Practice Test


1) How many electrons will constitute a charge of one coulomb ?


2) S.I unit of permittivity is


3) The ratio of the forces between two small spheres with constant charge 'a' in air and 'b' in a medium of dielectric constant k is


4) The force between two electrons separated by a distance 'r' is proportional to


5) The relation between permittivity of medium, permittivity of vaccum and dielectric constant is given as


6) Three charges 4q, Q and q are in a straight line in the position 0,l/2 and l respectively. The resultant force on q will be zero if Q =


7) Two small spheres each having the charge +Q are suspended by insulating threads of length L from a hook. This arrangement is taken in space where there is no gravitational effect then the angle between the two suspensions and the tension in each will be


8) Linear charge density for circle of radius r is


9) The number of electrons carrying a charge of 8 C is


10) The minimum magnitude of charge that a particle can have is


11) A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to


12) Unit of surface charge density is


13) The magnitude of electric field intensity E is such that an electron placed in it would experience force equal to its weight given by


14) Two charge +4e and +e are at distance x apart. At what distance a charge q must be placed from charge +e so that it is in equilibrium ?


15) Intensity of an electric field E due to a dipole, depends on distance 'r' as


16) The acceleration of a particle of charge of 0.5 C and 500 mg mass kept in an electric field of intensity 200 N/C is


17) The SI unit and dimensions of dipole moment respectively are


18) In vector form dipole moment can be expressed as


19) When axis of electric dipole lies along the direction of field then torque acting in dipole is


20) Which of the following charges can form an electric dipole ?


21) The value of electric potential at any point due to any electric dipole is


22) For a two charge system separated by distance r, the potential energy is


23) Dimensions of electric potential is


24) The potential at a point due to an electric dipole will be maximum and minimum when the angle between the axis of the dipole and the line joining the point to the dipole are


25) When a charged particle of charge q and mass m is accelerated from rest by a potential difference V, then velocity attained by particle is


26) SI unit of electric flux is


27) The electric flux through a surface is maximum when angle between electric field E and normal to area S is


28) The SI unit of electric flux density is


29) When surface is parallel to electric field, the electric flux becomes


30) A charge Q is divided into two charges q and (Q-q). What should be the relation between Q and q so that force between q and (Q-q) is maximum ?


31) Electric charges q, q and -2q are placed at the corners of an equilateral triangle ABC of side l. The magnitude of electric dipole moment of the system is


32) A current of 5 A flows through a conductor for 1 s then how many electrons would flow through the conductor in the same time ?


33) The moment of couple acting on an electric field is maximum when


34) When a charge of 3 coulomb is placed in a uniform electric field it experience a force of 3000 N with in this field, the potential difference between two points seperated by a distance of 1 cm is


35) Electrostatic means study of


36) Which of the following is NOT an example of static electricity ?


37) When a glass rod is rubbed with silk cloth, then


38) Frictional electricity is produced on the two objects due to


39) Like charges repel each other and unlike charges attract each other. This phenomenon was proved by


40) The positive and negative names of the charges were given by


41) The property of attraction or repulsion acquired by the material body when it rubbed with another body is


42) When the distance between the charged particles is halved the force between them becomes


43) There are two charges +1 micro coulombs and +3 micro coulombs. The ratio of the forces acting on them will be


44) Dielectric constant of a medium is also known as


45) Which of the following is NOT true about dielectric constant ?


46) Force between two charges, when placed in free space is 10 N. If they are in a medium of relative permittivity 5, the force between them will be


47) The superposition of forces is a method to find force on a charge when


48) Volume charge density is


49) Charge per unit area is called as


50) We can define the term charge density when distribution of charge is


51) When the charge is not accumulated in some part of a conductor but spread evenly then it is called a


52) When any physical quantity exists in the form of discrete packets it is said to be


53) The unit of intensity of electric field is


54) The electric field inside a spherical shell of uniform surface charge density is


55) The unit of electric field is NOT equivalent to


56) Electric lines of force about negative point charge are


57) An electric lines of force is


58) Which of the following is NOT true about electric lines of forces ?


