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CBSE Class 12 Sample / Model Paper 2022 : Physics - Term I (with Marking Scheme / Solutions)

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Sample Question Paper 2021-22 Term 1 Subject: Physics (042) Time: 90 Minutes Max. Marks 35 General Instructions: 1. The Question Paper contains three sections. 2. Section A has 25 questions. Attempt any 20 questions. 3. Section B has 24 questions. Attempt any20 questions. 4. Section C has 6 questions. Attempt any 5 questions. 5. All questions carry equal marks. 6. There is no negative marking. SECTION A This section consists of 25 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable numberof questions are attempted, ONLY first 20 will be considered for evaluation. Q1.Which of the following is NOT the property of equipotential surface? (i) They do not cross each other. (ii) The rate of change of potential with distance on them is zero. (iii) For a uniform electric field they are concentric spheres. (iv) They can be imaginary spheres. Q2. Two point charges +8q and -2q are located at x=0 and x=L respectively. The point on x axis at which net electric field is zero due to these charges is(i) 8L (ii) 4L (iii) 2L (iv) L Q3. An electric dipole of moment p is placed parallel to the uniform electric field. The amount of work done in rotating the dipole by 90 is0 (i) 2pE (ii) pE (iii) pE/2 (iv) Zero Q4. Three capacitors 2 F, 3 F and 6 F are joined in series with each other. The equivalent capacitance is(i) 1/2 F (ii) 1 F (iii) 2 F (iv) 11 F Q5. Two point charges placed in a medium of dielectric constant 5 are at a distance r between them, experience an electrostatic force F . The electrostatic force between them in vacuum at the same distance r will be(i) 5F (ii) F (iii) F/2 (iv) F/5 Q6. Which statement is true for Gauss law(i) All the charges whether inside or outside the gaussian surface contribute to the electric flux. (ii) Electric flux depends upon the geometry of the gaussian surface. (iii) Gauss theorem can be applied to non-uniform electric field. (iv) The electric field over the gaussian surface remains continuous and uniform at every point. Q7.A capacitor plates are charged by a battery with V volts. After charging battery is disconnected and a dielectric slab with dielectric constant K is inserted between its plates, the potential across the plates of a capacitor will become (i) Zero (ii) V/2 (iii) V/K (iv) KV Q8.The best instrument for accurate measurement of EMF of a cell is(i) Potentiometer (ii) metre bridge (iii) Voltmeter (iv) ammeter and voltmeter Q9.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 (i) 2:3 (ii) 3:2 (iii) 8:27 (iv) 27:8 Q10.By increasing the temperature, the specific resistance of a conductor and a semiconductor(i) increases for both. (ii) decreases for both. (iii) increases for a conductor and decreases for a semiconductor. (iv) decreases for a conductor and increases for a semiconductor. Q11.We use alloys for making standard resistors because they have (i) low temperature coefficient of resistivity and high specific resistance (ii) high temperature coefficient of resistivity and low specific resistance (iii) low temperature coefficient of resistivity and low specific resistance (iv) high temperature coefficient of resistivity and high specific resistance Q12. 