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Latest WB Police Wireless Operator Exam Question (Objective Questions), MCQ in English

Subjects : Physics, Mathematics

Question Bank WB Police Wireless Operator Mains Exam (Part I) - English
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Physics

Question 1Single Answer
In ruby laser, the stimulated emission is due to transition from
  1. A
    metastable state to any lower state
  2. B
    any higher state of lower state
  3. C
    metastable state to ground state
  4. D
    any higher state to ground state
Question 2Single Answer
A direct current I flows along the length of an infinitely long straight thin walled pipe, then the magnetic field is
  1. A
    uniform throughout the pipe not zero
  2. B
    zero only along the axis of the pipe
  3. C
    zero at any point inside the pipe
  4. D
    maximum at the centre and minimum at the edge
Question 3Single Answer
convex lens made of glass has focal length 0.15m in air. If the refractive index of glass is 3/2, and that of water is 4/3 the focal length of lens when immersed in water is
  1. A
    0.45 m    
  2. B
    0.15 m
  3. C
    0.30 m       
  4. D
    0.6 m
Question 4Single Answer
Two sources are said to be coherent if they produce waves
  1. A
    having a constant phase difference
  2. B
    of equal wavelength
  3. C
    of equal speed
  4. D
    having same shape of wavefront
Question 5Single Answer
Three resistors 1 Ω, 2 Ω, 3Ω resistor a 3 V battery is connected. The current through 3 Ω resistor is -
  1. A
    0.75 A     
  2. B
    1 A
  3. C
    2 A         
  4. D
    1.5 A
Question 6Single Answer
In a common emitter amplifier the input signal is applied across
  1. A
    anywhere 
  2. B
    emitter-collector
  3. C
    collector-base
  4. D
    base-emitter
Question 7Single Answer
Adding detergents to water helps in removing dirty greasy stains. This is because
1. It increases greasy stains. This is because
2. It decreases the oil-water surface tension
3. It increases the viscosity of the solution
4. Dirt is held suspended surrounded by detergent molecules
  1. A
    2 and 4
  2. B
    1 only
  3. C
    3 and 4
  4. D
    4 only
Question 8Single Answer
Choose the correct statement (a) for a cricket ball that is spinning clockwise through air
S1 : Statemlines of air are symmetric around the ball.
S2 : The velocity of air above the ball relative to it is larger than that below the ball.
S3 : The velocity of air above the ball relative to it is smaller than that below the ball.
S4 : There is a net upward force on the ball.
  1. A
    S1,S2 and S4
  2. B
    S2 and S4
  3. C
    S4 only
  4. D
    S3 only
Question 9Single Answer
Ferromagnetic materials used in a transformer must have
  1. A
    low permeability and high hysterisis loss
  2. B
    high permeability and low hysterisis loss
  3. C
    high permeability and high hysterisis loss
  4. D
    low permeability and low hysterisis loss
Question 10Single Answer
According to Newton’s corpuscular theory, the speed of light is
  1. A
    same in all the medium
  2. B
    lesser in rarer medium
  3. C
    lesser in denser medium
  4. D
    independent of the medium
Question 11Single Answer
For the constructive interference the path difference between the two interfering waves must be equal to
  1. A
    (2𝜋 + 1)λ  
  2. B
    2n𝜋
  3. C
    nλ
  4. D
    n
Question 12Single Answer
The accurate measurement of emf can be obtained using
  1. A
    multimeter 
  2. B
    voltmeter
  3. C
    voltameter
  4. D
    potentiometer
Question 13Single Answer
A person, with outstretched arms, is spinning on a rotating stool. He suddenly brings his arms down to his sides. Which the following is true about his kinetic energy K and angular momentum L?
  1. A
    Both K and L increase
  2. B
    Both K and L remain unchanged
  3. C
    K remains constant, L increases
  4. D
    K increases but L remains constant
Question 14Single Answer
Which of the following is not a thermodynamic coordinate?
  1. A
    Gas constant (R)   
  2. B
    Pressure (p)
  3. C
    Volume (V) 
  4. D
    Temperature (T)
Question 15Single Answer
An antenna uses electromagnetic waves of frequency 5 MHz . For proper working, the size of the antenna should be
  1. A
    300 m
  2. B
    3 km
  3. C
    15 m
  4. D
    15 km
Question 16Single Answer
The amount of energy released when one microgram of matter is annihilated is
  1. A
    25 kWh  
  2. B
    9 x 1010 kWh
  3. C
    3 x 1010 kWh
  4. D
    0.5 x 105 kWh
Question 17Single Answer
The number of significant figures in the numbers 4.8000 x 104 48000.50 are respectively
  1. A
    5 and 6
  2. B
    5 and 7
  3. C
    2 and 7
  4. D
    2 and 6
Question 18Single Answer
β-decay means emission of electron from
