Electric Charges and Fields

A line charge of length a2 is kept at the center of an edge BC of a cube ABCDEFGH having edge length ' a ' as shown in the figure. If the density of line charge is C per unit length, then the total electric flux through all the faces of the cube will be . (Take, 0 as the free space permittivity) [figure]

1. a2 0
2. a8 0
3. a4 0
4. a16 0

An electron is made to enter symmetrically between two parallel and equally but oppositely charged metal plates, each of 10 cm length. The electron emerges out of the electric field region with a horizontal component of velocity 106 m/s. If the magnitude of the electric field between the plates is 9.1 V/cm, then the vertical component of velocity of electron is (mass of electron =9.1 10-31 kg and charge of electron =1.6 10-19 C )

1. 1 106 m/s
2. 16 106 m/s
3. 16 104 m/s
4. 0

Five charges +q, +5q, -2q, +3q and -4q are situated as shown in the figure. The electric flux due to this configuration through the surface S is : [figure]

1. q 0
2. 3q 0
3. 5q 0
4. 4q 0

An electric field E = (2x i) NC-1 exists in space. A cube of side 2 m is placed in the space as per figure given below. The electric flux through the cube is Nm2/C. [figure]

An electric field, E = 2 i + 6 j + 8 k 6 passes through the surface of 4 m2 area having unit vector n = ( 2 i + j + k 6 ). The electric flux for that surface is V m.

If the net electric field at point P along Y axis is zero, then the ratio of | q2q3 | is 85 x, where x = . [figure]

is the uniform surface charge density of a thin spherical shell of radius R. The electric field at any point on the surface of the spherical shell is :

1. / 0 R
2. / 0
3. / 2 0
4. / 4 0

Three infinitely long charged thin sheets are placed as shown in figure. The magnitude of electric field at the point P is x 0. The value of x is (all quantities are measured in SI units). [figure]

Two identical conducting spheres P and S with charge Q on each, repel each other with a force 16 N. A third identical uncharged conducting sphere R is successively brought in contact with the two spheres. The new force of repulsion between P and S is :

1. 1 N
2. 6 N
3. 12 N
4. 4 N

In hydrogen like system the ratio of coulombian force and gravitational force between an electron and a proton is in the order of :

1. 1019
2. 1039
3. 1029
4. 1036