Tiêu đề NT 18 PAPER.pdf ✅

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PHYSICS 1. What equal charges would to be placed on earth and moon to neutralize their gravitational attraction (Use mass of earth = 1025 kg, mass of moon = 1023 kg) (A) 8.6 × 1013 C (B) 6.8 × 1026 C (C) 8.6 × 103 C (D) 9 × 106 C 2. In the half-wave rectifier circuit shown. Which one of the following wave forms is true for VCD, the output across C and D? (A) (B) (C) (D) 3. The linear charge density on upper half of a segment of ring is  and at lower half, it is –. The direction of electric field at centre O of ring is : A B C D O + + + + – – – – (A) along OA (B) along OB (C) along OC (D) along OD 4. The total flux associated with given cube will be where 'a' is side of cube : ( 0 1  = 4 × 9 × 109 ) 2 C 1 C 4 C 8 C 6 C 3 C 7 C 5 C a a a (A) 162  × 104 Nm2 /C (B) 162  × 103 Nm2 /C (C) 162  × 105 Nm2 /C (D) 162  × 106 Nm2 /C 5. If mass of the fissionable material is less than the critical mass, then (A) fission and chain reactions both are impossible (B) fission is possible but chain reaction is impossible (C) fission is impossible but chain reaction is possible (D) fission and chain reaction both are possible. 6. The electric potential in volt due to an electric dipole of dipole moment 2 × 10–8 C-m at a distance of 3m on a line making an angle of 600 with the axis of the dipole is : (A) 0 (B) 10 (C) 20 (D) 40 7. The charge on each capacitors shown in figure and the potential difference across them will be respectively: C1 C2 3 F C3 4 F 120V 2 F (A) 240C, 80C, 160C and 80V, 40V, 40V (B) 300C, 75C, 150C and 40V, 80V, 60V (C) 220C, 70C, 140C and 60V, 50V, 40V (D) None of these P Q A B D C ~ VCD RL PW – AITS_NT-18
8. If potential difference across a capacitor is changed from 15V to 30V, work done is W. The work done when potential difference is changed from 30V to 60V, will be : (A) W (B) 4 W (C) 3 W (D) 2 W 9. When the key K is pressed at time t = 0, which of the following statements about the current  in the resistor AB of the given circuit is true : C 2V K 1000 A B 1 F 1000 (A)  = 2 mA at all t (B)  oscillates between 1 mA and 2mA (C)  = 1 mA at all t (D) At t = 0,  = 2 mA and with time it goes to 1 mA 10. A charge of 2 × 10–2 C moves at 30 revolution per second in a circle of diameter 0.80 m. The current linked with the circuit will be - (A) 0.1 A (B) 0.2 A (C) 0.4 A (D) 0.6 A 11. When a potential difference (V) is applied across a conductor, the thermal speed of electrons is - (A) zero (B) proportional to T (C) proportional to T (D) proportional to V 12. A galvanometer having a coil resistance of 60  shows full scale deflection when a current of 1.0 A passes through it. It can be converted into an ammeter to read currents upto 5.0 A by : (A) putting in parallel a resistance of 240  (B) putting in series a resistance of 15  (C) putting in series a resistance of 240  (D) putting in parallel a resistance of 15  13. An electron of kinetic energy of 7.2 × 10–18 J is revolving on circular path in magnetic field 9 × 10–5 wb/m2 , then radius of its circular path is : (A) 1.25 cm. (B) 2.5 m. (C) 2.5 cm. (D) 25.0 cm. 14. A coil of 100 turns is lying in a magnetic field of 1T as shown in the figure. A current of 1A is flowing in this coil. The torque acting on the coil will be (A) 1N–m (B) 2N–m (C) 3N–m (D) 4N–m 15. Two identical magnetic dipoles of magnetic moments 1.0 A-m2 each, placed at a separation of 2 m with their axes perpendicular to each other. The resultant magnetic field at a point midway between the dipole is: 2m (A) 5 × 10–7 T (B) 5 × 10–7 T (C) 10–7 T (D) 2 × 10–7 T 16. A conducting loop of radius R is present in a uniform magnetic field B perpendicular to the plane of the ring. If radius R varies as a function of time ‘t’, as R = R0+ t. The e.m.f induced in the loop is (A) 2(R0 + t) B clockwise (B) (R0 + t) B clockwise (C) 2(R0+t) B anticlockwise (D) zero 0.2 m S 0.1 m N
17. The figure shows a part of a complete circuit. The potential difference VB – VA when the current I is 5A and is decreasing at a rate of 103 As–1 is given by (A) 15 V (B) 10 V (C) –15 V (D) 20 V 18. A conducting rod moves with constant velocity  perpendicular to the long, straight wire carrying a current I as shown. The emf generated between the ends of the rod is (A) μ I 0 r   (B) μ I 0 2 r   (C) 0 2μ I r   (D) μ I 0 4 r   19. An AC voltage of V = 220 2 sin 100 t 2       +   is applied across a DC voltmeter, its reading will be: (A) 220 2 V (B) 2 V (C) 220 V (D) zero 20. A power (step up) transformer with an 1 : 8 turn ratio has 60 Hz, 120 V across the primary; the load in the secondary is 104 . The current in the secondary is (A) 96 A (B) 0.96 A (C) 9.6 A (D) 96 mA 21. Find the effective value of current i = 2 + 4 cos 100  t. (A) 2 3 (B) 2 2 (C) 3 (D) 4 3 22. The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milli watts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current - (A) 1.5  (B) 5  (C) 6.67  (D) 200  23. Two mirrors are inclined at an angle  as shown in the figure. Light ray is incident parallel to one of the mirrors. Light will start retracing its path after third reflection if : (A)  = 45° (B)  = 30° (C)  = 60° (D) all three 24. A convex lens forms a real image 9 cm long on a screen. Without altering the position of the object and the screen, the lens is displaced and we get again a real image 4 cm long on the screen. Then the length of the object is- (A) 9 cm (B) 4 cm (C) 6 cm (D) 36 cm 25. If refractive index of red, violet and yellow lights are 1.42, 1.62 and 1.50 respectively for a medium, its dispersive power will be - (A) 0.4 (B) 0.3 (C) 0.2 (D) 0.1 26. A person can see clearly only upto a distance of 25cm. He wants to read a book placed at a distance of 50cm. What kind of lens does he required for his spectacles and what must be its power ? (A) concave, – 1.0 D (B) Convex, + 1. 5 D (C) Concave, – 2.0 D (D) Convex, + 2.0 D R 0.5V 1.5V