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

An infinite number of charges, each of charge 1 μC, are placed on the x-axis with co-ordinates x = 1, 2, 4, 8, ....∞. If a charge of 1 C is kept at the origin, then what is the net force acting on 1 C charge?

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: 

 
1. \(\frac{1}{4\pi\epsilon _0}\frac{q}{r^{2}}\)
2. \(\frac{1}{4\pi\epsilon _0}\frac{q}{r^{}}\)
3. zero
4. \(\frac{1}{4\pi\epsilon _0}\frac{3q}{r^{2}}\)

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

A charge particle is free to move in an electric field. It will travel 

(1) Always along a line of force

(2) Along a line of force, if its initial velocity is zero

(3) Along a line of force, if it has some initial velocity in the direction of an acute angle with the line of force

(4) None of the above

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 electric field near a conducting surface having a uniform surface charge density σ is given by 

(1) $\frac{\sigma }{{\epsilon }_0}$ and is parallel to the surface

(2) $\frac{2\sigma }{{\epsilon }_0}$ and is parallel to the surface

(3) $\frac{\sigma }{{\epsilon }_0}$ and is normal to the surface

(4) $\frac{2\sigma }{{\epsilon }_0}$ and is normal to the surface 

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