Question

a point charge is placed at the centre of a hemispherical sphere electric flux is nearest to

Answer 1

Any charge placed inside hallow spherical conductor attracts opposite charge from sphere. That means, lets say sphere is neutral and charge inside is positive and sphere thickness is ‘t’. Now this positive charge attracts equal negative charge. Since sphere is neutral an equal and opposite positive charge appears on outer surface of sphere.

Using gauss law flux inside sphere is (charge/epsilon) and flux between inner surface and outer surface is zero, since net charge is zero. And flux outside sphere is again (charge/epsilon).