WBJEE | 2016

Q. In case of bipolar transistor

β = 45

. The potential drop across the collector resistance of

1 k Ω

5 V

. The base current is approximately

$55 μ A$
$222 μ A$
$111 μ A$
$45 μ A$

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Q. The vectors

\to A

and

\to B

are such that

∣ ∣ \to A + \to B ∣ ∣ = ∣ ∣ \to A - \to B ∣ ∣

. The angle between the two vectors will be

$0^{o}$
$60^{o}$
$90^{o}$
$45^{o}$

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Q. A gas bubble of

2 c m

diameter rises through a liquid of density

1.75 g

{c m}^{- 3}

with a fixed speed of

0.35 {c m s}^{- 1}

. Neglect the density of the gas. The co-efficient of viscosity of the liquid is

$870$ poise
$1120$ poise
$982$ poise
$1089$ poise

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Q. Equivalent capacitance between

A

and

B

in the figure is

$20 μ F$
$8 μ F$
$16 μ F$
$12 μ F$

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Q. If

x = a t + b t^{2}

where

x

is in metre (

m

) and

t

is in hour (

h

) then unit of

b

will be :

$m$
$m^{2} / h$
$m / h$
$m / h^{2}$

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Q. The work function of Cesium is

2.27 e V

. The cut-off voltage which stops the emission of electrons from a cesium cathode irradiated with light of

600 n m

wavelength is

$0.5 V$
$- 0.2 V$
$0.2 V$
None of the above
$- 0.5 V$

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Q. Two equal resistances,

400 Ω

each, are connected in series with a

8 V

battery. If the resistance of first one increases by

0.5

%, the change required in the resistance of the second one in order to keep the potential difference across it unaltered is to

increase it by $2 Ω$
increase it by $1 Ω$
increase it by $4 Ω$
decrease it by $4 Ω$

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Q. Two wires of same radius having lengths

l_{1}

and

l_{2}

and resistivities

ρ_{1}

and

ρ_{2}

are connected in series. The equivalent resistivity will be

$\frac{ρ_{1} l_{1} - ρ_{2} l_{2}}{l_{1} - l_{2}}$
$\frac{ρ_{1} l_{2} + ρ_{2} l_{1}}{l_{1} + l_{2}}$
$\frac{ρ_{1} l_{1} + ρ_{2} l_{2}}{l_{1} + l_{2}}$
$\frac{ρ_{1} l_{2} + ρ_{2} l_{1}}{ρ_{1} ρ_{2}}$

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Q. If the temperature of the Sun gets doubled, the rate of energy received on the Earth will increase by a factor of:

$2$
$4$
$8$
$16$

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Q. Light travels through a glass plate of thickness

t

having refractive index

μ

. If

c

be the velocity of light in vacuum, time taken by the light to travel through this thickness of glass is :

$\frac{t}{μ c}$
$\frac{t c}{μ}$
$\frac{μ t}{c}$
$μ t c$

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Q. The number of De-Broglie wavelengths contained in the second Bohr orbit of Hydrogen atom is

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Q. Two coils of self inductances

6 m H

and

8 m H

are connected in series and are adjusted for highest co-efficient of coupling. Equivalent self inductance

L

for the assembly is approximately

$50 m H$
$36 m H$
$28 m H$
$18 m H$

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Q. A Zener diode having break-down voltage

5.6 V

is connected in reverse bias with a battery of emf

10 V

and a resistance of

100 Ω

in series. The current flowing through the Zener is

$88 m A$
$4.4 m A$
$0.88 m A$
$44 m A$

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Q. At a particular height, the velocity of an ascending body is

\to u

. The velocity at the same height while the body falls freely is

$- \to u$
$2 \to u$
$\to u$
$- 2 \to u$

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1000

droplets of water having

2 m m

diameter each coalesce to form a single drop. Given the surface tension water is

0.72 N m^{- 1}

. The energy loss in the process is

$2.108 \times 10^{- 5} J$
$8.146 \times 10^{- 4} J$
$4.7 \times 10^{- 1} J$
$4.4 \times 10^{- 4} J$

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Q. Two bodies of masses

m_{1}

and

m_{2}

are separated by a distance

R

. The distance of the centre of mass of the bodies from the mass

m_{1}

$\frac{m_{2} R}{m_{1} + m_{2}}$
$\frac{m_{1} R}{m_{1} + m_{2}}$
$\frac{m_{1} m_{2}}{m_{1} + m_{2}} R$
$\frac{m_{1} + m_{2}}{m_{1}} R$