59) An electric dipole is kept in non-uniform electric field. It experiences


60) A region surrounded a stationary electric dipole has


61) The work done in bringing a charge from infinity to any point in the field is


62) The electric potential due to a charged metallic sphere is constant


63) A hollow metal sphere of radius 10 cm is charged such that the potential on its surface is 80 volt. The potential at the centre of the sphere is


64) Which of the following is NOT true about electric potential ?


65) The electric potential is independent of which of the following ?


66) The rate of change of potential with respect to distance in direction of electric intensity is called


67) An electric dipole has the magnitude of charge q and dipole moment p. It is placed in a uniform electric field. If its dipole moment is along the direction of the field then the force on it and its potential energy are rspectively


68) Coulombs law is applicable for stationary point charges and not for the extended bodies. This statement is


69) Two bodies get charged when they rubbed with each other due to transfer of


70) The work done to move a charge from one point to another is


71) As we move in the direction of electric intensity the electrical potential


72) Electric potential due to positive and negative charges respectively is


73) Example of equipotential surface is


74) If a unit charge is taken from one part to another over an equipotential surface


75) The law governing the force between electric charge is known as


76) Which of the following represents electric field neither constant in magnitude nor in direction ?


77) A unit charge is taken from one point to another over an equipotential surface. Work done in this process will be :


78) A parallel plate capacitor with oil as dielectric( dielectric constant of oil K=2) has a capacitance C. If the oil is removed, then capacitance of a capacitor becomes:


79) Two point charges +q and -q are held fixed at (-d,0) and (d,0) respectively of a (X,Y) coordinate system. Then


80) The respective radii of the two spheres of a spherical condenser are 12 cm and 9 cm. The dielectric constant of the medium between them is 6. The capacity of the condenser will be


81) An uncharged conductor A connected with earth is brought with another charged conductor B. Thereby :


82) A condenser having capacity 2.0 microfarad is charged to 200 volt and then the plates of the capacitor are connecated to a resistance wire. Thus, heat produced in joule will be:


83) Two charges Q and q are placed at a distance d from each other. If the magnitude of each charge is doubled and the distance between them halved, the force between them will be:


84) Two small spheres each carrying a charge (q) are placed (r) meter apart. If one of the spheres is taken around the other in a circular path, then work done will be equal to :


85) The electrostatic energy stored in a capacitor is :


86) The electric field required to keep a water drop of mass m just to remain suspended, when charged with one electron is :


87) A point charges Q and -2Q are placed at some distance apart. If the electric field at the location of Q is E, then the electric field at the location of -2Q will be:


88) A charge (q ) is enclosed in a cube. What is electric flux associated with one of the faces of the cube?


89) A uniform electric field pointing in positive X - direction exists in a region. Let A be the origin, B be the point on x - axis at X = +1 cm and C be the point on the y - axis at Y = +1 cm. Then the potentials at the points A, B and C satisfy :


90) Three positive charges of equal value q are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as in (see fig.) :


91) A charge of Q coulomb is placed on a solid piece of metal of irregular shape. The charge will distribute itself :


92) If a charged spherical conductor of a radius 10 cm has potential V at point distant 5 cm from its centre, then the potential at a point distant 15 cm from the centre will be :


93) A point Q lies on the perpendicular bisector of an electric dipole of dipole moment p. If the distance of Q from the dipole is r (much larger than the size of the dipole) then electric filed at Q is proportional to :


94) The capacity of a conductor does not depend upon :


95) If the distance parallel plates of a capacitor is halved and dielectric constant is doubled then the capacitance :


96) If the accelerating potential of an electron is doubled, then its velocity will :


97) A point Q lies on the perpendicular bisector of an electrical dipole moment p. If the distance of Q from the dipole is r (much larger than the size of the dipole), then electric field at Q is proportional to :


