CLASS XII WB SET A PHYSICS

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Asher Fowler
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1 PHYSICS 1. Two cylindrical straight and very long non magnetic conductors A and B, insulated from each other, carry a current I in the positive and the negative z-direction respectively. The direction of magnetic field at origin is:- (a) (b) (c) (d) 2. Current I is flowing along the path ABCD, along the four edges of the cube (figure-a), creates a magnetic field in the centre of the cube of. Find the magnetic field B created at the centre of the cube by a current I flowing along the path of the six edges ABCGHEA (figure-b) (a) (b) (c) (d) Ans : (d) Towards corner G Towards corner E Towards corner H Towards corner F 3. A current carrying loop is placed in a uniform magnetic field pointing in negative z direction. Branch PQRS is a three quarter circle, while branch PS is straight. If force on branch PS is F, force on branch PQR is 1

(a) (b) (c) (d) 4. A conducting wire bent in the form of a parabola carries a current i=2a as shown in figure. This wire is placed in a uniform magnetic field Tesla.

2 (a) (b) (c) (d) 4. A conducting wire bent in the form of a parabola carries a current i=2a as shown in figure. This wire is placed in a uniform magnetic field Tesla. The magnetic force on the wire is (in newton) (a) (b) (c) (d) 5. A straight wire of length L carries a current I in the positive z direction in a region where the magnetic field is uniform and specified by 3B, 2B, and B, where B is a constant. What is the magnitude of the magnetic force on the wire? (a) 1.0 ILB (b) 5.0 ILB (c) 3.6 ILB (d) 4.2 ILB 6. Find equivalent capacitance between A and B. [Assume each conducting plate is having same dimensions and neglect the thickness of plate, where A is area of plates, A>>d] (a) (c) (b) (d) 2

7. In the circuit, if no current flows through the galvanometer when the key K is closed, the bridge is balanced. The balancing condition for bridge is (a) (b) (c) (d) 8.

3 7. In the circuit, if no current flows through the galvanometer when the key K is closed, the bridge is balanced. The balancing condition for bridge is (a) (b) (c) (d) 8. The switch in circuit shifts from 1 to 2 when and goes back to 1 from 2 when. The voltmeter reads voltage as plotted.what is the period T of the wave form in terms of R and C? (a) (b) (c) (d) 3

4 9. In the circuit shown, the charge on the capacitor at steady state will be (a) (b) 4 (c) (d) In a meter bridge experiment, we try to obtain the null point at the middle. This (a) reduces systematic error as well as random error. (b) reduces systematic error but not the random error. (c) reduces random error but not the systematic error. (d) reduces neither systematic error nor the random error. 4

5 Paragraph Question 11,12 & 13 An ammeter and a voltmeter are connected in series to a battery with an emf of 10V. When a certain resistance is connected in parallel with the voltmeter, the reading of the voltmeter decreases three times, whereas the reading of the ammeter increases the two times. Find the voltmeter reading after the connection of the resistance. 11. Find the voltmeter reading after the connection of the resistance. (a) 1V (b) 2V (c) 3V (d) 4V 12. If resistance of the ammeter is 2, then resistance of the voltmeter is :- (a) 1 (b) 2 (c) 3 (d) If resistance of the ammeter is 2, then resistance of the resistor which is added in parallel to the voltmeter is :- (a) (b) (c) (d) None of these 5

6 14. The volume charge density as a function of distance X from one face inside a unit cube is varying as shown in the figure. The total flux (in S.I. units) through the cube is ( (a) 1/4 (b) 1/2 (c) 3/4 (d) A system consists of uniformly charged sphere of radius R and a surrounding medium filled by a charge with the volume density, where is a positive constant and r is the distance from the centre of the sphere. The charge of the sphere for which electric field intensity E outside the sphere is independent of r will be (a) (b) (c) (d) 16. The resistance of a metallic conductor increases with temperature due to Ans : (d) (a) Change in carrier density (b) Change in the dimensions of the conductor (c) increase in the number of collisions among the carriers (d) increase in the rate of collisions between the carriers and the lattice. 6

