Electric Charges and Fields

A thin conducting ring of radius R is given a charge +Q. The electric field at the centre O of the ring due to the charge on the part AKB of the ring is E. The electric field at the centre due to the charge on the part ACDB of the ring is [figure]

1. E along KO
2. 3E along OK
3. 3E along KO
4. E along OK

A hollow cylinder has a charge q coulomb within it. If is the electric flux in units of volt-metre associated with the curved surface B, the flux linked with the plane surface A in units of V-m will be [figure]

1. q2 0
2. 3
3. q 0 -
4. 12 ( q 0 - )

Three point charges +q, -2q and + q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are

1. 2qa along the line joining points (x = 0, y = 0, z = 0) and (x = a, y = a, z = 0)
2. qa along the line joining points (x = 0, y = 0, z = 0) and (x = a, y = a, z = 0)
3. 2qa along +x direction
4. 2qa along +y direction

A square surface of side L metres is in the plane of the paper. A uniform electric field E (volt/m), also in the plane of the paper is limited only to the lower half of the square surface (see figure). The electric flux in SI units associated with the surface is [figure]

1. EL2
2. EL2/2 0
3. EL2/2
4. zero

The unit of permittivity of free space, 0, is

1. coulomb/newton-metre
2. newton-metre2/coulomb2
3. coulomb2/newton-metre2
4. coulomb2/(newton-metre)2

A charge q is located at the centre of a cube. The electric flux through any face is

1. 2 q6(4 0)
2. 4 q6(4 0)
3. q6(4 0)
4. q6(4 0)

An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius r. The Coulomb force F between the two is

1. K e2r2 r
2. -K e2r3 r
3. K e2r3 r
4. -K e2r2 r

A dipole of dipole moment p is placed in uniform electric field E then torque acting on it is given by

1. = p E
2. = p E
3. = p + E
4. = p - E

A charge Q is placed at the centre of a cube, the flux coming out from each face will be

1. Q6 0 10-6
2. Q6 0 10-3
3. Q24 0
4. Q8 0

A charge Q is situated at the corner of a cube, the electric flux passed through all the six faces of the cube is

1. Q6 0
2. Q8 0
3. Q 0
4. Q2 0