A metal sphere with radius r = 1.10 cm is supported on an insulating stand at the center of a hollow, metal, spherical shell with radius r = 9.00 cm . Charge +q is put on the inner sphere and charge −q−q on the outer spherical shell. The magnitude of qq is chosen to make the potential difference between the spheres 400 VV , with the inner sphere at higher potential.

The magnitude of q = 0.612nC

Explanation:

The concept of coulomb's law was applied as it relates to the potential of each surface mentioned in the question. we are considering an inner sphere and a spherical shell each with its own radius.

The potential at each sphere was gotten, thereafter the potential differences between each sphere was equated to get the magnitude of the charge as it is shown in the attached file.

The steps and the mathematical explanation are as shown in the attachment.