Electric Field and Potential Questions and Answers

22 STATEMENT 1 A parallel plate capacitor is charged using a battery and 1 point then a dielectric slab is inserted completely filling space between plates without disconnecting battery Electric field between plates of capacitor will decrease STATEMENT 2 If battery remains connected then charge on plates of capacitor increases O A O B O C D Jorn

2 3 The magnetic field in a region is given by B B 1 k A straight conduction AB of length 2L placed with its ends at points A a 0 0 and B a 2L 0 current I A to B The magnetic force on the conductor is A zero B IB 2L a j C IB L a j D 21B L a j Two particles X and Y having equal charges after being accelerated through the same potential difference enter a region of uniform magnetic field and describe circular paths of radii R and R respectively The ratio of the masses of X to that of Y

21 STATEMENT 1 When a neutral body is charged negatively its mass increases slightly STATEMENT 2When a body is charged negatively it gains some electrons and electron has finite mass though quite small O A O B C D

A charge particle having charge 4 x 10 C moves from state of rest in uniform electric field of magnitude 5 x 10 V m What is its KE after 10 second m 2 10 kg 1013 J 10 J 5 x 10 2 J

R A line charge of total charge of is formed into three quarters of a circular are of radius R around the origin as shown in the figure Note that one quarter of the circular are is missing Fived the electrostatic field at the origin

Three charges A B C are positioned as shown in the diagram A 3 00 C B 4 00 C C 6 58 C X 1 36 m Y 2 00 m What is the magnitude of the force on charge C in units of newtons Give the answer as a positive number X A B Y C

If and be respective electric fields at equatorial position and axial position of electric dipole at same distance then 0 0 x 0 0

Q 1 A hollow metal sphere of radius 5 cm is charged such that the potential on its surface is 10 V the potential at the centre of the sphere will be a OV b 10 V c 5 V Q 2 In the given group the negative resistance region is a OA b AB c BC d 20 V d CD VA C 1

20 STATEMENT 1 A conducting sphere charged up to 50V is placed at the 1 point center of a conducting shell charged up to 100V and then connected by a wire All the charge of the shell flows to the outer sphere STATEMENT 2The positive charge always flows from higher to lower potential O A B C D 4

The electric potential due to a linear 2 points quadrupole moment varies O proportional to the cube of the distance O inversely as the square of the distance O inversely with the distance inversely as the cube of the distance

Two point charges q and 9q are kept at r 12 cm apart as shown The electric field is zero at q 9q A B 1 6 cm from point A toward B 2 3 cm from point A opposite to B 3 9 cm from point B towards A 4 18 cm from the point B towards A

A Statement 1 is True Statement 2 is True Statement 2 is a correct explanation for Statement 1 B Statement 1 is True Statement Statement 1 C Statement 1 is True Statement 2 is False D Statement 1 is False Statement 2 is True 2 is True Statement 2 is NOT a correct explanation for 17 STATEMENT 1 Electric field may be present in the vicinity of a current 1 p carrying wire STATEMENT 2The principle of conservation of charge is not followed when charges are in motion O A O B O C O D

Two charges Q and Qe are separated by a distance D IF Q Q and D are doubled the electrostatic Force in same medium Increases by a factor of 4 Decreases by a factor of 2 Increases by a factor of 2 Remains unchanged

A molecule with dipole moment p is placed in an electric field of strength E Initially the dipole is aligned parallel to the field If the dipole is to be rotated to be anti parallel to the field the work required to be done by the external agency is 1 Point O 2pE O 2pE O PE

12 A hollow charged conductor has a tiny hole cut into its surface What is the electric field in the hole remember is the unit vector in the outward normal direction and a is the surface charge density near the hole a G 2 0 A O b o e0 A c 2 G E0 A d 4 6 20 h

When a point charge in front of an insulated and uncharged conducting sphere as in Fig then D a tea f f fe 1 point Charge density at the point C is positive but at D is negative Charge density at the both point C and D is positive Charge density at the point C is negative but at D is positive Charge density at the both point C and D is negative

