The open-loop transfer function of a dc motor is given as $\frac{\omega(s)}{V_a(s)}=\frac{10}{1+10s}.$ When connected in feedback as shown below, the approximate value of $K_a$ that will reduce the time constant of the closed loop system by one hundred times as compared to that of the open-loop system is
- $1$
- $5$
- $10$
- $100$