Which one of the following does represent the electric field lines for the $$T{E_{02}}$$ mode in the cross-section of a hollow rectangular metallic waveguide?

Two identical and parallel dipole antennas are kept apart by a distance $$\lambda /4$$ of in the H-plane. They are fed with equal currents but the right most antenna has a phase shift of +90°. The radiation pattern is given as

A silicon sample 'A' is doped with 10¹⁸ atoms/cm³ of Boron. Another sample 'B' of identical dimensions is doped with 10¹⁸ atoms/cm³ of Phosphorus. The ratio of electron to hole mobility is 1/3. The ratio of conductivity of the sample A to B is

The Zener diode in the regulator circuit shown in figure has a Zener voltage of 5.8 Volts and a Zener knee current of 0.5 mA. The maximum load current drawn from this circuit ensuring proper functioning over the input voltage range between 20 and 30 Volts, is