A point charge is placed at 1 2 3 Match statements in column 1 with appropriate points given in column II Column l Q1 Point which have same electric field intensity as at 5 2 4 Q2 Point which have same potential as at 5 2 4 Q3 Point which have same direction of electric field as at 5 2 4 Q4 Point which have same magnitude of electric field as at 5 2 4 01 A1 2009 A3 A4 A5 SUT Column Il A1 2 6 3 A2 9 2 5 A3 5 3 3 A4 3 2 2 A5 ne

1 15 A system has two charges qA 2 5 x 10 7 C and qB 2 5 10 7 C located at points A 0 0 15 cm and B 0 0 15 cm respectively What is the electric dipole moment of the system a 7 5 x 10 8 C m along X axis b 7 5 x 10 8 C m along Y axis c 7 5 x 10 8 C m along z axis d 3 75 x 10 8 C m along X axis

3 Three charges each of magnitude q are placed at the corners of an equilateral triangle the electrostatic force on the charge placed at the centre is each side of triangle is L a Zero 1 q b 4ne 1 c 1 3q 4 L q COR A FB q d FA 1 q 12 1 5 FC B 2L q

In the electric field of a point charge q at O a certain test charge is carried from point A to B C D and E Then the work done 1 Point C A O q is least along the path AB is least along the path AD D is zero along all the paths AB AC AD and AE is least along the path AE

Two point charges are separated by distance of 10 cm One charge is 25 C and other is 50 C The electric field at P which is a point between two charges 2 cm from negative charge is 25 C P 50 C 10 cm 6 33 108 N C 3 66 107 N C 4 56 x 108 N C 8 110

Figures show charged beads with charges 9 each placed at vertices Rank the magnitude of electric field at centre in decreasing order L X X L a c L b a a c a b a b a c d a c b b a a c 751 L L

Two conducting spheres of radii 5 cm and 10 cm are given a charge of 15 C each After the two spheres are joined by a conducting wire the charge on the smaller sphere is NCERT XII 1 88 1 5 C 2 10 C 3 15 C 4 20 C

uniform electric field of magnitude 350 V m is directed in the negative y direction as shown in the figure below The coordinates of point are 0 250 0 200 m and those of point are 300 0 400 m Calculate the electric potential difference VB VA using the dashed line path V B ff

Is the electric force that which one point charge exerts on another charge change if other charges are brought near by State yes or no and the name of principle being followed 1 Point

2 There is a uniform electric field of intensity E which is as shown How many labelled points have the same electric potential as the fully shaded point a 2 c 8 b 3 d 11 o o o E ro

A 2 00 x10 4 C charged particle of mass 3 00x10 5 kg initially moving with a speed of 20 0 m s in the positive x direction enter an electric field of 489 N C directed in the positive y direction The speed of the particle after a time of 0 200 s is m s Hint you must consider the x and y components of the velocity and combine these to find the speed

7 If a charged spherical conductor of radius 10 cm has potential V at a point distant 5 cm from its centre then the potential at a point distant 15 cm from the centre will be a V 3312 c V 2 b V 3 d 3V 655 K4 x 10 15 3

each of the three charges 3 5 A thin wire ring of radius r has an electric charge q What will be the increment of the force stretching the wire if a point charge is placed at the ring s centre nd the C is located in

A 81 2 nC charge is positioned 2 61 Im from a 16 5 nC charge What is the magnitude of the electric field at the midpoint of these charges in units of N C Give the answer as a positive number

Dipole moment of the arrangement of the charges shown in figure is 9 a 3q a a 2qai gai 2qai 9 L X

3 Two identical 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 electric potential energy of Q when it is displaced by a small distance x along the x axis is approximately proportional to lloa pnitoubno 1 x ger 3 X3 x3 2 x2 4 X S

equal positive charge Q coulomb on each are suspended by two insulated string of equal length L meter from a hook fixed to a stand The whole set up is taken in satellite DAY into space where there is no gravity state of weightlessness Then the angle between the string and tension in the string is 1 Q 2L a 180 4 a 1808 1 0 b 90 1 Q 4 E L d 180 Q 1 QL Q

Consider a uniform electric field E 3x10 1 N C What is flux of this field through a square of side 10 cm whose plane makes an angle of 30 with x axis 30 Nm C 20 Nm C

