What is the charge on the bead?
A 2.10 mm-diameter glass bead is positively charged. The potential difference between a point 2.10 mm from the bead and a point 4.50 mm from the bead is 500 V.
you have to include the radius of the bead. The diameter is 2.1mm then for both r1 and r2 you must add half of that, which is the radius. then you’ll get the right answer.
Source(s): I just did it on masteringphysics
What is the charge on the bead?