  1. A
    innermost electron orbit
  2. B
    a stable nucleus
  3. C
    outermost electron orbit
  4. D
    radioactive nucleus
Question 19Single Answer
An electric heater rated 220 V and 550 W is connected to AC mains. The current drawn by it is
  1. A
    0.8 A          
  2. B
    2.5 A
  3. C
    0.4 A        
  4. D
    1.25 A
Question 20Single Answer
A string is wound round the rim of a mounted flywheel of mass 20 kg and radius 20 cm. A steady pull of 25 N is applied on the cord. Neglecting friction and mass of the string, the angular acceleration of the wheel is
  1. A
    50 s-2
  2. B
    25 s-2
  3. C
    12.5 s-2
  4. D
    6.25 s-2
Question 21Single Answer
A billiards player hits a stationary ball by an identical ball to pocker the target ball in a corner pocket that is at an angle of 35o with respect to the direction of motion of the first ball. Assuming the collision as elastic and that frictional and rotational motions are not important, the angle made by the target ball with respect to the imcoming ball is
  1. A
    35o
  2. B
    50o
  3. C
    55o
  4. D
    60o
Question 22Single Answer
A body of mass 0.05 kg is observed to fall with an acceleration of 9.5 ms-2. The opposing force of air on the body is (g = 9.8 ms-2)
  1. A
    0.015 N
  2. B
    0.15 N
  3. C
    0.030 N
  4. D
    zero
Question 23Single Answer
The colloidal solution in which both the dispersed phase and dispersion medium are liquids are called
  1. A
    emulsions
  2. B
    gels
  3. C
    foams 
  4. D
    liquid crystals
Question 24Single Answer
In fog, photographs of the objects taken with infrared radiations are more clear than those obtained during visible light because
  1. A
    I-R radiation has lesser wavelength than visible radiation
  2. B
    scattering of I-R light is more the object is less
  3. C
    the intensity of I-R light is more the object is less
  4. D
    scattering of I–R light is less than visible light
Question 25Single Answer
Three concurrent co-planar forces 1 N, 2 N and 3 N acting along different directions on a body
  1. A
    can keep the body in equilibrium if 1 N and 3 N act at right angle
  2. B
    can keep the body in equilibrium if 1 N and 2 N act at right angle
  3. C
    cannot keep the body in equilibrium
  4. D
    can keep the body in equilibrium in 1 N and 3 N act at an acute angle
Question 26Single Answer
Sound waves transfer
  1. A
    only energy not momentum
  2. B
    energy
  3. C
    momentum
  4. D
    both (a) and (b)
Question 27Single Answer
G P Thomson experimentally confirmed the existence of matter waves by the phenomena
  1. A
    diffraction
  2. B
    refraction
  3. C
    polarisation
  4. D
    scattering
Question 28Single Answer
The resistance of a wire at 300 K is found to be 0.3 Ω. If the temperature coefficient of resistance of wire is 1.5 x 10-3 K-1, the temperature at which the resistance becomes 0.6 Ω is
  1. A
    720 K
  2. B
    345 K
  3. C
    993 K
  4. D
    690 K
Question 29Single Answer
Two luminous points sources separated by a certain distance are at 10 km from an observer. If the aperture of his eye is 2.5 x 10-3 m and the wavelength of light used is 500 nm the distance of separation between the point sources just seen to be resolved is
  1. A
    12.2 m     
  2. B
    24.2 m
  3. C
    2.44 m  
  4. D
    1.22 m
Question 30Single Answer
A door 1.6 m wide requires a force of N to be applied at the free end to open or close it. The force that is required at a point 0.4 m distance from the hinges for opening or closing the door is
  1. A
    1.2 N          
  2. B
    3.6 N
  3. C
    2.4 N      
  4. D
    4 N
Question 31Single Answer
0.1 m3 of water at 80o C. The final temperature of the mixture is
  1. A
    65oC
  2. B
    70oC
  3. C
    60oC
  4. D
    75oC
Question 32Single Answer
The spectral series of the hydrogen atom that lies in the visible region of the electromagnetic spectrum
  1. A
    Paschen 
  2. B
    Balmer
  3. C
    Lyman  
  4. D
    Brackett
Question 33Single Answer
A resistor and a capacitor are connected inseries  with an AC source. If the potential drop across the capacitor is 5 V and that across resistor is 12 V, then applied voltage is
  1. A
    13 V
  2. B
    17 V
  3. C
    5 V
  4. D
    12 V
Question 34Single Answer
The amount of heat energy radiated by a metal at temperature T is E. When the temperature is increased to 3T, energy radiated is
  1. A
    8 1E
  2. B
    9 E
  3. C
    3 E
  4. D
    27 E
Question 35Single Answer
A man, of mass 60 kg, is riding in a lift. The weights of the man, when the lift is accelerating upwards and down wards at 2m/s2 are respectively (Taking g=2m/s2)
  1. A
    720 N and 480 N
  2. B
    480 N and 720 N
  3. C
    600 N and 800 N
  4. D
    None of these