98) If a charged spherical conductor of radius 10 cm has potential V at a point distance 5 cm from its centre, then the potential at a point distant 15 cm from the centre will be :


99) The number of electrons to be put on spherical conductor of radius 0.1 m. To produce an electric field of 0.036 N/C just above its surface, is :


100) Two identical mercury drops, each of radius r are charged to the same potential V. If the mercury drops coalesce to form a big drop, each of radius R, then potential of the combined drop will be


101) If identical charges (-q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q) which is placed at centre of the cube will be :


102) If the distance between the plates of a parallel plate condenser is halved and the dielectric is doubled, then its capacity increases by :


103) Two equal point charges are fixed at x = -a and x = +a on the X-axis. Another point charge Q is placed at the origin. The change in the electrical potential energy of Q, when it is displayed by a small distance x along the X-axis, is approximately proportional to :


104) A metallic particle having no net charge is placed near a finite metal plate carrying a positive charge. The electric force on the particle will be :


105) A pellet carrying a charge of 0.5 coulomb is accelerated through a potential of 2000 volt. It attains a kinetic equal to :


106) Proton is nearly 1836 times more massive than the electron. The Coulomb force of repulsion between two protons separated by a finite distance is F. The electrostatic force between two electrons separated by the same distance is :


107) The capacity of a parallel plate capacitor depends on :


108) Two point charges are +2C and +6C repel each other with a force of 12 newton. If a charge of -4C is given to each of these charges the force now is :


109) The electrostatic capacitance depends on :


110) A charge q is located at the centre of a cube. The electric flux through any face is :


111) An electric dipole placed in a non-uniform electric field experiences :


112) If an uncharged capacitor is charged by connecting it to a battery, then the amount of energy lost as heat is :


113) A metallic shell has a point charge 'q' kept inside its cavity. Which one of the following diagram correctly represents the electric lines of forces ?


114) A parallel plate capacitor has a capacitance of 100 pF, when the plates of the capacitor are separated by a distance of t. Then, a metallic foil of thickness t/3 is introduced between the plates. The capacitance will then become :


115) Two charges -10, + 20 e.s.u are separated by 1 m. The electric potential will be zero at a point :


116) Two equal small metal balls are given charges equal to 10 e.s.u. and -20 e.s.u. They are allowed to touch each other and are again separated to the same distance as before. The ratio of the force between the two balls in the two cases respectively is :


117) A variable parallel plate capacitor and an electroscope are connected in parallel to battery. The reading of the electroscope would be decreased by :
(i) increasing the area of overlap of the plates.
(ii) placing a block of paraffin wax between the plates.
(iii) decreasing the distance between the plates.
(iv) decreasing the battery potential Then state if :


118) Dielectric polarisation means:


119) A parallel plate capacitor has a capacitance of 100 pF, when the plates of the capacitor are separated by a distance of t. Then a metallic foil of thickness t/3 is introduced between the plates.


120) Using mass (M), length (L), time (T) and current (A) as fundamental quantities, the dimensions of permittivity is :


121) Equipotential surfaces associated with an electric field, which is increasing in magnitude along the x-direction, are :


122) The electric field (E) due to a uniformly charged sphere of radius (R) as function of the distance from its centre (r) is represented graphically by


123) An electric dipole has the magnitude of its charge as q, and its dipole moment as p. It is placed in a uniform electric field E. If its dipole moment is along the direction of the field, then force acting on it and its potential energy are respectively :


124) A thin aluminium sheet is placed between the plates of a parallel capacitor. Its capacitance will :


125) A simple pendulum has time period T. The bob is given negative charge and surface below it is given positive charge. The new time period will be :


126) Two insulated charged spheres of radii 20 cm and 25 cm respectively and having an equal charge Q are connected by a copper wire, then they are separated by a copper wire, then they are separated :


127) Work done in moving a positive charge on an equipotential surface is :


128) The capacity of a condenser in which a dielectric of dielectric constant 5 has been used, is C. If the dielectric is replaced by another with dielectric constant 20, the capacity will become: