Electromagnetic Induction PYQs Set 1 (PDF)

Set 1 of 10 · Questions 1-30 of 274

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Mere Teacher · Previous Year Questions NEET Physics · Electromagnetic Induction · Set 1 (Q1-30)
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1. $A generator with a circular coil of 100 turns of area 2 \times 10^{- 2} m^{2} is immersed in a 0.01 T magnetic field and rotated at a frequency of 50 Hz, The maximum emf which is produced during a cycle is$ (1) $6.28 V$ (2) $3.44 V$ (3) $10 V$ (4) $1.32 V$ 2. $If N is the number of turns in a circular coil then the value of self inductance varies as$ (1) $N^{0}$ (2) $N$ (3) $N^{2}$ (4) $N^{- 2}$ 3. $A rectangular coil of 20 turns and area of cross‐section 25 sq . cm has a resistance of 100Ω . If a magnetic field which is perpendicular to the plane of coil changes at a rate of 1000 tesla per second, the current in the coil is$ (1) $1 A$ (2) $50 A$ (3) $0.5 A$ (4) $5 A$ 4. $A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are$ (1) $300 V, 15 A$ (2) $450 V, 15 A$ (3) $450 V, 13.5 A$ (4) $600 V, 15 A$ 5. $If the number of turns per unit length of a coil of solenoid is doubled, the self‐ inductance of the solenoid will$ (1) $remain unchanged$ (2) $be halved$ (3) $be doubled$ (4) $become four times$ 6. $A coil of resistance 400 Ω is placed in a magnetic field. If the magnetic flux ϕ (Wb) linked with the coil varies with time t (sec) as ϕ = 50 t^{2} + 4 . The current in the coil at t = 2 sec is$ (1) $0.5 A$ (2) $0.1 A$ (3) $2 A$ (4) $1 A$ 7. $A uniform magnetic field of 0.4 T acts perpendicular to a circular copper disc 20 cm in radius. The disc is having a uniform angular velocity of 10 π rads^{- 1} about an axis through its centre and perpendicular to the disc. What is the potential difference developed between the axis of the disc and the rim? (π = 3.14)$ (1) $0.5024 V$ (2) $0.0628 V$ (3) $0.2512 V$ (4) $0.1256 V$ 8. $The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA . This inductor is of inductance$ (1) $0.138 H$ (2) $138.88 H$ (3) $1.389 H$ (4) $13.89 H$ 9. $A transistor‐oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in seriesproduce oscillations of frequency f . If L is doubled and C is changed to 4 C, the frequency will be$ (1) $f /2$ (2) $f /4$ (3) $8 f$ (4) $f /2 2$ 10. $In an a . c . circuit with phase voltage V and current I, the power dissipated is$ (1) $V . I$ (2) $depends on phase angle between V and I$ (3) $\frac{1}{2} \times V . I$ (4) $\frac{1}{2} \times V . I$ 11. $An inductor 20 mH, a capacitor 100 μF and a resistor 50Ω are connected in series across a source of emf, V = 10 sin 314 t . The power loss in the circuit is$ (1) $0.79 W$ (2) $0.43 W$ (3) $2.74 W$ (4) $1.13 W$ 12. $A small signal voltage V (t) = V_{0} sin ω t is applied across an ideal capacitor C$ (1) $Current I (t) is in phase with voltage V (t) .$ (2) $Current It leads voltage Vt by 18 0^{o}$ (3) $Current It , lags voltage Vt by 9 0^{o}$ (4) $Over a full cycle the capacitor C does not consume any energy from the voltage source.$ 13. $In a coil, the current changes from - 2 A to + 2 A in 0.2 s and induces an emf of 0.1 V . The self inductance of the coil is:$ (1) $4 mH$ (2) $1 mH$ (3) $5 mH$ (4) $2.5 mH$ 14. $A long solenoid of diameter 0.1 m has 2 \times 1 0^{4} turn per meter. At the center of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to 0A from 4 A in 0.05 s. If the resistance of the coil is 10 π^{2} Ω, the total charge flowing through the coil during this time is$ (1) $32 πµC$ (2) $16 µC$ (3) $32 µC$ (4) $16 πµC$ 15. $A long solenoid has 1000 turns. When a current of 4A flows through it, the magnetic flux linked with each turn of the solenoid is 4 \times 1 0^{-3} Wb. The self-inductance of the solenoid is$ (1) $1H$ (2) $4H$ (3) $3H$ (4) $2H$ 16. $A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be$ (1) $2.0 A$ (2) $4.0 A$ (3) $8.0 A$ (4) $\frac{20}{13} A$ 