Tag: movement of charge

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Questions Related to movement of charge

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

A 220 V, 50 Hz AC source is connected to an inductance of 0.2 H and resistance of 20 $\Omega$ in series. The current in the circuit is :

  1. $3.33 A$
  2. $33.3 A$
  3. $15 A$
  4. $5 A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given, V =220 volts, f=50 Hz, L =0.2 H, R = 20 $\Omega$


$X _L =2\pi fL=2 \times 3.14 \times 50 \times 0.2$

$= 100 \times  0.628 = 62.80\Omega$

$Z = \sqrt{X^2 _L + R^2} = \sqrt{(62.8)^2 + 20^2}$

$I = \displaystyle \frac{V}{Z} = \frac{220}{\sqrt{43473.84}} = 3.33A$

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

An alternating voltage $E=200\sqrt{2}\sin (100t)$ is connected to $1$ microfarad capacitor through AC ammeter. The reading of ammeter shall be.

  1. $10$mA
  2. $20$mA
  3. $40$mA
  4. $80$mA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reading of ammeter $=I _{rms}=\displaystyle \frac{V _{rms}}{X _C}=\frac{V _0\omega C}{\sqrt 2}$
$=\displaystyle\frac{200\sqrt 2\times 100\times (1\times 10^{-6})}{\sqrt 2}=2\times 10^{-2} A$
$=20 mA$

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

A bulb  is connected  to an ideal battery of emf 10 V so that the resulting current is 10 mA . When the bulb is connected to 220 V mains (ideal), the current is 50 mA. choose the correct alternative

  1. the resistance of the bulb is 1 k ohm and in the second case, it is 4.4 k ohm

  2. it is not possible since ohm's law is not followed

  3. the increase in resistance is due to heating of the filament of the bulb when it is connected to 220 V main

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A bulb is connected to an ideal battery of emf$=10V$

Current$=10mA\=10\times10^{-3}A$
when the bulb connected $220V$ (main)
and current$=50\times10^{-3}A$
Using Ohm's law,
First case:
$I=\cfrac{10\times10^3}{10}=1K\Omega$
Second case 
$I^{\prime}=\cfrac{220\times10^3}{50}=4.4k\Omega$
Hence answer $(A)$ will be correct.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

In a transformer the immediate cause of the induced A. C. in the secondary coil is

  1. A varying electric field

  2. A varying magnetic field

  3. A motion of the secondary coil

  4. Efficiency of the operator
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Faraday's law of induction, a changing magnetic flux through a coil induces an electromotive force (EMF). In a transformer, the alternating current in the primary coil creates a varying magnetic field that links with the secondary coil.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

Alternating current is one which changes in its :

  1. direction

  2. magnitude

  3. magnitude and direction both

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Answer is C.

An alternating current (AC) is an electric current of which magnitude and direction vary, unlike direct current, whose direction remains constant.
The usual waveform of an AC power circuit is a sine wave, because this leads to the most efficient transmission of energy. However, in certain applications different waveforms are used, such as triangular or square waves.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

An alternating voltage is given by $e = (6\sin \omega t + 8\cos \omega t)volt$. The instantaneous value of voltage is given by

  1. $5\sqrt {2}V$
  2. $10V$
  3. $10\sqrt {2}V$
  4. $\dfrac {10}{\sqrt {2}}V$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The expression e = 6*sin(wt) + 8*cos(wt) can be written as e = 10 * (0.6*sin(wt) + 0.8*cos(wt)). Using sin(A+B), this is e = 10*sin(wt + alpha), where the amplitude is 10V.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

The simplest type of AC voltage or current is the one which

  1. Varies exponentially

  2. Varies sinusoidally

  3. Varies linearly

  4. Does not vary uniformly
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:-

AC wave can be of any form but mathematical techniques are easier for the sine waveform such as any wave can be represent as combination of sine waves using fourier transform and integration and differentiation of sine wave is sine wave only.

Option B is correct.

Multiple choice physics alternating currents sinusoidal current types of current movement of charge

Choose the incorrect statement.

  1. Alternating current is oscillatory

  2. Electric power is transmitted over long distances using alternating current.

  3. Frequency of alternating current in India is 50 Hz.

  4. Alternating current can be used for electrolysis of copper chloride.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Even if it were current-limited, alternating current (AC) would not be appropriate for electrolysis. Because the "cathode" and "anode" will be constantly switching places as the polarities will change with time. Therefore, direct current (DC) is used for electrolysis.