# CBSE Class 12 Physics Sample Paper Solution - 2021-22 | Bzziii

3. An electric dipole of moment p is placed parallel to the uniform electric field. The amount of work done in rotating the dipole by 900 is-

4. Three capacitors 2µF, 3µF and 6µF are joined in series with each other. The equivalent capacitance is-

6. Which statement is true for Gauss law-

9. An electric current is passed through a circuit containing two wires of same material, connected in parallel. If the lengths and radii of the wires are in the ratio of 3:2 and 2:3, then the ratio of the current passing through the wire will be

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12. A constant voltage is applied between the two ends of a uniform metallic wire, heat ‘H’ is developed in it. If another wire of the same material, double the radius and twice the length as compared to original wire is used then the heat developed in it will be-

16. The coil of a moving coil galvanometer is wound over a metal frame in order to

17. Two wires of the same length are shaped into a square of side 'a' and a circle with radius 'r'. If they carry same current, the ratio of their magnetic moment is

20. Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon the

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21. A conducting square loop of side 'L' and resistance 'R' moves in its plane with the uniform velocity 'v' perpendicular to one of its sides. A magnetic induction 'B' constant in time and space pointing perpendicular and into the plane of the loop exists everywhere as shown in the figure. The current induced in the loop is

22. The magnetic flux linked with the coil (in Weber) is given by theequation – Փ = 5t2 + 3t + 16 The induced EMF in the coil at time, t=4 will be-

23. Which of the following graphs represent the variation of current(I) with frequency (f) in an AC circuit containing a pure capacitor?

24. A 20 volt AC is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 volt, the voltage across the coil is-

26. A cylinder of radius r and length l is placed in an uniform electric field parallel to the axis of the cylinder. The total flux for the surface of the cylinder is given by-

27. Two parallel large thin metal sheets have equal surface densities 26.4x10-12 C/m2 of opposite signs. The electric field between these sheets is-

28. Consider an uncharged conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,

29. Three Charges 2q, -q and -q lie at vertices of a triangle. The value of E and V at centroid of triangle will be-

30. Two parallel plate capacitors X and Y, have the same area of plates and same separation between plates. X has air and Y with dielectric of constant 2 , between its plates. They are connected in series to a battery of 12 V. The ratio of electrostatic energy stored in X and Y is-

32. An alternating voltage source of variable angular frequency ‘w’ and fixed amplitude ‘V’ is connected in series with a capacitance C and electric bulb of resistance R(inductance zero). When ‘w’ is increased-

33. A solid spherical conductor has charge +Q and radius R. It is surrounded by a solid spherical shell with charge -Q, innerradius 2R, and outer radius 3R. Which of the following statements is true?

34. A battery is connected to the conductor of non-uniform cross section area. The quantities or quantity which remains constant is-

35. Three resistors having values `"R"_{1}`, `"R"_{2}`, and `"R"_{3}`, are connected in series to a battery. Suppose R1 carries a current of 2.0 A, `"R"_{2}`, has a resistance of 3.0 ohms, and `"R"_{3}`, dissipates 6.0 watts of power. Then the voltage across `"R"_{3}`, is-

(i) 1V

(ii) 2V

(iii) 3V

(iv) 4V

37. A 10 m long wire of uniform cross-section and 20 Ω resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 balanced at 6.0 m length of the wire, then the value of unknown emf is-

38. The current sensitivity of a galvanometer increases by 20%. If its resistance also increases by 25%, the voltage sensitivity will

39. Three infinitely long parallel straight current carrying wires A, B and C are kept at equal distance from each other as shown in the figure . The wire C experiences net force F .The net force on wire C, when the current in wire A is reversed will be

(ii) F/2

(iii) F

(iv) 2F

40. In a hydrogen atom the electron moves in an orbit of radius 0.5 Ao making 10 revolutions per second, the magnetic moment associated with the orbital motion of the electron will be

(i) 2.512 x `10^{-38}"Am"^{2}`

(ii) 1.256 x `10^{-38}"Am"^{2}`

(iii) 0.628 X `10^{-38}"Am"^{2}`

(iv) zero

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41. An air-cored solenoid with length 30 cm, area of cross-section 25 cm2 and number of turns 800, carries a current of 2.5 A. The current is suddenly switched off in a brief time of `10^{-3}`s. Ignoring the variation in magnetic field near the ends of the solenoid, the average back emf induced across the ends of the open switch in the circuit would be

42. A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which R = 3 Ω, L = 25.48 mH, and C = 796 µF, then the power dissipated at the resonant condition will be-

43. A circular loop of radius 0.3cm lies parallel to much bigger circular of radius 20 cm. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with the bigger loop is

(ii) 6 X `"10"^{-11}`weber

(iii) 6.6 X `"10"^{-9}`weber

(iv) 9.1 X `"10"^{-11}`weber

44. If both the number of turns and core length of an inductor is doubled keeping other factorsconstant, then its self-inductance will be-

50. A small object with charge q and weight mg is attached to one end of a string of length ‘L’ attached to a stationary support. The system is placed in a uniform horizontal electric field ‘E’, as shown in the accompanying figure. In the presence of the field, the string makes a constant angle θ with the vertical. The sign and magnitude of q-

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51. A free electron and a free proton are placed between two oppositely charged parallel plates. Both are closer to the positive plate than the negative plate. See the diagram below. Which of the following statements is true?

(i) the voltage is stepped-up (Vs >Vp ) and arrangement is called a step-up transformer

(ii) the voltage is stepped-down (Vs <Vp ) and arrangement is called a step-down transformer

(iii) the current is stepped-up (Is >Ip ) and arrangement is called a step-up transformer

(iv) the current is stepped-down (Is <Ip ) and arrangement is called a step-down transformer

(i) the current is reduced and consequently, the `"l"^{2}`R loss is cut down

(ii) the voltage is increased , the power losses are also increased

(iii) the power is increased before transmission is done

(iv) the voltage is decreased so `"V"^{2}`/R losses are reduced