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An electric motor runs a `D.C.` source of e.m.f. `200 V` and draws a current of `10A`. If the efficiency is `40%`, then ressistance of the armature is:A. `5Omega`B. `12Omega`C. `120Omega`D. `160Omega` |
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Answer» Correct Answer - B Here `eta=(e)/(E)xx100` `(40)/(100)=(e)/(E)=(4)/(10)=(2)/(5)` `e=(2E)/(5)=(2xx200)8/(5)=80V` But `I+(E-e)/(R )` :. `10=(200-80)/(R )` :. `R=12Omega` |
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