Revision 1. The opposite figure represents a part of an electric circuit that carries an electric current, then the value of VB is ……… a. 30 V b. 20 v c. 25 V d. 15 V 2. The opposite graph represents the change of the induced electromotive force (emf) in the dynamo's coil with respect to the angle between the normal to the coil's plane and the direction of the magnetic flux (θ), so the magnitude of the average induced emf in the dynamo's coil 1 during cycle from the starting of the coil's 3 rotation equals ………… a. 3.002 V b. 6.369 V c. 9.006 V d. 10.132 V 3. The opposite graph represents the relation between the average induced electromotive force (emf) in a metallic ring and the time (t), then the ratio between the magnitudes of the change in the magnetic flux through the ring in the two intervals (x) and (y) respectively is ……… 1 a. b. c. d.
3 3 1 2 3 1 6
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Physics
4. In the dynamo, which of the following graphs represents the relation between the instantaneous induced electromotive force and time if the coil starts its rotation from the position in which the plane of the coil is inclined to the field by an angle 60°? …………
5. The opposite two figures represent two models for the coils of an AC dynamo (1) and (2) of number of turns 10 and 20 turns respectively. The flux density that acts on each of the two coils is B and each of them rotates such that the linear velocity of the side that is parallel to the axis of rotation is v, then the ratio 𝑒𝑚𝑓𝑚𝑎𝑥 1 is …….. 𝑒𝑚𝑓𝑚𝑎𝑥 2 1
a.
b. c. d.
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6. The opposite graph represents the relation between the generated electromotive force (emf) in an AC dynamo's coil within a complete cycle and time (t), then the value of the average electromotive force within the time interval from t to 2 t is greater than the value of the average electromotive force within the time interval………. a. from 0 to t b. from 2 t to 3 t c. from 0 to 2 t d. from t to 4 t 7. A series AC circuit consists of a resistance of 12 Ω, an inductor of zero ohmic resistance, a capacitor and an AC source of potential difference 100 V and frequency 50 Hz, so the inductive reactance of the coil is 47.14 Ω and the capacitive reactance of the capacitor is 31.82 Ω, then the electric current intensity passes in the circuit is ………… a. 5.14 A b. 7.12 A c. 3.28 A d. 14.24 A 8. An inductor that has an inductance of 0.01 H and a resistance of 1 Ω is connected to an AC source that has a potential difference of 200 V and a frequency of 50 Hz, then the maximum value of the current …………. a. lags the maximum value of the voltage by 0.004 s b. leads the maximum value of the voltage by 0.003 s c. lags the maximum value of the voltage by 0.002 s d. leads the maximum value of the voltage by 0.001 s
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9. The opposite figure represents an AC dynamo, if the output voltage was +10 V when the dynamo's position was as in the figure, so it becomes −10 V when the coil rotates by an angle of ………. a. 90° b. 180° c. 270° d. 360° 10. In the opposite electric circuit if the pointer of the galvanometer has stopped at zero, then the value of the resistor R equals ……….. a. 12 Ω b. 16 Ω c. 15 Ω d. 18 Ω 11. According to Bohr's model, if the wavelength of the wave associated with the motion of the electron in one of the energy levels of the 𝜋𝑟 hydrogen atom is equivalent to 𝑛 where rn is the radius of the orbit in 2 which the electron is rotating, then this electron is rotating in the energy level …….. a. L b. M c. N d. O 12. In the opposite figure, when the magnet moves in the shown direction, the light intensity of the bulb ………. a. increases instantaneously b. decreases instantaneously c. vanishes d. remains constant
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13. In the opposite electric circuit, if the pointer of the galvanometer deflects to the end of the scale, then the value of the shunt resistance Rs equals ………… a. 1.2 Ω b. 2.5 Ω c. 3.1 Ω d. 4.2 Ω
14. In the opposite circuit, a solenoid is connected to a resistor and two identical batteries, each of electromotive force VB and of negligible internal resistance, then ………. The magnetic pole The magnetic which is formed at pole which is y formed at x a. north north b. north south c. south north d. south south 15. The opposite figure shows a circular coil of radius 14 cm and number of turns 10 turns moving in a direction parallel to its plane with a uniform velocity 1.42 m/s through a uniform magnetic field of flux density 0.24 T that is perpendicular to the plane of the coil, then the value of the average induced electromotive force in the coil when half the area of the coil becomes inside the magnetic field is ……….. a. 0.75 V b. 1.5 V c. 2.5 V d. 3 V
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Physics
16. If the wavelength of the wave associated with the motion of an electron in one of the energy levels of the hydrogen atom is 9.98 × 1010 m, then the speed of the electron in this level is approximately equal to………. (Where: h = 6.625 × 10-34 J.s, me = 9.1 × 10-31 kg) a. 6.2 × 105 m/s b. 7.3 × 105 m/s c. 5.4 × 105 m/s d. 6.2 × 105 m/s 17. In an ammeter device, 2 % of the total current passes through the galvanometer, so if the resistance of the galvanometer is Rg, then the resistance of the ammeter equals ………… 𝑅𝑔 a. b. c.
49 49𝑅𝑔 50 𝑅𝑔
50 50𝑅𝑔
d. 49 18. The opposite graph shows the emitted spectrum of X-rays from a Coolidge tube, so the potential difference between the filament and the target equals …………. (Where: e = 1.6 x 10-19 C, c = 3 × 108 m/s, h= 6.625 × 10-34 J.s) a. b. c. d.
3
39.67 × 10 V 3 36.21 × 10 V 3 38.42 × 10 V 3 34.51 × 10 V
19. In the opposite electric circuit, if the total voltage lags the current by an angle of 45°, then component A is ……….. a. an inductor of reactance 20 Ω b. an inductor of reactance 80 Ω c. a capacitor of reactance 20 Ω d. a capacitor of reactance 60 Ω
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22
20. In the opposite figure, a solenoid of length m and number of turns 70 500 turns carries an electric current of 20 A, so if the solenoid is being subjected to a magnetic flux of density 0.02 T whose direction is parallel to the axis of the solenoid and to the east, then the value of the magnetic flux at the center of the axis of the solenoid is ………... (Where: 𝜇 =4𝜋 × 10-7 wb/A.m) a. zero b. 0.02 T to the east c. 0.02 T to the west d. 0.06 T to the east 21. The opposite figure represents an electric circuit. If V2 = 4 V1, then the value of I equals …….. a. 2 A b. 64 A c. 6 A d. 8 A
22. The opposite figure shows a wire (A) which is perpendicular to the plane of the page while carrying an electric current. If the horizontal component of the magnetic flux density of the Earth is H tesla in the shown direction and if the resultant magnetic flux density at point q equals zero, then the resultant of magnetic flux density at point p equals ………… a. 0 b. H T c. √2 H T d. 2 H T
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Physics
23. An electron of mass me moves with a speed v where the wavelength of the wave associated with its motion is 𝜆, if the electron speed is increased to three times as its initial value, then the wavelength of the wave associated with its motion becomes ……………… a. 9 𝜆 𝜆 b. 3 𝜆
c. 9 d. 3 𝜆 24. In which of the following circuits a half-wave rectified current passes in resistor R? ……… a. Circuit (1) only. b. Circuit (2) only. c. Circuit (3) only. d. All the three circuits.
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Answer 1. d 2. d 3. d 4. a 5. c 6. d 7. a 8. a 9. b 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
d c a d d a b c d d c a d b d
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Physics