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CLASS XII CBSE

PHYSICS Set | A – 1 | B – 21 |

1. Plate separation of a F15 capacitor is 2 mm. A dielectric slab (K = 2) of thickness 1

mm is inserted between the plates. Then new capacitance is given by

(a) F15 (b) F20 (c) F30 (d) F25

Set | A – 2 | B – 22 | 2. Two point charges +4q and +q are placed at a distance L apart. A third charge Q is so placed that all the three charges are in equilibrium. Then location and magnitude of third charge will be

(a) At a distance3

L from +4q charge,

4

9

q

(b) At a distance 3

L from +4q charge,

4

9

q

(c) At a distance 2

3

L from +4q charge,

4

9

q

(d) At a distance 2

3

Lfrom +q charge,

4

9

q

Set | A – 3 | B – 23 |

3. A drop of 610 kg water carries 610 C charge. What electric field should be applied to balance it’s weight (assume g = 10 m/sec2)

(a) 10 / ,V m Upward (b) 10 / ,V m Downward

(c)0.1 V/m Downward (d) 0.1 / ,V m Upward

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CLASS XII CBSE

Set | A – 4 | B – 24 | 4. A telephone wire of length 200 km has a capacitance of 0.014 F per km. If it carries an ac of frequency 5 kHz, what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum

(a) 0.35 mH (b) 35 mH (c) 3.5 mH (d) Zero ,

Set | A – 5 | B – 25 | 5. In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An e.m.f. )cos(0 tEE is applied to the circuit. The power consumed in the circuit is

(a) R

E20 (b)

R

E

2

20 (c)

R

E

4

20 (d)

R

E

8

20

Set | A – 6 | B – 26 | 6. An LCR series circuit is connected to an external e.m.f. te 100sin200 . The values of the capacitance and resistance in the circuit are F2 and 100 respectively. The

amplitude of the current in the circuit will be maximum when the inductance is

(a) 100 Henry (b) 2/50 Henry (c) 100 Henry (d) 2100 Henry

Set | A – 7 | B – 27 |

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CLASS XII CBSE

7. A very small circular loop of area A and the resistance R and negligible inductance is initially coplanar and concentric with a much larger fixed loop of radius x. A constant current i is passed in the bigger loop and the smaller loop is rotated with constant angular velocity about a diameter then induced current in the smaller loop as a function of time will be

(a) txR

iA

sin

2

0

(b) t

xR

iA

sin

2

0

(c) t

xR

iA

2sin

2

0

(d) 0

Set | A – 8 | B – 28 | 8. A metal aeroplane having a distance of 50 meter between the edges of its wings is flying horizontally with a speed of 360 km/hour. At the place of flight, the earth’s total magnetic field is 4.0 × 10–5 weber/meter2 and the angle of dip is 30o. The induced potential difference between the edges of its wings will be

(a) 0.1 V (b) 0.01 V (c) 1 V (d) 10 V

Set | A – 9 | B – 29 | 9. The distance between the poles of a horse shoe magnet is 0.1 m and its pole strength is 0.01 amp-m. The induction of magnetic field at a point midway between the poles will be

(a) T5102 (b) T6104 (c) T7108 (d) Zero

x

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CLASS XII CBSE

Set | A – 10 | B – 30 | 10. A particle carrying a charge equal to 100 times the charge on an electron is rotating per second in a circular path of radius 0.8 metre. The value of the magnetic field produced at the centre will be 0( permeability for vacuum)

(a) 0

710

(b) 01710 (c) 0

610 (d) 0710

Set | A & B – 11 | 11. Magnetic field due to a current carrying loop or a coil at a distant axial point P is B1

and at an equal distance in it's plane is B2 then 2

1

B

B is

(a) 2 (b) 1 (c) 2

1 (d) 4

Set | A & B – 12 | 12. A proton of mass 271067.1 kg and charge 19106.1 C is projected with a speed of

sm /102 6 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

(a) A circle of radius = 0.2 m and time period 710 s

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CLASS XII CBSE

(b) A circle of radius = 0.1 m and time period 7102 s (c) A helix of radius = 0.1 m and time period 7102 s (d) A helix of radius = 0.2 m and time period 7104 s

Set | A & B – 13 | 13. A conductor PQRSTU, each side of length L, bent as shown in the figure, carries a current 𝑖 and is placed in a uniform magnetic induction B directed parallel to the positive Y-axis. The force experience by the wire and its direction are

(a) 2iBL directed along the negative Z-axis (b) 5iBL directed along the positive Z-axis (c) iBL direction along the positive Z-axis (d) 2iBL directed along the positive Z-axis

Set | A & B– 14 | 14. 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. Length 𝑎𝑏 = 𝑙 and 𝑎𝑏𝑐 = 45°. The ratio of force on 𝑎𝑏 and on 𝑏𝑐 is

l

B

45o

a

c i

i

b

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CLASS XII CBSE

(a) 2

1 (b) 2 (c) 1 (d)

3

2

Set | A & B– 15 | 15. A steady current 𝑖 flows in a small square loop of wire of side 𝐿 in a horizontal plane. The loop is now folded about its middle such that half of it lies in a vertical plane. Let

