The ratio of surface areas of the two spheres is 9:16.They are put in contact and a charge of 7μC is given to the system and they are separated. Then the intensity of the electric field at a distance of 100m from the centre of smaller sphere is

A. 2.7V/m

B. 27V/m

C. 9V/m

D. 18V/m

In a parallel plate air capacitor of capacitance 4 farad, if the lower half of air space is filled with a material of dielectric constant 3 its capacitance changes to

A. (4/3) F

B. (8/3)F

C. 6F

D. 12F

Two charges of +200μC and -200μC are placed at the corners B and C of an equilateral triangle ABC of side 0.1m.The force on a charge of 5μC placed at A is

A. 900N

B. 600√3N

C. 1200√3N

D. 1800N

A rod with linear charge density λ is bent in the shape of circular ring.The electric potential at the centre of the circular ring is

A. 2λ/ε0

B. λ/ε0

C. λ/2ε0

D. λ/4ε0

A proton of mass m charge e is released from rest in a uniform electric field of strength E.The time taken by it to travel a distance d in the field is

A. √(2ae/mE)

B. √(2am/Ee)

C. √(2aE/me)

D. √(2Ee/dm)

The energy stored in a sphere of 10cm radius when the sphere is charged to a potential of 300 volt is

A. 5x10-7J

B. 2 x10-6J

C. 4 x10-7J

D. 3 x10-6J

The potential energy of a proton is 3.2x10-18J at a particular point. The electric potential at this point is

A. 15V

B. 20V

C. 10V

D. 5V

Capacitance of a capacitor becomes 7/6 times its original value if a dielectric slab of thickness,t=2/3d is introduced in between the plates.d is the separation between the plates.The dielectric constant of the di-electric slab is

A. 14/11

B. 11/14

C. 7/11

D. 11/7

Two wires A and B,made of same material and having their lengths in the ratio 6:1 are connected in series.The potential differences across the wires are 3V and 2V respectively.If rA and rB the radii of A and B respectively,then rA/rB is

A. 1/4

B. 1/2

C. 1

D. 2

When a dielectric slab of the same area of cross-section and thickness equal to 2/3 of the separation is introduced between the plates of a parallel plate capacitor, its capacitance becomes 2.25 times the original value. The dielectric constant of the material of the slab is

A. 1.5

B. 4.5

C. 5.0

D. 6.0

A charge of 10 units is divided so that force between the two charges is maximum when placed 2cm apart. The two charges are

A. 5,5

B. 1,9

C. 3,7

D. 6,4

A condenser of 20μF is charged to a certain voltage and then discharged through a 4x106Ω resistor.The time taken for the condenser to lose 63% of its charge is

A. 50s

B. 8s

C. 80s

D. 5s

The charge stored in a capacitor is 20μC and the potential difference across the plates is 500V,its capacity is

A. 250 μF

B. 2x10-6 μF

C. 10-2μF

D. 0.04μF

Two spheres of radii 12 cm and 16 cm have equal charge. The ratio tstored in the condenser is

A. 2 : 1

B. 1 : 2

C. 4 : 3

D. 3 : 4

Charges +50,+20,+30 and -100 nano coulomb are placed at the four corners of a square of side 5√2cm.The potential at the intersection point of diagonals is

A. Zero

B. 1.8x104V

C. 3.6x104V

D. 1.8√2x104V

A condenser of capacity 10 μF is charged to a potential of 500 V. Its terminals are then connected to those of an uncharged condenser of capacity 40 μF. The loss of energy in connecting them together is

A. 1J

B. 2.5J

C. 10 J

D. 12 J

Two point charges are separated by 3 cm of air and 3 cm of a dielectric of relative permittivity 4.The equivalent air separation between them is (as far as their coulombic interaction is concerned)

A. 6 cm

B. 9 cm

C. 12 cm

D. 15 cm

Two charges each of 100 micro coulomb are separated in a medium of relative permittivity 2 by a distance of 5cm.The force between them is

A. 1.8x104N

B. 1.8x104dyne

C. 3.6x105N

D. 0.36x105N

Two condensers of capacities 4 μF and 5 μF are joined in series. The potential difference across 5 μF is 10 V then the potential difference across 4 μF condenser is:

A. 25 V

B. 12.5 V

C. 10 V

D. 22.5 V

A 2μF condenser is charged to 500 V and then the plates are joined through a resistance in joule is

A. 0.5 x 10-2 Joule

B. 0.25 x 10-2 Joule

C. 25 x 10-2 Joule

D. 5010-2 Joule

A dielectric of thickness 5cm and dielectric constant 10 is introduced between the plates of a parallel plate capacitor having plate area 500 sq.cm and separation between the plates 10cm.The capacitance of the capacitor with dielectric slab is(ε0=8.8x10-12/N-m2)

A. 4.4pF

B. 6.2pF

C. 8pF

D. 10pF

A 4μF capacitor is charged by a 200V battery.It is then disconnected from the supply and is connected to another uncharged 2μF capacitor.During this process,Loss of energy(in J)is

A. zero

B. 5.33x10-2

C. 4 x10-2

D. 2.67x10-2

a spark is produced between two insulated surfaces maintained at a potential difference of 5 x 106 volt. The energy output is 10-5 J. The charge transferred during the spark is

A. 2 x 10-12 C

B. 2 x 1012 C

C. 5 x 10-11 C

D. 5 x 1011 C

A capacitor of 8 μF is charged to a potential of 1000V. The energy stored in the capacitor is

A. 4 J

B. 2 J

C. 12 J

D. 8 J

A 100 PFcapacitor is charged to a potential difference of 24V.It is connected to an uncharged capacitor 20PF.what will be the new potential difference across 100PF capacitor

A. 12V

B. 24V

C. 20V

D. 32V

Charge 20,30,-40 and 50 μC are at the corners of a square of 10cm. The field at the point of intersection of the diagonals is

A. (360√10×105)N/C

B. (360×105)N/C

C. (360×106)N/C

D. (36√10×105)N/C

Three condensers 1μF,2μF and 3μF are connected in series to a p.d of 330volt.The PD across the plates of 3μF is

A. 270V

B. 60V

C. 300V

D. 180V

Two parallel plate air capacitors have the same separation. The plates of the first are squares of side 10cm.The plates of the second are squares of side 20cm.The ratio of the capacities respectively is

A. 1:4

B. 4:1

C. 1:2

D. 2:1

The capacity of a parallel plate condenser consisting of two plates each 10 cm square and are separated by a distance of 2mm is (Take air as the medium between the plate):

A. 88.5 x 10-13 F

B. 44.42 x 10-12 F

C. 4.42 x 10-11 F

D. 8.85 x 10-13 F

Two positive charges q1=4x10-6C and q2=9x10-6C are placed 10cm apart in air.The position of a third charge to be placed between them,such that there will be no resultant force on it is

A. 6cm from q1

B. 3cm from q1

C. 4cm from q1

D. 7cm from q1