Electromagnetic Induction & AC · JEE Main previous year questions

2021 9 questions

1. Q442021 · 26 Aug 2021 · Shift 2

   Match List - I with List - II | List-I | List-II | | :--- | :--- | | (a) Magnetic Induction | (i) ${\mathrm{ML}}^2{\mathrm{T}}^{-2}{\mathrm{A}}^{-1}$ | | (b) Magnetic Flux | (ii) ${\mathrm{M}}^0{\mathrm{L}}^{-1}\mathrm{A}$ | | (c) Magnetic Permeability | (iii) ${\mathrm{MT}}^{-2}{\mathrm{A}}^{-1}$ | | (d) Magnetization | (iv) ${\mathrm{MLT}}^{-2}{\mathrm{A}}^{-2}$ | Choose the most appropriate answer from the options given below :

   1. A.(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
   2. B.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
   3. C.(a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
   4. D.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
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   Answer: D

2. Q382021 · 27 Jul 2021 · Shift 2

   A $100\Omega$ resistance, a $0.1\mu \mathrm{F}$ capacitor and an inductor are connected in series across a 250 V supply at variable frequency. Calculate the value of inductance of inductor at which resonance will occur. Given that the resonant frequency is 60 Hz.

   1. A.0.70 H
   2. B.70.3 mH
   3. C.$7.03\times 10^{-5}$ H
   4. D.70.3 H
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   Answer: D

3. Q332021 · 22 Jul 2021 · Shift 2
   
   1. A.
   2. B.
   3. C.
   4. D.
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   Answer: C

4. Q562021 · 20 Jul 2021 · Shift 1· Numerical answer

   In an LCR series circuit, an inductor $30\text{ mH}$ and a resistor $1\Omega$ are connected to an AC source of angular frequency $300\text{ rad/s}$. The value of capacitance for which, the current leads the voltage by $45^{\circ }$ is $\frac{1}{x}\times 10^{-3}\text{ F}$. Then the value of x is ________.

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   Answer: 3

5. Q342021 · 18 Mar 2021 · Shift 2

   In a series LCR circuit, the inductive reactance ($X_L$) is $10\Omega$ and the capacitive reactance ($X_C$) is $4\Omega$. The resistance (R) in the circuit is $6\Omega$. The power factor of the circuit is :

   1. A.$\frac{1}{2}$
   2. B.$\frac{\sqrt{3}}{2}$
   3. C.$\frac{1}{\sqrt{2}}$
   4. D.$\frac{1}{2\sqrt{2}}$
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   Answer: C

6. Q562021 · 16 Mar 2021 · Shift 1· Numerical answer

   A sinusoidal voltage of peak value 250 V is applied to a series LCR circuit, in which $\mathrm{R}=8\Omega$, $\mathrm{L}=24\mathrm{mH}$ and $\mathrm{C}=60\mu \mathrm{F}$. The value of power dissipated at resonant condition is 'x' kW. The value of x to the nearest integer is _________.

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   Answer: 4

7. Q322021 · 26 Feb 2021 · Shift 1

   An alternating current is given by the equation $i=i_1\sin \omega t+i_2\cos \omega t$. The rms current will be :

   1. A.$\frac{1}{\sqrt{2}}{\left(i_1^2+i_2^2\right)}^{\frac{1}{2}}$
   2. B.$\frac{1}{\sqrt{2}}(i_1+i_2)$
   3. C.$\frac{1}{\sqrt{2}}(i_1+i_2{)}^2$
   4. D.$\frac{1}{2}{\left(i_1^2+i_2^2\right)}^{\frac{1}{2}}$
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   Answer: A

8. Q312021 · 25 Feb 2021 · Shift 2

   An LCR circuit contains resistance of $110\Omega$ and a supply of 220 V at 300 rad/s angular frequency. If only capacitance is removed from the circuit, current lags behind the voltage by $45^{\circ }$. If on the other hand, only inductor is removed the current leads by $45^{\circ }$ with the applied voltage. The rms current flowing in the circuit will be :

   1. A.1 A
   2. B.2.5 A
   3. C.2 A
   4. D.1.5 A
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   Answer: C

9. Q382021 · 25 Feb 2021 · Shift 2

   Match List I with List II. | | List I | | List II | | :--- | :--- | :--- | :--- | | (a) | Rectifier | (i) | Used either for stepping up or stepping down the a.c. voltage | | (b) | Stabilizer | (ii) | Used to convert a.c. voltage into d.c. voltage | | (c) | Transformer | (iii) | Used to remove any ripple in the rectified output voltage | | (d) | Filter | (iv) | Used for constant output voltage even when the input voltage or load current change | Choose the correct answer from the options given below :

   1. A.(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
   2. B.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
   3. C.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
   4. D.(a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
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   Answer: A