Class 12th CBSE Term 1, Physics Board Exam Question Paper and Answers Key 2021-22
- SUBJECT- Physics
- Term- I
- Time allowed- 90 minutes
- Maximum Marks- 40
Q1. A negative charged object X is repelled by another charged object Y. However an object Z is attracted to object Y. Which of the following is the most possibility for the object Z?
a. positively charged only
b. negatively charged only
c. neutral or positively charged
d. neutral or negatively charged
The correct answer is: neutral or positively charged
Q2. In an experiment three, microscopic latex spheres are sprayed into a chamber and became charged with charges +3e, +5e and -3e respectively. All the three spheres came in contact simultaneously for a moment and got separated. Which one of the following are possible values for the final charge on spheres?
a. +5e, -4e, +5e
b. +5e, +6e, -7e
c. -4e, +3.5e, +5.5e
d. +5e, -8e, +7e
The correct answer is: +5e, +6e, -7e
Q3. An object has charged of 1 C and gains 5.0 x 10 to the power 18 electrons, The net charge on the object becomes:
a. -0.80 C
b. +0.80 C
c. +1.80 C
d. +0.20 C
The correct answer is: +0.20 C
Q4. Kirchhoff’s first rule I = 0 and second rule IR = E (where the symbols have their usual meanings) are respectively based on:
a. conservation of momentum and conservation of charge
b. conservation of energy, conservation of charge
c. conservation of charge, conservation of momentums
d. conservation of charge, conservation of energy
The correct answer is: conservation of charge, conservation of energy
Q5. The electric power consumed by a 220 V – 100 W bulb when operated at 110 V is:
a. 25 w
b. 30 W
c. 35 W
d. 45 W
The correct answer is: 25 w
Q6. Which one of the following has negative temperature coefficient of resistivity?
a. metal
b. metal and semiconductor
c. semiconductor
d. metal and alloy
The correct answer is: semiconductor
Q7. Two wires carrying currents I1,I2 lie, one slightly above the other, in a horizontal plane as shown in figure. The region of vertically upward strongest magnetic field is:
a. I
b. II
c. III
d. IV
The correct answer is: II
Q8. Two parallel conductors carrying 0f 3.0 A and 10.0 A are placed 2.5 cm apart in vacuum. The force per unit length between them is:
a. 6.4 x 10 power -5 N/m
b. 6.4 x 10 power -2 N/m
c. 4.6 x 10 power -4 N/m
d. 3.2 x 10 power -4 N/m
The correct answer is: 3.2 x 10 power -4 N/m
Q9. If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a:
a. low resistance in parallel
b. low resistance in series
c. high resistance in parallel
d. high resistance in series
The correct answer is: low resistance in parallel
Q10. The magnetic field at the centres of a current carrying circular loop of radius R1 is B2. The magnetic field at a point on its axis at distance R from the center of the loop B2. Then the ratio (B1, B2) is:
a. 2√2
b. 1/√2
c. √2
d. 2
The correct answer is: √2
Q11. The self-inductance of a solenoid of 600 turns is 108 mH. The self-inductance of a coil having 500 turns with the same length, the same radius and the same medium will be
a. 95mH
b. 90mH
c. 85mH
d. 75mH
The correct answer is: 75mH
Q12. The rms current in a circuit connected to a 50 Hz ac source is 15 A. The value of the current in the circuit (1/600)s after the instant the current is zero, is:
a. 15/√2 A
b. 15√2 A
c. √2/15 A
d. 8 A
The correct answer is: 15/√2 A
Q13. In a circuit the phase difference between the alternating current and the source voltage is π/2. Ehich of the following cannot be the elements of the circuit?
a. only C
b. Only L
c. L and R
d. L or C
The correct answer is: only C
Q14. The electric potential V at any point (x, y, z) is given by V = 3x power 2 where x is in meters and V in volts. The electric field at the point (1 m, 0, 2m) is:
a. 6 V/m along -x axis
b. 6 V/m along +x axis
c. 1.5 V/m along -x axis
d. 1.5 V/m along +x axis
The correct answer is: 6 V/m along -x axis
Q15. Which of the diagrams correctly represents the electric field between two charged plates if a neutral conductor is placed in between the plates ?