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(i) H/2 (ii) H (iii) 2H (iv) 4H Q13.If the potential differenc nce V applied across a conductor is increa eased to 2V with its tempera rature kept constant, the drift velocity of the th free electrons in a con onductor will (i) (ii) (iii) (iv) remain the same e. become half off itits previous value. be double of itss iinitial value. become zero. nce between A and B isQ14.The equivalent resistan (i) 3 ohms (ii) 5.5 ohms (iii) 7.5 ohms (iv) 9.5 ohms Q15. The SI unit of magnetic tic field intensity is (i) AmN-1 (ii) NA-1m-1 (iii) NA-2m-2 (iv) NA-1m-2 oil galvanometer is wound over a metal Q16.The coil of a moving co frame in order to (i) (ii) (iii) (iv) reduce hysteressis increase sensitiv itivity increase momen ent of inertia provide electrom magnetic damping Q17.Two wires of the same e length are shaped into a square of side ''a' and a circle with radius 'r'.. IIf they carry same current, the ratio of the heir magnetic moment is (i) (ii) (iii) (iv) 2: :2 :4 4: Q18. The horizontal component of earth s magnetic field at a place is 3 times the vertical component. The angle of dip at that place is (i) /6 (ii) /3 (iii) /4 (iv) 0 Q19. The small angle between magnetic axis and geographic axis at a place is(i) Magnetic meridian (ii) Geographic meridian (iii) Magnetic inclination (iv) Magnetic Declination Q20.Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon the (i) rate at which current change in the two coils (ii) relative position and orientation of the coils (iii) rate at which voltage induced across two coils (iv) currents in the two coils Q21. 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 (i) BLv/R Clockwise (ii) BLv/R Anticlockwise (iii) 2BLv/R Anticlockwise (iv)Zero Q22. The magnetic flux linked with the coil (in Weber) is given by theequation = 5t2 + 3t + 16 The induced EMF in the coil at time, t=4 will be(i) -27 V (ii) -43 V (iii) -108 V (iv) 210 V Q23. Which of the following graphs represent the variation of current(I) with frequency (f) in an AC circuit containing a pure capacitor? (i) (ii) (iii) (iv) Q24. 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(i) 16 V (ii) 10 V (iii) 8 V (iv) 6 V Q25. The instantaneous values of emf and the current in a series ac circuit areE = Eo Sin t and I= Io sin( t+ /3) respectively, then it is (i) Necessarily a RL circuit (ii) Necessarily a RC circuit (iii)Necessarily a LCR circuit (iv) Can be RC or LCR circuit SECTION B This section consists of 24 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable number of questions are attempted, ONLY first 20 will be considered for evaluation. Q26. 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(i) zero (ii) r2 (iii) E r2 (iv) )2 E r2 Q27. Two parallel large thin metal sheets have equal surface densities 26.4x10-12 C/m2of opposite signs. The electric field between these sheets is(i) 1.5N/C (ii) 1.5 x 10-16 N/C (iii) 3 x 10-10N/C (iv) 3N/C Q28. Consider an uncharged conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then, (i) negative and uniformly distributed over the surface of sphere (ii) positive and uniformly distributed over the surface of sphere (iii) negative and appears at a point the surface of sphere closest to point charge. (iv) Zero Q29. Three Charges 2q, -q and -q lie at vertices of a triangle. The value of E and V at centroid of triangle will be(i) E#0 and V#0 (ii) E=0 and V=0 (iii) E#0 and V=0 (iv) E=0 and V#0 Q30. 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(i) 4:1 (ii) 1:4 (iii) 2:1 (iv) 1:2 Q31.Which among the following, is not a cause for power loss in a transformer(i) (ii) Eddy currents are produced in the soft iron core of a transformer. Electric Flux sharing is not properly done in primary and secondary coils. (iii) (iv) Humming sound produed in the tranformers due to magnetostriction. Primary coil is made up of a very thick copper wire. Q32.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(i) The bulb glows dimmer. (ii) The bulb glows brighter. (iii) Net impedance of the circuit remains unchanged. (iv) Total impedance of the circuit increases. Q33. 