Electric Field and Potential Questions and Answers

Three identical point charges are placed on the vertices of an equilateral triangle ABC as shown in the igure Consider a median AD where point O is the centroid As we move from point A to point D Answer A B C OB Your Attempt Correct answer Electric field vanishes only once at O between points A and D Rate this question Electric field vanishes two times first at O and then somewhere between 0 and D Electric field vanishes two times first at a point somewhere between A and O and then At O

Conducting shell of radius R carries charge Q another charge Q is placed at 3R distance from centre of the shell If the potential at point P due to 14 KQ 3n R Then the value of n is charge on shell is x x R X X xxxx A 9 3 3R where K 1 4 EO

The variation of electric field between the two charges 9 and 92 along the line joining the charges is plotted against distance from 9 taking rightward direction of electric field as positive as shown in the figure Then the correct statement is 9 and 92 are positive and 19 1 1921 9 and 92 are positive and 19 1 19 1 91 9 is positive and q2 is negative 9 19 1 9 is negative and q2 is positive 9 1921

1 Charges q and q are placed at points A and B respectively which are at a distance 2L apart C is the mid point between A and B The work done in moving a charge Q along the semicircle CRD is 1 q 9 A C B D qQ 2 L R qQ 3 6TI 2 4 qQ 3 L qQ ATTE I

The diagrams below show regions of equipotentials 20 V 40 V a C 10 V 10 V A 30 V 30 V B B b d A 20 V 40 V 10 V 30 V 20 V A 10 V B 30 V 40 V B 20 V 40 V A positive charge is moved from A to B in each diagram NEET 2017 1 Maximum work is required to move q in figure c 2 In all the four cases the work done is the same 3 Minimum work is required to move q in figure a 4 Maximum work is required to move q in figure 6

39 A sphere made of lead and radius R is given charge q The variation of electric potential V with radial distance r from the centre of sphere is given by 1 3 VA r R r R 2 4 VA VA r R r R

24 Two point charges q and q2 of magnitude 10 8 C and 10 8 C respectively are placed 0 1 m apart Calculate the electric field at point A B and C as shown in figure How to decide the direction B 0 1 m 0 1 m 0 05 m q 0 05 m A 0 05 m 92

Two charges are separated as shown in the diagram A below Each charge has a magnitude of 50 nC in diagram A If the charge on the right is moved further to the right as depicted in diagram B additional charge that must be removed from the left in order to maintain the initial electric field magnitude at the center in nC is given by nC Fill the value of a in OMR sheet B 9 7 t 1m 9 r Im q r 1m r 3m

The magnitude of the earth s magnetic field at a place is B and the angle of dip is 8 A horizontal conductor of length 1 lying north south moves eastwards with a velocity v The emf induced across the rod is 1 Zero 3 Bolvsind 2 Bolv 4 Blvcos8

38 Which of the following is incorrect regarding equipotential surfaces 1 Equipotential surface is spherical for point charge 2 Equipotential surface is flat for uniform electric field 3 Equipotential surface is cylindrical for infinite uniform linear charge 4 At equipotential surface electric field is uniform

172 Electrostatic Potential and 18 Figure shows a set of equipotential surface An electron is being moved from one point to other 20 V 30 V 40 V B c A Work done by the electric field in moving the electron 1 From A to B is more than from B to C 2 From A to B is less than from B to C 3 From A to B and from B to C are zero 4 From A to B is same as from B to C An uncharged parallel pl

Two conducting solid spheres of radii R and 2R are given equal charges Q each When they are connected t a thin conducting wire the charges get redistributed The ratio of charge Q on smaller sphere to charge Q2 c larger sphere becomes MP PET 2001 b Q 2 0 a d None of these

Example 32 An electron is liberated from the lower of the two large parallel metal plates separated by a distance of 20 mm The upper plate has a potential of 2400 V relative to the lower plate How long does the electron take to reach the upper plate Take of electrons 1 8 x 10 1 C kg e m

of a simple pendulum has mass 1 kg and charge qo Tension in the string doubles when another charge qo is fixed at position Pas shot e period of simple pendulum for the small oscillation is ns another charge qo remains fixed at P Find value of n g n 1 6m 6 m

1 A hollow conducting sphere has inner radius 5 cm and outer radius 8 cm then find maximum possible potential of conductor if breakdown electric field of air is 3 x 106 V m 1 240 kV 3 960 kV 2 480 kV 4 720 kV

