Positively charged rod to an uncharged electroscope

[PhysKid24]

Hi I was just wondering what the answer to the following question would be:

If you bring a positively charged rod to an uncharged electroscope causing the vanes or leaves inside to diverge, are negative charges attracted to the knob of the electroscope or do positive charges repel to the vanes of the electroscope? I think it's the latter, but not sure why it also couldn't be the first.

 

[Doc Al]

In the electroscope, which is a solid conductor, only the negative charges (electrons) are free to move. The positive charges (protons in the metal atoms) are fixed in a lattice structure (the metal atoms are not free to move).

 

[Graeme Robinson]

The correct answer is that positive charges repel to the vanes of the electroscope. This is because the positively charged rod will induce a separation of charges within the electroscope, with the positively charged rod attracting negative charges to the knob of the electroscope and repelling positive charges to the vanes. This creates a net positive charge on the vanes, causing them to diverge. The knob of the electroscope remains neutral in this scenario.