1.

    An AC circuit with a non-ohmic resistive element has a current described by i(t)=5sin(ωt+π/3)i(t) = 5\sin(\omega t + \pi/3). If the voltage across the element is v(t)=10sin(ωt)v(t) = 10\sin(\omega t), which statement BEST describes the relationship between instantaneous power, average power, and RMS power?

    A

    The instantaneous power is constant, the average power is zero, and the RMS power is equal to the peak power.

    B

    The instantaneous power fluctuates, the average power is non-zero, and the RMS power is greater than the average power.

    C

    The instantaneous power fluctuates, the average power is zero, and the RMS power is equal to the average power.

    D

    The instantaneous power is constant, the average power is non-zero, and the RMS power is less than the average power.

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    4.

    The r.m.s value of an a.c. of 50 Hz is 10 A. the time taken by the alternating current in reaching from zero to maximum value and the peak value of current will be

    A

    2imes102secand14.14A2 imes {10^{ - 2}}{\rm{sec}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{and}}{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\rm{14}}.{\rm{14}}\,\,{\rm{A}}

    B

    1imes102secand7.07A1 imes {10^{ - 2}}{\rm{sec}}\,\,\,\,{\rm{and}}\,\,\,\,{\rm{7}}.{\rm{07}}\,{\rm{A}}

    C

    5imes103secand7.07A5 imes {10^{ - 3}}{\rm{sec}}\,\,\,{\rm{and}}\,\,\,{\rm{7}}.{\rm{07}}\,\,{\rm{A}}

    D

    5imes103secand14.14A5 imes {10^{ - 3}}{\rm{sec}}\,\,{\rm{and}}\,\,\,{\rm{14}}.{\rm{14}}\,\,{\rm{A}}

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    5.

    The voltage of an ac supply varies with time (t) as V=120sin100πtcos100πtV = 120\sin 100\pi t\cos 100\pi t The maximum voltage and frequency respectively are

    A

    12  volts,  100  Hz12\;volts,\;100\;Hz

    B

    1202  volts,  100  Hz\frac{{120}}{{\sqrt 2 }}\;volts,\;100\;Hz

    C

    60  volts,  200  Hz60\;volts,\;200\;Hz

    D

    60  volts,  100  Hz60\;volts,\;100\;Hz

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