12th Physics MCQs Preparation 2022 and Onwards (Unit: Alternating Current: Set-2 (15 MCQs)) for National MDCAT, ECAT, FPSC, PPSC, JOB Exam, Physics Lecturer, SSC, HSSC (F.Sc.), BS, MS Exams NTS, ETS ETc..



1. The r.m.s. value of a sine wave is 100 A. Its peak value is




... Answer is B. 141.4 A
`\I_{rms}=`\frac {l₀}{sqrt 2}`= 0.707 l₀


2.A sine wave has a frequency of 50 Hz. Its angular frequency is ___________________ radian/second.




... Answer is A. 100 ã„«
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3. Equation for Root mean square value of alternating current is




... Answer is D. `\I_{rms}`=0.707 l₀
`\I_{rms}`=`\frac {l₀}{sqrt 2}`= 0.707 l₀ = 70.7% of l₀


4. Equation for Root mean square value of alternating Voltage is




... Answer is D. `\V_{rms}`=0.707 V₀
`\V_{rms}`=`\frac {V₀}{sqrt 2}`= 0.707 V₀ = 70.7% of V₀


5.  Root mean square value of alternating voltage is equal to




... Answer is A. 70.7% of V₀
`\V_{rms}=0.707 V₀ = 70.7% of V₀


6. When the frequency of A.C. is increased then the reactance of the capacitor will




... Answer is B. Decreased
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7. When the frequency of A.C. is increased then the reactance of the inductor will :




... Answer is C. Increased
 `\X_L` = 2 π f L (directly proportional)


8. In case of D.C.(direct current) f = 0 Hz then the reactance of the inductor will




... Answer is D. Zero
`\X_L` = 2 π f L (when f = 0 then `\X_L` = 0)


9. The unit of impedance is




... Answer is C. Law of conservation energy
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10. The impedance of choke oil is




... Answer is C. Both (A) and (B)
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11. An alternating quantity (voltage or current) is completely known if we know it's




... Answer is B. both (a) and (b)
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12. For electromagnetic waves, Maxwell generalized




... Answer is D. amperes law
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13. An electromagnetic wave goes from air to glass which of the following does not change?




... Answer is D. Ultra sound waves
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14.  The circuit in which current and voltage are in phase, the power factor




... Answer is B. 1
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15.  With increase in frequency of an AC supply, the impedance of an RLC series circuit




... Answer is B. increases
Given: -----------------------------






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