Question

A point charge of magnitude 1µC is fixed at (0, 0, 0). An isolated uncharged spherical conductor is fixed with its centre at (4 cm, 0, 0). What is the potential and the induced electric field at the centre of the sphere? Please also explain why the electric field inside the sphere won't be 0.

Answer 1

q=1μC=1×10^−6 C

r=4cm=4×10^−2m

Potential V=kq/r

= (9×10^9 × 10−^6) / ( 4×10^−2)

=2.25×10^5V.

Induced electric field E=kq/ r^2

=( 9×10^9 × 1× 10−^6 )/(16×10^−4)=−5.625×10^6V/m

Electricfield inside a conducting spherical shell is equal to 0.

So,

1. If a +Q charge is placed at the centre of sphere, polarisation takes place as an equal and opposite -Q appears on the surface of shell.
2. Now , since net charge inside shell is Q-Q =zero ,therefore Flux inside is zero

But here we are finding the electric field induced at the centre of the sphere by the point charge before polarisation .But in effective the net flux will be zero due to polarisation.