GATE 2014 EE (EE2) – Question 58
Ammeters X,Y have resistances 1.2 Ω,1.5 Ω and full-scale currents 150 mA,250 mA respectively. Shunts extend each to 15 A full scale. The shunted meters are connected in parallel in a circuit carrying total 15 A. Find X’s indicated current (A).
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Correct answer: 9.9 to 10.3
Explanation
At15Afull scale,the Xmeter drop is0.15×1.2=0.18V,giving effective resistance0.18/15=0.012Ω. For Ythe corresponding drop is0.25×1.5=0.375V and effective resistance0.025Ω. In parallel,Xtakes15×0.025/(0.012+0.025)=10.1351A. Since its shunt was calibrated to a15Arange,the indicated current is **10.1351A**,rather than the smaller coil current.