Subject

Physics

Class

JEE Class 12

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JEE Physics 2008 Exam Questions

Multiple Choice Questions

11.

A jar filled with two non-mixing liquids 1 and 2 having densities ρ1 and ρ2 respectively. A solid ball, made of a material of density ρ3, is dropped in the jar. It comes to equilibrium in the position shown in the figure.
Which of the following is true for ρ1, ρ2 and ρ3?

  • ρ3 < ρ1 < ρ2

  • ρ1 < ρ3 < ρ2

  • ρ1 < ρ2 < ρ3

  • ρ1 < ρ3 < ρ2


D.

ρ1 < ρ3 < ρ2



As liquid 1 floats above liquid 2,
ρ1 < ρ2
The ball is unable to sink into liquid 2, ρ3 < ρ2
The ball is unable to rise over liquid 1
ρ1 < ρ3 Thus, ρ1 < ρ3 < ρ2

577 Views

12.

A spherical solid ball of volume V is made of a material of density ρ1. It is falling through a liquid of density ρ221). Assume that the liquid applies a viscous force on the ball that is proportional to the square of its speed v, i.e., Fviscous = −kv2 (k>0). The terminal speed of the ball is

  • square root of fraction numerator Vg left parenthesis straight rho subscript 1 minus straight rho subscript 2 right parenthesis over denominator straight k end fraction end root
  • Vgρ subscript 1 over straight k
  • square root of Vgρ subscript 1 over straight k end root
  • fraction numerator Vg left parenthesis straight rho subscript 1 minus straight rho subscript 2 right parenthesis over denominator straight k end fraction

A.

square root of fraction numerator Vg left parenthesis straight rho subscript 1 minus straight rho subscript 2 right parenthesis over denominator straight k end fraction end root

ρ1Vg − ρ2Vg = kv2T

rightwards double arrow space straight V subscript straight T space equals space square root of fraction numerator Vg space left parenthesis straight rho subscript 1 minus straight rho subscript 2 right parenthesis over denominator straight k end fraction end root

442 Views

13.

The speed of sound in oxygen (O2) at a certain temperature is 460 ms−1. The speed of sound in helium (He) at the same temperature will be (assumed both gases to be ideal)

  • 1420 ms−1

  • 550 ms−1

  • 375 ms−1

  • 650  ms−1


A.

1420 ms−1

straight v equals space square root of fraction numerator straight gamma space RT over denominator straight M end fraction end root
fraction numerator straight V subscript 1 over denominator space straight V subscript 2 end fraction space equals space square root of fraction numerator straight gamma subscript 1 straight M subscript 2 over denominator straight gamma subscript 2 straight M subscript 1 end fraction end root space equals space square root of fraction numerator begin display style 7 over 5 end style straight x 4 over denominator begin display style 5 over 3 end style straight x 32 end fraction end root
460 over straight V subscript 2 space equals space square root of fraction numerator 21 over denominator 25 space straight x 8 end fraction end root
rightwards double arrow space straight v subscript 2 space space equals space fraction numerator 460 space straight x space 5 space straight x space 2 square root of 2 over denominator square root of 21 end fraction space equals 1420 space ms to the power of negative 1 end exponent
886 Views

14.

While measuring the speed of sound by performing a resonance column experiment, a student gets the first resonance condition at a column length of 18 cm during winter. Repeating the same experiment during summer, she measures the column length to be x cm for the second resonance.Then 

  • 18 > x

  • x >54

  • 54 > x > 36 

  • 36 > x > 18


B.

x >54

straight n space equals space fraction numerator 1 over denominator 4 straight x end fraction space square root of γRT over straight M end root
xn space equals space 1 fourth square root of γRT over straight M end root
straight x space proportional to space square root of straight T
435 Views

15.

A parallel plate capacitor with air between the plates has a capacitance of 9 pF. The separation between its plates is ‘d’. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant k1 = 3 and thickness d/3 while the other one has dielectric constant k2 = 6 and thickness 2d/3 . Capacitance of the capacitor is now 

  • 1.8 pF 

  • 45 pF

  • 40.5 pF

  • 20.25 pF 


C.

40.5 pF

fraction numerator Aε subscript 0 over denominator begin display style straight d subscript 1 over 3 plus straight d subscript 2 over 6 end style end fraction space equals space fraction numerator Aε subscript 0 over denominator begin display style straight d over 9 plus fraction numerator 2 straight d over denominator 18 end fraction end style end fraction space equals space fraction numerator 18 space Aε subscript 0 over denominator 4 straight d end fraction


C' = 40.5 PF
162 Views

16.

