Question with Solution
In a solid sphere two small symmetrical cavities are created whose centres lie on a diameter AB of sphere on opposite sides of the centre.
Options:(select one or more)
Answer:
Solution:
(A) correct: the two cavities are symmetric about the centre, so their (negative) field contributions at the centre cancel; the solid sphere's own field at its centre is also zero.
(B) wrong: removing mass makes the potential at the centre less negative; it does not remain unaffected.
(C) wrong: the potential inside the cavities is not uniform - it varies from point to point because the remaining mass distribution is not spherically symmetric about points inside the cavities.
(D) correct: by symmetry, all points of a circle lying in the plane perpendicular to AB and centred on AB are equidistant from both cavities and from the spherical mass distribution, so they have the same potential.
Ans (A, D)
