CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 13 - MCQExams.com

The potential at a point $$(x, 0, 0)$$ is given by $$V = \left(\dfrac{1000}{x} + \dfrac{1500}{x^2} + \dfrac{500}{x^3}\right)$$. The intensity of the electric field at $$x = 1$$ will be
  • $$550 V/m$$
  • $$55 V/m$$
  • $$55000 V/m$$
  • $$5500 V/m$$
Four changed particles, each having a charge $$q$$, are placed at the four vertices of a regular pentagon. The sides of the Pentagon have equal length '$$a$$'. The electric field at the centre of the Pentagon is :
1016438_5a6ab6107d9d45aeb4ce38c54b39ac0f.PNG
  • $$\dfrac{q}{4\pi \varepsilon_0 a}$$
  • $$\dfrac{2q}{4\pi \varepsilon_0 a^2}$$
  • $$\dfrac{q}{4\pi \varepsilon_0 a^2}$$
  • None of these
An electron is projected from a distance $$d$$ and with initial velocity $$u$$ parallel to a uniformly charged flat conducting plate as shown. It strikes the plate after travelling a distance $$\ell$$ along the direction of projection. The surface charge density of the conducting plate is equal to
1017274_126cd76ba16d457f8f98e47260744633.PNG
  • $$\dfrac{2d\varepsilon_0mu^2}{e\ell^2}$$
  • $$\dfrac{2d\varepsilon_0mu}{e\ell^2}$$
  • $$\dfrac{d\varepsilon_0mu^2}{e\ell}$$
  • $$\dfrac{d\varepsilon_0mu}{e\ell}$$
An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the z-direction, then.
  • Positive ions deflects towards $$+$$y-direction and negative ions towards $$-$$y direction
  • All ions deflect towards $$+$$y -direction
  • All ions deflect towards $$-$$y direction
  • Positive ions deflect towards $$-$$y direction and negative ions towards y-direction
Six point charges are kept at the vertices of a regular hexagon of side $$L$$ and centre $$O$$, as shown in the figure. Given that $$ \dfrac { 1 }{ 4\pi { \varepsilon  }_{ 0 } } \dfrac { q }{ { L }^{ 2 } }$$, which of the following statement(s) is(are) correct?
1011069_4fa8c98a1f374001b370686801531ee9.png
  • The electric field at $$O$$ is $$6K$$ along $$OD$$.
  • The potential at $$O$$ is zero.
  • The potential at all points on the line $$PR$$ is zero.
  • The potential at all points on the line $$ST$$ is same.
Fill in the blanks.
A field normal to the plane of a circular wire n turns and radius r which carries a current I is measured on the axis of the coil at small h distance h from the centre of the coil. This is smaller than the field at the centre by a friction ____
  • $$3\dfrac{3h^2}{2r^2}$$
  • $$\dfrac{h^2}{2r^2}$$
  • $$\dfrac{4h^2}{2r^2}$$
  • $$\dfrac{3h^2}{2r^2}$$
A "dipole" is formed from a rod of length 2 a and two charges +q and -q. Two such dipoles are oriented as shown in figure, their centers being separated by the distance R. The force exerted on the left dipole is         . 
1018729_a1630b0b24cd486da142779428b99b07.png
  • $$\dfrac{6kP_1P_2}{r^4}$$
  • $$\dfrac{3kP_1P_2}{r^4}$$
  • $$\dfrac{2kP_1P_2}{r^4}$$
  • $$\dfrac{4kP_1P_2}{r^4}$$

Two identical conducting spheres $$M$$ and $$N$$ has charges $${q_m}$$ and $${q_n}$$ respectively. A third identical neutral sphere $$P$$ is brought in contact with $$M$$ and then separated. Now sphere $$P$$ is brought in contact with $$N$$ and then separated. Final charge on sphere $$P$$ will be:

  • $$\dfrac{q_m + 2q_n}{6}$$
  • $$\dfrac{q_m + q_n}{4}$$
  • $${q_m}$$ + $$\dfrac{ q_n}{4}$$
  • $$\dfrac{q_m + 2q_n}{4}$$
An elliptical cavity is charge within perfect conductors. A positive charge $$q$$ is placed at the centre of the cavity. The points $$A$$ and $$B$$ are on the cavity surface as shown, Then:
1031264_b4d281148ef44cdd983bfc01cb8126f7.png
  • Electric field near $$A$$ in the cavity $$=$$ electric field near $$B$$ in the cavity.
  • Charge density at $$A=$$ charge density at $$B$$.
  • Potential at $$A=$$ potential at $$B$$.
  • Total electric field flux through the surface of the cavity is $$q/\ \varepsilon_{0}$$
A charge of $$1 \mu C$$ is divided into two parts such that their charges are in the ratio of $$1:3$$ . These two charges are kept at distance $$1m$$ apart in vacuum. Then, the electric force between them (in newton) is :
  • $$ 1.7 \times 10^{-3} $$
  • $$ 1.7 \times 10^{-4} $$
  • $$ 3.4\times 10^{-3} $$
  • $$ 3.4\times 10^{-5} $$
Consider a hemispherical surface of radius $$r$$, a positive point charge $$q$$ is kept at the centre of hemisphere. The electric flux through this hemisphere is :
  • zero
  • $$\dfrac{q}{\varepsilon_0}$$
  • $$\dfrac{q}{2\varepsilon_0}$$
  • $$\dfrac{2q}{\varepsilon_0}$$
A thin non-conducting ring of radius $$R$$ has a linear charge $$ \lambda = \lambda_0 \cos \theta $$ where $$\lambda_0$$ is the value of $$\lambda$$ at $$ \theta = 0 $$ . The net electric dipole moment for this charge distribution is :
1034018_36e72dd019bd4c45a94d383c0110ad4f.JPG
  • $$ \pi R^2 / \lambda_0 $$
  • $$ \lambda_0 / \pi R^2 $$
  • $$ \pi R^2 \lambda_0 $$
  • $$ \dfrac {\lambda_0 \pi}{ R^2} $$
A particle of mass $$m$$ and charge $$q$$ at rest is released in a uniform electric field between parallel planes of charge $$+q$$ and $$-q$$ respectively. The particle accelerates towards the other place a distance $$'d'$$ away. The speed at which it strikes the opposite plane is:
  • $$ \sqrt{qEd/m}$$ and $$j$$
  • $$ \sqrt{2qEd/m}$$ along $$-j$$
  • $$ \sqrt{qm/Ed}$$ along $$j$$
  • $$ \sqrt{qm/Ed}$$ along $$-j$$
The diode 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:
  • $$\frac{2\sqrt{2} qR}{\pi}$$
  • $$\frac{\sqrt{2} qR}{\pi}$$
  • $$\frac{qR}{\pi}$$
  • $$\frac{2qR}{\pi}$$
Electric field at a distance $$4R$$ from the surface of a charge cylinder is $$E$$ . If $$R$$ is the radius of the cylinder and $$L$$ is the length of the cylinder then surface charge density of the cylinder is:
  • $$ \dfrac { 4 \epsilon E }{L} $$
  • $$ \dfrac { 5 \epsilon E }{L} $$
  • $$5 \epsilon E$$
  • $$4 \epsilon E$$
A cubical region of side $$'a'$$ has its centre at the origin. It encloses three fixed point charges, $$-q$$ at $$(0, -a/4, 0), +3q$$ at $$(0, 0, 0)$$ and $$-q$$ at $$(0, +a/4, 0)$$. Choose the incorrect option
1063340_584627db5208471e8fcfd04be12c1c04.jpg
  • The net electric flux crossing the plane $$x = + \dfrac {a}{2}$$ is equal to the net electric flux crossing the plane $$x = -\dfrac {a}{2}$$
  • The net electric flux crossing the plane $$y = +\dfrac {a}{2}$$ is more than the net electric flux crossing the plane $$y = -\dfrac {a}{2}$$
  • The net electric flux crossing the entire region is $$\dfrac {q}{\epsilon_{0}}$$
  • The net electric flux crossing the plane $$z = \dfrac {a}{2}$$ is equal to the net electric flux crossing the plane $$x = + \dfrac {a}{2}$$
An electric dipole is kept on the axis of a uniformly charged ring at distance $$\sqrt 2 R$$ from the centre of  the ring. The direction of the dipole moment is along the axis. the dipole moment is $$P$$, charge of the ring  is $$Q$$ and radius of the ring is $$R$$. The force on the dipole is:
  • $$\dfrac{4 k p Q}{3 \sqrt 3 R^S}$$
  • $$\dfrac{k p Q}{3 \sqrt 3 R^S}$$
  • $$\dfrac{2 k p Q}{3 \sqrt 3 R^S}$$
  • Zero
A square surface of side $$L$$ metre in the plane of the paper is placed in a uniform electric field $$E(V/m)$$ acting along the same place at an angle $$\theta$$ with the horizontal side of the square as shown in figure. The electric flux linked to the surface in unit of $$V-m$$, is
1113045_034046dbb7934a18ad9e49d401eadac6.png
  • $$EL^{2}$$
  • $$EL^{2}\cos \theta$$
  • $$EL^{2}\sin \theta$$
  • Zero
A negative charged object reples another charged object kept close to it. What is the nature of the charge on the other object?
  • positive
  • negative
  • both
  • none.
electric intensity in axis of dipole at dist. $$2m$$ from its centre is $$9\times 10^{3}\ N/C$$. Electric dipole moment of dipole is
  • $$4\times 10^{-6}\ cm$$
  • $$8\times 10^{-6}\ cm$$
  • $$2\times 10^{-6}\ cm$$
  • $$16\times 10^{-6}\ cm$$
A square loop of side b is rotating with angular speed $$\omega$$ about one of the diagonals as axis. At $$t=0$$, the plane of the loop is perpendicular to the magnetic field B. If the number of turns of the loop be N then what is the instantaneous flux through the coil
  • BAN
  • BAN $$sin \omega t$$
  • BAN $$cos \omega t$$
  • BAN $$ \omega t$$
A negative charged object attracts another charged object kept close to it. What is the nature of the charge on other object?
  • positive
  • negative
  • both
  • none
Two charges, each equal q, are kept at $$x=-a$$ and $$x=a$$ on the x-axis. A particle of mass $$m$$ and charge $${q_0} = \frac{q}{2}$$ is placed at the origin. If  charge $${q_0}$$ is given a small displacement $$(y<<a)$$ along the y-axis, the net force acting on the particle is proportional to: 
  • $$y$$
  • $$-y$$
  • $$\frac{1}{y}$$
  • $$-\frac{1}{y}$$
A negatively charged rod is held close to one side of a metal ball and the other side is earthed. Which of the following diagrams is correctly shows the charge distribution?
A positively charged glass rod is brought near the disc of uncharged gold leaf electroscope. The leaves diverge. Which of the following statements is correct?
  • No charge is present on the leaves
  • Positive charge is induced on the leaves
  • Negative charge is induced on the leaves
  • Positive charge is induced on the leave and negative charge on the other.
 When alternating current flows through a conductor, the rate of flux change 
