Electric Field and Potential Questions and Answers

1 Two particles carrying charges q and q and having equal masses m each are fixed at the ends of a light rod of length a to form a dipole The rod is clamped at an end and is placed in a uniform electric field E with the axis of the dipole along the electric field The rod is slightly tilted and then released Neglecting gravity find the time period of small oscillations

A conducting spherical shell is given charge 2Q A point charge Q is kept inside the shell at point O as shown Now if charge Q is shifted from point O to point P then magnitude of electric field at point A outside the shell will 2Q O P Conducting shell 26 2 fr 26 5 26 Action Y W 335 20 1 Increase 2 Decrease 3 Remain constant AY Ipproppo or decrease depending on distance

20 Three charges Q q and q are placed at the vertices of a right angle triangle isosceles triangle as shown If the net electrostatic potential energy of the configuration is zero value of Qis 1 3 q 2 2 2q 2 2 a q a 9 9 2 2 2 4 2q 2 2

equilateral triangle with the ends of the piece 6 A long straight wire carries a current i Let B be the magnetic field at a point P at a distance d from the wire Consider a section of length 1 of this wire such that the point P lies on a perpendicular bisector of the section Let B be the magnetic field at this point due to this section only Find the value of d l so that B differs from B by 1

Two free positive charges 4q and q are a distance apart What charge Q is needed to achieve equilibrium for the entire system and where should it be placed from charge q 4 1 Q q negative at 3 4 2 Q q positive at 3 3 Q q positive at 4 Q q negative at 1 3 1 3

0 Three concentric metallic shells A B and C of radii a b and c a b c have surface charge densities o o and o respectively i Find the potentials of three shells A B and C ii It is found that no work is required to bring a charge q from shell A to shell C then obtain the relation between the radii a b and c O

30 Equal charges q are placed at the four corners A B C D of a square of length a The magnitude of the force on the charge at B will be MP PMT 1994 DPMT 2001 1 b a 39 4 4q 2 4 2 q X 1 2 2 1 2 2 d 2 2 24 a

Answer the following questions in brief A glass rod is rubbed against a silk cloth Which object s gets get charged in this process 1 3 4 5 neither between two opposite charged clouds nor between a charged cloud and the ground 6 Name two objects a that can be charged by rubbing b that do not get charged on rubbing State the main difference between a conductor and an insulator Name the device used for protecting tall buildings from lightning strikes Give the meaning of the term earthing List down two precautions that a person can take if he is caught outside in the open during a lightning strike stions the dod plastic straw that

ILLUSTRATION 3 51 Figure shows three thin concentric spherical shells A B and C with initial charges on A B and Cas 30 20 and Q respectively The shells A and C are connected by a wire such that it does not touch B Shell B is earthed Determine the final charges 9 9 and a 3 R R 20 30 2 R Q B

5 placed at vertex A due to the other charges Four charges each of Q Coulomb are situated at the four vertices of square of side length a Find the net force on the charge placed at vert A due to the other charges

2 Two infinitely long uniformly charged non conducting sheets of charge density o 2 x10 each are placed perpendicular to each other as shown in figure What is the resultant electric field intensity at point P O at Isitms P O 0153 976 rito8 odt noiget al AV

1 ABC is an equilateral triangle of side 2m If E 10NC then V V is A A 1 10Y 2 10V B 3 20V 4 20V Ya and x 2a If the potential energ

11 Positive and negative point charges of equal magnitude are kept at 0 0 a 2 and 0 0 a 2 respectively The work done by the electric field when another positive point charge is moved from a 0 0 to a 0 0

A short dipole of dipole moment pj is the centre of a spherical cavity inside a solid metal sphere as shown Electric field at point P as shown on the x axis due to charges induced on the surfaces of the metal sphere is of 1 koj 3 2kn V A iO R P X 2 k ng 3 r

Take g 10 m s Two like charged infinitely long parallel wires with the same linear charge density of 3 10 C cm are 2 cm apart The work done against electrostatic force per unit length to be done in bringing them closer X by 1 cm is 100 J m Find the integer closest to x Corporate Office CG Tower A 46 52 IPIA Near City Mall Jhalawar Road Kota Raj 324005 in IF mail contact resonance ac in ADVES 122

2 Two opposite and equal charges 4 108 coulomb when placed 2 102 cm away form a dipole If this dipole is placed in an external electric field 4 x 108 newton coulomb the value of maximum torque and the work done in rotating it through 180 will be a 64 104 Nm and 64 104 J b 32 10 Nm and 32 104 J c 64 104 Nm and 32 104 J d 32 104 Nm and 64 104 J