ELECTROSTATICS (XII)

1. Force of attraction between two point charges Q and – Q separated by d is F . When these charges are placed on two identical spheres of radius R=0.3d whose centres are distance d apart, the force of attraction between them is

• Greater than F

• EQUAL TO F

• Less than F

• INITIALLY Less than F THEN FINALLY EQUAL TO F

2. One metallic sphere A is given positive charge whereas another identical metallic sphere B of exactly same mass as of A is given equal amount of negative charge. Then

• (a) Mass of A and mass of B still remain equal

• (b) Mass of increases A

• (c) Mass of decreases B

• (d) Mass of increases B

Four metal conductors having different shapes

1. A sphere 2. Cylindrical

3. Pear 3. Lightning conductor

are mounted on insulating stands and charged. The one which is best suited to retain the charges for a longer time is

• 1

• 2

• 3

• 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

• $-\frac{Q}{2}$

• $-\frac{Q}{4}$

• $+\frac{Q}{4}$

• $+\frac{Q}{2}$

 The electric potential V at any point O (x, y, z all in metres) in space is given by V= 4 $X^2$    . The electric field at the point (1,0,2)  in volt/m  is

• 8 along negative  X axis

• 8 along positive X  axis

• 16 along negative  X axis

• 16 along positive X axis

A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V. The potential at the centre of the sphere is

• 0V

• 10V

• Same as at point 10 cm away from the surface

• Same as at point 25 cm away from the surface

If a unit positive charge is taken from one point to another over an equipotential surface, then

• Work is done on the charge

• Work is done by the charge

• Work done is constant

• No work is done

Electric lines of force about negative point charge are

• Circular, anticlockwise

• Circular, clockwise

• Radial, inward

• Radial, outward

Two charged spheres of radii 10 cm and 15 cm are connected by a thin wire. No charge will flow, if they have

• The same charge on each

• The same potential

• The same energy

• The same field on their surfaces

 $Ch\arg es\ of\ \frac{10}{3}\times10^{-9}C$  

   are placed at each of the four corners of a square of side 8cm . The potential at the intersection of the diagonals is                             
     

•   $150\sqrt{2\ }volt$  

•  $1500\sqrt{2\ }\ volt$  

•  $900\sqrt{2}\ volt$  

• 900 volt