  • Is higher in the inner part of the conductor
  • is lower in the inner part of the conductor
  • is uniform throughout the conductor
  • Depends on the resistivity of the conductor
A point charge $$q=10^{-11}\ C$$, is placed at $$4\ cm$$ above a square plate $$(8\ cm\ \times 8\ cm)$$, having charge density $$0.5\ \times 10^{-8}\ C/m^{2}$$. Find the flux related with it.
  • $$0.188\ V-m$$
  • $$0.12\ V-m$$
  • $$0.288\ V-m$$
  • $$0.388\ V-m$$
A charge q is distributed uniformly on a ring of radius R. A sphere of equal radius R is constructed with its centre at the periphery of the ring, Find the flux of the electric field through the surface of the sphere
1136650_b953e8c8eb8a4058b07d4a29fbd24855.png
  • $$\dfrac{q}{\epsilon_0}$$
  • $$\dfrac{q}{2\epsilon_0}$$
  • $$\dfrac{q}{3\epsilon_0}$$
  • Zero.
What is the electric flux linked with closed surface?
1134210_97be74d146c24ae9b08fb640e7996415.jpg
  • $$10^{11} Nm^2/C$$
  • $$10^{12} Nm^2/C$$
  • $$10^{10} Nm^2/C$$
  • $$8.85\times10^1{3} Nm^2/C$$
The electric field in a region of space is given by $$E=(5\ \hat {i}+2\hat {j})N/C$$. The electric flux through an area of $$2\ m^{2}$$ lying in the $$YZ$$ plane, in $$S.I.$$. units is ?
  • $$10$$
  • $$20$$
  • $$10\sqrt {2}$$
  • $$2\sqrt {29}$$
The volume charge density as a function of distance $$x$$ from one face inside a unit cube is varying as shown in the figure. Then the total flux $$(in S.I units)$$ through the cube if $$(p-{0}=8085\times10^{-12}Cm^{3})$$ is
  • $$\dfrac{1}{4}$$
  • $$\dfrac{1}{2}$$
  • $$\dfrac{3}{4}$$
  • $$1$$
A spherical shell of radius $$R$$ has two holes $$A$$ and $$B$$ through which a ring having charge positive through without touching the shell. The flux through spherical shell is $$\dfrac{q}{3 \varepsilon_0}$$. Find the radius of the ring:-
1113137_7ab59f04651d40048533d99c70d6c438.png
  • $$R\sqrt{2}$$
  • $$2 R$$
  • $$0.5 R$$
  • $$R$$
If the electronic charge is $$1.6\times 10^{-19}$$C, then the number of electrons passing through a section of wire per second, when the wire carries a current of $$2$$ ampere is?
  • $$1.25\times 10^{17}$$
  • $$1.6\times 10^{17}$$
  • $$1.25\times 10^{19}$$
  • $$1.6\times 10^{19}$$
Four charge particle of charges -q,-q,-q and 3q are place at the vertices pf a square of side as shown.The magnitude of dipole moment of the arrangement is
1165731_284338915c894efe94fcded59c241a71.png
  • $$2\sqrt 2 \;qa$$
  • qa
  • 3qa
  • $$\left( {2 + \sqrt 2 } \right)qa$$
Three point charges $$+q,\ -2q$$ and $$+q$$, are passed at points $$(x=0,\ y=a,\ z=0),\ (x=0,\ y=0,\ z=0)$$ and $$(x=a,\ y=0,\ z=0 )$$ respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are ?
  • $$\sqrt{2}\ qa$$ along + $$x$$ direction
  • $$\sqrt{2}\ qa$$ along + $$y$$ direction
  • $$\sqrt{2}\ qa$$ 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 $$(x=a,\ y=z,\ z=0)$$
Twelve infinite long wire of uniform linear charge density $$\left( \lambda  \right)$$  are passing along the twelve edges of a cube. Find electric flux through any face of cube 
1174997_c818de18256f43a696521b16c59a4f31.png
  • $$\left( \frac { \lambda l }{2 \varepsilon _{ { 0 } } } \right)$$
  • $$\left( \frac { \lambda l }{ \varepsilon _{ { 0 } } } \right)$$
  • $$\left( \frac { \lambda l }{3 \varepsilon _{ { 0 } } } \right)$$
  • $$\left( \frac { 3\lambda l }{ \varepsilon _{ { 0 } } } \right) $$
A conducting sphere of radius a has charge Q on it. It is enclosed by a neutral conducting concentric concentric spherical shell having inner radius 2a and outer radius 5a. Find electrostatic energy of system.
  • $$\dfrac{5}{12} \dfrac{kQ^2}{a}$$
  • $$\dfrac{11}{12} \dfrac{kQ^2}{a}$$
  • $$]dfrac{kQ^2}{2a}$$
  • $$none$$
Charges $$q$$ and $$q$$ are given to the conducting shells in figure (i) and $$q$$ and $$-q$$ are given to the identical pair in figure (ii).
1138522_0d9db065c3854cfa8747842179452413.png
  • force of interaction between the shells in the figure (i) will be greater than that in figure (ii)
  • force of interaction between the shells in the figure (i) will be smaller than that in figure (ii)
  • force of interaction will be same in both the figures
  • nothing can be said
Figure shows electric field lines in which an electric dipole $$\rho$$ is placed as shown. Which of the following statements is correct?
1138382_3a1f0e6824dc4ddbb88e07c3636566ba.png
  • The dipole will not experience any force
  • The dipole will not experience a force towards right
  • The dipole will not experience a force towards left
  • The dipole will not experience a force upwards
A non conducting sphere of radius $$'a'$$ has a type charge $$'+q'$$ uniformly distributed throughout in volume. A hollow spherical conductor having inner and  outer, radii $$'b'$$ and $$'c'$$ and net charge $$'-q'$$ is concentric with the sphere (see the figure)
Read the following statements
(i) The electric field at a distance $$r$$ from the center of the sphere $$ = \frac{1}{{4\pi {\varepsilon _0}}}\frac{{qr}}{{{a^3}}}$$ for $$r<a$$.
(ii) The electric field at distance $$r$$ from the center of the sphere for $$a<r<b=0$$
(iii) The electric field at distance $$r$$ from the center of the sphere for $$ b<r<c<=0$$
(iv) The charge on the inner surface of the hollow sphere $$=-q$$
(v) The charge on the outer surface of the hollow sphere $$=+q$$.
1137796_c4c98f5bc12743bc86ff67bc8052e5e6.PNG
  • (i),(ii) and (v)
  • (i),(iii) and (iv)
  • (ii),(iii) and (v)
  • (ii),(iii) and (iv)
An inductor having $$400$$ turns, carrying of $$8 m A$$ and inductances $$5 mH$$ then flux is:
  • $$\mu_0$$
  • $$4 \pi/\mu_0$$
  • $$\mu_0/4 \pi$$
  • $$4 \pi$$
A point charge $$50 \: \mu C$$ is located in the $$XY $$ plane at the point of position vector $$ r_1 = 2i + 3j $$ . What is the electric field at the point of position vector $$r_2 = 8i-5j$$.
  • $$1200 v/m$$
  • $$0.04 V/m$$
  • $$900 V/m$$
  • $$4500 V/m$$
The ratio of the forces between two charges placed at a certain distance apart in air and at half of the distance apart in medium of dielectric '2' is 
  • 1 : 4
  • 1 : 2
  • 4 : 1
  • 2 : 1

