The radiation resistance of an antenna having a power of 120 units and antenna current of 5A is :
MH SET - 2025, SET Exam - 2025,
Answer: A
The radiation resistance is 4.8 ohms.
Radiation resistance is the resistance that would dissipate the radiated power when carrying the antenna current:
\[ \begin{aligned} P &= I^{2}R_{r} \\ R_{r} &= \frac{P}{I^{2}} = \frac{120}{5^{2}} = \frac{120}{25} \\ &= 4.8\ \Omega \end{aligned} \]
9.6 is twice this, what you get with \(P = I^{2}R/2\), the form used when I is a peak rather than an rms value. 3.6 and 1.8 do not follow from the given data.
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