When a neutral metal sphere is charged by contact with a positively charged glass rod, the sphere.

The sphere becomes positively charged.

i guess that visual aids present persuasive examples to what you are presenting, some factors would be theme (does it fit with the color, information, what you are presenting), size (can you see it, is it a big enough span of data/information), and overall look of the visual aid.

hope this : )

im sorry i dont know