Focus Guide for 12th Physics. We covered all the Focus Guide for 12th standard Physics pdf free download in English Medium in this post for free so that you can practice well for the exam.
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Focus Guide for 12th Physics Objective for Students
Which one among the following doesn’t have any effect on the velocity of sound?
(a) Pressure
(b) Temperature
(c) Humidity
(d) Density
Option a – Pressure
Sound waves are similar to the waves:
(a) of laser light passing through the air
(b) generated in a stretched wire by hitting or plucking the wire
(c) generated in a pipe filled with air by moving the piston attached to the pipe up and down
(d) generated by the mobile phone towers
Option c – generated in a pipe filled with air by moving the piston attached to the pipe up and down
Planet A has double the radius than that of Planet B. If the mass of Planet A is 4 times heavier than the mass of Planet B, which of the following statements regarding the weight of an object is correct?
(a) Heavier on Planet A than on Planet B
(b) Heavier on Planet B than on Planet A
(c) Same on both the Planets
(d) Cannot be measured on Planet B
Option c – Same on both the Planets
A fuse is used in an electric circuit to:
(a) break the circuit when excessive current flows through the circuit
(b) break the circuit when the power goes off
(c) indicate if the current is flowing uninterrupted
(d) complete the circuit for the flow of current
Option a – break the circuit when excessive current flows through the circuit
In optical instruments, the lenses are used to form an image by the phenomenon of:
(a) reflection
(b) refraction
(c) scattering
(d) diffusion
Option b – refraction
The motion of a body around a circular path is an example of:
(a) Uniform velocity, variable acceleration
(b) Uniform speed, uniform velocity
(c) Uniform speed, variable velocity
(d) Uniform speed, variable acceleration
Option c – Uniform speed, variable velocity
A current-carrying conductor is associated with:
(a) a magnetic field
(b) an electric field
(c) an electromagnetic field
(d) an electrostatic field
Option a – a magnetic field
The linear expansion of a solid rod is independent of its:
(a) initial length
(b) material
(c) increase in temperature
(d) time of heat flow
Option d – time of heat flow
Heat is transferred most rapidly by the process of
(A) Conduction
(B) Convection
(C) Radiation
(D) Combustion
Option c – Radiation
For a perfectly black body, its absorptive power is :
(A) 1
(B) 0.5
(C) 0
(D) infinity
Option a – 1
Heat is transmitted from higher to lower temperatures through the actual mass motion of the molecules in
(A) Conduction
(B) Convection
(C) Radiation
(D) Combustion
Option b – Convection
An electric heater, kept in a vacuum, is heated continuously by passing an electric current. Its temperature :
(A) Will go on rising with time
(B) Will stop rising after some time as it will lose heat to the surroundings by conduction
(C) Will rise for some time and thereafter will start falling
(D) Will become constant after some time because of loss of heat due to radiation
Option d – Will become constant after some time because of loss of heat due to radiation
Calculate the RMS velocity of molecules of a gas of which the ratio of two specific heats is 1.42 and the velocity of sound in the gas is 500 m/s :
(A) 727 m/s
(B) 527 m/s
(C) 927 m/s
(D) 750 m/s
Option a – 727 m/s
Sun’s heat reaches us by
(A) Conduction
(B) Convection
(C) Radiation
(D) Scattering
Option c – Radiation
The ratio of specific heat of a gas is 1.4. Its specific heat at a constant volume is 4.96 cal/mol K. Then the universal gas constant is
(A) 8.3 cal/mol K
(B) 0.0821 cal/mol K
(C) 1.984 cal/mol K
(D) 62.3 cal/mol K
Option c – 1.984 cal/mol K
Specific heats of carbon dioxide at constant pressure and constant volume are 833 J/kg Kand 641 J/kg K respectively. The universal gas constant Ris :
(A) 192 J/kmol K
(B) 0.821 J/kmol K
(C) 8.31 J/kmol K
(D) 8448 J/kmol K
Option d – 8448 J/kmol K
The factor not needed to calculate heat lost or gained when there is no change of state is :
(A) Weight
(B) Specific heat
(C) Change in temperature