Mathematics

Question 36Single Answer
The elements of the set {x : x is an integer, x2 : 4} can be represent as .....Z..... . Here, Z refers to
  1. A
    {–2, 2} 
  2. B
    {–1, 0, 1}
  3. C
    {–2, –1, 0, 1, 2}
  4. D
    {0, 1, 2}
Question 37Single Answer
 
  1. A
  2. B
  3. C
  4. D
    None of these
Question 38Single Answer
If Y = {x : x is a positive factor of the number 2p – 1(2p – 1), where 2p – 1 is a prime number}, then Y can be represent in roster form as
  1. A
    {2}
  2. B
    {1, 2}  
  3. C
    {1, 2, 22, ....., 2p – 1}
  4. D
    {1, 2, 22, 23,.... 2p – 1, (2p – 1)}
Question 39Single Answer
The set {x : x is a positive integer less than 6 and 3x – 1 is an even number} in roster form is
  1. A
    {1, 2, 3, 4, 5}
  2. B
    {1, 2, 3, 4, 5, 6}  
  3. C
    {2, 4, 6}
  4. D
    {1, 3, 5}
Question 40Single Answer
If A B and A B, then
  1. A
    A is called a proper subset of B
  2. B
    A is called a super set of B
  3. C
    A is not a subset of B 
  4. D
    B is a subset of A
Question 41Single Answer
The number of non-empty subsets of the set{1, 2, 3, 4} is
  1. A
    15
  2. B
    14
  3. C
    16
  4. D
    17
Question 42Single Answer
The number of elements of the power set of a set containing m elements is
  1. A
    2m – 1
  2. B
    m 
  3. C
    m2
  4. D
    2m
Question 43Single Answer
If A = {x : x = n2, n = 1, 2, 3}, then number of proper subsets is
  1. A
    3
  2. B
    8
  3. C
    7
  4. D
    None of these
Question 44Single Answer
If A = {x : x = 4n + 1, 2 £ n £ 5},then number of subsets of A is
  1. A
    16
  2. B
    15  
  3. C
    4 
  4. D
    None of these 
Question 45Single Answer
Let A and B be two non-empty subsets of a set X such that A is not a subset of B, then
  1. A
    A is always a subset of the complement of B
  2. B
    B is always a subset of A  
  3. C
    A and B are always disjoint
  4. D
    A and the complement of B are always non-disjoint  
Question 46Single Answer
Which of the following is/are empty set? 
A = {x : x2 + x + 1 = 0 and x Î Z}   B = {x : x is a prime number and 19 < x < 23}
  1. A
    A
  2. B
    B  
  3. C
    Both A and B
  4. D
    None of the above 
Question 47Single Answer
The set {x : x4 = 1 and x R} is .....X.... set. Here, X refers to
  1. A
    empty
  2. B
    finite
  3. C
    infinite
  4. D
    singleton 
Question 48Single Answer
The universal set for the sets   
A = {x : x2 – 5x + 6 = 0} and   
B = {x : x2 – 3x + 2 = 0} having least number of elements is
  1. A
    {1, 2}
  2. B
    {1, 3}
  3. C
    {1, 2, 3}
  4. D
    {0, 1, 2, 3}
Question 49Single Answer
If A = {1, 2, 3}, B = {x € R : x2 – 2x + 1 = 0}, 
C = {1, 2, 2, 3} and 
D = {x € R : x3 – 6x2 + 11x – 6 = 0}, then the equal sets are
  1. A
    A and B
  2. B
    A and C  
  3. C
    A, B and C 
  4. D
    A, C and D
Question 50Single Answer
If A = (–3, 5) and  B = [–7, 9], then
  1. A
    A = B
  2. B
    A B 
  3. C
    B A
  4. D
    None of these 
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