एक 25 mV, 2 mA डी'आर्सोनवल (D'Arsonval) संचलन का उपयोग एक वोल्टमीटर में किया जाना है जिसका पूर्ण-पैमाना (full-scale) पाठ्यांक 100 V है। इस 100 V वोल्टमीटर द्वारा परिपथ में प्रविष्ट कराया गया कुल प्रतिरोध ज्ञात कीजिए।

A wattmeter has pressure coil ranges of 500/250/125 V and current coil ranges of 20/10/5 A. The full scale deflection (FSD) of the meter is 625 W. Determine the multiplying factor (meter constant) when connected to 500 V and 10 A range.

A permanent magnet moving coil (PMMC) instrument has a coil of dimensions 15 mm × 12 mm. The flux density in the air gap is 1.8 × 10-3 Wb/m2 and the spring constant is 0.14 × 10-6 N·m/rad. Determine the number of turns required to produce an angular deflection of 90° when a current of 5 mA is flowing through the coil.