Question

Electric field due to a uniformly charged hollow sphere at a distance of r (where r is greater than the radius of the sphere) is __________

(a) Proportional to r

(b) Inversely proportional to r

(c) Proportional to r^2

(d) Inversely proportional to r^2

The question was asked in an interview for job.

My question is based upon Electric Field in division Charges and Fields of Physics – Class 12

Answer 1

Correct option is (d) Inversely proportional to r^2

Easy explanation: If the total charge of the sphere is q then the electric field at a distance of r is equal to \(\frac {q}{4\pi\varepsilon_o r^2}\).Therefore the electric field is proportional is \(\frac {1}{r^2}\) (if r > radius of the sphere). But if r < radius of the sphere the electric field will be zero i.e. electric field inside a hollow sphere is always zero.