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Alternating Current Physics - Alternating Current

Bihar Board (BSEB) - STD 12 Science - Physics (BSEB - English Medium). 122 questions in this chapter.

Question types

Alternating Current question types

122 questions across 7 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

122
Questions
7
Question groups
5
Question types
Sample Questions

Alternating Current questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q [1M]1 Mark
Peak value of applied alternating voltage in a LR cir- cuit is 5 V. If magnitude of maximum voltage across the ends of resistor is 3 V. then maximum value of voltage across the inductor is
  • A
    2 V
  • ✓
    4 V
  • C
    $5 \sqrt{2} V$
  • D
    Zero

Answer: B.

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Q 2M.C.Q [1M]1 Mark
Alternating current cannot be measured by de ammeter because:
  • A
    Alternating current does not pass through ammeter.
  • ✓
    Average value of current for a complete cycle is zero.
  • C
    Some part of alternating current does not pass through ammeter.
  • D
    None of the above

Answer: B.

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Q 3M.C.Q [1M]1 Mark
Frequency and potential difference of AC sent to homes in India is:
  • ✓
    50 Hz, 220 V
  • B
    60 Hz, 220 V
  • C
    60 Hz, 110 V
  • D
    50 Hz, 110 V

Answer: A.

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Q 4M.C.Q [1M]1 Mark
Impedance of a circuit of inductance L and resis- tance R is denoted by:
  • A
    LR
  • B
    $\frac{ L }{ R }$
  • ✓
    $\sqrt{L^2 \omega^2+R^2}$
  • D
    $\sqrt{ R ^2 \omega^2+ L ^2}$

Answer: C.

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Q 5M.C.Q [1M]1 Mark
Magnitude of potential difference across L. C and R in a series LCR circuit is 100 V. If resistor is re- moved, then magnitude of current in the circuit is:
  • A
    Zero
  • ✓
    Infinite
  • C
    10 A
  • D
    20 A

Answer: B.

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Q 71 Marks Question1 Mark
A 100 Ω resistor is connected to a 220 V, 50 Hz supply.
(a) What is the rms value of the current?
(b) What is the net power consumed over a full cycle?
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Q 81 Marks Question1 Mark
The instantaneous magnitudes of current and voltage in an ac circuit are given as $I =10 \sin 314 t A$ and $V =50 \sin \left(314 t +\frac{\pi}{2}\right) \quad V$ respectively. What is the dissipation of average power in the circuit?
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Q 11Short Answer Type Questions [2M]2 Marks
A series LCR circuit with R = 20 Ω L = 1.5 H and $C=35 \mu F$ is connected to a variable frequency 200 V ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle?
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Q 183 Marks Question3 Marks
An electric bulb is marked $220 V, 100 W$. Calculate : (i) resistance of the bulb (ii) peak voltage of the source (iii) rms current flowing through the bulb.
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Q 193 Marks Question3 Marks
A capacitor and a resistor are joined in series with an ac source. If voltage across the ends of $C$ and $R$ be 120 V and 90 V respectively and root mean square value of current is 3 A , then calculate (i) impedance (ii) power factor of the circuit.
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Q 203 Marks Question3 Marks
An ac circuit is made from series combination of components of circuits X and Y . Current is ahead of voltage by $\frac{\pi}{4}$. If component $X$ is pure resistor whose value is $100 \Omega$ then (i) what is the name of component $Y$ ? (ii) If root mean square value of voltage is 141 V , then find the root mean square value of the current.
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Q 22Long Answer Type Questions [5M]5 Marks
(a) Prove that the peak value ( $I_m$ ) of an alternating current is $\sqrt{2}$ times its root mean square ( rms ) value.(b) If alternating current $I=4 sin \omega t$ of and voltage $V =200 \sin (\omega t+\pi / 3)$, calculate the dissipated average power in the circuit.
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Q 23Long Answer Type Questions [5M]5 Marks
(a) Prove that the mean power supplied to the inductor in a complete cycle is zero. (b) If in an LCR alternatin current circuit $R =$ $24 \Omega, X _{ L }=110 \Omega$, and $X _{ C }=110 \Omega$, then find the impednce of the current.
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Q 24Long Answer Type Questions [5M]5 Marks
Figure shows a series LCR circuit connected to a variable frequency 230 V source.
$\begin{array}{l} L =5.0 H , C =80 \mu F, \\ =40 \Omega .\end{array}$
(a) Determine the source frequency which drives the circuit in resonance
(b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency.
(c) Determine the rms potential drops across the three elements of the circuit. Show that the potential drop across the LC combination is zero at the resonating frequency.
Image
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Q 25Long Answer Type Questions [5M]5 Marks
(a) Obtain an expression for current flowing through an ideal inductor joined with an ac source of voltage $v=v_0 \sin \omega t$ by using phasor diagram. Draw a graph between (i) voltage applied and (ii) current as a function of (wt.).
(b) Obtain an expression for average power dissipation in any series LCR circuit.
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