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M P Keshari » PHYSICS

PHYSICS

This item was filled under [ COMPETITION ]

 

PHYSICS – XII

 

OBJECTIVE

 

MULTIPLE CHOICE

 

 

Direction :- Choose the correct alternative from the following :

 

Q.1.     When air is replaced by a dielectric medium of dielectric constant K, the

 

maximum force of attraction between two charges separated by a distance :

 

(a) decreases K times                          (b) remains constant

 

(c) increases K times                           (d) decreases K2 times

 

Q.2.     A given charge situated at a certain distance from an electric dipole of very small

 

length along its axial line experience a force F. If the distance of the charge is

 

doubled, the force on charge will become :

 

(a) 2F                           (b) F/2                         (c) F/4                          (d) F/8

 

Q.3.     Two small spheres each carrying a charge q placed r metre apart repel each other

 

with a force F. If one of the spheres is taken around the other one in a circular

 

path of radius r, the work done will be :

 

(a) F × r                       (b) F × 2πr                   (c) F/(2πr)                    (d) zero

 

Q.4.     A parallel plate capacitor is charged. If the plates are pulled apart,

 

(a) the potential difference increases.

 

(b) the capacitance increases.

 

(c) the total charge increases.

 

(d) the charge and the potential difference remain same.

 

Q.5.     Two copper wires, one of length 1 m and the other of length 9 m, are found to

 

have the same resistance. Their diameters are in the ratio :

 

(a) 3 : 1                        (b) 1 : 9                        (c) 9 : 1                        (d) 1 : 3

 

Q.6.     The instrument for the accurate measurement of the e. m. f. of a cell is :

 

(a) a voltmeter                                                 (b) an ammeter

 

(c) a potentiometer                                          (d) a slide wire bridge

 

Q.7.     A current of 2 A passing through conductor produces 80 J of heat in 10 seconds.

 

The resistance of the conductor is :

 

(a) 0.5 Ω                     (b) 2 Ω                         (c) 4 Ω                         (d) 20 Ω

 

Q.8.     The electrochemical equivalent of a metal is 3.3 × 10-7 kg C-1. The mass of the

 

metal liberated at the cathode, when a 3 A current is passed for 2 s will be :

 

(a) 1.1 × 10-7 kg                                               (b) 6.6 × 10-7 kg

 

(c) 9.9 × 10-7 kg                                               (d) 19.8 × 10-7 kg

 

Q.9.     In SI system, permeability has the units :

 

(a) weber metre-1 ampere-1 (b) weber metre ampere-1

 

(c) weber metre-1 ampere-2 (d) weber metre ampere

 

Q.10.   An electron moves with a velocity of 103 ms-1 in a magnetic field of induction 0.3

 

T at an angle 30º. If e/m of electron is 1.76×1011 Ckg-1, the radius of the path is

 

nearly :

 

(a) 10-8 m         (b) 2×10-8 m                (c) 10-6 m                     (d) 10-10 m

 

Q.11.   The work done in turning a magnet of magnetic moment M through an angle θ

 

from the meridian is :

 

(a) M B (1 – cosθ)       (b) M B cosθ              (c) m B            (d) M B sinθ

 

Q.12.   An example of paramagnetic substance is :

 

(a) Alnico                    (b) Antimony              (c) Silver                      (d) Marble

 

Q.13.   A magnetic field of 2×10-2 T acts at right angle to a coil of area 100 cm2 with 50

 

turns. The average e. m. f. induced in the coil is 0.1 V, when it is removed from

 

the field in the time t. The value of t is :

 

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

 

Q.14.   The time constant of CR-circuit is :

 

(a) 1/(CR)                    (b) C/R                        (c) CR                                     (d) R/C

 

Q.15.   In an LCR-series a. c. circuit, the current :

 

(a) is always in phase with the voltage

 

(b) always lags the generator voltage

 

(c) always leads the generator voltage

 

(d) may lag behind or lead the voltage

 

Q.16.   Among the following, the longest wave is :

 

(a) radio wave.            (b) γ-ray           (c) microwave.            (d) X-ray.

 

Q.17.   Time taken by the sun light to pass through a glass slab of 4 mm thickness, whose

 

refractive index is 1.5, is :

 

(a) 2×10-1 s                  (b) 2×108 s                   (c) 2×10-11 s                 (d) 2×1011 s

 

Q.18.   Refractive indices of a prism material for two wavelengths are 1.66 and 1.64. The

 

dispersive power is :

 

(a) 0.02                        (b) 0.012                      (c) 0.01                        (d) 0.03

 

Q.19.   An astronomical telescope of ten fold angular magnification has a length of

 

44 cm. The focal length of the objective is :

 

(a) 4 cm                       (b) 40 cm                     (c) 44 cm                     (d) 440 cm

 

Q.20.   The interference phenomenon can take place :

 

(a) in all waves                                     (b) in transverse waves only

 

(c) in longitudinal waves only             (d) in standing waves only

 

Q.21.   Two points separated by a distance of 0.1 mm can just be inspected in a

 

microscope, when light of wavelength 6000 Å is used, the limit of resolution

 

will become :

 

(a) 0.8 mm                   (b) 0.12 mm                 (c) 0.1 mm                   (d) 0.08 mm

 

Q.22.   Electron volt is a unit of :

 

(a) charge        (b) momentum             (c) potential difference           (d) energy

 

Q.23.   The packing fraction for 7N14 isotope, whose mass is 14.0003 a. m. u. is :

 

(a) 7.8×10-3 (b) 2.1×10-4 (c) 1.0002                    (d) 0.9

 

Q.24.   A positron has the same mass as :

 

(a) proton                    (b) α-particle                (c) neutron                   (d) electron

 

Q.25.   The number of atoms per unit cell in BCC lattice is :

 

(a) 1                             (b) 2                             (c) 4                                         (d) 9

 

ANSWERS

 

1.(a)     2.(d)    3.(d)    4.(a)     5.(d)    6.(c)     7.(b)     8.(d)    9.(a)    10.(a)

 

11.(a)   12.(b)   13.(a)   14.(c)   15.(d) 16.(a)   17.(c)   18.(d) 19.(b)   20.(a)

 

21.(a)   22.(d) 23.(a)   24.(d) 25.(b).

 

Contact : mpkeshari@yahoo.com

 

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