Tiêu đề 19. Moving Charges And Magnetism.pdf ✅

1. If wire of length L form a loop of radius R and have n turn. Find magnetic field at centre of loop if current flowing in loop is I :- 2. A coil of 50 turns and 4cm radius carries 2A current then magnetic field at its centre is :- (1) 3.14 mT (2) 157 mT (3) 15.7 mT (4) 1.57 mT 3. The magnetic needle of a tangent galvanometer is deflected at an angle 30° due to a magnet. The horizontal component of the earth's magnetic field is 0.34 × 10–4 T which is along the plane of the coil. The magnetic field due to magnet is :- (1) 1.96 × 10–4 T (2) 1.96 × 10–5 T (3) 1.96 × 104 T (4) 1.96 × 10 T 4. Shown in the figure is a conductor carrying a current I. The magnetic field intensity at the point O (common centre of all the three arcs) is :- 5. Current I flows through a long conducting wire bent at right angles as shown in the figure. The magnetic field at a point P on the right bisector of the angle XOY at a distance r from O is :- 6. The magnetic induction at the centre O of the current carrying bent wire shown in the adjoining figure is :- 7. The cyclotron frequency of an electron gyrating in a magnetic field of 1 T is approximately : (1) 28 MHz (2) 280 MHz (3) 2.8 GHz (4) 28 GHz 8. A current of 3 amp is flowing in a plane circular coil of radius 4 cm and number of turns 20. The coil is placed in a uniform magnetic field of magnetic induction 0.5 tesla. Then, the dipole moment of the coil is :- (1) 3000 A-m (2) 0.3 A-m 2 (3) 75 A-m 2 (4) 300 A-m 2 9. An electron moves along the line AB, which lies in the same plane as a circular loop of conducting wires as shown in diagram. What will be the direction of current induced if any, in the loop :- (1) No current will be induced (2) The current will be clockwise (3) The current will be anticlockwise (4) The current will change direct ion as the electron crosses the loop 10. A moving coil galvanometer of resistance 100is used as an ammeter using a shunt resistance0.1. The maximum deflection current in the galvanometer is 100μA. Find the minimum current in the circuit so that the ammeter shows maximum deflection. (1) 100.1 mA (2) 1000.1 mA (3) 10.01 mA (4) 1.01 mA 11. A charged particle is whirled in a horizontal circle on a frictionless table by attaching it to a string fixed at one point. If a magnetic field is switched on in the vertical direction, the tension in the string:- (1) will increase (2) will decrease (3) will remain the same (4) may increase or decrease Moving Charges and Magnetism
A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion. B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion. C. If Assertion is True but the Reason is False. D. If both Assertion & Reason are False. 12. Assertion :- A small coil carrying current, in equilibrium, its plane is perpendicular to the direction of the uniform magnetic field. Reason :- Torque is maximum when plane of coil and direction of the magnetic field are parallel to each other. (1) A (2) B (3) C (4) D 13. An infinitely long, straight conductor AB is fixed and a current is passed through it. Another movable straight wire CD of finite length and carrying current is held perpendicular to it and released. Neglect weight of the wire (1) The rod CD will move upwards parallel to itself (2) The rod CD will move downward parallel to itself (3) The rod CD will move upward and turn clockwise at the same time (4) The rod CD will move upward and turn anti-clockwise at the same time 14. Current flows due north in a horizontal transmission line. Magnetic field at a point P vertically above it directed (1) North wards (2) South wards (3) Toward east (4) Towards west 15. A wire abc is carrying current i. It is bent as shown in fig and is placed in a uniform magnetic field of magnetic induction B B . Length ab = and 0  = abc 45 . The ratio of force on ab and on bc is 16. What will be the resultant magnetic field at origin due to four infinite length wires. If each wire produces magnetic field ‘B’ at origin (1) 4 B (2) 2 B (3) 2 2 B (4) Zero 17. A particle having a charge of 10.0 C and mass1 g moves in circle of radius 10 cm under the influence of a magnetic field of induction0.1 T. When the particle is at a point P, a uniform electric field is switched on so that the particle starts moving along the tangent with a uniform velocity. The electric field is (1) 0.1 V/m (2) 100 V/m (3) 10.0 V/m (4) 1.0 V/m 18. Two thick wires and two thin wires, all of the same materials and same length form a
