Question

A particle of mass $M$ is at a distance '$a$' from surface of a thin spherical shell of equal mass and having radius '$a$'. Select correct alternative.

• A. Gravitational field and Potential both are zero at centre of the shell.
• B. Gravitational field is zero not only inside the shell but at a point outside the shell also.
• C. Inside the shell,gravitational field alone is zero.
• D. Neither gravitational field nor gravitational potential is zero inside the shell.

Answer 1

Answer: (D)

According to the question, there can be two cases in which the point mass is at a distance $a$ from the surface of the spherical shell.

$1$. The point mass is at the center of the shell

$2$. The point mass is outside the shell at a distance $2a$ from the center of the shell.

Superposition principle dictates that the potential and field at any point will be the sum of the potentials and fields respectively at that point due to the individual masses.

It can be seen that in both the cases, neither field nor potential is zero inside the shell. This is due to the contribution of the point mass.