Two equally charged, identical metal spheres A and B repel each other with a force 'F'. The spheres are kept fixed with a distance 'r' between them. A third identical, but uncharged sphere C is brought in contact with A and then placed at the mid-point of the line joining A and B. The magnitude of the net electric force on C is 

(1) F

(2) 3F/4

(3) F/2

(4) F/4

A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium, if q is equal to 

(1) $-\frac{Q}{2}$

(2) $-\frac{Q}{4}$

(3) $+\frac{Q}{4}$

(4) $+\frac{Q}{2}$ 

The figure shows the electric lines of force emerging from a charged body. If the electric fields at A and B are E_A and E_B respectively and if the distance between A and B is r, then:

1. \(E_{A}~>~E _{B}\)
2. \(E_{A}~<~E _{B}\)
3. \(E_{A}~=~\frac{E_{B}}{r^{}}\)
4. \(E_{A}~=~\frac{E_{B}}{r^{2}}\)

\(ABC\) is an equilateral triangle. Charges \(+q\)  are placed at each corner. The electric intensity at \(O\) will be: 

The magnitude of electric field intensity E is such that, an electron placed in it would experience an electrical force equal to its weight is given by 

(1) mge

(2) $\frac{mg}{e}$

(3) $\frac{e}{mg}$

(4) $\frac{e^2}{m^2}g$

An uncharged sphere of metal is placed in between two charged plates as shown. The lines of force look like 

(1) A

(2) B

(3) C

(4) D

The magnitude of electric field E in the annular region of a charged cylindrical capacitor 

(1) Is same throughout

(2) Is higher near the outer cylinder than near the inner cylinder

(3) Varies as 1/r, where r is the distance from the axis

(4) Varies as 1/r², where r is the distance from the axis