An infinite line charge produces an electric field of 18 105 N C at perpendicular distance of 4 cm What is linear charge density 4 C m 6 C m 9 C m 2 C m

Figure shows a set of equipotential surfaces The magnitude and direction of electric field that exists in the region will be y axis 5 V 10 V 15 V 20 V IIIII 1 3 4 12 10 V m along positive x axis 5 V m along positive y axis 50 V m along negative x axis 500 V m along negative x axis hr m x axis cm

Two point charges 10 C and 4 C are placed 20 cm apart The electrostatic potential energy of the system is 2 4 J 1 8 J 3 6 J

particles X and Y having equal charges after being accelerated through the same potential difference enter a region of uniform magnetic field and describes circular path of radius R and R respectively The ratio of mass of X to that of Y is 1 2 1 R R 2 R R 3 R R 4 R R

Two large metallic plates are fixed horizontally parallel to each other one above the other The upper plate carries charge Q and the lower plate carries charge Q A particle is in equilibrium in between the plates Then select the correct options among the following statements a Particle must carry negative charge b Particle must carry positive charge c If one of the plate is suddenly removed then acceleration of the particle will be g 2 downward d If one of the plate is suddenly removed then acceleration of the particle will be g downward

The electric field on two sides of a large charged plane sheet is shown in fig The charge density on the sheet in S I units is given by is the permittivity of free space in S I units E 8 Vm E2 12 Vm

The potential barrier for germanium p n junction is 0 3 V If the width of the depletion layer is 1 micron then field strength at the junction is 3 x 105 V m 1 0 3 10 4 V m 1 O 3 x 10 5 V m O 3 33 x 106 V m 1

A B and C are three concentric metallic shells Shell A is the innermost and shell C is the outermost A is given some charge Then a Inner surfaces of B and C will have same charge b Inner surfaces of B and C will have same charge density c Outer surfaces of A B and C will have same charge d Outer surfaces of A B and C will have same charge densit A LA C

65 The electric potential in a certain region is expressed by V 6x 8xy 8y 6yz 4z volts The magnitude of the force acting on a charge of 2 C situated at the origin will be charge B 2 N 6 N

7 A non conducting ring of mass m and radius R is charged as shown The linear charge density for corresponding region shown is It is placed on tough horizontal surface A uniform electric field Ei is switched on and the ring starts rolling without sliding Angular velocity acquired by the ring when it turns through XE in Sl unit is m an angle of T 2 is 16 rad s Value of X

Example 1 9 Two point charges q and q2 of magnitude 10 C and 10 respectively are placed 0 1 m apart Calculate the electric fields at points A B and C shown in Fig 1 14 E B 0 05 m 0 1 m 9 0 05 m C E IC Exc A EA 0 1 m 0 05 m

Adipole is placed in an electric field as shown In which direction will it move 88 89 towards the right as its potential energy will increase towards the left as sta potential energy will In increase towards the right as its potential energy will decrease towards the left axits potential energy will decrease

A disk of radius a 4 having distributed charge 6 C is placed on the x y plane with its centre at a 2 0 0 A rod of length a carrying a uniformly distributed charge 8 C is placed in the x axis from x a 4 to x 5a 4 Two point charges 7C and 3C are placed at a 4 a 4 0 and 3a 4 3a 4 0 respectively Consider a cubical surface formed by six surfaces x ta 2 y ta 2 z ta 2 The electric flux through this cubical surface is A 0 20 Eo 10C 2C B Eo 120

Three identical plates of area A are arranged as shown A charge Q is giver to plate 2 Then 1 2 3 ALE 2d a charge 2Q 3 appears on plate 1 b chare 2Q 3 appears on plate 1 c charge Q 3 appears on plate 3 d charge on two faces of plate 2 are 2Q 3 and Q 3

a Two rods of the same weight and equal length have different thickness They are held vertically on the surfac of sand Which one of them will sink more Why Give an example that illustrates that change in temperatu may cause change in atmospheric pressure

A marble is allowed to roll down an inclined plane from a fixe height At the foot of inclined plane it moves on a horizontal surface a covered with silk b covered with a layer of sand and c covered with a glass sheet On which surface marbles move the shortest distance Give reason for your answer