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? (i)The electric potential has a maximum magnitude at C and the electric field has a maximum magnitude at A (ii) The electric potential has a maximum magnitude at D and the electric field has a maximum magnitude at B. (iii) The electric potential at A is zero and the electric field has a maximum magnitude at D. (iv). Both the electric potential and electric field achieve a maximum magnitude at B. Q34. A battery is connected to the conductor of non-uniform cross section area. The quantities or quantity which remains constant is(i) electric field only (ii) drift speed and electric field (iii)electric field and current (iv) current only Q35. Three resistors having g values R1, R2, and R3 are connected in series s to a battery. Suppose R1 carries c a current of 2.0 A, R2 has a resista tance of 3.0 ohms, and R3 dissipa ates 6.0 watts of power. Then the voltage e across R3 is(i) 1V (ii) 2V (iii) 3V (iv) 4V Q36.A straight line plot show owing the terminal potential difference (V) V) of a cell as a function of curre rent (I) drawn from it, is shown in the figur ure. The internal resistance off the cell would be then(i) 2.8 ohms (ii) 1.4 ohms (iii) 1.2 ohms (iv) zero Q37. A 10 m long wire of un niform cross-section and 20 resistance e is used in a potentiometer. The e wire is connected in series with a battery ry of 5 V along with an externa al resistance of 480 . If an unknown emff E is balanced at 6.0 m leng ngth of the wire, then the value of unknow wn emf is- (i) 1.2 V (ii) 1.02 V (iii) 0.2 V (iv) 0.12 V Q38.The current sensitivity of a galvanometer increases by 20%. If its resistance also increases by 25%, the voltage sensitivity will (i ) decrease by 1% (ii) increased by 5% (iii) increased by 10% (iv ) decrease by 4% Q39. 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 (i) Zero (ii) F/2 (iii) F (iv) 2F Q40. In a hydrogen atom the electron moves in an orbit of radius 0.5 A making 10 revolutions per second, the magnetic moment associated with the orbital motion of the electron will be o (i) 2.512 x 10-38 Am2 (ii) 1.256 x 10-38 Am2 (iii) 0.628 X10-38 Am2 (iv) zero Q41. An air-cored solenoid with length 30 cm, area of cross-section 25 cm and number of turns 800, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10-3s. 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 2 (i) zero (ii)3.125 volts (iii) 6.54 volts (iv) 16.74 volts Q42. A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which R = 3 , L = 25.48 mH, and C = 796 F, then the power dissipated at the resonant condition will be(i)39.70 kW (ii) 26.70 kW (iii)13.35 kW (iv)Zero Q43. 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 (i) 3.3 X 10-11weber (ii) 6 X 10-11weber (iii) 6.6 X 10-9weber (iv) 9.1 X 10-11weber Q44.If both the number of turns and core length of an inductor is doubled keeping other factorsconstant, then its self-inductance will be(i) Unaffected (ii) doubled (iii) halved (iv) quadrupled 45. Given below are two statements labelled as Assertion (A) and Reason (R) Assertion (A): To increase the range of an ammeter, we must connect a suitable high resistance in series to it. Reason (R): The ammeter with increased range should have high resistance. Select the most appropriate answer from the options given below: (i) Both A and R are true and R is the correct explanation of A (ii) Both A and R are true but R is not the correct explanation of A. (iii)A is true but R is false. (iv) A is false and R is also false. 46. Given below are two statements labelled as Assertion (A) and Reason (R) Assertion (A): An electron has a high potential energy when it is at a location associated with a more negative value of potential, and a low potential energy when at a location associated with a more positive potential. Reason (R):Electrons move from a region of higher potential to region of lower potential. Select the most appropriate answer from the options given below: (i) Both A and R are true and R is the correct explanation of A (ii) Both A and R are true but R is not the correct explanation of A. (iii)A is true but R is false. (iv) A is false and R is also false. 