Tiêu đề 4 JULY PAPER.pdf ✅

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PHYSICS 1. A current of 5.0 A is passed through the coil of a galvanometer having 500 turns and each turn has an average area of 3 × 10–4 m2 . If a torque 1.5 N m is required for this coil carrying same current to set it parallel to a magnetic field, the strength of the magnetic field is (A) 2 T (B) 5 T (C) 3 T (D) 1 T 2. In the circuit shown, the voltage V1, across capacitor C (A) is in phase with the source voltage V (B) leads the source voltage V by 90° (C) leads the source voltage V by an angle between 0° and 90° (D) lags behind the source voltage V by an angle between 0° and 90°. 3. The electric potential V at any point (x, y, z) in space is given by V = 4x2V. The electric field at the point (1 m, 0, 2 m) in V m–1 is (A) –8 ˆ i (B) +8 ˆ i (C) –16 ˆ i (D) 16 ˆ k 4. A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively. (A) 40 A, 16 A (B) 16 A, 40 A (C) 20 A, 40 A (D) 40 A, 20 A 5. Figure below shows a portion of an electric circuit with the currents in amperes and their directions. The magnitude and direction of the current in the portion PQ is (A) 0 A (B) 3 A from P to Q (C) 4 A from Q to P (D) 6 A from Q to P 6. A radioactive nucleus undergoes a series of decay according to the scheme A A A A A 1 2 3 4         If the mass number and atomic number of A are 180 and 72 respectively, then what are these numbers for A4. (A) 172 and 69 (B) 174 and 70 (C) 176 and 69 (D) 176 and 70 7. The reactance of a capacitance C is X. If both the frequency and capacitance be doubled, then new reactance will be (A) X (B) 2X (C) 4X (D) 4 X 8. For what value of R the net resistance of the circuit will 18 Ω ? (A) 8 Ω (B) 10 Ω (C) 16 Ω (D) 24 Ω 9. The semiconductor at room temperature (A) the valence band is partially empty and the conduction band is partially filled. (B) the valence band is completely filled and the conduction band is partially filled. (C) the valence band is completely filled. (D) the conduction band is completely empty. 10. After absorbing a slowly moving neutron of mass mN (momentum ~ 0) a nucleus of mass M breaks into two nuclei of masses m1 and 5m1 (6m1 = M + mN), respectively. If the de Broglie wavelength of the nucleus with mass m1 is λ, then de Broglie wavelength of the other nucleus will be (A) 25λ (B) 5λ (C) 5  (D) λ 11. The refractive index of a material of a plano concave lens is 5/3, the radius of curvature is 0.3 m. The focal length of the lens in air is (A) – 0.45 m (B) – 0.6 m (C) – 0.75 m (D) – 1.0 m PW-AITS_NT-12
12. When a battery connected across a resistor of 16 Ω, the voltage across the resistor is 12 V. When the same battery is connected across a resistor of 10 Ω, voltage across it is 11 V. The internal resistance of the battery is (A) 10 7 Ω (B) 20 7 Ω (C) 25 7 Ω (D) 30 7 Ω 13. In the Davission and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by (A) increasing the potential difference between the anode and filament (B) increasing the filament current (C) decreasing the filament current (D) decreasing the potential difference between the anode and filament 14. A coil has 1,000 turns and 500 cm2 as its area. The plane of the coil is placed at right angles to a magnetic field of 2 × 10–5 Wb m–2 . The coil is rotated through 180° in 0.2 s. The average emf induced in the coil is (A) 5 mV (B) 10 mV (C) 15 mV (D) 20 mV 15. The activity of a radioactive sample is measured as N0 counts per minute at t = 0 and N0/e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is (A) ln 2 5 (B) 5 ln 2 (C) 5 log102 (D) 5 ln 2 16. A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a (A) convex mirror of focal length 10 cm (B) concave mirror of focal length 40 cm (C) concave mirror of focal length 60 cm (D) concave mirror of focal length 10 cm 17. The diode used in the circuit shown in figure has a constant voltage drop at 0.5 V at all currents and a maximum power rating of 100 mW. What should be the value of the