }i$$ and $$E _ { x } j$$
  • $$E _ { x }i$$ and $$-E _ { x } j$$
  • $$-E _ { x }i$$ and $$-E _ { x } j$$
An electric field $$ \xrightarrow [ E ]{  } =\left( 25\hat { i } +30\hat { j }  \right) NC^{-1} $$ exists in a region of space. If the potential at the origin is taken to be zero then potential at X = 2m,y = 2 m is 
  • - 110 V
  • - 140 V
  • - 120 V
  • - 130 V
When a test charge is brought in from infinity along the perpendicular bisector of an electric dipole ,the work done is 
  • positive
  • Zero
  • Negative
  • None of theses
An electric charge produces an electric intensity of $$500 N/C$$ at a point in air. If the air is replaced by a medium of dielectric constant $$2.5$$, then the intensity of the electric field due to the same charge at the same point will be:
  • $$100N/C$$
  • $$150N/C$$
  • $$200N/C$$
  • $$300N/C$$

The magnetic induction field at the centre C of
the wire which is in the shape as shown in figure carrying current $$'i'$$ is
  • $$\cfrac {\mu_o i}{4 \pi r}(1 + \pi) $$
  • $$\cfrac {\mu_o i}{2 \pi r}(1 + \pi) $$
  • $$\cfrac {\mu_o i}{\pi r}(1 + \pi) $$
  • $$\cfrac {\mu_o i}{r}(1 + \pi) $$
The force of attraction between two charges $$8\mu C$$ and $$0.2 \,N$$. Find the distance of separation.
  • $$412$$ meter
  • $$1.2$$ meter
  • $$120$$ meter
  • $$0.12$$ meter
Determine the electric dipole moment of the system of three charges,placed on the vertices of an equilateral triangle ,as shown in the figure:
1333326_b13730933efa41b68c02d31f0991ca5a.png
  • $$(ql)\dfrac{\hat{i}+\hat{j}}{\sqrt{2}}$$
  • $$\sqrt{3}ql\dfrac{\hat{j}-\hat{i}}{\sqrt{2}}$$
  • $$-\sqrt{3}ql\hat{j}$$
  • $$2ql\hat{j}$$
Which potential graph describes the electric field shown ? 
1339188_f8ada76d485642d2841e3bb49eb50af5.png
The electric flux over the surface of a sphere if it is charged with $$10 \mu C$$ is 
  • $$36\pi \times { 10 }^{ 4 }{ \quad Nm }^{ 2 }/{ C }$$
  • $$36\pi \times { 10 }^{ -4 }{ \quad Nm }^{ 2 }/{ C }$$
  • $$36\pi \times { 10 }^{ 6 }{ \quad Nm }^{ 2 }/{ C }$$
  • $$36\pi \times { 10 }^{ -6 }{ \quad Nm }^{ 2 }/{ C }$$
A charge is placed at the edge of a cube of each side $$'a'.$$ Calculate the electric flux through each face of the cube$$.$$
  • $$ \frac{Q}{{4{e_0}}}$$
  • $$ \frac{Q}{{24{e_0}}}$$
  • $$ \frac{Q}{{2{e_0}}}$$
  • $$ \frac{Q}{{15{e_0}}}$$
Force of attraction between two point charges $$Q$$ and $$-Q$$ separated by $$d$$ meter is $$F_e$$. When these charges are placed two identical sphere of radius $$R=0.3\ d$$ whose centries are $$d$$ meter apart the force of attraction between them is 
  • Greater than $$F_{e}$$
  • Equal to $$F_{e}$$
  • Less than $$F_{e}$$
  • None of these
A system of charge as shown in figure.  The magnitude net electric dipole moment of the system of charges will be 
1416399_2c0eb1ff1be74e0b97fd5eb22d97584f.PNG
  • $$2 ql$$
  • $$4 ql$$
  • $$3 ql$$
  • zero
An electric dipole is situated in an electric field of uniform intensity E whose dipole moment is p and moment of inertia is I. if the dipole is displaced then the angular frequency of its oscillation is
  • $$ ( \dfrac {pE}{I} )^{1/2} $$
  • $$ ( \dfrac {pE}{I} )^{3/2} $$
  • $$ ( \dfrac {I}{pE} )^{1/2} $$
  • $$ ( \dfrac {p}{IE} )^{1/2} $$
An electric dipole of moment P is placed along the lines of force of electric field E and is in equilibrium. the work done in deflecting it through an angle of $$ 180^0 $$ is equal to-
  • $$PE$$
  • $$+2PE$$
  • $$-2PE$$
  • $$ZERO$$
Which of the following is not a unit of charge ?
