The transformer connection given in the figure is part of a balanced 3-phase circuit where the phase sequence is "abc". The primary to secondary turns ratio is $2: 1$. If ( $I_a+I_b+I_c=0$ ), then the relationship between $l_A$ and $l_{\text {ad }}$ will be

Consider two coupled circuits having self inductances $L_1$ and $L_2$ that carry non-zero currents $I_1$ and $I_2$ respectively. The mutual inductance between the circuit is $M$ with unity coupling coefficient. The stored magnetic energy of the coupled circuit is minimum at which of the following value(s) of $I_1 / I_2$ ?

The switch ( S ) closes at $t=0 \mathrm{sec}$. The time, in sec the capacitor takes to charge to 50 V is __________ . (Round off to one decimal places)

In an experiment to measure the active power drawn by a single-phase RL Load connected to an AC source through a $2 \Omega$ resistor, three voltmeters are connected as shown in the figure below. The voltmeter readings are as follows : $\mathrm{V}_{\text {source }}=200 \mathrm{~V}$, $V_R=9 \mathrm{~V}, V_{\text {Load }}=199 \mathrm{~V}$. Assuming perfect resistors and ideal voltmeters, the Load-active power measured in this experiment, in $W$, is ___________ .