# WBJEE Previous Year (2010)

## 70 Questions MCQ Test WBJEE Sample Papers, Section Wise & Full Mock Tests | WBJEE Previous Year (2010)

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Attempt WBJEE Previous Year (2010) | 70 questions in 140 minutes | Mock test for JEE preparation | Free important questions MCQ to study WBJEE Sample Papers, Section Wise & Full Mock Tests for JEE Exam | Download free PDF with solutions
QUESTION: 1

### Experimental investigations show that the intensity of solar radiation is maximum for a wavelength 480 nm in the visible region. Estimate the surface temperature of sun. Given Wein’s constant b = 2.88 × 10–3 mK.

Solution:

λm × T = b
λm = 480 nm QUESTION: 2

### The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K, the root mean square speed of gas molecules is v, then at 480 K it will be

Solution:  QUESTION: 3

### Two mirrors at an angle θº produce 5 images of a point. The number of images produced when θ is decreased to θº – 30º is

Solution:

No. of images = 5
∴ θ = 60º
New angle = θ – 30º = 30º. No of images QUESTION: 4

he radius of the light circle observed by a fish at a depth of 12 meter is (refractive index of water = 4/3)

Solution: QUESTION: 5

In Young’s double slit experiment, the fringe width is β. If the entire arrangement is placed in a liquid of refractive index n, the fringe width becomes :

Solution:
QUESTION: 6

A plano-convex lens (f = 20 cm) is silvered at plane surface. Now focal length will be :

Solution: P = 2PL + PM
PM = 0 QUESTION: 7

The light beams of intensities in the ratio of 9 : 1 are allowed to interfere. What will be the ratio of the intensities of maxima and minima ?

Solution:  QUESTION: 8

If x1 be the size of the magnified image and x2 the size of the diminished image in Lens Displacement Method, then the size of the object is :

Solution:
QUESTION: 9

A point charge +q is placed at the centre of a cube of side L. The electric flux emerging from the cube is

Solution: Concept: Gauss Law. By Gauss theorem ... Total electric flux = Total charge inside cube /€. Flux = q/€. (where € is permittivity). Hence answer is 'A'.
QUESTION: 10

Two capacitors of equal capacity are first connected in parallel and then in series. The ratio of the total capacities in the two cases will be

Solution:
QUESTION: 11

n identical droplets are charged to v volt each. If they coalesce to form a single drop, then its potential will be

Solution:   QUESTION: 12

The reading of the ammeter in the following figure will be Solution:  QUESTION: 13

A wire of resistance R is elongated n-fold to make a new uniform wire. The resistance of new wire

Solution:

R' = n2R

QUESTION: 14

The ratio of magnetic field and magnetic moment at the centre of a current carrying circular loop is x. When both the current and radius is doubled the ratio will be

Solution:  QUESTION: 15

The current through a coil of self inductance L = 2mH is given by I = t2 e–t at time t. How long it will take to make the e.m.f. zero?

Solution:

I = t2 e–t  QUESTION: 16

The magnetic flux through a loop of resistance 10 Ω is given by φ = 5t2 – 4t + 1 Weber. How much current is induced in the loop after 0.2 sec ?

Solution:   QUESTION: 17

The decimal equivalent of the binary number (11010.101)2 is

Solution:

(11010.101) = 0 × 2º + 1 × 21 + 0 × 22 + 1 × 23 + 1 × 24 + 1 × 2–1 + 0 × 2–2 + 1 × 2–3 = 2 + 8 + 16 QUESTION: 18

In a common emitter configuration, a transistor has β = 50 and input resistance 1 kΩ. If the peak value of a.c. input is 0.01 V then the peak value of collector current is

Solution:  QUESTION: 19

Half-life of a radioactive substance is 20 minute. The time between 20% and 80% decay will be :

Solution:

For 20% decay For 80% decay On dividing QUESTION: 20

The energy released by the fission of one uranium atom is 200 MeV. The number of fissions per second required to produce 3.2 W of power is (Take 1 eV = 1.6 × 10–19 J)

Solution:

u = 200 MeV = 200 × 106 eV = 200 × 106 × 1.6 × 10–19 J
E = 3.2 J
No of fissions QUESTION: 21

A body is projected with a speed u m/s at an angle β with the horizontal. The kinetic energy at the highest point is 3/4th of the initial kinetic energy. The value of β is :

Solution: K.E. = K cos2 β QUESTION: 22

A ball is projected horizontally with a velocity of 5 m/s from the top of a building 19.6 m high. How long will the ball take of hit the ground ?

Solution:  QUESTION: 23

A stone falls freely from rest and the total distance covered by it in the last second of its motion equals the distance covered by it in the first three seconds of its motion. The stone remains in the air for

Solution:

u = 0 QUESTION: 24

Two blocks of 2 kg and 1 kg are in contact on a frictionless table. If a force of 3 N is applied on 2 kg block, then the force ofcontact between the two blocks will be : Solution: QUESTION: 25

If momentum is increased by 20%, then kinetic energy increases by

Solution: QUESTION: 26

A boy of mass 40 kg is climbing a vertical pole at a constant speed. If the coefficient of friction between his palms and the poleis 0.8 and g = 10 m/s2, the horizontal force that he is applying on the pole is

Solution: QUESTION: 27

The value of ‘λ’ for which the two vectors a =5iˆ+λ jˆ+kˆ  and b =iˆ−2jˆ+kˆare perpendicular to each other is

