The difference btw. the radii of the two spheres of a spherical conductor is increased. will thecapacitance increase or decrease?

If the radius of inner sphere is decreased then capcitance will decrease and if radius of outer speher is incresed it will increse(capacitance).

decreases!

c=4pie epsilon ab/b-a

The capacitance is directly proportional to the radius of the spherical conductor.