A wave travelling along the x-axis is described by the equation y(x, t) = 0.005 cos (αx −βt). If the wavelength and the time period of the wave are 0.08 m and 2.0 s, respectively, then α and β in appropriate units are 

  • α = 25.00 π, β = π

  • α = 0.08/ π,  2.0/π

  • α = 0.04 / π , β =1.0/π

  • α = 12.50 , β =π/ 2.0


A.

α = 25.00 π, β = π

y = 0.005 cos (αx − βt)
comparing the equation with the standard form,

straight y space equals space straight A space cos space open square brackets open parentheses straight x over straight lambda minus straight t over straight T close parentheses 2 straight pi close square brackets
2 straight pi divided by straight lambda space equals space straight alpha space and space 2 straight pi divided by straight T space equals space straight beta
straight alpha space equals space 2 straight pi divided by 0.08
space equals space 25.00 space straight pi
straight beta space equals space straight pi

349 Views

17.

Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer.

The value of the unknown resistor R is

  • 13.75 Ω

  • 220 Ω

  • 110 Ω

  • 55 Ω


B.

220 Ω

50 over 22 space equals space straight R over 80 space
rightwards double arrow space straight R space equals space fraction numerator 55 space straight x space 8 over denominator 2 end fraction space equals space 220 space straight capital omega space
124 Views

18.

Two full turns of the circular scale of a screw gauge cover a distance of 1 mm on its main scale. The total number of divisions on the circular scale is 50. Further, it is found that the screw gauge has a zero error of − 0.03 mm while measuring the diameter of a thin wire, a student notes the main scale reading of 3 mm and the number of circular scale divisions in line with the main scale as 35. The diameter of the wire is

  • 3.32 mm 

  • 3.73 mm

  • 3.67 mm

  • 3.38 mm


D.

3.38 mm

Diameter = M.S.R. + C.S.R × L.C. + Z.E.
= 3 + 35 × (0.5/50) + 0.03
= 3.38 mm

245 Views

19.

A capillary tube (A) is dropped in water. Another identical tube (B) is dipped in a soap water solution.Which of the following shows the relative nature of the liquid columns in the two tubes? 


C.

Capillary rise h = 2T cosθ /ρgr. As soap solution has lower T, h will be low. 

796 Views

20.

An insulated container of gas has two chambers separated by an insulating partition. One of the chambers has volume V1 and contains ideal gas at pressure P1 and temperature T1. The other chamber has volume V2 and contains ideal gas at pressure P2 and temperature T2. If the partition is removed without doing any work on the gas, the final equilibrium temperature of the gas in the container will be

  • fraction numerator straight T subscript 1 straight T subscript 2 space left parenthesis straight P subscript 1 straight V subscript 1 space plus space straight P subscript 2 straight V subscript 2 right parenthesis over denominator straight P subscript 1 straight V subscript 1 straight T subscript 2 space plus space straight P subscript 2 straight V subscript 2 straight T subscript 1 end fraction
  • fraction numerator left parenthesis straight P subscript 1 straight V subscript 1 space straight T subscript 1 plus space straight P subscript 2 straight V subscript 2 straight T subscript 2 right parenthesis over denominator straight P subscript 1 straight V subscript 1 space plus space straight P subscript 2 straight V subscript 2 end fraction
  • fraction numerator left parenthesis straight P subscript 1 straight V subscript 1 space straight T subscript 2 plus space straight P subscript 2 straight V subscript 2 straight T subscript 1 right parenthesis over denominator straight P subscript 1 straight V subscript 1 space plus space straight P subscript 2 straight V subscript 2 end fraction
  • fraction numerator straight T subscript 1 straight T subscript 2 space left parenthesis straight P subscript 1 straight V subscript 1 space plus space straight P subscript 2 straight V subscript 2 right parenthesis over denominator straight P subscript 1 straight V subscript 1 straight T subscript 1 space plus space straight P subscript 2 straight V subscript 2 straight T subscript 2 end fraction

A.

fraction numerator straight T subscript 1 straight T subscript 2 space left parenthesis straight P subscript 1 straight V subscript 1 space plus space straight P subscript 2 straight V subscript 2 right parenthesis over denominator straight P subscript 1 straight V subscript 1 straight T subscript 2 space plus space straight P subscript 2 straight V subscript 2 straight T subscript 1 end fraction
405 Views

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