ISRO Scientist or Engineer Electronics 2018

Which of the following statement is not true about delay line cancellers?

An air filled rectangular waveguide with dimensions a = 75 mm, b = 37.5 mm has same guide wavelength at frequencies $$f_1$$ and $$f_2$$ when operated at $$TE_{10}$$ and $$TE_{20}$$ modes respectively. If the frequency $$f_1$$ is $$\sqrt{13}$$ GHz, what is frequency $$f_2$$ in GHz?

A waveguide of dimensions a = 15 mm and b = 7.5 mm is used as a high-pass filter. If the stop band attenuation required at 8 GHz is ~ 109.2 dB, whatis the length of the filter?
(assume conductor losses to be zero, approximate $$\pi = 3.14$$ and 1 Np ~ 8.69 dB) ($$log_{10}e = 0.4343$$)

An RF signal is applied to a 50 Ω lossless transmission line which is terminated in a load with impedance, $$Z_L = j 50$$. The wave length is 8 cm. Find the position of voltage and current maximum respectively nearest to the load measured from load end?

Which of the following Oscillation types this waveform represents when the difference between input frequency and natural frequency is small? Assume the generating system to be a lossless mechanical system.

Identify the correct sequence of stages in charging of a Lead-Acid battery.

A rocket with lift-off mass of m, is launched from groundlevel. During flight, fuel burns at a constant rate for $$\tau$$ seconds and exhaust gasesare ejecting from the bottom of the rocket at $$\beta$$ Kg/sec with speed of c m/s relative to the rocket. Ignoring air resistance and assume acceleration due to gravity, g as constant, which of the following expression represents velocity of rocket v(t).

For a conservative vector field F below, which of the following is the scalar potential?
$$F = (y^2 \cos x + az^3)\overrightarrow{i}+(2y \sin x - 4)\overrightarrow{j}+(3xz^2 + 2)\overrightarrow{k}$$ a is an integer

Acylindrical waveguide with radius of 3.5 cm has waves travelling in $$TM_{12}$$ mode. The value of $$1^{st}$$ zero of $$2^{nd}$$ order Bessel function is 7. Find the cut-off wavelength for this mode.

Consider a mechanical system shown in figure. Masses are free to slide over frictionless horizontal surface. The equation of motion of mass $$m_1$$ is