47. Given below are two statements labelled as Assertion (A) and Reason (R) Assertion(A): A magnetic needle free to rotate in a vertical plane, orients itself (with its axis) vertical at the poles of the earth. Reason (R): At the poles of the earth the horizontal component of earth s magnetic field will be zero. Select the most appropriate answer from the options given below: (i) Both A and R are true and R is the correct explanation of A (ii) Both A and R are true but R is not the correct explanation of A. (iii)A is true but R is false. (iv) A is false and R is also false. 48. Given below are two statements labelled as Assertion (A) and Reason (R) Assertion(A): A proton and an electron, with same momenta, enter in a magnetic field in a direction at right angles to the lines of the force. The radius of the paths followed by them will be same. Reason(R): Electron has less mass than the proton. Select the most appropriate answer from the options given below: (i) Both A and R are true and R is the correct explanation of A (ii) Both A and R are true but R is not the correct explanation of A. (iii)A is true but R is false. (iv) A is false and R is also false. 49. Given below are two statements labelled as Assertion (A) and Reason (R) Assertion (A):On Increasing the current sensitivity of a galvanometer by increasing the number of turns, may not necessarily increase its voltage sensitivity. Reason(R ): The resistance of the coil of the galvanometer increases on increasing the number of turns. Select the most appropriate answer from the options given below: (i) Both A and R are true and R is the correct explanation of A (ii) Both A and R are true but R is not the correct explanation of A. (iii)A is true but R is false. (iv) A is false and R is also false. SECTION C This section consists of 6 multiple choice questions with an overall choice to attempt any 5. In case more than desirable number of questions are attempted, ONLY first 5 will be considered for evaluation. Q50. 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 with the vertical. The sign and magnitude of q(i) positive with magnitude mg/E (ii) positive with magnitude (mg/E)tan (iii) negative with magnitude mg/E tan (iv) positive with magnitude E tan /mg Q51.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. Which of the following statements is true? I. The force on the proton is greater than the force on the electron. II. The potential energy of the proton is greater than that of the electron. III. The potential energy of the proton and the electron is the same. (i) I only (ii) II only (iii) III and I only (iv)II and I only Case study : Read the following paragraph and answers the questions: The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped-up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes. Q52. Which of the following statement is true? (i) Energy is created when a transformer steps up the voltage (ii) A transformer is designed to convert an AC voltage to DC voltage (iii) Step up transformer increases the power for transmission (iv) Step down transformer decreases the AC voltage Q53. If the secondary coil has a greater number of turns than the primary, (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 stepdown 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 stepdown transformer Q54. We need to step-up the voltage for power transmission, so that (i) the current is reduced and consequently, the I2R 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 V2/R losses are reduced Q55. A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns. The number of turns in the secondary in order