Tag: direct current

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Questions Related to direct current

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

An alternating voltage is connected across a series $RLC$ Circuit through an $a.c.$ ammeter. The ammeter reading is the.....

  1. The peak current

  2. The peak current in resonance condition

  3. rms current

  4. zero
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An AC ammeter measures the root mean square (rms) value of an alternating current rather than the peak or instantaneous values.

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

What will be the reading of a hot wire voltmeter if it is connected across the terminals of a generator whose voltage wave form is represented by 
$V = 200\sin \omega t + 100\sin 3\omega t + 50\sin 5\omega t$?

  1. 100V

  2. 162 V

  3. 150 V

  4. 200 V
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The RMS value of a complex waveform is the square root of the sum of the squares of the RMS values of its individual harmonic components. RMS = sqrt((200/sqrt(2))^2 + (100/sqrt(2))^2 + (50/sqrt(2))^2) = sqrt(20000 + 5000 + 1250) = sqrt(26250) approx 162V.

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

Which of the following is wrong?

  1. It is not possible to have electrolysis by a.c.

  2. Ordinary batteries cannot be changed by a.c.

  3. In a circuit containing L, C and R in series across a steady source, poer is dissipated in R, at steady state

  4. For current dirven from a steady source by an ohmic conductor, mean value and r.m.s. value of current will be same
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

If the instantaneous emf and the instantaneous current equations of an A.C. circuit are respectively 
$e = E _0 sin(\omega t - \pi/6), i = I _0 sin (\omega t + \pi/6)$, then the phase difference between voltage and current is :

  1. $\dfrac{\pi}{3}$

  2. zero
  3. $\dfrac{\pi}{2}$
  4. $\dfrac{\pi}{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phase of current   $\phi _1 = wt +\dfrac{\pi}{6}$

Phase of emf    $\phi _2 = wt-\dfrac{\pi}{6}$
Phase difference   $\Delta \phi = \phi _1-\phi _2$
$\implies \Delta \phi = (wt+\dfrac{\pi}{6})-(wt-\dfrac{\pi}{6}) = \dfrac{\pi}{3}$