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Q. The velocity of sound in air at

20^{o} C

and

1

atm pressure is

344.2 m / s

. At

40^{o} C

and

2

atm pressure the velocity of sound in air is approximately

$356 m / s$
$350 m / s$
$363 m / s$
$370 m / s$

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Q. The wavelength of second Balmer line in Hydrogen spectrum is

600 n m

. The wavelength for its third line in Lyman series is :

$800 n m$
$400 n m$
$600 n m$
$200 n m$
None of the above

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Q. An electron enters an electric field having intensity

\to E = 3^i + 6^j + 2^k

V m^{- 1}

and magnetic field having induction

\to B = 2^i + 3^j T

with a velocity

\to V = 2 \to i + 3 \to j

{m s}^{- 1}

. The magnitude of the force acting on the electron is (Given

e = - 1.6 \times 10^{- 19} C

)

$2.02 \times 10^{- 18} N$
$5.16 \times 10^{- 16} N$
$3.72 \times 10^{- 17} N$
None of the above
$4.41 \times 10^{- 18} N$

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Q. A particle vibrating simple harmonically has an acceleration of

16 {c m s}^{- 2}

when it is at a distance of

4 c m

from the mean position. Its time period is

$1 s$
$6.028 s$
$3.142 s$
$2.572 s$

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Q. An

1 μ F

capacitor

C

is connected to a battery of

10 V

through a resistance

1 M Ω

. The voltage across

C

after

1

sec is approximately

$5.6 V$
$6.3 V$
$10 V$
$7.8 V$

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Q. If the r.m.s velocity of Hydrogen gas at a certain temperature is

c

, then the r.m.s velocity of Oxygen gas at the same temperature is

$\frac{c}{8}$
$\frac{c}{10}$
$\frac{c}{4}$
$\frac{c}{2}$

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Q. A ray of light strikes a glass plate at an angle of

60^{o}

. If the reflected and refracted rays are perpendicular to each other, the refractive index of glass is

$\frac{3}{2}$
$\frac{1}{2}$
$\sqrt{3}$
$\frac{\sqrt{3}}{2}$

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Q. The temperature of the water of a pond is

0^{o} C

while that of the surrounding atmosphere is

- 20^{o} C

. If the density of ice is

ρ

, coefficient of thermal conductivity is

k

and latent heat of melting is

L

then the thickness

Z

of ice layer formed increases as a function of time

t

as :

$Z^{2} = \frac{60 k}{ρ L} t$
$Z = \sqrt{\frac{40 k}{ρ L} t}$
$Z^{2} = \frac{40 k}{ρ L} \sqrt{t}$
$Z^{2} = \frac{40 k}{ρ L} t$

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Q. Angle between an equipotential surface and electric lines of force is :

$0^{o}$
$90^{o}$
$180^{o}$
$270^{o}$

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Q. The potential difference

V

required for accelerating an electron to have the de Broglie wavelength of

1 ˚ A

$100 V$
$125 V$
$150 V$
$200 V$

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Q. Work done for certain spring when stretched through

1 m m

10

joule. The amount of work that must be done on the spring to stretch it further by

1 m m

$30 J$
$40 J$
$10 J$
$20 J$

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Q. The perfect gas equation for

4 g

of hydrogen gas is

$P V = 2 R T$
$P V = R T$
$P V = \frac{1}{2} R T$
$P V = 4 R T$

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Q. For air at room temperature the atmospheric pressure is

1.0 \times 10^{5}

N m^{- 2}

and density of air is

1.2 k g

m^{- 3}

. For tube of length

1.0 m

closed at one end the lowest frequency generated is

84 H z

. The value of

γ

(ratio of two specific heats) for air is:

$2.1$
$1.5$
$1.8$
$1.4$

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Q. A hollow metal sphere of radius

R

is charged with a charge

Q

. The electric potential and intensity inside the sphere are respectively:

$\frac{Q}{4 π ϵ_{0} R^{2}}$ and $\frac{Q}{4 π ϵ_{0} R}$
$\frac{Q}{4 π ϵ_{0} R}$ and zero
Zero and sero
$\frac{4 π ϵ_{0} Q}{R}$ and $\frac{Q}{4 π ϵ_{0} R^{2}}$

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