to get output power at 230 V are (i) 4 (ii) 40 (iii) 400 (iv) 4000 Physics Marking Scheme For SQP 45 XII I Term Q.1 Which of the_____________________ Ans. 1 (iii) As all other statements are correct. In uniform electric field equipotential surfaces are never concentric spheres but are planes to Electric field lines. Q.2 Two Point charges_____________________ Ans. 2 (iii) Let P is the observation point at a distance r from -2q and at (L+r) from +8q. Given Now, Net EFI at P = 0 E1 = EFI (Electric Field Intensity) at P due to +8q E 2 = EFI (Electric Field Intensity) at P due to -2q E1 = E 2 k(8q) k(2q) 2 2 (L r) r 4 1 2 2 (L r) (r) 4r2 = (L+r)2 2r = L+r r=L P is at x = L + L = 2L from origin Correct Option is (iii) 2L Q3. An electric______________________ Ans. 2 (ii) W = pE (cos 1 cos 2) 1 = 0 2 = 90 W = pE (cos 0 - cos 90 ) = pE (1 0) = pE Q4. Three Capacitors______________ Ans.4. (ii) 1 1 1 1 Cseries C1 C2 C3 1 1 1 1 Cseries 2 3 6 3+2+1 6 6 6 Cseries 1 F Q5. Two Point Charges___________________ Ans.5. (i) Q2 r K=5 F 1 Q1 Q2 4 ok r 2 Q2 Force in the charges in the air is F 1 Q1 Q2 4 o r 2 =K F =5F Q6. Which statement is true________________ Ans.6. (iv) All other statements except (iv) are in correct The electric field over the Gaussian surface remains continuous and uniform at every point. Q7. A capacitor plates Ans.7. (iii) + + C + Battery is disconnected` + kC + + Q = Charge remains context C = K C Q = C V Q = C V Q = K C V V = = Q.8. The best instrument for_________________ Ans.8. (i) Potentiometer Q9. An electric current___________________ Ans.9. (iii) 8:27 R1 l1 : l2 = 3 : 2 r1 : r2 = 2 : 3 I1 : I2 = ? R2 + - l1 r12 l2 R2 2 r 2 R1 R1 l1 r 2 2 l1 r 22 = R 2 l2 r12 l2 r12 2 3 3 (3)3 27 = = 3 2 2 (2) 8 I1 V / R1 R2 = 8 / 27 = I2 V / R2 R1 Q.10. By increasing the temperature___________________ Ans. 10. (iii) Specific resistance of a conductor increases and for a semiconductor decreases with increase in temperature because for a conductor, a temperature. coefficient of resistivity = + ve and for a semiconductor, = -ve Q.11. We use alloys___________________ Ans. 11 (i) Alloys have low temperature coefficient of resistivity and high specific resistance. If = low , the value of R with temperature will not change much and specific resistance is high then required length of the wire will be less. Q.12. A constant Voltage___________________ Ans. 12. (iii) 2l (2r) 2 l 2l R = 2 R r 4r 2 V2 V2 H t & H 1t R R R l A R V = constant H V R t H R V2 t R l 2 r 2 = 2 r l R H 2 = H 1 H 2H Correct option is (iii) 2 Q.13. If the potential diff____________________ Ans.13. We know eE ml V =e ml Vd If temperature is kept constant, relaxation time - will remain constant, and e, m are also constants. Vd V Vd 2V Correct option is (ii) Q.14. The equivalent resistance _________________ Ans. 14. (iii) Redrawing the circuit, we get 3 6 8 B 30 3 & 6 are in parallel. 3 6 18 R1 2 3 6 9 Now R1 and 8 in series R2 = R1 + 8 = 2 + 8 = 10 Now R2 and 30 in parallel R 2 30 10 30 Rep = R 2 30 10 30 300 30 15 40 4 2 = 7.5 (iii) correct option = Q.15. The SI unit of magnetic field intensity is ______________ Ans.15. We know B F Il sin N NA 1m 1 Am Correct option is (ii) SI Unit of B = Q16. The coil of _____________________ Ans. (iv) Correct Option The coil of a moving coil galvanometer is wound over metallic frame to provide electromagnetic damping so it becomes dead beat galvanometer. Q.17. Two wires of__________________ Ans.17. Correct option (iii) l Square A a Area of a Square a2 B a r Circle Area of a Circle r 2 Also here, 2 r l l r= 2 Also here l = 4a l a= 4 l2 Area = 16 2 l A1 = 16 l Now Area = 2 2 l A2 = 4 Now Magnetic moment = I A M1 = IA, & l M2 = I A 2 Since I (current) is same in both M1 A1 l 2 4 = 2 M2 A2 16 l 4 M1 M2 = : 4 Correct option is (iii) Q.18. The horizontal comp________________ Ans.18. Correct option (i) Target law Bv = BH tan 2 BV BH Given BH = 3 Bv Bv 1 tan = 3 Bv 3 = 300 or radians. 