question_answer

As shown in Fig. a thin spherical shell carries a charge \[\mathbf{Q}\] on its surface. A point charge \[\mathbf{Q}\text{ }/\text{ }\mathbf{2}\]is placed at its centre O and another charge \[\mathbf{2Q}\] placed outside. If all the charges are positive, what will be the force on the charge at the centre?

Answer:

                Zero, because the electric field inside the spherical shell is zero.