resistor R, connected in series with diode, for obtaining maximum current ? (A) 6.76 Ω (B) 20 Ω (C) 5 Ω (D) 5.6 Ω 18. Light from a hydrogen discharge tube is incident on the cathode of a photoelectric cell. The work function of the cathode surface is 4.2 eV. In order to reduce the photocurrent to zero, the voltage of the anode relative to the cathode must be made (A) – 4.2 V (B) – 9.4 V (C) – 17.8 V (D) + 9.4 V 19. The weight based ratio of U238 and Pb226 in a sample of rock is 4 : 3. If the half life of U238 is 4.5 × 109 years, then the age of rock is (A) 9.0 × 109 years (B) 6.3 × 109 years (C) 4.5 × 109 years (D) 3.78 × 109 years 20. A 16μF capacitor is charged to a 20V potential. The battery is then disconnected and a pure 40mH coil is connected across the capacitor so that LC oscillations are set up. The maximum current in the coil is (A) 0.2 A (B) 40 mA (C) 2 A (D) 0.4 A 21. In a common emitter amplifier, using output resistance of 5000 Ω and input resistance of 2000 Ω, if the peak value of input signal voltage is 10 mV and β = 50, then peak value of output voltage is (A) 5 × 10–6 V (B) 12.5 × 10–4 V (C) 1.25 V (D) 125 V 22. The maximum wavelength of radiation that can produce photoelectric effect in certain metal is 200 nm. The maximum kinetic energy acquired by electron due to radiation of wavelength 100 nm will be (A) 12.4 eV (B) 6.2 eV (C) 100 eV (D) 200 eV 23. The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are (A) 10 cm, 10 cm (B) 15 cm, 5 cm (C) 18 cm, 2 cm (D) 11 cm, 9 cm 24. In Young’s double slit experiment, the distance between two sources is 0.1 mm. The distance of the screen from the source is 20 cm. Wavelength of light used is 5460 Å. The angular position of the first dark fringe is (A) 0.08° (B) 0.16° (C) 0.20° (D) 0.32° 25. What is the current through an ideal p – n junction diode shown below? 100 1V 3V – + – + (A) Zero (B) 10 mA (C) 20 mA (D) 40 mA
26. Match the quantities of Column I with their values in Column II and choose the correct option from the codes given below Column I Column II A. Planck constant 1. h p B. Stopping potential 2. E0 – KEmax C. Work function 3. KEmax e D. de-Broglie wavelength 4. E v Codes (A) A – 1, B – 3, C – 2, D – 4 (B) A – 3, B – 2, C – 1, D – 4 (C) A – 4, B – 3, C – 1, D – 2 (D) A – 4, B – 3, C – 2, D – 1 27. A voltmeter has a resistance of 90 Ω is connected across a cell of emf 10 V and internal resistance 10 Ω. The voltmeter reads the voltage of (A) 12 V (B) 6 V (C) 3 V (D) 9 V 28. In the given circuit (as shown in the figure) neglecting source resistance, then voltmeter and ammeter reading will be (A) 120 V, 3A (B) 120 V, 6A (C) 0V, 8A (D) 0V, 3A 29. Electron revolving in circular path of radius r with speed υ produced magnetic field B at centre. Then, correct relation among υ, B and r is (A) 2 2 1 B r v   (B) 2 2 1 B v r   (C) 2 1 B v r   (D) 2 1 1 B v r   30. Electron in hydrogen atom first jumps form third excited state to second excited state and then from second excited state to first excited state, then the ratio of wavelengths λ1 : λ2 emitted in two cases is (A) 27 : 5 (B) 7 : 5 (C) 20 : 7 (D) 27 : 20 31. In the circuit shown below, A is joined to B for a long and then, A is joined to C. The total heat produced in R is (A) 2 2 8 Le R (B) 2 2 2 Le R (C) 2 2 4 Le R (D) 2 2 Le R 32. The width of one slit is double the another slit in Young’s double slit experiment, then the ratio of maximum intensities to minimum intensities in the interference pattern is (A) 9 : 1 (B) 1 : 9 (C) 3 : 1 (D) 1 : 3 33. In the following circuit, current through 2Ω resistor just after switch closed is (A) 3A (B) 2.25A (C) 0.71A (D) 0A 34. The name of the following gate that the circuit shown in the figure (A) AND gate (B) OR gate (C) NOT gate (D) NOR gate 35. A ray of light falls on a transparent glass slab of refractive index 1.73. If the reflected ray and the refracted ray are mutually perpendicular, the angle of incidence is (A) 30° (B) 48° (C) 60° (D) 75.2°