6 tan = Q.19. The small___________________ Ans. 19. Correct option is Magnetic declination or Angle of declination. It is the small angle between geographic axis & magnetic axis. Q.20. Two coils___________________ Ans.20. Correct option is (ii) Mutual inductance of a pair of two coils depends on the relative position and orientation of two coils, other statements are incorrect. Q.21. A conducting__________________ Ans. 21. Correct option is (iv) Current induced is I = Now lel = lel R d dt But there is no change of flux with time, as B, A & all remain constant with time. No current is induced Q22. The magnetic flux___________ Ans.22. 5t 2 3t 16 e d dt d 5t 2 3t 16 dt 10t + 3 e t=4 = 10(4)+3 = 43V e = -43Volts Correct option is (ii) Q23 Which of the following_______________ Ans.23. Correct option is (iii) V in Pure Capacitor XC V = V 2 fc 1 2 fc I f other parameters kept cosntant I Straight line paragraph f Q24. A 20 Volt AC________________ Ans.24. Correct option is (i) VR VL VR = Effective Voltage across R VR Ieff R VL = Effective Voltage across L VL Ieff L Net V = VR 2 VL2 Ieff 2 R 2 Ieff 2 L2 = 20 = (12)2 VL2 (20)2 (12)2 VL2 400 = 144 + VL2 VL = 400 144 = 256 16 Volts Q25. The instantaneous_________________ Ans. 25. E = E0 sin t I = I0 sin t + 3 Correct option is (iv) as I can lead the Voltage in RC and LCR circuit, so it can be RC or LCR circuit. (iv) is correct option. Section - B Q26. r Correct option is (i) Since ve electric flux = + ve flux electric flux enclosed with a cylinder here Total Electric Flux = 0. l Q27. Two Parallel______________________ Ans. 27. (iv) Correct option. E + + Surface Charge density, = 26.4 10 12 + 2 0 2 0 2 = = 0 2 0 26.4 10 12 = 8.85 10 12 N = 3 C C m2 E= N C Correct option is (iv) Q28. Consider__________________ + +Q -Q Ans.28. Equal and Opposite charges appear on the nearby conductor due to induction, but still net charge on the conductor is zero. Correct option (iv) Q29. Three Charges_________________ Ans.29. Net E F I at G O Net Potential at G, K2Q KQ r r KQ r =0 Correct option is (iii) V= r E2 r -q G r E2 -q E1 Q30. Two parallel______________ Ans.30. k=2 A = Same d = Same Q = Same in Series 12V 2 0 A 0 A Cy = d d 2 Q Q2 Ux = Uy = 2Cx 2Cy Ux Cy 2Cx 2 = = Uy Cx Cx 1 Cx = Correct Option is (iii) Q31. Which among_________________ Ans.31. Correct statement is option (iv) as Primary coil made of Thick Coper wire has very less R. Therefore negligible power loss. Rest all options are reasons for power losses in a transformer. Q32. An alternating Voltage_______________ Ans.32. B C V 1 1 i.e. Xc 2 fc c I Brightness of the bulb will . Correct option is (ii) Xc Q.33. A solid Sphere______________ Ans.33. Correct option is (4) As all other statements seem incorrect in context with the given figure. Q. 34. A atter is o Ans. e ted .. Correct option is (iv). Rest all quantities change with area of cross-section of a conductor. Q. 35. Three resistors R1 R2 + Ans. R3 Given I = 2 A, R2 = 3 , P3 = 6 W Power across R3 = V3I 6 W = I2 R3 6 3 = R3 = = 1.5 4 2 V3 = I R3 = 2 (1.5) = 3 V Correct option is (iii). Q. 36. A straight li e Ans. I = O, V = E, E = 5.6 V r = Correct option is (i). E 5.6 2.8 I 2.0 Q. 37. A 10 m long potentiometer .. Ans. Let PQ is a potentiometer wore of length 10m, E 5 5 R R 480 20 500 I = = 1 0.01 A 100 VPQ = I RPQ = 0.01 20 = 0.2 V If 10 m potentiometer wire balances 0.2 V Then 1 m potentiometer wire balances 0.2 V 10 Then 6 m potentiometer wire balances 0.2 6V 10 = 1.2 0.12 V 10 Correct option is (iv). Q. 38. The urre t se siti it Ans. Given, I g = I g = 20 Ig 100 120 I g 1.2 I g 100 R = R 25 125 R R 100 100 = 1.25 R Vg = ? Vg = = I g 1.2 I g R 1.25 R 120 25 Vg Vg 125 25 % change = Vg Vg