Find time constant of the following circuits.
(a)
(b)
(c )
(d)

Explanation

To find time constant, first find equivalent resistance `R_(eq) ` across capacitor by short - circuiting the battery i.e., replace battery by a wire and then constant `tau = R_(eq) C`.

(b)
(c) Parallel, `(6Rxx3R)/(6R+3R) = 2R`

(d) Parallel, `(Rxx2R)/(R+2R) = (2R)/(3)`

`R_(eq) = 2R//3`
`tau =R_(eq) C = (2RC)/(3)` .