NEET Physics PYQ – Electromagnetic Waves Chapter Wise Questions

Q 1 :
A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is [2025]

non-zero everywhere with maximum at the imaginary cylindrical surface connecting peripheries of the plates
zero between the plates and non-zero outside
zero at all places
constant between the plates and zero outside the plates.

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(1)

The magnetic field arising due to displacement current is non zero everywhere with maximum at the imaginary cylindrical surface connecting peripheries of the plates. This is because the displacement current is strongest there, where the changing electric field is most concentrated.

Q 2 :
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $I$ is the current in the circuit, then in the gap between the plates [2024]

there is no current.
displacement current of magnitude equal to $I$ flows in the same direction as $I$ .
displacement current of magnitude equal to $I$ flows in a direction opposite to that of $I$ .
displacement current of magnitude greater than $I$ flows but can be in any direction.

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(2)

Displacement current is equal to the conduction current and flows from positive plate towards negative plate in the direction of conduction current.

Q 3 :
To produce an instantaneous displacement current of 2 mA in the space between the parallel plates of a capacitor of capacitance 4 $μ F$ , the rate of change of applied variable potential difference $(\frac{d V}{d t})$ must be [2023]

800 V/s
500 V/s
200 V/s
400 V/s

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(2)

Displacement current, $I_{D} = ε_{0} \frac{d ϕ_{E}}{d t} = ε_{0} \frac{d}{d t} (E A)$

$= ε_{0} A \frac{d}{d t} (\frac{V}{d}) or I_{D} = \frac{ε_{0} A}{d} \frac{d V}{d t}$

$\Rightarrow I_{D} = \frac{C d V}{d t} or \frac{d V}{d t} = \frac{I_{D}}{C}$

Given, $I_{D} = 2 mA = 2 \times 10^{- 3} A;$ $C = 4 \times 10^{- 6} F$

So, $\frac{d V}{d t} = \frac{2 \times 10^{- 3}}{4 \times 10^{- 6}} = 500 V/s$

Q 4 :
An AC source is connected to a capacitor C. Due to decrease in its operating frequency [2023]

displacement current decreases
capacitive reactance remains constant
capacitive reactance decreases
displacement current increases

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(1)

Capacitive inductance, $X_{C} = \frac{1}{2 π f C}$

As frequency decreases, $X_{C}$ increases.

[IMAGE 264]------------------------------

So, conduction current decreases. Hence, displacement current decreases.

Q 5 :
A capacitor of capacitance $' C',$ is connected across an AC source of voltage $V$ , given by

$V = V_{0} \sin ω t$

The displacement current between the plates of the capacitor, would then be given by [2021]

$I_{d} = V_{0} ω C \sin ω t$
$I_{d} = V_{0} ω C \cos ω t$
$I_{d} = \frac{V_{0}}{ω C} \cos ω t$
$I_{d} = \frac{V_{0}}{ω C} \sin ω t$

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(2)

The instantaneous voltage, $V = V_{0} \sin ω t$ ...(i)

Displacement current is given by

$i_{d} = \frac{C d V}{d t}$ ...(ii)

$i_{d} = \frac{C d}{d t} (V_{0} \sin ω t) \Rightarrow i_{d} = C V_{0} ω \cos ω t$

Q 6 :
A parallel plate capacitor of capacitance 20 $μ F$ is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively [2019]

zero, zero
zero, 60 $μ A$
60 $μ A$ , 60 $μ A$
60 $μ A$ , zero

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(3)

Here, $C = 20$ $μ F$

The rate of change of potential, $\frac{d V}{d t} = 3$ $V/s$

The charge on the capacitor, $Q = C V$

$∴$ $\frac{d Q}{d t} = I_{D} = C \frac{d V}{d t} = 20 μ F \times \frac{3 V}{s} = 60 μ A$

Displacement current is equal to the conduction current.

Q 7 :
A 100 $Ω$ resistance and a capacitor of 100 $Ω$ reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is [2016]

2.2 A
11 A
4.4 A
$11 \sqrt{2}$ A

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(1)

Here, $R = 100 Ω, X_{C} = 100 Ω$

Net impedance, $Z = \sqrt{R^{2} + X_{C}^{2}} = 100 \sqrt{2} Ω$

Peak value of displacement current = Maximum conduction current in the circuit

$= \frac{ε_{0}}{Z} = \frac{220 \sqrt{2}}{100 \sqrt{2}} = 2.2 A$

Topic Question Set

Q 1 :
A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is [2025]

Q 2 :
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $I$ is the current in the circuit, then in the gap between the plates [2024]

Q 3 :
To produce an instantaneous displacement current of 2 mA in the space between the parallel plates of a capacitor of capacitance 4 $μ F$ , the rate of change of applied variable potential difference $(\frac{d V}{d t})$ must be [2023]

Q 4 :
An AC source is connected to a capacitor C. Due to decrease in its operating frequency [2023]

Q 5 :
A capacitor of capacitance $' C',$ is connected across an AC source of voltage $V$ , given by

$V = V_{0} \sin ω t$

The displacement current between the plates of the capacitor, would then be given by [2021]

Q 6 :
A parallel plate capacitor of capacitance 20 $μ F$ is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively [2019]

Q 7 :
A 100 $Ω$ resistance and a capacitor of 100 $Ω$ reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is [2016]

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Topic Question Set

Q 1 : A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is [2025]

Q 2 : A parallel plate capacitor is charged by connecting it to a battery through a resistor. If I is the current in the circuit, then in the gap between the plates [2024]

Q 3 : To produce an instantaneous displacement current of 2 mA in the space between the parallel plates of a capacitor of capacitance 4 μF, the rate of change of applied variable potential difference (dVdt) must be [2023]

Q 4 : An AC source is connected to a capacitor C. Due to decrease in its operating frequency [2023]

Q 5 : A capacitor of capacitance 'C', is connected across an AC source of voltage V, given by V=V0sinωt The displacement current between the plates of the capacitor, would then be given by [2021]

Q 6 : A parallel plate capacitor of capacitance 20 μF is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively [2019]

Q 7 : A 100 Ω resistance and a capacitor of 100 Ω reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is [2016]

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Q 1 :
A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is [2025]

Q 2 :
A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $I$ is the current in the circuit, then in the gap between the plates [2024]

Q 3 :
To produce an instantaneous displacement current of 2 mA in the space between the parallel plates of a capacitor of capacitance 4 $μ F$ , the rate of change of applied variable potential difference $(\frac{d V}{d t})$ must be [2023]

Q 4 :
An AC source is connected to a capacitor C. Due to decrease in its operating frequency [2023]

Q 5 :
A capacitor of capacitance $' C',$ is connected across an AC source of voltage $V$ , given by

$V = V_{0} \sin ω t$

The displacement current between the plates of the capacitor, would then be given by [2021]

Q 6 :
A parallel plate capacitor of capacitance 20 $μ F$ is being charged by a voltage source whose potential is changing at the rate of 3 V/s. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively [2019]

Q 7 :
A 100 $Ω$ resistance and a capacitor of 100 $Ω$ reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is [2016]