( ri′zis·təns kə′pas·əd·əns ′kän·stənt ) (electricity) Time constant of a resistivecapacitive circuit,
http://www.answers.com/topic/resistancecapacitanc...

The time constant doesn't depend on the emf. It's simply. RC. the product of (resistance) x (capacitance)
http://wiki.answers.com/Q/How_do_you_find_time_con...

voltage on a cap, discharging. v = v₀e^–t/RC) You have your units screwed up again. substitute into the equation above and solve for C. time constant is RC.
http://answers.yahoo.com/question/index?qid=201002...
