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WBJEE | 2012
Q. A charge +q is placed at the origin O of XY axes as shown in the figure. The work done in taking a charge Q from A to B along the straight line AB is :
466932_2feb6e057a104fd19f14bb4fa1156a13.png
  1. qQ4πϵ0(abab)
  2. qQ4πϵ0(baab)
  3. qQ4πϵ0(ba21b)
  4. qQ4πϵ0(ab21b)
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Q. What is the phase difference between two simple harmonic motions represented by x1=Asin(ωt+π6) and x2=Acos(ωt)?
  1. π6
  2. π3
  3. π2
  4. 2π3
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Q. A particle is projected from the ground with a kinetic energy E at an angle of 60 with the horizontal. Its kinetic energy at the highest point of its motion will be :
  1. E2
  2. E4
  3. E2
  4. E8
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Q. What current will flow through the 2kΩ resistor in the circuit shown in the figure?
466956_57359931fbdf4f6fbd48fcba296f9c23.png
  1. 3 mA
  2. 6 mA
  3. 12 mA
  4. 36 mA
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Q. An electric bulb marked as 50 W200 V is connected across a 100 V supply. The present power of the bulb is
  1. 37.5 W
  2. 10 W
  3. 12.5 W
  4. 25 W
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Q. In a mercury thermometer, the ice point (lower fixed point) is marked as 100 and the steam point (upper fixed point) is marked as 1300. At 400C temperature, what will this thermometer read?
  1. 780
  2. 660
  3. 580
  4. 620
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Q. The de-Broglie wavelength of an electron moving with a velocity c2 (where c is velocity of light in vacuum) is equal to the wavelength of a photon. The ratio of the kinetic energies of electron and photon is:
  1. 2:1
  2. 1:2
  3. 1:1
  4. 1:4
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Q. The decimal number equivalent to a binary number 1011001 is:
  1. 13
  2. 178
  3. 17
  4. 89
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Q. A particle is travelling along a straight line OX. The distance x (in metre) of the particle from O at a time t is given by x=37+27tt3, where 't' is time in second. The distance of the particle from O , when it comes to rest is:
  1. 81 m
  2. 111 m
  3. 91 m
  4. 101 m
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Q. A Wheatstone bridge has the resistance 10Ω, 10Ω, 10Ω and 30Ω in its four arms. What resistance joined in parallel to 30Ω resistance will bring it to the balanced condition?
  1. 2Ω
  2. 10Ω
  3. 15Ω
  4. 5Ω
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Q. If A, B and C have scalar magnitudes of 5, 4, 3 units respectively, then the angle between A and C is:
469864.png
  1. cos1(3/5)
  2. cos1(4/5)
  3. π/2
  4. sin1(3/4)
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Q. The frequency of the first overtone of a closed pipe of length l1 is equal to that of the first overtone of an open pipe of length l2. The ratio of their lengths (l1:l2) is
  1. 3:4
  2. 2:3
  3. 4:5
  4. 3:5
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Q. Two element A and B with atomic numbers ZA and ZB are used to produce characteristic X-rays with frequencies vA and vB respectively. If ZA:ZB=1:2, then vA:vB will be
  1. 1:8
  2. 1:4
  3. 4:1
  4. 1:2
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Q. A box of mass 2 kg is placed on the roof of a car. The box would remain stationary until the car attains a maximum acceleration. Coefficient of static friction between the box and the roof of the car is 0.2 and g=10 ms2. This maximum acceleration of the car, for the box to remain stationary is :
  1. 6 ms2
  2. 4 ms2
  3. 2 ms2
  4. 8 ms2
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Q. Water is flowing through a very narrow tube. The velocity of water below which the flow remains a streamline flow is known as:
  1. relative velocity
  2. terminal velocity
  3. critical velocity
  4. particle velocity
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Q. If the velocity of light in vacuum is 3×108ms1, the time taken (in nanosecond) to travel through a glass plate of thickness 10 cm and refractive index 1.5 is :
  1. 0.5
  2. 1.0
  3. 2.0
  4. 3.0
