Does the computer charger draws electicity when not connected to computer but connected to a power surce?

Yes. The little box on the power cable houses a transformer, it will draw power at all time when plugged in even though the laptop is not plugged in. Same thing goes for chargers for batteries, R/C cars/toys, etc. I got this information from my dad who is an arson and insurance fraud investigator. He spent about 3 weeks learning about electricity and electrical fires at FLETC (Federal Law Enforcement Training Center).