If the instantaneous current is given by $i = 4 \cos(\omega t + \phi)$ amperes,then the $r.m.s.$ value of the current is:

  • A
    $4 \text{ amperes}$
  • B
    $2\sqrt{2} \text{ amperes}$
  • C
    $4\sqrt{2} \text{ amperes}$
  • D
    $\text{Zero amperes}$

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