17. $A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s^{- 1} . The induced emf when the radius is 2 cm, is$ (1) $2 πμV$ (2) $πμV$ (3) $π2 μV$ (4) $2 μV$ 18. $A uniform magnetic field B exists in a direction perpendicular to the plane of a square loop made of a metal wire. The wire has a diameter of 4 mm and a total length of 30 cm . The magnetic field changes with time at a steady rate dB / dt = 0.032 Ts^{- 1} . The induced current in the loop is close to (Resistivity of the metal wire is 1.23 \times 10^{- 8} Ωm)$ (1) $0.34 A$ (2) $0.61 A$ (3) $0.53 A$ (4) $0.43 A$ 19. $A metal loop of area 10 cm^{2} is placed in a region such that its area vector points along k . The region contains a uniform magnetic field of magnitude 1.73 T that points in the direction i + j + k . When the magnetic field is switched off, the field decreases to zero at a steady rate in 10 s, then the magnitude of emf induced in the loop is$ (1) $0.10 mV$ (2) $0.17 mV$ (3) $1 mV$ (4) $1.7 mV$ 20. $For a series LCR circuit the power loss at resonance is$ (1) $\frac{V ^{2}}{( ωL - \frac{1}{( ω C )} )}$ (2) $I^{2} Lω$ (3) $I^{2} R$ (4) $\frac{V ^{2}}{Cω}$ 21. $The magnetic potential energy stored in a certain inductor is 25 mJ then the current in the inductor is 60 mA. This inductor is of inductance$ (1) $0.138 H$ (2) $13.89 H$ (3) $1.389 H$ (4) $138.88 H$ 22. $A 20 m long uniform copper wire held horizontally is allowed to fall under the gravity (g = 10 m / s^{2}) through a uniform horizontal magnetic field of 0.5 Gauss perpendicular to the length of the wire. The induced EMF across the wire when it travells a vertical distance of 200 m is____mV.$ (1) $2010$ (2) $0.2 10$ (3) $20010$ (4) $210$ 23. $Two coils have a mutual inductance of 0.01 H . The current in the first coil changes according to equation I = 5 sin 200 πt . The maximum value of e.m.f. induced in the second coil is$ (1) $10 π volt$ (2) $0.1 π volt$ (3) $π volt$ (4) $0.01 π volt$ 24. $Same current is flowing in two a.c. circuits. First contains only inductance and second contains only capacitance. If frequency of a.c. is increased for both, the current will$ (1) $increase in first circuit and decrease in second$ (2) $increase in both circuits$ (3) $decrease in both circuits$ (4) $decrease in first circuit and increase in second$ 25. $A conductor moving in the magnetic field B and the induced current is I . If the magnetic field is doubled the induced current will$ (1) $remain the same$ (2) $be half$ (3) $be doubled$ (4) $be four times$ 26. $Magnetic flux passing through a coil is initially 4 \times 10^{- 4} Wb . It reduces to 10 % of its original value in t second. If the e.m.f. induced is 0.72 mV then t in second is$ (1) $0.3$ (2) $0.4$ (3) $0.5$ (4) $0.6$ 27. $A transformer consisting of 300 turns in the primary and 150 turns in the secondary gives output power of 2.2kW. If the current in the secondary coil is10A, then the input voltage and current in the primary coil are:$ (1) $220V and 10A$ (2) $440V and 20 A$ (3) $440V and 5A$ (4) $220V and 20A$ 28. $There are two long co-axial solenoids of same length l . The inner and outer coils have radii r_{1} and r_{2} and number of turns per unit length n_{1} and n_{2} respectively. The rate of mutual inductance to the self-inductance of the inner-coil is:$ (1) $\frac{n _{1}}{n _{2}}$ (2) $\frac{n _{2}}{n _{1}} ∙ \frac{r _{1}}{r _{2}}$ (3) $\frac{n _{2}}{n _{1}} ∙ \frac{r _{1}^{2}}{r _{2}^{2}}$ (4) $\frac{n _{2}}{n _{1}}$ 29. $A current of 2.5 A flows through a coil of inductance 5 H. ne magnetic flux linked with the coil is$ (1) $0.5 Wb$ (2) $12.5 Wb$ (3) $zero$ (4) $2 Wb$ 30. $The magnetic flux through a circuit of resistance R changes by an amount Δ ϕ in a time Δ t . Then the total quantity of electric charge Q that passes any point in the circuit during the time Δ t is represented by$ (1) $Q = \frac{1}{R} \cdot \frac{Δ φ}{Δ t}$ (2) $Q = \frac{Δ φ}{R}$ (3) $Q = \frac{Δ φ}{Δ t}$ (4) $Q = R \cdot \frac{Δ φ}{Δ t}$