physics Electrostatics

a)Since like charges repel(1A),the positively-charged paint droplets repel each other(1A),and spread out much more than uncharged paint droplets.
b)The charge of the car body should be negative charge.(1A)Since unlike charges attract, the positively-charged droplets would stick to a negatively charged car better. (1A)

1. Because like charges repel, spray droplets with positive charges will not be accumulated at one spot. They will be spreaded over the car surface by the like charges they carry.

2. Negative charge.This helps to adhere the paint sprays onto the car surface because unlike charges attract.