# Stability Theory – 7

7. The transfer function of a control system is given as

$\dpi{100} T(s) = k/s^2+4s+k$
where k is the gain of the system in radians/amp. For this system to be critically damped, the value of k should be :

(a) 1
(b) 2
(c) 3
(d) 4