The input impedance of the permanent magnet moving coil $$(PMMC)$$ voltmeter is infinite. Assuming that the diode shown in the figure below is ideal, the reading of the voltmeter in Volts is

Three moving iron type voltmeters are connected as shown below. Voltmeter readings are $$V,$$ $${V_1}$$ and $${V_2}$$ , as indicated. The correct relation among the voltmeter readings is

A strain gauge forms one arm of the bridge shown in the figure below and has a nominal resistance without any load as $$\,{R_s} = 300\Omega .$$ Other bridge resistance are $$\,{R_1} = {R_2} = {R_3} = 300\Omega .\,\,$$ The maximum permissible current through the strain gauge is $$20$$ $$mA.$$ During certain measurement when the bridge is excited by maximum permissible voltage and the strain gauge resistance is increased by $$1$$% over the nominal value, the output voltage $${V_0}$$ in $$mV$$ is

A single-phase transformer has no-load loss of 64 W, as obtained from an open circuit test. When a short-circuit test is performed on it with 90% of the rated currents flowing in its both LV and HV windings, he measured loss is 81 W. The transformer has maximum efficiency when operated at