# Competitive Exams: Physics MCQs (Practice_Test 22 of 35)

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The gibb's function G in thermodynamics is defined as G = H-TS where H is the enthalpy, T is the temperature and S is the entropy. In an isothermal, isobaric, reversible process, G

remains constant, but not zero

varies linearly

varies non-linearly

is zero

Average of squares of displacements of particles in Brownian motion is

Directly proportional to temperature-T

directly proportional to viscosity-h

Directly proportional to radius of the particle-a

directly proportional to time-t

The order of magnitude of the mean free path of a diatomic molecule at STP is

1 cm

10 β 2 cm

10 β 5

10 β 8 cm

In the Vander Walls equation (p + a/v2) (v-b) = RT

βaβ and βbβ are the corrections for the cohesive forces

βaβ and βbβ are the corrections for the volume occupied by. The molecules

βaβ is the correction for the cohesive forces and βbβ is the correction for the volume occupied by the molecules

βaβ is the correction for the volume occupied by the molecules and βbβ is the correction for the cohesive forces

After Joule-Thomson expansion, the gas is

always heated

heated or cooled depending upon the initial temperature of the gas

neither heated nor cooled at any temperature

always cooled

If a black body radiation in a spherical cavity of volume V satisfies the relation, PVh = constant during a quasi-static isentropic process, then the numerical value of h should be

(7/5)

(5/3)

(4/3)

(3/2)

Consider the following statements regarding the paramagnetic materials:

Permanent magnetic moments interact with each other weakly.

Magnetization M varies inversely with absolute temperature T.

Magnetization M is much greater than the magnetic filed strength H.

Large permanent magnetization can be. Induced in these materials.

Of these statements

1 and 2 are correct

2 and 4 are correct

1, 2 and 3 are correct

1, 3 and 4 are correct

If a Rowland ring of mean radius 0.1 m had 2000 turns of wire wound on a ferromagnetic core of h = 1000, then, for a magnetizing current of 1.5 A, the magnetic field in the core would be

3 T

6 T

9 T

12 T

The electric potential point (x, y) in the x-y plane is given by V = -kxy. The field intensity at a distance βrβ from the origin varies as

r2

r

1/r

1/r2

A fast electron having a kinetic energy of 3.0 Γ 10 β 17 Joule enters a region of space containing a uniform electric field of E = 1000 volts/m. The field is parallel to the electron's motion and in a direction such as to decelerate it. The distance traveled by the electron before it is brought to rest (charge of electron = 1.6 Γ 10 β 19 C) will be

1.875 cm

18.75 cm

187.5 cm

1875 cm

At a point 20 cm from the centre of a uniformly k charged dielectric sphere of radius 10 cm, the electric field is 100 V/m. The electric field at3 cm from the centre of the sphere will be

150 V/m

125 V/m

120 V/m

zero

Two identical charged spheres of density 2.4 gm/cm3 suspended from the same point by strings of equal length 1.5 m, make an angle of 30 degree in air. If suspended in a liquid of density 0.8 gm/cm3 the angle remains the same. The dielectric constant of the liquid is

1.2

1.5

2.4

3.0

Which one of the following statements regarding the electric fields E1 = xi + yi and E2 = xy2 i + y3 j is correct?

Both E1 and E2 can represent electrostatic field

Neither E1 nor E2 can represent electrostatic field

Only E1 can represent electrostatic field

Only E2 can represent electrostatic field

The equivalent capacitance of the given circuit is

0.5 m f

1 m f

6.75 m f

9 m f

Consider the following statements: In electronics, capacitors are used for

tuning the resonant circuits.

bypassing alternating voltages.

storing electrical energy in the form of magnetic field.

blocking D C voltages from parts of an electrical circuit.

Of these statements

1, 2 and 4 are correct

1 and 2 are correct

2, 3 and 4 are correct

1 and 4 are correct