Solution: QUESTION: 28

If , then the angle included between and is

Solution: QUESTION: 29

The height vertically above the earth’s surface at which the acceleration due to gravity becomes 1% of its value at the surface is (R is the radius of the Earth)​

Solution: QUESTION: 30

The change in the gravitational potential energy when a body of mass m is raised to a height nR above the surface of the Earth is (here R is the radius of the Earth)

Solution: QUESTION: 31

A particle of mass m is attached to three identical massless springs of spring constant ‘k’ as shown in the figure. The time period of vertical oscillation of the particle is Solution: QUESTION: 32

A spring of force constant k is cut into three equal parts. The force constant of each part would be

Solution: QUESTION: 33

A body floats in water with 40% of its volume outside water. When the same body floats in oil, 60% of its volume remains outside oil. The relative density of the oil is ​

Solution:  QUESTION: 34

A uniform long tube is bent into a circle of radius R and it lies in vertical plane. Two liquids of same volume but densities ρ and δ fill  half the tube. The angle θ is Solution: QUESTION: 35

Two solid spheres of same metal but of mass M and 8 M fall simultaneously on a viscous liquid and their terminal velocities are v and nv then value of n is ​

Solution: QUESTION: 36

A particle is executing linear simple harmonic motion of amplitude A. At what displacement is the energy of the particle half potential and half kinetic ?

Solution: QUESTION: 37

The equation of a progressive wave is y = 4 sin (4πt – 0.04 x  + π/3) where x is in meter and t is in second. The velocity of the wave is

Solution: QUESTION: 38

A longitudinal wave is represented by x = x0 sin 2π(nt – x/λ). The maximum particle velocity will be four times the wave velocity if :

Solution: QUESTION: 39

A block of ice at temperature –20 ºC is slowly heated and converted to steam at 100 ºC. Which of the following diagram is most appropriate ?

Solution: QUESTION: 40

Two black bodies at temperatures 327 ºC and 427 ºC are kept in an evacuated chamber at 27 ºC. The ratio of their rates of loss of heat are :

Solution:  QUESTION: 41

At identical temperature and pressure, the rate of diffusion of hydrogen gas is 33 times that of a hydrocarbon having molecular formula CnH2n–2 . What is the value of ‘n’ ?​

Solution: QUESTION: 42

Dipole moment of is 1.5D. The dipole moment of is​

Solution: QUESTION: 43

Which of the following thermodynamic relation is correct ? ​

Solution: QUESTION: 44

In the hydrolysis of an organic chloride in presence of large excess of water; RCI + H2O → ROH + HCl​

Solution: QUESTION: 45

The potential of a hydrogen electrode at pH = 10 is​

Solution: QUESTION: 46

Calculate KC for the reversible process given below if KP = 167 and T = 8000C 32CaCO (s)  CaO(s) + CO (g)​

Solution: QUESTION: 47

For a reversible chemical reaction where the forward process is exothermic, which of the following statements is correct ?​

Solution: QUESTION: 48

In Sommerfeld’s modification of Bohr’s theory, the trajectory of an electron in a hydrogen atom is​

Solution:
QUESTION: 49

In the reaction of sodium thiosulphate with I2 in aqueous medium the equivalent weight of sodium thiosulphate is equal to ​

Solution: QUESTION: 50

0.1 (M) HCI and 0.1 (M) H2SO4 each of volume 2ml are mixed and the volume is made up to 6 ml by adding 2ml of 0.01 (N) NaCl solution. The pH of the resulting mixture is ​

Solution: QUESTION: 51

The molarity of a NaOH solution by dissolving 4 g of it in 250 ml water is ​

Solution: QUESTION: 52

If a species has 16 protons, 18 electrons and 16 neutrons, find the species and its charge​

Solution: QUESTION: 53

In a periodic table the basic character of oxides​

Solution:
QUESTION: 54

Which one of the following contains P – O – P bond ?​

Solution: QUESTION: 55

Which of the following orders regarding ionization energy is correct ? ​

Solution: QUESTION: 56

Which of the following statements regarding ozone is not correct ?​

Solution: QUESTION: 57

P4O10 is the anhydride of​

Solution:
QUESTION: 58

Which of the following metals has the largest abundance in the earth’s crust ?​

Solution:
QUESTION: 59

Which of the following orbitals will have zero probability of finding the electron in the yz plane ? ​

Solution:
QUESTION: 60

What type of orbital hybridisation is considered on P in PCl5 ? ​

Solution:
QUESTION: 61

For which element the inertness of the electron pair will not be observed?​

Solution:
QUESTION: 62

In which of the following molecules is hydrogen bridge bond present? ​ Solution:
QUESTION: 63

When a manganous salt is fused with a mixture of KNO3 and solid NaOH the oxidation number of Mn changes from +2 to​

Solution: QUESTION: 64

In hemoglobin the metal ion present is​

Solution:
QUESTION: 65

Ortho-and para-hydrogens have​

Solution:
QUESTION: 66

The bond order of CO molecule is ​

Solution:
QUESTION: 67

Vitamin  C is​

Solution:
QUESTION: 68

On mixing an alkane with chlorine and irradiating with ultra-violet light, it forms only one mono-chloro-alkane. The alkane is​

Solution:
QUESTION: 69

Keto-enol tautomerism is not observed in​

Solution:
QUESTION: 70

What is obtained when nitrobenzene is treated sequentially with (i) NH4Cl/Zn dust and (ii) H2SO4/Na2Cr2O7  ?

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