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Q. In a slide caliper, (m+1) number of vernier divisions is equal to m number of smallest main scale divisions. If d units is the magnitude of the smallest main scale division, then the magnitude of the vernier constant is:
  1. dm units
  2. d(m+1) units
  3. md(m+1) units
  4. (m+1)dm units
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Q. Two infinite parallel metal planes, contain electric charges with charge densities +σ and σ respectively and they are separated by a small distance in air. If the permittivity of air is ϵ0, then the magnitude of the field between the two planes with its direction will be:
  1. σ/ϵ0 towards the positively charge plane
  2. σ/ϵ0 towards the negatively charged plane
  3. σ/(2ϵ0) towards the positively charged plane
  4. 0 and towards any direction
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Q. Heat is produced at a rate given by H in a resistor when it is connected across a supply of voltage V. If now the resistance of the resistor is doubled and the supply voltage is made V/3, then the rate of production of heat in the resistor will be
  1. H18
  2. 6H
  3. H9
  4. 18H
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Q. The magnetic flux linked with a coil satisfies the relation ϕ=4t2+6t+9 Wb, where t is the time in second. The emf induced in the coil at t=2s is
  1. 18 V
  2. 16 V
  3. 22 V
  4. 40 V
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Q. Average distance of the Earth from the Sun is L1. If one year of the Earth is equal to D days, then one year of another planet whose average distance from the Sun is L2 will be:
  1. D(L2L1)12days
  2. D(L2L1)32days
  3. D(L2L1)23days
  4. D(L2L1)days
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Q. When a spring is stretched by 10 cm, the potential energy stored is E. When the spring is stretched by 10 cm more, the potential energy store in the spring becomes:
  1. 2 E
  2. 4 E
  3. 6 E
  4. 10 E
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Q. From the top of a tower, 80 m high from the ground, a stone is thrown in the horizontal direction with a velocity of 8 ms1. The stone reaches the ground after a time 't' and falls at a distance of 'd' from the foot of the tower.
Assuming g=10 m/s2, the time 't' and distance 'd' are given respectively by:
  1. 6 s, 48 m
  2. 4 s, 16 m
  3. 4 s, 32 m
  4. 6 s, 64 m
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Q. A straight wire of length 2 m carries a current of 10 A. If this wire is placed in a uniform magnetic field of 0.15 T making an angle of 45 with the magnetic field, the applied force on the wire will be:
  1. 1.5 N
  2. 32 N
  3. 32N
  4. 3 N
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Q. A spherical ball A of mass 4 kg, moving along a straight line strikes another spherical ball B of mass 1 kg at rest. After the collision, A and B move with velocities v1 ms1 and v2 ms1 respectively making angles of 30 and 60 with respect to the original direction of motion of ball A. The ratio v1v2 will be:
  1. 34
  2. 43
  3. 13
  4. 3
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Q. In a region, the intensity of an electric field is given by E=2i+3j+k in NC1. The electric flux through a surface S=10i m2 in the region is:
  1. 10 Nm2C1
  2. 5 Nm2C1
  3. 20 Nm2C1
  4. 15 Nm2C1
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Q. The IV characteristics of a metal wire at two different temperatures (T1 and T2) are given in the adjoining figure. Here, we can conclude that:
469873.png
  1. T1>T2
  2. T1=T2
  3. T1=2T2
  4. T1<T2
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Q. A bullet on penetrating 30 cm into its target loses its velocity by 50%. What additional distance will it penetrate into the target before it comes to rest?
  1. 30 cm
  2. 10 cm
  3. 20 cm
  4. 5 cm
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Q. A train approaching a railway platform with a speed of 20 ms1, starts blowing the whistle. Speed of sound in air is 340 ms1. If the frequency of the emitted sound from the whistle is 640 Hz, the frequency of sound to a person standing on the platform will appear to be:
  1. 600 Hz
  2. 680 Hz
  3. 720 Hz
  4. 640 Hz
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Q. The dimension of angular momentum is
  1. [M1L2T2]
  2. [M0L1T1]
  3. [M1L2T1]
  4. [M2L1T2]
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