In the circuit shown in Figure, it is desired to have a constant direct current $$i(t)$$ through the ideal inductor $$L.$$ The nature of the voltage source $$v(t)$$ must be

A d.c. voltmeter has a sensitivity of $$1000$$$$\Omega /volt.$$ When it measures half full scale in $$100$$ $$V$$ range, the current through the voltmeter is

A moving coil galvanometer is made into a d.c. ammeter by connecting

A symmetrical $$400V,$$ $$3$$-$$\phi $$ supply is connected to the network shown in fig. The phase sequence is $$RYB.$$ Find the reading on the wattmeter

$${R_1} = 30\Omega ,\,\,{X_1} = 50\Omega ,\,\,$$ and $${X_2} = 40\Omega $$