How long it takes for someone to become infectious after exposure to covid-19 and how long does the infectious time period last?

One is generally positive for COVID-19 after 5-7 days from exposure to an infected individual. After a positive PCR test , you should ideally quarantine for 14 days. If respiratory symptoms begin, go to an emergency room for evaluation immediately.

From couple of days after exposure to 20 days after onset of symptoms. For info: https://www.google.com/search?q=infectious+period+covid&rlz=1C1GCEV_enUS890US890&ei=Do7LYaeENZmawbkPvdWb6Ac&oq=Infecious+pe&gs_lcp=Cgdnd3Mtd2l6EAEYADIKCAAQsQMQgwEQCjIKCAAQsQMQgwEQCjIKCAAQsQMQgwEQCjIKCAAQsQMQgwEQCjIECAAQCjIECAAQCjIICAAQsQMQgwEyBAgAEAoyBAgAEAoyBAgAEAo6BAgAEEM6BQgAEIAEOgsIABCABBCxAxCDAToOCC4QgAQQsQMQxwEQ