1.Two similar spheres having +q and -q charge are kept at a certain distance. F force acts between the two. If in the middle of two spheres, another similar sphere having +q charge is kept, then it experience a force in magnitude and direction as      

2.Equal charges q are placed at the four corners A, B, C, D  of a square of length a. The magnitude of the force on the charge at B will be

3. 

4. Two metal pieces having a potential difference of 800 V are  0.02 m apart horizontally. A particle of mass 1.96 x 10 ⁻¹⁵ kg is suspended in equilibrium between the plates. If e is the elementary charge, then charge on the particle is

5.A charged ball B hangs from a silk thread S, which makes an angle θ with a large charged conducting sheet P, as shown in the figure. The surface charge density σ of the sheet is proportional to

6. A molecule with a dipole moment p is placed in an electric field of strength E. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency is

7.The capacity of a condenser is 4 x 10⁻⁶ farad and its potential is 100 V. The energy released on discharging it fully will be

8. A parallel plate condenser has a capacitance 50 μF in air and 110 μF when immersed in an oil. The dielectric constant  ‘k’ of the oil is

9. Eight small drops, each of radius r and having same charge q are combined to form a big drop. The ratio between the potentials of the bigger drop and the smaller drop is

10.In the circuit diagram shown in the adjoining figure, the resultant capacitance between P and Q is