In a science museum demonstration, a person on an insulated stand touches a metal sphere. the sphere has a large charge. explain why the person's hair stands on end

When the person touches the charge filled sphere, the excess charge goes through the person's body. The person is protected from the ground as they are standing on an insulated stand, thereby preventing the charges from getting to the ground.

The person is now filled with charges (electrons) and these electrons repel each other and are trying to move as far away from each other as possible. This makes the hair on the person stand up as it is filled with electrons that repel each other.