7 17. In the given black box unknown emf sources and unknown resistance are connected by an unknown method such that (i) when terminals of 10 ohm resistance are connected to box then 1 ampere current flows and (ii) when 18 ohm resistance are connected then 0.6 A current flows then for what value of resistance does 0.1 A current flow? (a) 118 (b) 98 (c) 18 (d) 58 Paragraph Question 18, 19 & 20 The major error in the experiment to determine specific resistance of the material of a wire using meter bridge are due to the heating effect, end correction introduced due to shift of the zero of the scale at A and B, stray resistances in gaps of meter bridge and due to non-uniformly of wire. 18. The major errors mentioned above are (a) systematic in nature (b) random in nature (c) neither systematic nor random (d) both systematic & random 19. End correction and can be estimated by including known resistances, and in the two gaps and finding the null point using equations (a) (c) (b) (d) 20. Error due to non-uniformity of meter bridge wire can be reduced by interchanging the resistances in the gaps of the meter bridge. 7

8 Error in specific resistance is given by Here depends on (a) error in the measurement of resistance in R.B. (b) error in the measurement of unknown resistance (c) error in the measurement of balancing length (d) All of the above. Paragraph Question 21 & 22 A smooth circular wire track of radius R and mass m is lying in gravity free space. Two small conducting rings each of charge +q and mass m which can slide freely on circular trac are released fro rest whe shortest dista ce betwee the is as shown in figure. At the instant when the two rings come to diametrically opposite points. 21. Displacement of wire track is (a) (b) (c) (d) zero 22. Velocity of wire track is (a) (b) (c) (d) 23. The following figure shows a block of mass m suspended from a fixed point by means of a vertical spring. The block is oscillating simple harmonically and carries a charge q. There also exists a uniform electric field in the region. Consider four different cases. The electric field is zero, in case-1, downward in case-2, upward in case-3 and downward in case-4. The speed at mean position is same in all cases. Select the correct alternative (a) Time periods of oscillation are different in case-1 and case-3 8

9 (b) Amplitudes of displacement are different in case-2 and case-3 (c) The maximum elongation (increment in length from natural length) is minimum in case-4. (d) Time periods of oscillation are equal in case-2 and case-4 Ans : (d) 24. In a region of space, the electric field E = Consider an i agi ary cubical volu e of edge a with its edges parallel to the axes of coordinates. Find the correct statement (a) the total electric flux through the faces 1 and 3 is (b) the charge inside the cubical volume is a (c) the total electric flux through the faces 2 and 4 is (d) the charge inside the cubical volume is a a a Ans : (d) 25. A thin-walled, spherical conducting shell S of radius R is given charge Q. The same amount of charge is also placed at its centre C. Which of the following statement is correct? (a) On the outer surface of S, the charge density is. (b) The electric field is zero at all points inside S. (c) At a point just outside S, the electric field is double the field at a point just inside S. (d) At any point inside S, the electric field is directly proportional to the square of its distance from centre C. 26. Figure shows a copper wire of non uniform cross section carrying current towards right for sectors A, B and C. Find out the correct relation 9

10 (a) i i i i curre t (b) electric field (c) drift velocity (d) curre t de sity Ans : (d) 27. The current in a wire varies with time according to the equation I = 4 + 2t, where I is in ampere and t is in sec. The quantity of charge which has passed through a cross-section of the wire during the time t = 2 sec to t = 6 sec will be (a) 60 coulomb (b) 24coulomb (c) 48 coulomb (d) 30 coulomb Integrate I = 4 + 2t w.r.t. time 28. A parallel plate capacitor with plate area A and separation d has charge Q. A slab of dielectric constant k is inserted in space between the plates almost completely fills the space. If and be the electric field and capacitance before inserting the slab, then find the correct statement (a) the electric field after inserting the slab is (b) the capacitance after inserting the slab is k. (c) the induced charge on the slab is ( ) (d) the energy stored in the capacitor becomes being the energy of the capacitor before inserting the slab 29. A capacitor of capacitance C is connected to two voltmeters A and B. A is an ideal voltmeter having infinite resistance, while B has resistance R. The capacitor is uncharged and then the switch S is closed at t = 0, Find the correct statement (a) Reading of B and A will be and 1 at t = 0 (b) During time interval (0 t readings of B and A are constant (c) Reading of A and B will be equal at t = RC ln 2 (d) Reading of A and B will be equal at t = RC ln A particle of mass m and charge q has been projected from ground as shown in the figure below. Mark out the correct statement :- 10

11 (a) The path of motion of the particle is parabolic (b) The path of motion of the particle is a straight line (c) Time of flight of particle is (d) Range of motion of the particle will be less than 11

A) I B) II C) III D) IV E) V

A) I B) II C) III D) IV E) V 1. A square loop of wire moves with a constant speed v from a field-free region into a region of uniform B field, as shown. Which of the five graphs correctly shows the induced current i in the loop as