Question

A shunt-type ohmmeter uses a 2 mA basic d'Arsonval movement with an internal resistance of 25 Ω. The battery emf is 1.5 V. 

Calculate:-

 (a) Value of the resistor in series with the battery to adjust the Full Scale Deflection (FSD) 

 (b) At what point (percentage) of full-scale will 100 Q be marked on the scale?

Rx = unknown resistance R1 = scale adjusting resistance E = omf of intemal battery Rm= PMMC meter resistance S = switch EI

Answer 1

When resistance taken infinite in first bit,by making it open ckt ,I applied kvl in first loop which passes same current I1 through R1 and meter.