Why Charged Ballon Getting Repelled

Explain why a charged balloon is repelled

by another charged balloon whereas an

uncharged balloon is attracted by another charged balloon? 

The charged balloons have similar charges on the surfaces. Since like charges repel each other, that's why the charged balloon is repelled by another charged balloon. When an uncharged

balloon is brought near a charged one, the uncharged balloon acquires some opposite charge.

Since unlike charges attract each other, therefore a charged balloon attracts an uncharged one.