1 and 2 respectively denote the magnetic moments due to the current loop

before and after folding. Then

(a) 02 (b) 1 and 2 are in the same direction

(c) 2||

||

2

1

(d)

2

1

||

||

2

1

Set | A & B – 16 |

16. A point source of electromagnetic radiation has an average power output of 800𝑊. The maximum value of electric field at a distance 3.5 𝑚 form the source will be

(a) 56.7 𝑉/𝑚 (b) 62.6 𝑉/𝑚 (c) 39.3 𝑉/𝑚 (d) 47.5 𝑉/𝑚

Set | A & B – 17 | 17. The diameter of the eye-ball of a normal eye is about 2.5𝑐𝑚. The power of the eye lens varies from

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CLASS XII CBSE

(a) 2 𝐷 to 10 𝐷 (b) 40 𝐷 to 32 𝐷 (c) 9 𝐷 to 8 𝐷 (d) 44 𝐷 to 40 𝐷

Set | A & B – 18 | 18. Two point light sources are 24𝑐𝑚 apart. Where should a convex lens of focal length 9𝑐𝑚 be put in between them from one source so that the images of both the sources are formed at the same place

(a) 6 cm (b) 9 cm (c) 12 cm (d) 15 cm

Set | A & B – 19 | 19. The power of a thin convex lens )5.1( ga is + 5.0 D. When it is placed in a liquid

of refractive index ,la then it behaves as a concave lens of local length 100𝑐𝑚. The

refractive index of the liquid la will be

(a) 5 / 3 (b) 4 / 3 (c) 3 (d) 5 / 4

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CLASS XII CBSE

Set | A & B – 20 | 20. A candle flame 3𝑐𝑚 is placed at distance of 3𝑚 from a wall. How far from wall must a concave mirror be placed in order that it may form an image of flame 9𝑐𝑚 high on the wall

(a) 225 cm (b) 300 cm (c) 450 cm (d) 650 cm

Set | A – 21 | B – 1 | 21. When radiation of wavelength is incident on a metallic surface the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts. Then the threshold wavelength for the surface is

(a) 2 (b) 4 (c) 6 (d) 8

Set | A – 22 | B – 2 | 22. The minimum intensity of light to be detected by human eye is 210 /10 mW . The number of photons of wavelength m7106.5 entering the eye, with pupil area 2610 m , per second for vision will be nearly

(a) 100 (b) 200 (c) 300 (d) 400

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CLASS XII CBSE

Set | A – 23 | B – 3 | 23. The de-Broglie wavelength of an electron having 80𝑒𝑉 of energy is nearly

( JeV 19106.11 , Mass of electron kg31109 and Plank's constant 34106.6 𝐽 − 𝑠𝑒𝑐)

(a) 140 Å (b) 0.14 Å (c) 14 Å (d) 1.4 Å

Set | A – 24 | B – 4 | 24. The wavelength of radiation emitted is 𝜆0 when an electron jumps from the third to the second orbit of hydrogen atom. For the electron jump from the fourth to the second orbit of the hydrogen atom, the wavelength of radiation emitted will be

(a) 025

16 (b) 0

27

20 (c) 0

20

27 (d) 0

16

25

Set | A – 25 | B – 5 | 25. In the Bohr model of the hydrogen atom, let 𝑅, 𝑣 and 𝐸 represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number 𝑛

(a) 𝑅/𝐸 (b) 𝐸/𝑣 (c) 𝑅𝐸 (d) 𝑣𝑅

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CLASS XII CBSE

Set | A – 26 | B – 6 | 26. In a Young’s double slit experiment, the slit separation is 1 mm and the screen is 1 m from the slit. For a monochromatic light of wavelength 500 nm, the distance of 3rd minima from the central maxima is

(a) 0.50 𝑚𝑚 (b) 1.25 𝑚𝑚 (c) 1.50 𝑚𝑚 (d) 1.75 𝑚𝑚

Set | A – 27 | B – 7 | 27. The two slits at a distance of 1 𝑚𝑚 are illuminated by the light of wavelength

7105.6 𝑚. The interference fringes are observed on a screen placed at a distance of 1𝑚. The distance between third dark fringe and fifth bright fringe will be (a) 0.65 𝑚𝑚 (b) 1.63 𝑚𝑚 (c) 3.25 𝑚𝑚 (d) 4.88 𝑚𝑚

Set | A – 28 | B – 8 | 28. If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li is (a) 122.4 𝑒𝑉 (b) 30.6 𝑒𝑉 (c) 13.6 𝑒𝑉 (d) 3.4 𝑒𝑉

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CLASS XII CBSE

Set | A – 29 | B – 9 | 29. A new flashlight cell of emf 1.5 𝑣𝑜𝑙𝑡𝑠 gives a current of 15 𝑎𝑚𝑝𝑠, when connected directly to an ammeter of resistance 0.04 . The internal resistance of cell is

(a) 0.04 (b) 0.06 (c) 0.10 (d) 10

Set | A – 30 | B – 10 | 30. A potential difference of 𝑉 is applied at the ends of a copper wire of length 𝑙 and diameter 𝑑. On doubling only 𝑑, drift velocity

(a) Becomes two times (b) Becomes half (c) Does not change (d) Becomes one fourth Solution: (c) Drift velocity doesn’t depends upon diameter.