1)If potential at the surface of earth is assumed 2 b 0  then what is the potential at centre of earth & at infinity?

2)A CHARGE PARTICLE OF CHARGE +q is placed inside a spherical shell(NOT at CENTRE!) definitely, it will induce a -ve charge of same magnitude at inside the suface of spherical shell........now due to opp. charge ther will b a force of attraction between them.....(colombs law)... just consider q=1C now force,, F=K(9000000000N if q=1Cand r=1m)  due to this enormous force the charge placed inside must be accelerated of an enormous accn. (of the order of 20) .Can a shell resist such an enormous accn.? def. not! the is it ever possible 2 keep a charge inside a spherical shell(not at CENTRE!)??

Gravitational potential is scalar description of gravitational field.

The definition of gravitational potential energy is extended to unit mass to define gravitational potential.

Definition 1: Gravitational potential

The gravitational potential at a point is equal to “negative” of the work by the gravitational force as a particle of unit mass is brought from infinity to its position in the gravitational field.

Or

Definition 2: Gravitational potential

The gravitational potential at a point is equal to the work by the external force as a particle of unit mass is brought from infinity to its position in the gravitational field

 

NOTE: Here Gravitational Potential is simply gravitational potential energy per unit mass. The variation of potential is same as potential energy as follows

Taking the potential energy zero at infinity gives the simple form

 U(r) = -GMm/r

we plot it below with r in units of Earth radii. The energy units are GMm/r_E, the -1 at the far left being at the Earth’s surface (r = 1), and the first steep almost linear part corresponds to mgh. (Chech the attached JPEG file for the plot)