Electric Charges and Fields

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

Electric field at centre O of semicircle of radius a having linear charge density is given as [figure]

1. 2 0 a
2. 0 a
3. 2 0 a
4. 0 a