Topic: Electromagnetics
The input impedance of short circuited line of length l where $\frac{\lambda}{4}<l<\frac{\lambda}{2}$ is
- A. Capacitive
- B. Inductive
- C. Resistive
- D. None of these
Answer: A. Capacitive
Explanation: For a short-circuited lossless transmission line, the input impedance is $Z_{in}=jZ_{0}\tan(\beta l)$. Since $\beta=2\pi/\lambda$, the given length range $\lambda/4<l<\lambda/2$ corresponds to $\pi/2<\beta l<\pi$. In this second quadrant, the tangent function is negative, making the input impedance purely capacitive.