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Alternating Current Physics - Alternating Current

Jharkhand Board (JAC) - STD 12 Science - Physics (Jharkhand - English Medium). 37 questions in this chapter.

Question types

Alternating Current question types

37 questions across 4 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

37
Questions
4
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 2M.C.Q (1 Marks)1 Mark
The AC voltage across a resistance can be measured using:
  • A
    A potentiometer.
  • ✓
    A hot-wire voltmeter.
  • C
    A moving-coil galvanometer.
  • D
    A moving-magnet galvanometer.

Answer: B.

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Q 3M.C.Q (1 Marks)1 Mark
An $AC$ source is rated $220V, 50Hz$. The average voltage is calculated in a time interval of $0.01s$, It :
  • A
    Must be zero.
  • ✓
    May be zero.
  • C
    Is never zero.
  • D
    Is $\Big(\frac{200}{\sqrt{2}}\Big)\text{V}.$

Answer: B.

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Q 4M.C.Q (1 Marks)1 Mark
The magnetic field energy in an inductor changes from maximum value to minimum value in 5.0ms when connected to an AC source. The frequency of the source:
  • A
    20Hz.
  • ✓
    50Hz.
  • C
    200Hz.
  • D
    500Hz.

Answer: B.

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Q 5M.C.Q (1 Marks)1 Mark
An $AC$ source producing emf $\in=\in_{0}\Big[\cos\big(100\pi\text{s}^{-1}\big)\text{t}+\cos\big(500\pi\text{s}^{-1}\big)\text{t}\Big]$ is connected in series with a capacitor and a resistor. The steady-state current in the circuit is found to be $\text{i}=\text{i}_1\cos\Big[\big(100\pi\text{s}^{-1}\big)\text{t}+\phi_1\Big]+\text{i}_2\cos\Big[\big(500\pi\text{s}^{-1}\big)\text{t}+\phi_2\Big].$
  • A
    $i_1  > i_2$
  • B
    $i_1 = i_2$
  • ✓
    $i_1 < i_2$
  • D
    The information is insufficient to find the relation between $i_1$ and $i_2$

Answer: C.

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Q 61 Marks Question1 Mark
When an AC source is connected to a capacitor there is a steady-state current in the circuit. Does it mean thatthe charges jump from one plate to the other to complete the circuit?
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Q 71 Marks Question1 Mark
An AC source is connected to a capacitor. Will the rms current increase, decrease or remain constant if a dielectric slab is inserted into the capacitor?
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Q 101 Marks Question1 Mark
In a circuit containing a capacitor and an AC source the current is zero at the. stant the source voltage is maximum. Is it consistent with Ohm's law?
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Q 112 Marks Questions2 Marks
A transformer is designed to convert an AC voltage of 220V to an AC voltage of 12V. If the input terminals are connected to a DC voltage of 220V, the transformer usually burns. Explain.
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Q 122 Marks Questions2 Marks
The peak power consumed by a resistive coil, when connected to an AC source, is 80W. Find the energy consumed by the coil in 100 seconds, which is many times larger than the time period of the source.
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Q 132 Marks Questions2 Marks
The current in a discharging LR circuit is given by $\text{i}=\text{i}_0\text{e}^{\frac{-\text{t}}{\tau}}$ where $\tau$ is the time constant of the circuit. Calculate the rms current for the period $\text{t}=0$ to $\text{t}=\tau.$
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Q 142 Marks Questions2 Marks
A resistance is connected to an AC source. If a capacitor is included in the series circuit, will the average power absorbed by the resistance increase or decrease? If an inductor of small inductance is also included in the series circuit, will the average power absorbed increase or decrease further?
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Q 152 Marks Questions2 Marks
The dielectric strength of air is $3.0 \times 10^6V/m.$ A parallel-plate air-capacitor has area $20cm^2$ and plate separation 0.10mm. Find the maximum rms voltage of an AC source that can be safely connected to this capacitor.
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Q 163 Marks Question3 Marks
An inductor-coil, a capacitor and an AC source of rms voltage 24V are connected in series. When the frequency of the source is varied, a maximum rms current of 6.0A is observed. If this inductor coil is connected to a battery of emf 12V and internal resistance $4.0\Omega,$ what will be the current?
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Q 183 Marks Question3 Marks
A bulb rated 60W at 220V is connected across a household supply of alternating voltage of 220V. Calculate the maximum instantaneous current through the filament.
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Q 193 Marks Question3 Marks
Consider the situation of the previous problem. Find the average electric field energy stored in the capacitor and the average magnetic field energy stored in the coil.
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Q 203 Marks Question3 Marks
A coil of inductance 5.0mH and negligible resistance is connected to the oscillator of the previous problem. Find the peak currents in the circuit for $\omega=100\text{s}^{-1},500\text{s}^{-1},1000\text{s}^{-1}.$
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