A point charge $$ + 20\mu C$$ is at a distance 4 cm above the center of a square of side 8 cm. What is the magnitude of electrostatic flux through the square?

  • $$3.76 \times {15^5}{\text{N}}{{\text{m}}^2}{{\text{C}}^{ - 1}}$$
  • $$4.2 \times {15^5}{\text{N}}{{\text{m}}^2}{{\text{C}}^{ - 1}}$$
  • $$2.9 \times {15^5}{\text{N}}{{\text{m}}^2}{{\text{C}}^{ - 1}}$$
  • $$5.1 \times {15^5}{\text{N}}{{\text{m}}^2}{{\text{C}}^{ - 1}}$$
Two charges $$q$$ each attract each by a force of $$100 N$$. Now, the entire space is filled with a medium of relative permittivity $$10$$. The force exerted on any one of the charges by the medium is
  • $$90 N$$
  • $$10 N$$
  • $$110 N$$
  • $$Zero$$
If the electric lines of force are as shown in figure. Electric field intensities at $$A$$ and $$B$$ are $$E_{A}$$ and $$E_{B}$$ respectively.
1187708_1824a6f2eee2420285324d225e82abe1.png
  • $$E_{A} < E_{B}$$
  • $$E_{A} > E_{B}$$
  • $$E_{A} = E_{B}$$
  • $$E_{A} = E_{B} = 0$$
A capacitor is a perfect insulator for:
  • constant direct current
  • alternating current
  • direct as well as alternating current
  • variable direct current.