The correct answer is: d
Q16. A variable capacitor is connected to a 200 V battery. If its capacitance is changed from 2 uF to X uF, the decrease in energy of the capacitor is 2 x 10-2 J. The value of X is –
(a) 1 uF
(b) 2uF
(c) 3 uF
(d)) 4uF
The correct answer is: 4uF
Q17. A potential difference of 200 V is maintained across a conductor of resistance 100 2. The number of electrons passing through it in ls is
(a) 1.25 x 1019
(b) 2.5 x 1018
(c) 1.25 x 1018
(d) 2.5 x 1016
The correct answer is: 1.25 x 1019
Q18. The impedance of a series LCR circuit is –
The correct answer is: d
Q19. When an alternating voltage E = Eo sin wt is applied to a circuit, a current I = Io sin (wt+𝜋/2) flows through it. The average power dissipated in the circuit is
(a) Erms. Irms
(b) Eo Io
(c) Eo Io/√2
(d) Zero
The correct answer is: Zero
Q20. A current carrying wire kept in a uniform magnetic field, will experience a maximum force when it is
(a) perpendicular to the magnetic field
(b) parallel to the magnetic field
(c) at an angle of 45° to the magnetic field
(d) at an angle of 60° to the magnetic field
The correct answer is: perpendicular to the magnetic field
Q21. The voltage across a resistor, an inductor, and a capacitor connected in series to an ac source are 20 V, 15 V and 30 V respectively. The resultant voltage in the circuit is
(a) 5 V
(b) 20 V
(c) 25 V
(d) 65 V
The correct answer is: 25 V
Q22. In a dc circuit the direction of current inside the battery and outside the battery respectively are –
(a) positive to negative terminal and negative to positive terminal
(b) positive to negative terminal and positive to negative terminal
(c) negative to positive terminal and positive to negative terminal
(d) negative to positive terminal and negative to positive terminal
The correct answer is: negative to positive terminal and positive to negative terminal
Q23. The magnitude of electric field due to a point charge 2q, at distance r is E. Then the magnitude of electric field due to a uniformly charged thin spherical shell of radius R with total charge q at a distance – (r >> R) will be
(a) E/4
(b) 0
(c) 2E
(d) 4E
The correct answer is: 2E
Q24. The horizontal component of earth’s magnetic field at a place is 0.2 G whereas it’s total magnetic field is 0.4 G. The angle of dip at the place is
(a) 30°
(b) 45°
(c) 60°
(d) 90°
The correct answer is: 60°
Q25. The current in the primary coil of a pair of coils changes from 7 A to 3 A in 0.04 s. The mutual inductance between the two coils is 0.5 H. The induced emf in the secondary coil is –
(a) 50 V
(b) 75 V
(c) 100 V
(d) 220 V
The correct answer is: 50 V
Q26. A square sheet of side ‘a’ is lying parallel to XY plane at z = a. The electric field in the region is E = cz2k. The electric flux through the sheet is
(a) a4c
(b) ⅓a3c
(c) ⅓a4c
(d) 0
The correct answer is: a4c
Q27. Three charges q, -q, q0 are placed as shown in figure. The magnitude of the net force on the charge q0 at point O is {k= 1/(4π e0}
a. 0
b. 2kqq0/n2
c. √ 2kqq0/a2
d. 1/√ 2 kqq0/a2
The correct answer is:
Q28. A + 3.0 nC charge Q is initially at rest at a distance of r; = 10 cm from a + 5.0 nC charge q fixed at the origin. The charge Q is moved away from q to a new position at r, = 15 cm. In this process work done by the field is
(a) 1.29 x 10-5 J
(b) 3.6 x 105 J
(c) -4.5 x 10-7J
(d) 4.5 x 10-7 J
The correct answer is: 4.5 x 10-7 J
Q29. A car battery is charged by a 12 V supply, and energy stored in it is 7.20 x 105 J. The charge passed through the battery is –
(a) 6.0 x 104 C
(b) 5.8 x 103 J
(c) 8.64 x 106 J
(d) 1.6 x 106c
The correct answer is: 8.64 x 106 J
Q30. A straight conducting rod of length I and mass m is suspended in a horizontal plane by a pair of flexible strings in a magnetic field of magnitude B. To remove the tension in the supporting strings, the magnitude of the current in the wire is
(a) mgB/l
(b) mgl/B
(c) mg/lB
(d) lB/mg
The correct answer is: mg/lB
Q31. A constant current is flowing through a solenoid. An iron rod is inserted in the solenoid along its axis. Which of the following quantities will not increase?
