What is Greek meaning of electrics ?

How conductors and non-conductors are different ? Why are they not charged by rubbing them with our hands ?

What is static electrical induction ?

Which scientist represented the types of charges ?

Is the induced charge on the surface of metal or inside it ?

Five balls numbered $1$ to $5$ are suspended using separate threads. Pairs $(1, 2)$, $(2, 4)$ and $(4, 1)$ show electrostatic attraction, while pair $(2, 3)$ and $(4, 5)$ show repulsion. Therefore ball $1$ must be