What is the value of electric flux in SI unit in the Y-Z plane of area $$2{m^2}$$ , if intensity of electric field is $$\overrightarrow {\text{E}} {\text{ = }}\left( {{\text{5}}\widehat {\text{i}}{\text{ + 2}}\widehat {\text{j}}} \right){\text{N/C}}$$

  • $$10$$
  • $$20$$
  • $$10\sqrt 2 $$
  • $$2\sqrt {29} $$

An electric dipole ( dipole moment p) is placed at a radial distance r>>a ( Where a is dipole length) from an infinite line of charge having linear charge density $$ + \lambda $$. dipole moment vector is aligned along the radial vector $$\overrightarrow r $$ force experienced by the dipole is:-

  • $$\dfrac{{\lambda p}}{{2\pi {\varepsilon _o}{r^2}}},{\text{attractive}}$$
  • $$\dfrac{{\lambda p}}{{2\pi {\varepsilon _o}{r^3}}},{\text{attractive}}$$
  • $$\dfrac{{\lambda p}}{{2\pi {\varepsilon _o}{r^2}}},{\text{repulsive}}$$
  • $$\dfrac{{\lambda p}}{{2\pi {\varepsilon _o}{r^3}}},{\text{repulsive}}$$
A cone of base radius R and height $$h$$ is located in a uniform electric field $${\vec E}$$ parallel to its base. The electric flux entering the cone is 
  • $$EhR$$
  • $$\frac{1}{2}EhR$$
  • $$4EhR$$
  • $$2EhR$$
0:0:1


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