Electric charges and field -DPP2 (ISC)

 A charge   $q_1$   exerts some force on a second charge $q_2$   . If third charge  $q_3$   is brought  near, the force of  $q_1$   exerted on    

• Decreases 

• Increases

•                 Remains unchanged                

• Increases if  $q_3$   is of the same sign as  $q_1$   and decreases if $q_3$    is of opposite sign

Two small spheres each having the charge +Q are suspended by insulating threads of length L from a hook. This arrangement is taken in space where there is no gravitational effect, then the angle between the two suspensions and the tension in each will be

• $180\degree,\frac{1}{4\pi\epsilon_o}\frac{Q^2}{\left(2L\right)^2}$

• $90\degree,\frac{1}{4\pi\epsilon_o}\frac{Q^2}{\left(L\right)^2}$

• $180\degree,\frac{1}{4\pi\epsilon_o}\frac{Q^2}{2L^2}$

• $180\degree,\frac{1}{4\pi\epsilon_o}\frac{Q^2}{L^2}$

Electric charges of   $1\mu C,-1\mu C$  and $2\mu C$    are placed in air at the corners A, B and C respectively of an equilateral triangle ABC having length of each side 10 cm. The resultant force on the charge at C is

•  0.9 N

• 1.8 N

• 2.7 N

• 3.6 N

A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be

• $-\frac{2Q}{4\pi b^2},\frac{Q}{4\pi c^2}$

• $-\frac{Q}{4\pi b^2},\frac{Q}{4\pi c^2}$

• $0,\frac{Q}{4\pi c^2}$

• None of the above

Identify the wrong statement in the following. Coulomb's law correctly describes the electric force that

• Binds the electrons of an atom to its nucleus

• Binds the protons and neutrons in the nucleus of an atom

• Binds atoms together to form molecules

• Binds atoms and molecules together to form solids

A metallic solid sphere is placed in a uniform electric field. The lines of force follow the path(s) shown in figure as

• 1

• 2

• 3

• 4

The figure shows some of the electric field lines corresponding to an electric field. The figure suggests

• $E_A>E_B>E_C$

• $E_A=E_B=E_C$

• $E_A=E_C>E_B$

• $E_A\ =E_C<E_B$

Two electric charges  $12\mu C$   and  $-6\mu C$   are placed 20 cm apart in air. There will be a point P on the line joining these charges and outside the region between them, at which the electric potential is zero. The distance of P from   $-6\mu C$ charge is

•    0.10 m

• 0.15 m

• 0.20 m

• 0.25 m

The electric field due to a dipole at a distance r on its axis is

• Directly proportional to $r^3$

• Inversely proportional to $r^3$

• Directly proportional to $r^2$

• Inversely proportional to $r^2$

Two electric dipoles of moment P and 64 P are placed in opposite direction on a line at a distance of 25 cm. The electric field will be zero at point between the dipoles whose distance from the dipole of moment P is

• 5 cm

• $\frac{25}{9}$

• 10 cm

• $\frac{4}{13}$