An alternating current is given by $i = 2 \sin \omega t + 6 \cos \omega t$. The $R.M.S.$ current in amperes is,

  • A
    $2 \sqrt{5}$
  • B
    $2 \sqrt{10}$
  • C
    $\sqrt{5}$
  • D
    $10 \sqrt{2}$

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In an $AC$ generator, induced emf $\varepsilon = 0$ at $t = 0$, then its value . . . . . .

An electric bulb rated as $100 \ W-220 \ V$ is connected to an $ac$ source of $rms$ voltage $220 \ V$. The peak value of current through the bulb is: (in $A$)

$A$ $40 \ \Omega$ electric heater is connected to a $200 \ V, 50 \ Hz$ mains supply. The peak value of electric current flowing in the circuit is approximately......$A$

In general,in an alternating current circuit:

The instantaneous voltages at three terminals marked $X, Y$ and $Z$ are given by
$V_x = V_0 \sin \omega t$
$V_y = V_0 \sin \left(\omega t + \frac{2 \pi}{3}\right)$
$V_z = V_0 \sin \left(\omega t + \frac{4 \pi}{3}\right)$
An ideal voltmeter is configured to read the $rms$ value of the potential difference between its terminals. It is connected between points $X$ and $Y$ and then between $Y$ and $Z$. The reading$(s)$ of the voltmeter will be:
$[A]$ $V_{XY}^{rms} = V_0 \sqrt{\frac{3}{2}}$
$[B]$ $V_{YZ}^{rms} = V_0 \sqrt{\frac{1}{2}}$
$[C]$ $V_{XY}^{rms} = V_0$
$[D]$ independent of the choice of the two terminals

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