# Electrostatics

### Three concentric metal shells A, B and C of respective radii a, b and c

Three concentric metal shells A, B and C of respective radii a, b and c (a < b < c) have surface charge densities +σ, -σ and +σ respectively. The potential of shell B is

### A charged oil drop is suspended in a uniform field

A charged oil drop is suspended in a uniform field of 3×104 v/m so that it neither falls nor rises. The charge on the drop will be (Take the mass of the charge = 9.9×10-15 kg and g = 10 m/s2)

1. 1.6 X 10-18
2. 3.2 X 10-18
3. 3.3 X 10-18
4. 4.8 X 10-18

### A charge Q is placed at each of the opposite corners of a square

A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each of the other two corners. If the net electrical force on Q is zero, then Q/q equals

1. -1
2. 1
3. -2√2
4. -1/√2

### If a charge q is placed at the centre of the line joining

If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is

1. Q/4
2. -Q/4
3. Q/2
4. -Q/2

### On moving a charge of 20 coulombs by 2 cm, 2 J of work is done

On moving a charge of 20 coulombs by 2 cm, 2 J of work is done, then the potential difference between the points is

1. 8 V
2. 0.5 V
3. 0.1 V
4. 2 V

### An electric dipole is placed along the x-axis at the origin O

An electric dipole is placed along the x-axis at the origin P. A point P is at a distance of 20 cm from this origin such that OP makes an angle 60° with x axis. If electric field at P makes an angle θ with x-axis, the value of θ is?