CBSE Questions for Class 12 Medical Physics Electric Charges And Fields Quiz 6 - MCQExams.com

If the distance between two unlike poles is doubled then the force of attraction between them becomes ______ times its original value.
  • $$0.25$$
  • $$0.5$$
  • $$0.125$$
  • $$2$$
The number of electrons present in $$1\ C$$ of charge is ______.
  • $$4.25\times 10^{18}$$
  • $$6.25\times 10^{18}$$
  • $$3.25\times 10^{18}$$
  • $$2.25\times 10^{18}$$
SI unit of electric field is _______.
  • $$N\ C^{-3}$$
  • $$N\ C^{-2}$$
  • $$N\ C^{-1}$$
  • $$N\ C$$
Mass of negative ion is slightly greater than its neutral atom.
  • True
  • False
The tangent drawn on electric field lines at a point gives the direction of lines of force at that point.
  • True
  • False
A charge body cannot attract another uncharged body.
  • True
  • False
Electric charge is always conserved in physical process.
  • True
  • False
Charge of an object is affected by the motion of the object.
  • True
  • False
Only two equal charges can exert equal and opposite coulomb's forces on each other.
  • True
  • False
Choose the correct statement from the following
  • When same charges are separated by different distances in the same medium, $$Fd^{2} = constant$$
  • On doubling the distance of separation between two charges, the electric force between two charges becomes one fourth
  • Repulsion is the sure test of electrification
  • SI unit of electric field is farad
Two stationary point charges are separated by certain distance:
  • The force between then is either attractive or repulsive
  • The force is independent of the distance between them
  • Force depends on the medium between them
  • Force between them has only magnitude
If there is only one type of charge in the universe, then what is the flux to the entire universe.
($$\vec { E } \rightarrow $$ Electric field, $$\vec { ds } \rightarrow $$ Area vector)
  • $$\oint { \vec { E } \cdot \vec { ds } } \neq 0$$ on any surface
  • $$\oint { \vec { E } \cdot \vec { ds } } $$ could not be defined
  • $$\oint { \vec { E } \cdot \vec { ds } } =\infty $$ if charge is inside
  • $$\oint { \vec { E } \cdot \vec { ds } } =0$$ if charge is outside, $$=\dfrac { q }{ { \epsilon }_{ 0 } } $$ if charge is inside
A circular loop and a square loop are formed from the same wire and the same current is passed through them. Find the ratio of their dipole moments :
  • $$\dfrac { 2 }{ \pi } $$
  • $$4\pi $$
  • $$\dfrac { 4 }{ \pi } $$
  • $$2\pi $$
The line AA' is on a changed infinite conducting plane which is perpendicular to the plane of the paper. The plane has a surface density of charge  $$\sigma$$ and B is a ball of mass m with a like charge of magnitude q. B is connected by a string from a point on the line AA'. The tangent of the angle $$(\theta)$$ formed between the line AA' and the string is:
  • $$\frac{q\sigma }{2\epsilon _0\,\, mg}$$
  • $$\frac{q\sigma }{4 \pi \epsilon _0\,\, mg}$$
  • $$\frac{q\sigma }{2\pi \epsilon _0\,\, mg}$$
  • $$\frac{q\sigma }{\epsilon _0\,\, mg}$$
The S.I unit of permittivity of free space $$(\epsilon_{0})$$ is:
  • $$C\ N^{-1} - m^{-1}$$
  • $$N\ m^{-2}C^{-2}$$
  • $$C^{2}N^{-2}m^{-2}$$
  • $$C^{2}N^{-1}m^{-2}$$
Coulomb's Law agrees with________
  • Newtons $$3$$rd Law of Motion
  • Newtons $$1$$st Law of Motion
  • Newtons $$2$$nd Law of Motion
  • All of the above
Electric force can be_______
  • always attractive
  • always repulsive
  • attractive or repulsive
  • None of these
The dimensional formula for electric flux is
  • $$[ML^3I^{-1}T^{-3}]$$
  • $$[M^2L^2I^{-1}T^{-2}]$$
  • $$[ML^3I^{1}T^{-3}]$$
  • $$[ML^{-3}I^{-1}T^{-3}]$$
The force of interaction (attraction or repulsion) between two stationary point charges in vacuum is directly proportional to the product of the charges and inversely proportional to the square of distance between them. This is called_______
  • Curie's Law
  • Coulomb's law
  • Faraday's Law
  • Ampere's Law
If the electric field is given by $$(5i+4j+9k)$$, the electric flux through a surface of area $$20$$ unit lying in the Y-Z plane will be :
  • $$100$$ unit
  • $$80$$ unit
  • $$180$$ unit
  • $$20$$ unit
The force of interaction (attraction or repulsion) between two stationary point charges in vacuum is _____
  • directly proportional to the product of the charges
  • inversely proportional to the product of the charges
  • directly proportional to only the lower of the charges
  • inversely proportional to only the lower of the charges
$$\epsilon_0$$ is known as the ______
  • electrical permeability of free space
  • electrical permittivity of free space
  • magnetic permeability of free space
  • None of these
Electric force                   on the nature of the medium between the charges.
