Is zakat obligatory on electricity company shares purchased for the purpose of selling them for profit, knowing that they have not yet reached the purchase price, and how is zakat calculated on them?

Zakat is obligatory on shares if they are trade goods. Zakat is calculated based on their market value at the end of the hawl (one lunar year), not on their purchase price. If the shares reach the nisab (minimum threshold) either on their own or when combined with other money, then a quarter of a tenth (2.5%) is to be given as Zakat. If the state collects the Zakat, then one's obligation is fulfilled. As for shares held for investment, there is no Zakat on them except on their earnings, if a hawl passes over those earnings.