Electromagnetic Induction & AC · JEE Main previous year questions

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2022 11 questions

Q432022 · 28 Jul 2022 · Shift 1
The equation of current in a purely inductive circuit is $5 sin (49 π t - 3 0^{\circ})$ . If the inductance is $30 mH$ then the equation for the voltage across the inductor, will be : \{ Let $π = \frac{22}{7}$ \}
1. A. $1.47 sin (49 π t - 3 0^{\circ})$
2. B. $1.47 sin (49 π t + 6 0^{\circ})$
3. C. $23.1 sin (49 π t - 3 0^{\circ})$
4. D. $23.1 sin (49 π t + 6 0^{\circ})$
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Answer: D
Q442022 · 28 Jul 2022 · Shift 2
A transformer operating at primary voltage $8 kV$ and secondary voltage $160 V$ serves a load of $80 kW$ . Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be
1. A. $800 Ω$ and $1.06 Ω$
2. B. $10 Ω$ and $500 Ω$
3. C. $800 Ω$ and $0.32 Ω$
4. D. $1.06 Ω$ and $500 Ω$
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Answer: C
Q422022 · 27 Jul 2022 · Shift 2
A series LCR circuit has $L = 0.01 H$ , $R = 10 Ω$ and $C = 1 μ F$ and it is connected to ac voltage of amplitude $(V_{m}) 50 V$ . At frequency $60%$ lower than resonant frequency, the amplitude of current will be approximately :
1. A. $466 mA$
2. B. $312 mA$
3. C. $238 mA$
4. D. $196 mA$
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Answer: C
Q312022 · 25 Jul 2022 · Shift 2
The electric current in a circular coil of 2 turns produces a magnetic induction $B_{1}$ at its centre. The coil is unwound and is rewound into a circular coil of 5 turns and the same current produces a magnetic induction $B_{2}$ at its centre. The ratio of $\frac{B _{2}}{B _{1}}$ is
1. A. $\frac{5}{2}$
2. B. $\frac{25}{4}$
3. C. $\frac{5}{4}$
4. D. $\frac{25}{2}$
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Answer: B
Q492022 · 30 Jun 2022 · Shift 1
In series RLC resonator, if the self inductance and capacitance become double, the new resonant frequency ( $f_{2}$ ) and new quality factor ( $Q_{2}$ ) will be : ( $f_{1}$ = original resonant frequency, $Q_{1}$ = original quality factor)
1. A. $f_{2} = \frac{f _{1}}{2}$ and $Q_{2} = Q_{1}$
2. B. $f_{2} = f_{1}$ and $Q_{2} = \frac{Q _{1}}{Q _{2}}$
3. C. $f_{2} = 2 f_{1}$ and $Q_{2} = Q_{1}$
4. D. $f_{2} = f_{1}$ and $Q_{2} = 2 Q_{1}$
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Answer: A
Q542022 · 28 Jun 2022 · Shift 2· Numerical answer
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Answer: 0
Q432022 · 26 Jun 2022 · Shift 2
1. A. $\frac{1}{L _{1}} + \frac{1}{L _{2}} + \frac{1}{M}$
2. B. $L_{1} + L_{2} + M$
3. C. $L_{1} + L_{2} + 2 M$
4. D. $L_{1} + L_{2} - 2 M$
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Answer: D
Q392022 · 25 Jun 2022 · Shift 1
Match List-I with List-II. | | List - I | | List - II | | :--- | :--- | :--- | :--- | | (A) | AC generator | (I) | Detects the presence of current in the circuit | | (B) | Galvanometer | (II) | Converts mechanical energy into electrical energy | | (C) | Transformer | (III) | Works on the principle of resonance in AC circuit | | (D) | Metal detector | (IV) | Changes an alternating voltage for smaller or greater value | Choose the correct answer from the options given below :
1. A.(A) - (II), (B) - (I), (C) - (IV), (D) - (III)
2. B.(A) - (II), (B) - (I), (C) - (III), (D) - (IV)
3. C.(A) - (III), (B) - (IV), (C) - (II), (D) - (I)
4. D.(A) - (III), (B) - (I), (C) - (II), (D) - (IV)
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Answer: A
Q412022 · 25 Jun 2022 · Shift 1
If wattless current flows in the AC circuit, then the circuit is :
1. A.Purely Resistive circuit
2. B.Purely Inductive circuit
3. C.LCR series circuit
4. D.RC series circuit only
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Answer: B
Q582022 · 25 Jun 2022 · Shift 1· Numerical answer
The current in a coil of self inductance $2.0 H$ is increasing according to $I = 2 sin (t^{2}) A$ . The amount of energy spent during the period when current changes from $0$ to $2 A$ is $J$ .
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Answer: 4
Q422022 · 25 Jun 2022 · Shift 2
A sinusoidal voltage $V (t) = 210 sin 3000 t volt$ is applied to a series LCR circuit in which $L = 10 mH$ , $C = 25 μ F$ and $R = 100 Ω$ . The phase difference $(Φ)$ between the applied voltage and resultant current will be :
1. A. $tan^{- 1} (0.17)$
2. B. $tan^{- 1} (9.46)$
3. C. $tan^{- 1} (0.30)$
4. D. $tan^{- 1} (13.33)$
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Answer: A