Vg 100 24 Vg Vg 25 100 = Vg = (24 25) 100 25 = 1 100 = 4% 25 Decrease by 4%. Correct option is (iv). Q. 39. Three i fi itel lo g parallel .. F1 r r F2 2I I A Ans. B F2 I C Let F1 is force per unit, length between A & C i.e. F1 = 0 2 I I 4 2r And F2 is force per unit, length between B & C No F2 = 0 I I 4 r et for e o C is per unit length F1 F2 = = I2 (1 1) 4 r 2 0 I 2 F (given) 4 r B C I I 1 F1 2I 1 F1 F21 F21 Now Fig. r b r F1 = Repulsive force between A & C = 0 2 I 2 4 2r F2 = F2 = A reactive force between B & C Net for e o C F1 F2 = 0 F1 = F2 = Net For e o 2I 2 4 2r C is zero. Correct option is (i). Q. 40. In a H-ato Ans. . R = 0.5 A = 10 rps = 10 2 rad/s = 10 Hz M = I A = e r2 = 1.6 10 19 10 3.14 0.5 0.5 10 10 10 10 = 1.256 10 38 Am2 Ans. (ii). Q. 41. An air- ored sole oid .. Ans. Magnetic field inside a solenoid B = 0 N I' l Flu li ked ith N tur s Initial flux 1 = N B A = N 0 N IA l = 0 N2 IA l 4 10 7 800 800 2.5 2.5 10 4 = 0.30 = 16.74 10 3 Wb Final flux 2 = 0 Average back emf d 16.74 10 3 0 |e| = = dt 10 3 = 16.74 V Correct option is (ii). Vo = 283 V, f = 50 Hz Q. 42. R = 3 , L = 25.48 mH C = 796 F P |at resonance = ? P = I2 R Power dissipated I = I0 1 283 2 2 3 = 66.7 A P = I2 R = (66.7)2 3 = 13.35 kW Correct option is (iii). Q. 43. A ir ular loop .. Ans. Let flux linked with smaller loop is 1 and with bigger loop is 2. 2 1 R1 I1 Fig. Given R2 = 0.2 m R1 = 0.003 m x = 15 cm = 0.15 m Now 1 = B2 A1 = M = Now 0 2 R22 I 2 2 R1 4 ( R22 x 2 )3 / 2 1 0 2 R22 R12 I 2 4 ( R22 x 2 )3/ 2 2 = M I1 = 0 2 R22 R12 . I1 4 ( R22 x 2 )3/ 2 = 9.1 10 11 Weber Correct answer is (iv). Q. 44. If oth the o. of tur s .. N2 L = 0 A l Ans. L = 0 (2 N )2 A 2l = 2 0 N2 A 2L l Correct answer is (ii). Doubted. Q.45. Given below___________________ To increase the range Ans. 45. Correct option is (iv) as both statements are false. To increase the range of an ammeter, suitable low R (or shunt) should be connected in parallel to it. The ammeter with increased range has low resistance. Q.46. An electron____________________ Ans.46. Correct option is (iii) Statements correct but reason is wrong because electrons move from a region of low potential to high potential. Q. 47. A magnetic needle .. Ans. The given statement is correct and reason is the correct explanation of the above statement. At poles, magnetic needle orients itself vertically because horizontal components of earth s field is zero there. (correct option is (i)) Q. 48. A proto a d a ele tro , . 2 Ans. we know = = Centripetal force = magnetic Lorentz force sin = sin 9 2 = = = = = Since = = & =9 between Given p, B are same Also q for proton & electron is same except its sign Radius is same. So statement is correct but reason is not the correct explanation of the given assertion. correct option is (ii) Q. 49. O i reasi g .. Ans. 49. When we increase current sensitivity by increasing no. of turns, then resistance of coil also increases. So increasing current sensitivity does not necessarily imply that voltage sensitivity will increase because = if & by different amounts, then may increase or decrease. Correct option is (i). Q.50. A s all o je t Ans. 50. Ans is (ii) F = = = tan = tan E T q qE Correct ans. is (ii) Q. 51. A free ele tro Ans. 51. Correct ans. (ii) i.e. II only = = Now, = > . . = = Q. 52. Correct ans is (iv) i.e. step down transformer decreases the ac voltage. Q.53. correct ans is (i) i.e. = i.e. if no. of turns in secondary coil are more than no. of turns in primary, then voltage is increased or stepped up in secondary, so called step up transformer. Q.54 Correct ans. is (i). i.e. current is reduced if voltage is stepped up so corresponding Q. 55. Correct ans is (iii) Given = = = =? = 00 0 = = 000 = = No of turns in secondary coil losses are cut down.

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