Electric Charges and Fields

Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle with each other. When suspended in water the angle remains the same. If density of the material of the sphere is 1.5 g/cc, the dielectric constant of water will be . (Take density of water = 1 g/cc)

C1 and C2 are two hollow concentric cubes enclosing charges 2Q and 3Q respectively as shown in figure. The ratio of electric flux passing through C1 and C2 is : [figure]

1. 3:2
2. 5:2
3. 2:5
4. 2:3

Suppose a uniformly charged wall provides a uniform electric field of 2 104 N/C normally. A charged particle of mass 2 g being suspended through a silk thread of length 20 cm and remain stayed at a distance of 10 cm from the wall. Then the charge on the particle will be 1 x μC where x= . [use g=10 m/s2]

Two charges q and 3q are separated by a distance 'r' in air. At a distance x from charge q, the resultant electric field is zero. The value of x is :

1. r3(1+ 3)
2. (1+ 3)r
3. r(1+ 3)
4. r(1+ 3)

Force between two point charges q1 and q2 placed in vacuum at 'r' cm apart is F. Force between them when placed in a medium having dielectric constant K=5 at 'r/5' cm apart will be:

1. 5F
2. 25F
3. F/5
4. F/25

A particle of charge '-q' and mass 'm' moves in a circle of radius 'r' around an infinitely long line charge of linear charge density '+ '. Then time period will be given as : (Consider k as Coulomb's constant)

1. T2= 4 2m2k qr3
2. T= 12 r m2k q
3. T= 12 2k qm
4. T=2 r m2k q

Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 37 with each other. When suspended in a liquid of density 0.7 g/cm3, the angle remains same. If density of material of the sphere is 1.4 g/cm3, the dielectric constant of the liquid is ( 37 = 34 )

Two charges of 5Q and -2Q are situated at the points (3a,0) and (-5a,0) respectively. The electric flux through a sphere of radius '4a' having center at origin is :

1. 2Q 0
2. 7Q 0
3. 3Q 0
4. 5Q 0

An electron is moving under the influence of the electric field of a uniformly charged infinite plane sheet S having surface charge density + . The electron at t=0 is at a distance of 1 m from S and has a speed of 1 m/s. The maximum value of if the electron strikes S at t=1 s is [ m 0e ] Cm2, the value of is .

An electric field is given by (6 i+5 j+3 k) N/C. The electric flux through a surface area 30 i m2 lying in YZ-plane (in SI unit) is :

1. 60
2. 90
3. 180
4. 150