Two small charged spheres separated by a distance d exert a force F on each other If they are immersed in a liquid of dielectric constant 4 then new force on any of the spheres will be distance between the charge remains same 4F

Two charges each equal to 2 C are 0 5 m apart If both of them exist inside vacuum then net force on the system wil be 1 89 N 2 44 N 0 144 N Zero

A short dipole of dipole moment p is placed along x axis at a distance d from a long wire having uniform linear charge density wire is along Y axis as shown Find minimum work required to align this dipole along y axis so that dipole moment p is along y direction tels 1 P TE d l xx 9 q 2 X P

We have an infinite plane of uniform charge with charge density O and an infinite rod which is uniformly harged with charge density A as shown in figure Find the charge density of the infinitely long rod so that the Otal electric field at point P is zero 0 a www Infinite plane b Infinite line

Three charges and q are placed at the corner of an equilateral triangle of side a as shown in the figure The net electric dipole moment of the system will be q 2 a 3 qa 2 3 qa a a q 2

1 VA VB 8V 2 VA AB 4 V 3 VB VA 8V 4 VB VA 4V Charges q and q are placed at A and B respectively which are at a distance 2L apart If C is the midpoint between A and B then work done in moving charge Q from C to D through semicircular path CRD and form C to care respectively 1 90 2TE L and infinity 2 90 6TE L and zero 3 Zero zero 4 90 67 L and zero

The charge to be put on a spherical conductor of radius 0 2 m to produce an electric field of 0 072 N just above its surface is O 16 10 14C 8 x 10 14C 32 10 14C O4 x 10 14C

32 ABC is an equilateral triangle of side 10 m and D is the midpoint BC Charges of 100C 100C and 75C are placed at B C and respectively What is the magnitude of force experience by 1C placed at point A 1

Two short electric dipoles of moment P and 8P are placed opposite direction on a line at a distance of 15 cm The electric field will be zero at point between the dipoles whose distance from the dipole of moment Pis 10 cm 6 cm 12 cm 5 cm

3 7 a For the isolated charged conductor shown in the figure if the electric field at point A and B is E NCERT Pg 67 and Eg respectively then B x x 1 Eg EA x r a A 2 EA EB 4 F E 0

Three charges Q 2q q are placed at the vertices of an equilateral triangle of side a as shown in the figure If the ne electrostatic energy of the system is zero then Q is equal to Q q wie GIN 2 29

31 Two infinitely long parallel wires having linea charge densities and respectively are placed at a distance R The force per unit length on either wire will be 1 3 k2 R k 1 D2 2 4 k2 2 R K 1 2

Part A Electric Field Strength versus distance relationship for a point charge 1 Drag a 1nC charge at the middle of the grid Draw what the electric field field lines surrounding this positive charge look like and indicate their direction

65 Four identical charges are placed at the points 1 0 0 0 1 0 1 0 0 and 0 1 0 The potential at the origin is zero i The field at the origin is zero iii The potential at all points on the z axis other than the origin is zero iv The field at all points on the z axis other than the origin acts along the z axis a i ii c ii ii 66 If solid sphere of charge of radius Rhan ol b i iii d ii iv

7 A point charge q 2 x 10 C is placed at the centre a spherical cavity of radius 3 cm in a metal piece Points a and b are situated at distances 1 5 cm and 4 5 cm respectively from the centre of cavity The electric field intensities at a and bare a 8 x 10 N C and zero c zero and 8 9 x 105 N C d None of these b zero and zero

Consider the following statements Statement I Electric charge on any object is always quantised Statement II There is no analogous law on quantization of mass Choose the correct statement s X Statement I only Statement II only Both statements are correct Both statements are incorrect

A solid sphere conducting is surrounded by metalic shell of radius 2r Initial charges on them are 5 C 3 C respectively If both are connected by thin metallic wire then charge appearing on A and B are 1 4 C each 3 3 C and 5 C 5 C 2r A 3 C B 2 0 and 8 C 4 2u6 and fuc

Two straight non conducting wires parallel to the z axis pass through points O and A as shown in the figure below The wires carry equal and uniform charge density 0 4 C m Determine the electric field at point P EA 4 4 45 Eo 8 0 m

