A linear 2-port network is shown in Fig. (a). An ideal DC voltage source of 10 V is connected across Port 1. A variable resistance R is connected across Port 2. As R is varied, the measured voltage and current at Port 2 is shown in Fig. (b) as a V2 versus $$-$$I2 plot. Note that for V2 = 5 V, I2 = 0 mA, and for V2 = 4 V, I2 = $$-$$4 mA. When the variable resistance R at Port 2 is replaced by the load shown in Fig. (c), the current I2 is ________ mA (rounded off to one decimal place).
The Fourier transform X(j$$\omega$$) of the signal $$x(t) = {t \over {{{(1 + {t^2})}^2}}}$$ is ____________.
Let x1(t) = e$$-$$t u(t) and x2(t) = u(t) $$-$$ u(t $$-$$ 2), where u( . ) denotes the unit step function. If y(t) denotes the convolution of x1(t) and x2(t), then $$\mathop {\lim }\limits_{t \to \infty } y(t)$$ = __________ (rounded off to one decimal place).
The outputs of four systems (S1, S2, S3 and S4) corresponding to the input signal sin(t), for all time t, are shown in the figure.
Based on the given information, which of the four systems is/are definitely NOT LTI (linear and time-invariant)?
