The working of a PMMC (Permanent magnet moving coil) meter is described by a second order differential equation\(J\frac{{{d^2}\theta }}{{d{t^2}}} + D\frac{{d\theta }}{{dt}} + S'\theta = T\)WhereJ = Moment of inertia of the system,D = Damping coefficient,S’ = Spring constant,θ = Angular deflection andT = Activating torque,Assuming D = 0, an undamped natural angular frequency is

\(\frac{1}{{2\mu \sqrt {JS} }}\)

The working of a PMMC (Permanent magnet moving coil) meter is describe

1.	The working of a PMMC (Permanent magnet moving coil) meter is described by a second order differential equation\(J\frac{{{d^2}\theta }}{{d{t^2}}} + D\frac{{d\theta }}{{dt}} + S'\theta = T\)WhereJ = Moment of inertia of the system,D = Damping coefficient,S’ = Spring constant,θ = Angular deflection andT = Activating torque,Assuming D = 0, an undamped natural angular frequency is
A.	\(\sqrt {\frac{S}{J}} \)
B.	\(\sqrt {\frac{J}{S}} \)
C.	\(\frac{1}{{\sqrt {JS} }}\)
D.	\(\frac{1}{{2\mu \sqrt {JS} }}\)
Answer» B. \(\sqrt {\frac{J}{S}} \)