Tiêu đề ELECTROMAGNETIC INDUCTION.pdf ✅

CHAPTER ELECTROMAGNETIC INDUCTION 6 Exercise 1: NCERT Based Topic-wise MCQs 6.1 INTRODUCTION 1. Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called (a) electromagnetic induction NCERT Page-204 / N-154 (b) lenz's law (c) hysteresis loss (d) kirchhoff's laws 111 2. According to Faraday's law of electromagnetic induction NCERT Page-204 i N-157, 158 (a) electric field is produced by time varying magnetic flux. (b) magnetic field is produced by time varying electric flux. (c) magnetic field is associated with a moving charge. (d) None of these 6.2 THE EXPERIMENTS OF FARADAY AND HENERY 3. A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is NCERT Page-205/ N-155, 156 (a) larger in case (i) (b) smaller in case (i) (c) equal in both the cases (d) larger or smaller depending upon the radius of the coil 4. An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e:m.f. is independent of NCERT Page-205/ N-155, 156 (a) the strength of the magnet (b) number of turns of coil (c) the resistivity of the wire of the coil (d) speed with which the magnet is moved 5. A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because (a) the induced current is produced NCERT Page-205 / N-155, 156 (b) the coil acts like magnet (c) the number of turns in the coil of the galvanometer are changed (d) None of these 6.3 MAGNETIC FLUX 6. Flux of magnetic field through an area bounded by a closed conducting loop can be changed by changing (a) area of the loop NCERT Page-207 / N-157 (b) magnetic field B⃗ (c) angle between area vector and B⃗
(d) All of the above 7. In a coil of resistance 10Ω, the induced current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in weber is NCERT Page-207 / N-157 (a) 8 (b) 2 (c) 6 (d) 4 8. Fig shown below represents an area A = 0.5m2 situated in a uniform magnetic field B = 2.0 weber /m2 and making an angle of 60∘ with respect to magnetic field. NCERT Page-207 / N-157 The value of the magnetic flux through the area would be equal to (a) 2.0 weber (b) √3 weber (c) √3/2 weber (d) 0.5 weber 6.4 FARADAY’S LAW OF INDUCTION 9. In electromagnetic induction, the induced charge is independent of NCERT Page-207 / N-157 (a) change of flux (c) resistance of the coil (b) time (d) None of these 10. A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An e.m.f. is induced in the loop, if (a) it is translated NCERT Page-207. / N-157 (b) it is rotated about its axis (c) both (a) and (b) (d) it is rotated about its diameter 11. The expression for the induced e.m.f. contains a negative sign [e = − dφ dt ]. What is the significance of the negative sign? NCERT Page-208 / N-158 (a) The induced e.m.f. is produced only when the magnetic flux decreases. (b) The induced e.m.f. opposes the change in the magnetic flux.
(c) The induced e.m.f. is opposite to the direction of the flux. (d) None of the above. 12. The magnetic flux through a coil perpendicular to its plane is varying according to the relation φ = (5t 3 + 4t 2 + 2t − 5) Weber. If the resistant of the coil is 5ohm, then the induced current through the coil at t = 2sec will be: (a) 15.6A NCERT Page-208 / N-158 (b) 16.6A (c) 17.6A (d) 18.6A 13. A coil having an area A0 is placed in a magnetic field which changes from B0 to 4B0 in time interval t. The e.m.f. induced in the coil will be NCERT Page-208 / N-158 (a) 3A0B0/t (c) 3B0/A0t (b) 4A0B0/t (d) 4A0/B0t 14. The magnetic flux through a circuit of resistance R changes by an amount Δφ in a time Δt. Then the total quantity of electric charge Q that passes any point in the circuit during the time Δt is represented by NCERT Page-208 / N-158 (a) Q = R ⋅ Δφ Δt (b) Q = 1 R ⋅ Δφ Δt (c) Q = Δφ R (d) Q = Δφ Δt 15. If a current increases from zero to one ampere in 0.1 second in a coil of 5mH, then the magnitude of the induced e.m.f. will be NCERT Page-208 / N-158 (a) 0.005 volt (b) 0.5 volt (c) 0.05 volt (d) 5 volt 16. A coil has 200 turns and area of 70cm2 . The magnetic field perpendicular to the plane of the coil is 0.3Wb/m2 and take 0.1sec to rotate through 180∘ . The value of the induced e.m.f. will be NCERT Page-208 / N-158 (a) 8.4V (b) 84V (c) 42V (d) 4.2V 17. The magnetic flux linked with the coil (in Weber) is given by the equation φ = 5t 2 + 3t + 16 The induced EMF in the coil at time, t=4 will be- NCERT Page-208 / N-158 (a) −27V (b) −43V (c) −108V (d) 210V 18. A coil having n turns and resistance RΩ is connected with a galvanometer of resistance 4RΩ. This combination is moved in time t seconds from a magnetic field W1 weber to W2 weber. The induced current in the circuit is NCERT Page-208 / N-158 (a) − (W1−W2 ) Rnt (b) − n(W2−W1 ) 5Rt
(c) − (W2−W1 ) 5Rnt (d) − n(W2−W1 ) Rt 19. Magnetic flux φ in weber in a closed circuit of resistance 10Ω varies with time φ(sec) as φ = 6t 2 − 5t + 1. The magnitude of induced current at t = 0.25s is NCERT Page-208 (a) 0.2A (c) 1.2A (b) 0.6A (d) 0.8A 20. A conducting circular loop is placed in a uniform magnetic field, B = 0.025T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1mms −1 . The induced e.m.f. when the radius is 2cm, is NCERT Page-208 / N-158 (a) 2πμV (b) πqV (c) π 2 μV (d) 2μV 21. A coil of 50 turns is pulled in 0.02s between the poies of a magnet, where its area includes 31 × 10−6Wb to 1 × 10−6Wb. The average e.m.f. is NCERT Page-208 / N-158 (a) 7.5 × 10−2V (c) zero (b) 7.5 × 10−3V (d) 7.5 × 10−4V 22. A long solenoid having 200 turns per cm carries a current of 1.5amp. At the centre of it is placed a coil of 100 turns of cross-sectional area 3.14 × 10−4m2 having its axis parallel to the field produced by the solenoid. When the direction of current in the solenoid is reversed within 0.05sec, the induced e.m.f. in the coil is (a) 0.48V NCERT Page-208./ N-158 (b) 0.048V (c) 0.0048V (d) 48V 23. A 100 turns coil of area of cross section 200cm2 having 2Ω resistance is held perpendicular to a magnetic field of 0.1T. If it is removed from the magnetic field in one second, the induced charge produced in it is (a) 0.2C NCERT P Page-208 / N-158 (b) 2C (c) 0.1C (d) 1C 24. A thin circular ring of area A is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is NCERT Page-208 / N-158 (a) BR A (b) AB R (c) ABR (d) B 2A R2 25. A rectangular coil of 100 turns and size 0.1m × 0.05m is placed perpendicular to a magnetic field of 0.1T. The induced e.m.f. when the field drops to 0.05T in 0.05s is NCERT Page-208 / N-158 (a) 0.5V (b) 1.0V