  • coulomb
  • ampere-second
  • microcoulomb
  • ampere/second
The field potential inside a charged ball of radius R and centre at o depends only on distance from its center as $$ V(r) = \alpha r^2 + \beta $$ when $$ \alpha , \beta $$ are +ve constant. now choose correct options
  • electric field inside the ball $$ E_r = -2 \alpha r $$
  • electric flux passing through an imaginary sphere of radius r centre at O will be $$ - 2 \pi \alpha r^4 $$
  • volume charge density p(r) inside ball is $$ -6 \varepsilon_0 \alpha $$
  • electric energy of charged ball will be $$ \frac {48}{5} \pi \varepsilon_0 \alpha^2 R^5 $$
A problem of practical interest is to make a beam of electrons turn at $$90^{\circ}$$ corner. This can be done with the parallel plates shown in figure. An electron with kinetic energy $$8.0\times 10^{-17} J$$ enters through a small hole in the bottom plate. The strength of electric field that is needed if the electron is to emerge from an exit hole $$1.0\ cm$$ away from the entrance hole, traveling at right angles to its original direction is _______ $$\times 10^{5} N/C$$.
1374849_1fbd5cd8403d4feb81de5a5cc15442f2.jpg
  • $$3$$
  • $$1$$
  • $$6$$
  • $$2.5$$

A soap bubble is given a negative charge, then its radius  
  • Decreasing
  • Increasing
  • Remains unchanged
  • Nothing can be predicated as information is insufficient
For the following electric field lines electric field is 
1448122_6d53877f363b4f69ad0cbe8b8501d526.JPG
  • Non uniform
  • uniform
  • Both uniform & non uniform
  • can't be said
An electric field exists in the space between two charged metal plates.
which graph shows the variation of electric field strenth E with distance d from X along the line XY ?
1404294_5b548e744a6b47f4950d03e5e46d9e13.PNG
(i) Obtain the expression for the torque $$ \overrightarrow r $$ experienced by an electric dipole of dipole moment $$ \overrightarrow p $$ in a uniform electric field, $$ \overrightarrow E $$ (ii) what will happen if the field were not uniform? state the condition under which the dipole is in
  • stable equilibrium
  • unstable equilibrium
  • electric dipole
  • magnetic dipole
In the given figure, electric lines of force diagram is shown. Then:
1432768_7008014b6a994b6ea6a49c65cde1d820.png
  • $${E}_{A}<{E}_{B}$$
  • $${E}_{A}>{E}_{B}>{E}_{C}$$
  • $${E}_{C}>{E}_{B}$$
  • $${E}_{A}={E}_{B}={E}_{C}$$
The flux through the hemispherical surface in the figure shown below is
1389961_548a74d09ca3437ea577a82d7114f3de.PNG
  • $$\pi R^2E$$
  • $$2\pi R^2E$$
  • $$\pi RE$$
  • Zero
There are three concentric thin sphere of radius a, b, c ( a > b > c ) . the total surface charges densities on their surfaces are $$ \sigma , - \sigma , \ sigma $$ respectively. the magnitude of electric field at r ( distance from centre ) such that a > r > b is :
  • 0
  • $$ \dfrac { \sigma }{ \varepsilon_0 r^2 } (b^2-c^2) $$
  • $$ \dfrac { \sigma }{ \varepsilon_0 r^2 } (a^2+b^2) $$
  • none of these
An infinite large sheet has charge density $$\sigma C/m^2$$. Find electric field at a distance d perpendicular to the sheet.
