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 ___________ .

Using shunt capacitors, the power factor of a 3-phase, 4 kV induction motor (drawing 390 kVA at 0.77 pf lag) is to be improved to 0.85 pf lag. The line current of the capacitor bank, in $A$, is _________ (Round off to one decimal places)