  • depends
  • does not depend
  • sometimes depends
  • None of these
An electric field line 
  • is a continuous curve
  • can be a discontinuous curve
  • can have sudden breaks
  • vanishes at the origin
Coulomb's law is a confirmation of______
  • inverse cube law
  • product law
  • inverse square law
  • None of the above
A charge $$q$$ is placed at the centroid of an equilateral triangle. Three equal charges $$Q$$ are placed at the vertices of the triangle. The system of four charges will be in equilibrium if $$q$$ is equal to :-
  • $$\dfrac{-Q}{\sqrt{3}}$$
  • $$\dfrac{-Q}{3}$$
  • $$-Q\sqrt{3}$$
  • $$\dfrac{Q}{\sqrt{3}}$$
Why are electric field lines always emanate perpendicular to a charged surface?
  • To prevent surface potential
  • To prevent surface current
  • To prevent surface polarisation
  • All of the above
Which of these field lines emanate from the highest charge?
  • Cannot be ascertained
Why the electric field lines do not form closed loops?
  • It is always directed towards positive charge from negative charge.
  • It is always directed from positive charge to negative charge.
  • It is always directed away from negative charge.
  • It can be in any random direction
Which of the following can attract a stream of water?
  1. A negatively charged insulator.
  2. A negatively charged conductor.
  3. A neutral conductor.
  • 1 and 2 only
  • 1 and 3 only
  • 2 and 3 only
  • 1,2 and 3 only
Three point charges $$+q, -2q$$ and $$+q$$ are placed 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 :
  • $$\sqrt{2qa}$$ 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 $$(x=0, y=0, z=0) \ and \ (x=a, y=a, z=0)$$
  • $$\sqrt{qa}$$ along $$+x$$ direction
A negatively charged object attracts a suspended light conducting ball. The light conducting ball can be :
negatively charged
neutral
positively charged
  • 1 only
  • 3 only
  • 1 & 2 only
  • 2 & 3 only
The electric field lines involves drawing the lines of force             to the surfaces of objects at the locations where the lines connect to object's surfaces.
  • parallel
  • anti-parallel
  • perpendicular
  • tangent
Why should electric field lines never cross each other?
  • Electric field at any point is always singular in magnitude.
  • Electric field at any point is always singular in direction.
  • Electric field at any point cannot be multi-directional.
  • All of the above
The total number of lines of force passing through a surface is called
  • electric field
  • electric flux
  • electric potetial
  • electrical energy
Electric field lines                     inside a conductor.
  • exist
  • do not exist
  • may exist
  • None of these
Several electric field line patterns are shown in the diagrams below. Which of these patterns are incorrect?
The figure shows schematic field lines resulting from interaction between 
591179_b3623d2242a14f65880ef859988f1f71.png
  • two positive charges
  • two negative charges
  • a positive and a negative charge
  • None of these
Electric flux is a                  quantity.
  • scalar
  • vector
  • constant
  • independent
The concept of solid angle is a natural extension of a           angle to             dimensions. 
  • plane, two
  • line, three
  • plane, three
  • line, two
Consider the electric field lines shown in the diagram below. From the diagram, it is apparent that object A is ____ and object B is ____.
591173_df3644bb37d94fe5ab0ec2c0aeda40e2.png
  • $$+,+$$
  • $$-,-$$
  • $$+,-$$
  • $$-,+$$
Observe the electric field lines and rank the objects according to the magnitude of charge:
591200_56b6af359cb24322a549c45113c3555d.png
  • $$J=H=I$$
  • $$J>H>I$$
  • $$I>H>J$$
  • $$ I>J>H$$
Which of these points may be a null point?
591894.JPG
  • A
  • B
  • C
  • None of these
A right circular cone has a semi-vertical angle $$\alpha$$. Calculate the solid angle at the apex P of the cone.
  • $$d\Omega = 2\pi (1-\cos \alpha)$$
  • $$d\Omega = 2\pi (1-\sin \alpha)$$
  • $$d\Omega = 2\pi (cos \alpha)$$
  • $$d\Omega = 2\pi (\sin \alpha)$$
State whether the given statement is True or False :
Positive electrification is due to deficiency of electrons.
  • True
  • False
Electric flux per unit solid angle is defined as
  • Electric force
  • Electric field intensity
  • Electric potential
  • Electric power
A cylinder of length $$l$$ and radius $$R$$ is placed in a uniform electric field $$E$$ parallel to the cylindrical axis. The total flux through the surface of the cylinder is given by
  • $$2\pi R^2 E$$
  • $$\dfrac{\pi R^2}{E}$$
  • $$\pi (R^2 - Rl)E$$
  • $$0$$
A cube of side $$l$$ is placed in a uniform electric field $$E \hat i$$. Then the net flux through the cube is :
  • $$0$$
  • $$l^2E$$
  • $$4l^2E$$
  • $$6l^2E$$
Find the electric field at a distance "$$z$$" from the plane.
  • $$\vec{E} = \dfrac{\sigma}{2\epsilon_0} \hat k$$ for $$z>0$$
  • $$\vec{E} = -\dfrac{\sigma}{2\epsilon_0} \hat k$$ for $$z>0$$
  • $$\vec{E} = \dfrac{\sigma}{2\epsilon_0} \hat k$$ for $$z<0$$
  • $$\vec{E} = -\dfrac{\sigma}{2\epsilon_0} \hat k$$ for $$z<0$$
Find the electric field at $$z< -0.5d$$
593410.JPG
  • $$E=0$$
  • $$E=-\dfrac{\sigma}{\epsilon_0}\hat k$$
  • $$E=\dfrac{\sigma}{\epsilon_0}\hat k$$
  • $$E=\dfrac{\sigma}{2\epsilon_0}\hat k$$
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