(a) The magnetic field at the centre
(b) The magnetic flux linked with the solenoid
(c) The rate of heating
(d) The self-inductance of the solenoid
The correct answer is: The rate of heating
Q32. A circuit is connected to an ac source of variable frequency. As the frequency of the source is increased, the current first increases and then decreases. Which of the following combinations of elements is likely to comprise the circuit ?
(a) L, C and R
(b) L and C
(c) Land R
(d) R and C
The correct answer is: L, C and R
Q33. If n, e, t and m have their usual meanings, then the resistance of a wire of length l and cross-sectional area A is given by –
The correct answer is: b
Q34. A proton and an alpha particle move in circular orbits in a uniform magnetic field. Their speeds are in the ratio of 9:4. The ratio of radii of their circular orbits (rp/ralpha) is
(a) 3/4
(b) 4/3
(c) 8/9
(d) 9/8
The correct answer is: 9/8
Q35. A coil of area 100 cm2 is kept at an angle of 30° with a magnetic field of 10-1 T. The magnetic field is reduced to zero in 10-4 s. The induced emf in the coil is –
(a) 5/3 v
(b) 5073 V
(c) 5.0 V
(d) 50.0 V
The correct answer is: 5/3 v
Q36. A 15 2 resistor, an 80 mH inductor and a capacitor of capacitance Care connected in series with a 50 Hz ac source. If the source voltage and current in the circuit are in phase, then the value of capacitance is
(a) 100 uF
(b) 127 uF
(c) 142 uF
(d) 160 uF
The correct answer is: 127 uF
Q37. Four objects W, X, Y and Z, each with charge +q are held fixed at four points of a square of side d as shown in the figure. Objects X and Z are on the midpoints of the sides of the square. The electrostatic force exerted by object W on object X is F. Then the magnitude of the force exerted by object W on Z is
(a) F/7
(b) F/5
(c) F/3
(d) F/2
The correct answer is: F/5
Q38. Two sources of equal emf are connected in series. This combination is, in turn connected to an external resistance R. The internal resistance of two sources are r, and r, (r, >r,). If the potential difference across the source of internal resistance r, is zero, then R equals to
The correct answer is: (r2-r1)
Q39. Which of the following statements is correct?
(a) Magnetic field lines do not form closed loops.
(b) Magnetic field lines start from north pole and end at south pole of a magnet.
(c) The tangent at a point on a magnetic field line represents the direction of the magnetic field at that point.
(d) Two magnetic field lines may intersect each other.
The correct answer is: The tangent at a point on a magnetic field line represents the direction of the magnetic field at that point.
