In spherical coordinates, let $${{{\widehat a}_{_0}},\,{{\widehat a}_{_\phi }}}$$ denote unit vectors along the $$\theta ,\,\,\phi $$directions. $$$E = {{100} \over r}\sin \,\theta \cos \left( {\omega t - \beta r} \right){\widehat a_{_\theta }}\,\,V/m$$$
and $$$H = {{0.265} \over r}\sin \,\theta \cos \left( {\omega t - \beta r} \right){\widehat a_{_\phi }}\,\,A/m$$$

Represent the electric and magnetic field components of the EM wave at large distances $$r$$ from a dipole antenna, in free space. The average power $$(W)$$ crossing the hemispherical shell located at $$r = 1\,\,km$$, $$0 \le \theta \le \pi /2$$ _______.

A depletion type N -channel MOSFET is biased in its linear region for use as a voltage controlled resistor. Assume threshold voltage V_TH = -0.5 V, V_GS = 2.0 V, V_DS = 5 V, W/L=100, C_OX=10^-8 F/cm² and $${\mu _n}$$ = 800 cm²/V-s. The value of the resistance of the voltage controlled resistor (in $$\Omega $$ ) is _____.

When the optical power incident on a photodiode is 10μW and the responsivity is 0.8 A/W, the photocurrent generated (in μA) is ________.

In the ac equivalent circuit shown in the figure, if i_n is the input current and R_F is very large, the type of feedback