Kindly check i think answer should be zero A free point charge q and mass m is at rest at the origin A constant electric field E E and constant field Bk is in whole region If the charge reaches at 2 2 its speed will be kq Find value of k m Correct answer 8 User answer 0 Solution Answer 8 YA Ej 29E0 29E mv2 B Ei X

14 a D d Calculate the electric potential at the surface of a silver nucleus having radius 3 4 x 10 4m The atomic number of silver is 47 and charge on a proton is 1 6 x 10 1 9 x 10 V 2 4 x 10 V 11 x 10 V 2 x 10 V

12 Two equally charged identical small balls kep some fixed distance apart exert a repulsive forc F on each other A similar uncharged ball afte touching one of them is placed at the mid point line joining the two balls Force experienced b the third ball is 1 4F 3 F 2 2F F 2 4

A and B are two equipotential surfaces as shown in the figure A charge of 2 C is shot from origin with 102 m s Find work done by the field on the charge to cross the field If field extends upto 20 cm in Y axis Given V V 10 V V X 1 x 10 J 1 10 J A 14 0 0 0 10 cm B

A positive charge q is carried slowly from a point x to point y in an electric field of point charge Q The work done by external force is NCERT Pg 64 1 3 Q Qq 4TEO 1 b 1 a Qq 1 1 2 a b Tower 8 Puso Ro a b X 2 4 Qq 1 2 a Qq 2 EO FIL 11 OOF DE y b 1 1 b a 044 1760345

Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in the figure Which one of the arrows shown represents the net force acting on the point charge with a charge Q 2Q P Q OA Oc B d Net force is zero Q Q B D

A spherical volume contains a uniformly distributed charge of density 2 C m The electric field intensity at a point inside the volume at a distance 3 0 cm from the centre is 1 18 08 10 N C 2 9 04 10 N C X 3 4 52 10 N C 4 2 26 10 N C

Assertion A Electric filed lines do not form closed loops Reason R Electric filed lines are always normal to the surface of a conductor A A B B

lihes between the charge and the plate What is the nature of symmetry of electric field due to a 14 Figure shows a point charge 0 located at a distance point charge and ii a dipole R 2 from the center of a sph

Two identical capacitors have the same capacitance C One of them is charged to potential V and the other to V The negative terminals of the capacitors are connected together When the positive terminals are also connected the decrease in energy of the combined system is 1 1 C V V 2 1 C V V 3 C V V 4 4 C V V 4

Assertion A The electrostatics force increases with decrease in the distance between the charges Reason R The electrostatic force of attraction or repulsion between any two stationary point charges is inversely proportional to the square of the distance between them A A B B

7 A certain charge Q is divided at first into two parts q and Q q Later on the charges are placed at certain distance If the force of interaction between two charges is maximum then 1 Q q 4 1 Q3 05 9 1 L 47780

12 A thin dielectric spherical shell of radius R is divided into two equal parts These parts are held together forming a complete shell and are given uniformly distributed unlike charges Q and q If work done in making separation between the shells infinite is W determine self energy of a charge q uniformly distributed on a hemispherical shell radius r As I YhEor qwR 2YQ Cundii Rand T nswer is also mentioned in picture containing the estion Kindly check the answer before submitting solution

6 Three identical thin uniformly charged filaments are fixed along three sides of a cube as shown in the figure Length of each filament is I and line charge density on each of them is Determine electric field at the centre of the cube The cube is a geometrical construct and not made of any matter Zero N C

ALLE Planes x 2 and y 3 respectively carry charges 10 nC m and 15 nC m If the line x 0 z 2 carries charge 10 nC m calculate E at x y z due to the three charge distributions 1 A 0 0 4 5 7 5j 2 5k n 1 51 7 5j 2 5k n 1 C 0 0 0 5 7 5 2 5k n B 0 0 0 5 7 D E 0 0 4 51 7 5j 2 5k n N N

24 A hemispherical bowl of inner radii R and outer radii 2R is Find the electric field at point O 3p R 480 25 r charged with density p P R A C 2p R 3 3p R 8 B 3p R D 2 P ZA RO 2R 900 figure It ca

vi Total energy aquired by the charge during N complete revolution ET 2NqV where V is potential difference to which the charge is subjected every tim enters a dee This energy must be equal to the maximum kinetic energy of charge