Q40. The equivalent resistance between A and B of the network shown in figure is
(a) 3R Ω
(b) (3/2)R Ω
(c) 2R Ω
(d) (2/3) RΩ
The correct answer is: 2R Ω
Q41. A bar magnet has magnetic dipole moment M. Its initial position is parallel to the direction of uniform magnetic field B. In this position, the magnitudes of torque and force acting on it respectively are –
(a) 0 and MB
(b) MB and MB
(c) 0 and 0
(d) |M X B| and 0
The correct answer is: 0 and 0
Q43. A 300 Ω resistor and a capacitor of (25/𝜋)uF are connected in series to a 200V- 50Hz ac source. The current in the circuit is –
(a) 0.1 A
(b) 0.4 A
(c) 0.6 A
(d) 0.8 A
The correct answer is: 0.4 A
Q44. The core of a transformer is laminated to reduce the effect of:
(a) flux leakage
(b) copper loss
(c) hysteresis loss
(d) eddy current
The correct answer is: eddy current
Q45. Assertion (A): A negative charge in an electric field moves along the direction of the electric field.
Reason (R): On a negative charge a force acts in the direction of the electric field
(a) Both (A) and (R) are true and (R) is correct explanation of (A)
(b) Both (A) and (R) are true and (R) is not correct explanation of (A)
(c) (A) is true, but (R) is false
(d) (A) is false and (R) is also false
The correct answer is: (A) is false and (R) is also false
Q46. Assertion (A): The poles of a bar magnet cannot be separated
Reason (R): Magnetic monopoles do not exist
(a) Both (A) and (R) are true and (R) is correct explanation of (A)
(b) Both (A) and (R) are true and (R) is not correct explanation of (A)
(c) (A) is true, but (R) is false
(d) (A) is false and (R) is also false
The correct answer is: Both (A) and (R) are true and (R) is correct explanation of (A)
Q47. Assertion (A): When radius of a current carrying loop is doubled, its magnetic moment becomes four times
Reason (R): The magnetic moment of a current carrying loop is directly proportional to the area of the loop
(a) Both (A) and (R) are true and (R) is correct explanation of (A)
(b) Both (A) and (R) are true and (R) is not correct explanation of (A)
(c) (A) is true, but (R) is false
(d) (A) is false and (R) is also false
The correct answer is: Both (A) and (R) are true and (R) is correct explanation of (A)
Q48. Assertion (A): Higher the range, lower is the resistance of an ammeter
Reason (R): To increase the range of an ammeter additional shunt is added in series to it
(a) Both (A) and (R) are true and (R) is correct explanation of (A)
(b) Both (A) and (R) are true and (R) is not correct explanation of (A)
(c) (A) is true, but (R) is false
(d) (A) is false and (R) is also false
The correct answer is: (A) is true, but (R) is false
Q49. Assertion (A): A step-up transformer cannot be used as a step-down tranformer.
Reason (R): A transformer works only in one direction
(a) Both (A) and (R) are true and (R) is correct explanation of (A)
(b) Both (A) and (R) are true and (R) is not correct explanation of (A)
(c) (A) is true, but (R) is false
(d) (A) is false and (R) is also false
The correct answer is: (A) is false and (R) is also false
Q50. Equipotentials at a large distance from a collection of charges whose total sum is not zero are:
(a) spheres
(b) planes
(c) ellipsoids
(d) parabolas
The correct answer is: spheres
Q51. Four charges -q, ,-q, +q and +q are placed at the corners of a square of side 2 L is shown in figure. The electric potential at point A midway between the two charges +q and +q is:
(a)
(b)
(c)
(d)
The correct answer is: a
Q52. The points with the same potential are:
(a) b, c, d
(b) f, h, j
(c) d, e, f
(d) a, b, j
The correct answer is: f, h, j
Q53. The current through branch bg is:
(a) 1 A
(b) 1/3 A
(c) 1/2 A
(d) 2/3 A
The correct answer is: 1/2 A
Q54. The power dissipated in R1 is:
(a) 2 W
(b) 2.5 W
(c) 3 W
(d) 4.5 W
The correct answer is: 4.5 W
Q55. The potential difference across R3 is:
(a) 1.5 V
(b) 2 V
(c) 2.5 V
(d) 3 V
The correct answer is: 2 V