(D) Relative density
Option d – Relative density
Molar specific heat of oxygen at constant pressure Cp = 7.2 cal/mol °C and R 8.3 J/mol K. At F constant volume 5 mol of oxygen is heated from 10°C to 20°C, the quantity of heat required is :
(A) 25 cal
(B) 50 cal
(C) 260 cal
(D) 500 cal
Option c – 260 cal
The specific heat of a gas in an isothermal process is :
(A) Infinite
(B) Zero
(C) Negative
(D) Remains constant
Option a – Infinite
For a monoatomic gas, the molar specific heat at constant pressure divided by the molar gas constant R is equal to
(A) 2.5
(B) 1.5
(C) 5.0
(D) 3.5
Option a – 2.5
At constant pressure, the temperature of 56 grams of nitrogen is raised by 5°C. If the value of the universal gas constant is 8.31 J/mol K, then the work done by the gas will be :
(A) 8.31 J
(B) 41.5 J
(C) 83.1 J
(D) 8.15 J
Option c – 83.1 J
The RMS velocity of hydrogen gas molecules at NTP is V m/s. The gas is heated at constant volume till the pressure becomes four times. The final RMS velocity is :
(A) 2V
(B) 4V
(C) V
(D) V/2
Option c – V
A gas at a pressure P is contained in a vessel. If the masses of all the molecules are halved and their speeds doubled, the resulting pressure will be
(A) P/2
(B) P
(C) 2P
(D) 4P
Option c – 2P
Gases exert pressure on the walls of the container because the gas molecules :
(A) Have finite volume
(B) Obey Boyle’s law
(C) Possess momentum
(D) Collide with one another
Option d – Collide with one another
Gases exert pressure on the walls of the containing vessel because the gas molecules :
(A) Possess momentum
(B) Have finite volume
(C) Collide with each other
(D) Obey gas laws
Option a – Possess momentum
If a molecule of a gas encounter elastic collision against the wall of the vessel then :
(A) It will rebound with the same velocity
(B) It will rebound with the increased velocity
(C) It will rebound with the reduced velocity
(D) It will rebound with the same speed
Option d – It will rebound with the same speed
At constant volume, the temperature is increased. Then :
(A) Collisions on walls will be less
(B) the Number of collisions per unit of time will increase
(C) Collisions will be in straight lines
(D) Collisions will not change
Option b – the Number of collisions per unit of time will increase
The mean free path of a gas is directly proportional to
(A) Density
(B) Temperature
(C) Pressure
(D) Molecular diameter
Option b – Temperature
The mean free path is inversely proportional to
(A) Molecular diameter
(B) the Fourth power of the molecular diameter
(C) the Square root of the molecular diameter
(D) the Square of the molecular diameter
Option d – the Square of the molecular diameter
If a gas molecule of mass m moving with velocity u hits a wall and rebounds, then the change in momentum of the molecule is :
(A) mu
(B) – mu
(C) – 2mu
(D) 0
Option c – – 2mu
For the given gas, the molecular density at any point is :
(A) Variable
(B) Infinite
(C) Zero
(D) Constant
Option d – Constant
If the increase in the volume of a gas is dV against constant pressure P, the work done by the gas is :
(A) – PdV joule
(B) – PdV calorie
(C) + PdV joule
(D) + PdV calorie
Option c – + PdV joule
A gas exerts pressure on the walls of the container because
(A) Gas has weight
(B) Gas molecules have momentum
(C) Gas molecules collide with each other
(D) Gas molecules collide with the walls of the container
Option d – Gas molecules collide with the walls of the container
The pressure of a given mass of gas at constant temperature is P and its volume is V. Then PV versus V graph is :
(A) Hyperbola
(B) Straight line parallel to V- the axis
(C) Straight line parallel to PV – axis
(D) Straight line having slope 1
Option b – Straight line parallel to V- the axis
Molecules of a gas behave :
(A) An inelastic rigid sphere
(B) An elastic rigid sphere
(C) An inelastic nonrigid sphere
(D) Perfectly elastic nonrigid spheres
Option b – An elastic rigid sphere
A gas is enclosed in a container which is then kept on a fast-moving train. The temperature of the gas :
(A) Falls
(B) Remains unchanged
(C) Rises
(D) Becomes unsteady
Option b – Remains unchanged
The correct value of 0°C on the Kelvin scale is :
