https://physicsbyehab.com/2021/02/08/%d8%af%d8%a7%d8%a6%d8%b1%d8%a9-%d9%85%d9%82%d8%a7%d9%88%d9%85%d8%a9-%d9%88-%d9%85%d9%83%d8%ab%d9%81-rc-circuit/