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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.

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

Why the current produced by the generator is  called as alternating current.

  1. continuous decrease and increase of current occurs.

  2. after every half cycle direction of flow of current is reversed.

  3. both

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

We may say that after every half cycle direction of flow of current is reversed. Because of this reason the current produced by the generator is also called as alternating current.

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

A coil, a capacitor and an ac source of rms voltage $24V$ are connected in series. By varying the frequency of the source, a maximum rms current of $6A$ is observed. If this coil is connected to a battery of emf $12V$ and internal resistance $4\Omega$, the current through will be

  1. $2.4A$

  2. $1.8A$

  3. $1.5A$

  4. $1.2A$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At resonance, the impedance Z = R. Since V_rms = 24V and I_rms = 6A, R = 24/6 = 4 ohms. When connected to a 12V battery with 4 ohms internal resistance, the total resistance is 4+4 = 8 ohms. Current = V/R_total = 12/8 = 1.5A.

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

A mixer of $1000\Omega$ resistance is connected to an $A.C.$ source of $200\ volts$ and $50\ cycle/sec$. The value of average potential difference across the mixer will be:

  1. $308\ volts$

  2. $264\ volts$

  3. $220\ volts$

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

The average value of a symmetric alternating current (like a sine wave) over one full cycle is zero, as the positive and negative half-cycles cancel each other out.