A 20 volt AC is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 volt, the voltage across the coil is-
(i) 16 V
(ii) 10 V
(iii) 8 V
(iv) 6 V
(i) 16 V
Explanation:
A 20 volt AC is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 volt, the voltage across the coil is 16 V.
Net V = `\sqrt{"V"_{"R"^2}+"V"_{"L"^2}}`
= `\sqrt{"I"_{"eff"^2}"R"^{2} + "I"_{"eff"^2} \times "L"^{2}}`
= 20 = `\sqrt{12^{2}+"V"_{"L"^2}}`
= `(20)^{2}` = `12^{2}`+`"V"_{"L"^2}`
= 400 = 144 + `"V"_{"L"^2}`
= `"V"_{"L"}` = `\sqrt{400-144}`
= `\sqrt{256}` = 16 Volts.
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