# Competitive Exams: Physics MCQs (Practice_Test 1 of 35)

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The Farenheit and the Centrigrade scales have the same numerical value at a temperature of

-30 degrees

-40 degrees

-100degrees

-273degrees

van der Waals'equation of state of a gas takes into account

the intermolecular forces only

the size of the molecule only

both the intermolecular forces and the size of the molecule

the velocity of the molecules only

The First Law of Thermodynamics, U =? Q-? W indicates that when a system goes from its initial state to a final state

? U is the same for the every path

? Q is the same for every path

? W is the same for every path

? U and? Q are the same for every path

Which one of the following properties of a body remains constant during a reversible adiabatic process?

Enthalpy

Temperature

Specific heat

Entropy

A heat engine work on a Carnot cycle with the heat sink at a temperature of 27 degrees C. If the efficiency is 20%, then the temperature (in Kelvin) of the heat source will be

375 degrees

300 degrees

270 degrees

150 degrees

Which one of the following figures correctly represents the temperature (T) -entropy (S) diagram (T in absolute scale) of a Carnot cycle?

A

B

C

D

Given that H = the enthalpy of a system T = absolute temperature and S = entropy G = H-TS is the Gibbs function for the system. In the case of a reversible, isothermal, isobaric process

G = constant

G > 0 and changes with T

G < 0 and changes with S

G changes with both T and S

Maxwell's law of distribution of velocities shows that

all particles have the same velocity

all velocities are equally probable

the particles have varying energies depending on their speeds

all particles have the same energy but different velocities

A molecular is at temperature T (in Kelvin). According to the theorem of equi-partition of energy, the energy associated with each degree of freedom is

⅓ KBT

½ KBT

KBT

3/2 KBT

If the temperature of a black body is increased, then the maximum of the spectrum will

shift towards shorter wavelength

shift towards shorter frequency

shift towards the shorter or longer wavelength depending on the nature of the black body

not shift

If two particles of same mass having charges + q and + 9q, are allowed to fall from rest through the same electric potential difference, then their speeds will be in the ratio of

3: 1

1: 3

1: 9

9: 1

In the circuit shown in the above figure, the charge on capacitor C3 will be

1.7 m coulomb

1.5 m coulomb

2.5 m coulomb

5 m coulomb

Liquid dielectrics having polar molecules, such as water, always have dielectric constants that

increase with decreasing temperature

increase with increasing temperature

decrease with decreasing temperature

are independent of temperature

A parallel plate capacitor is connected to a battery. Consider the following statements in this regard: If a metal sheet of negligible thickness is placed parallel to the plates of the capacitor

the battery will supply more charge

the capacitance will increase

the potential difference between the plates will increase

equal and opposite charges will appear on the two faces of the metal plate

Which of the above statement (s) is/are correct?

1 alone

4 alone

1 and 2

2 and 3