square in the three different ways P, Q and R as shown in figure with current connection shown. The magnetic field at the centre of the square is zero in cases:- (1) in P only (2) in P and Q only (3) in Q and R only (4) P and R only 19. Full scale deflection current for galvanometer is1mA. For making its range upto 10 A. Find required shunt (Resistance of Galvanometer is 1000 ) :- (1) 1  (2) 10  (3) 0.3  (4) 0.1  20. A circular coil of wire carries a current. PQ is a part of a very long wire carrying a current and passing close to the circular coil. If the directions of currents are those shown in figure, what is the direction of force acting on PQ ? (1) Parallel to PQ, towards P (2) Parallel to PQ, towards Q (3) At right angles to PQ, to the right (4) At right angles to PQ, to the left 21. Two particles each of mass m and charge q are attached to the two ends of a light rod of length2R. The rod is rotated at constant angular speed about a perpendicular axis passing through its centre. The ratio of the magnitudes of the magnetic moment of the system and its angular momentum about the centre of the rod is: (1) (q/2m) (2) (q/m) (3) (2q/m) (4) (q/m) 22. A double ionized He2+ atom travels at right angle to a magnetic field of induction 0.4 T at a velocity of 105 m/s describing a circle of radius 'r'. A proton travelling with same speed in the same direction in the same field will describe a circle of radius (1) r/4 (2) r/2 (3) r (4) 2r 23. The coil of a galvanometer consists of 100 turns and effective area of 1 square cm. The restoring couple constant is 10– 8 N- m/rad. The magnetic field between the pole pieces is 5 T. The current sensitivity of this galvanometer will be :- (1) 5  104 rad/A (2) 5  10– 6 rad per amp (3) 2  10– 7 rad per amp (4) 5 rad./A 24. A cell is connected between the points A and Cof a circular conductor ABCD of centre 'O'.OC = 60o. If B1 and B2 are the magnitudes of the magnetic fields at O due to the currents in ABC and ADC respectively, the ratio 1 2 B B ,B is (1) 6 (2) 1 (3) 5 (4) 1/5 25. A proton of mass1.67 10−27 kg and charge1.6 10−19 C is projected with a speed of2 106 m/s at an angle of 600 to the X-axis. If a uniform magnetic field of 0.104 Tesla is applied along Y-axis, the path of proton is (1) A circle of radius = 0.2 m and time period10−7 s (2) A circle of radius = 0.1 m and time period210−7 s (3) A helix of radius = 0.1 m and time period210−7 s (4) A helix of radius = 0.2 m and time period410−7 s 26. A charged particle with specific charge S moves un deflected through a region of space containing mutually perpendicular uniform electric and magnetic fields E & B. When electric field is switched off, the particle will move in a circular path of radius:-
27. In the given figure force on wire ABC will be (B = 2T) :- (1) 4(3+2) N (2) 20 N (3) 10 N (4) 40 N 28. In the given figure magnetic field at centre will be- 29. In the given diagram loop tends to :- (1) expand (2) Contract (3) rotate about x–axis (4) rotate about y–axis 30. Two long straight wires, each carrying a current I in opposite direction are separated by a distance R. The magnetic induction at a point midway between the wire is :- (1) Zero 31. In the given diagram a rod is rotating with angular velocity . Mass of this rod is m, charge q and length then find out magnetic moment of this rod :- 32. Equal currents are flowing in three infinitely long wires along positive x, y and z direction. The magnetic field at a point (0, 0, –a) would be (i = current in each wire) :- 33. A long straight wire of radius 'a' carries a steady current i. The current is uniformly distributed across its cross section. The ratio of the magnetic field at distance a/2 and 2a is :- (1) 1/2 (2) 1/4 (3) 4 (4) 1 34. Two tangent galvanometer coils of same radius connected in series. The current flowing produces deflection of 60o& 45o . The ratio of number of turns in coil is :-