  • $$E=\dfrac{\sigma}{2\varepsilon_0}$$
  • $$E=\dfrac{\sigma}{\varepsilon_0}$$
  • $$E=\dfrac{2\sigma}{\varepsilon_0}$$
  • None of these
A charged oil drop is suspended in a uniform field of 3 x 104  v/m so that it neither falls nor rises. The charge on the drop will (Take the mass of the charge  = 9.9 x 10-15 kg  and g = 10 m/s2  )
  • $$3.3\times 10^{-18} N/C$$
  • $$2.25\times 10^{10} N/C$$
  • $$5\times 10^{10} N/C$$
  • None
If potential (in volts) in a region is expressed as V(x , y , z) = 6xy - y+ 2yz, the electric field (in N/C) at point (1 , 1 , 0) is
  • $$-(2\hat{i} + 3\hat{j} + \hat{k})$$
  • $$-(6\hat{i} + 9\hat{j} + \hat{k})$$
  • $$-(3\hat{i} + 5\hat{j} + 3\hat{k})$$
  • $$-(6\hat{i} + 5\hat{j} + 2\hat{k})$$
Two charges $$q$$ and $$-q$$ placed at $$(a, 0)$$ and $$(-a, 0)$$ on the x-axis. Another charge $$2q$$ is taken from $$(0,0)$$ to $$(0, a)$$, then the work done to do so 
  • $$\cfrac{q}{2\pi\varepsilon_0 a}$$
  • $$\cfrac{q}{4\pi\varepsilon_0 a}$$
  • Zero
  • Infinite
Which of the following is false for electric lines of force ?
  • They always start from positive charges and terminate on negative charges
  • They are always perpendicular to the surface of a charged conductors
  • They always form closed loops
  • They are parallel and equally spaced in a region of uniform electric field
If the surface normal vector $$  \hat{n}  $$ makes an angle $$  \theta  $$ withthe electric field $$  \vec{E}  $$ , then the electric flux through asurface of area $$  d S  $$ is given by
  • $$ \phi=E d S \sin \theta $$
  • $$ \phi=E d S \cos \theta $$
  • $$ \phi=d S \cos \theta $$
  • $$ \phi=E \cos \theta $$
When $${ 10 }^{ 14 }$$ electrons are removed from a neutral metal sphere, the charges on the sphere become 
  • $$16\mu C$$
  • $$-16\mu C$$
  • $$32\mu C$$
  • $$-32\mu C$$
Three charges $$+ 2 q , - q$$ and $$- q$$ are placed at pooul $$A$$ $$( a , 0 ) , B ( a , a )$$ and $$C( - a ,$$ a) respectively in $$x ^ { 2 } - y $$ plane. The magnitude of net electric dipole moment of the system will be
  • $$\sqrt { 11 } q a$$
  • $$q$$
  • 3$$q a$$
  • $$\sqrt { 4 } q a$$

What is the Coulomb's force between two $$\alpha  - $$particles separated by a distance of $$3.2 \times {10^{ - 15}}{\text{m}}$$
  • $$90 N$$
  • $$45N$$
  • $$60 N$$
  • $$75 N$$
in which case charges would be produce???
  • A plastic ruler is rubbed vigorously with a woollen cloth.
  • A glass rod rubbed with a piece of silk is brought near a negatively charged paper cylinder.
  • A positively charged rod is moved slowly towards an uncharged paper cylinder, which is suspended by a string, until the rod touches the cylinder.
  • all of these.
A dipole is placed in a uniform electric field with its axis parallel to the field. It experiences :
  • both a net force and torque
  • only a net force
  • neither a net force nor a torque
  • only a torque
In Region of Electric field Given by $$\vec{E} = (Ax + B) \hat{i}$$. Where $$A = 20$$ unit and $$B = 10$$ unit. If Electric potential at $$x = 1\,m$$ is $$V_1$$ and at $$x = -5 \,m$$ is $$V_2$$. Then $$V_1 - V_2$$ is equal to
  • $$150 \,V$$
  • $$170 \,V$$
  • $$140 \,V$$
  • $$180 \,V$$
Which of the following charges can from an electric dipole ?
  • $$+1\mu\, C, \, -1 m \, C$$
  • $$+1\times 10^{-3}m\, C, \, -1 \mu \, C$$
  • $$+5 \times 10^{-3}\, C, \, -2\times 10^{-3} \,C$$
  • $$-1 C, \, -1 C$$
Electric lines of forces.
  • May form closed path
  • Must form closed path
  • May be discontinuous
  • Both (a) and (c) are correct
The electric intensity at a point $$A$$ at distance $$x$$ from uniformly charged non-conducting plane is $$E$$. Then
  • The electric charge per unit area on the plane is $$2 \varepsilon E$$
  • Magnitude $$E/2$$ of field is due to the charges at points within distance $$2x$$ from the point $$'A'$$
  • Magnitude $$E$$ of field is due to the charges at points within distance $$2x$$ from point $$A$$
  • Both (a) and (c) are correct
Two positive charges and an negative charge, all of equal magnitude, are set at the corners of an equilateral triangle.
Which diagram best represents the electric field surrounding the charges?
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