(A) 273 K
(B) OK
(C) 273.15 K
(D) 273.16 K
Option c – 273.15 K
In the equation, PV = NkT, V stands for
(A) Volume of N liters of gas
(B) Volume of N-gram of gas
(C) Volume of N molecules of a gas
(D) Volume of N moles of gas
Option c – Volume of N molecules of a gas
The temperature at which the volume of all the gases is zero is :
(A) + 274 K
(B) – 273 °C
(C) 273 °C
(D) – 273 K
Option b – – 273 °C
Attractive forces and size effects in a real gas can be neglected at :
(A) Low pressure
(B) High temperature
(C) Low pressure and high temperature
(D) Low temperature and high pressures
Option c – Low pressure and high temperature
The relation PV = RT describes the behavior of a real gas at :
(A) High temperature and high density
(B) High temperature and low density
(C) Low temperature and low density
(D) Low temperature and high density
Option b – High temperature and low density
The perfect gas equation for 4 grams of hydrogen gas is :
(A) PV = RT
(B) PV = 2RT
(C) PV = RT/2
(D) PV = 4RT
Option b – PV = 2RT
According to the kinetic theory of gases, the intermolecular forces between the gas molecules are :
(A) Zero
(B) Small
(C) Large
(D) Very large
Option a – Zero
If the pressure in a closed vessel is reduced by drawing out some gas, the mean free path of the molecules :
(A) Is increased
(B) Is decreased
(C) Remains unchanged
(D) Increases or decreases according to the nature of the gas
Option a – Is increased
The absolute temperature of a gas is determined by :
(A) The average momentum of the molecules
(B) The velocity of sound in the gas
(C) The number of molecules in the gas
(D) The RMS velocity of the molecules
Option d – The RMS velocity of the molecules
The molar gas constant is the same for all gases because, at the same temperature and pressure, equal volumes of gases have the same :
(A) Density
(B) Kinetic energy
(C) Ratio of specific heat capacities
(D) Number of molecules
Option d – Number of molecules
An ideal gas is that which can : ( focus guide for 12th physics )
(A) Be solidified
(B) Be liquefied
(C) Not be liquefied
(D) Not be solidified
Option c – Not be liquefied
The product of the pressure and volume of an ideal gas is :
(A) A constant
(B) Approximately equal to the universal gas constant
(C) Inversely proportional to its temperature
(D) Directly proportional to its temperature
Option d – Directly proportional to its temperature
At a given volume and temperature the pressure of a gas :
(A) Varies inversely as its mass
(B) Varies inversely as the square root of its mass
(C) Varies linearly as its mass
(D) Is independent of its mass
Option c – Varies linearly as its mass
The mean free path in gas is : ( focus guide for 12th physics )
(A) The distance traveled by a molecule before hitting a wall
(B) The average distance traveled by a molecule in one second
(C) The average distance traveled by molecules between any two successive collisions
(D) The RMS velocity
Option c – The average distance traveled by molecules between any two successive collisions
At zero degree kelvin, which of the following properties of gas will be zero?
(A) Density
(B) Potential energy
(C) Kinetic energy
(D) Vibrational energy
Option c – Kinetic energy
The equation for an ideal gas is PV = RT, where V represents the volume of
(A) 1 gram of a gas
(B) Any mass of a gas
(C) One mole of a gas
(D) One liter of a gas
Option c – One mole of a gas
The change in temperature of a body is 50°C. The change on the Kelvin scale is :
(A) 50 K
(B) 323 K
(C) 70 K
(D) 30 K
Option a – 50 K
The kinetic theory of gases breaks down most at ( focus guide for 12th physics )
(A) Low-pressure and high temperature
(B) High pressure and low temperature
(C) Low pressure and low temperature
(D) High pressure and high temperature
Option b – High pressure and low temperature
The parts of motorcars are polished with chromium because the angle of contact between water and chromium is :
(A) 0⁰
(B) 90⁰
(C) Less than 90⁰
(D) More than 90⁰
Option d – More than 90⁰
Pure water has a surface tension of T. When soap is added to water, its surface tension becomes T₁, and when sugar is added to water the surface tension becomes T₂. Then :
(A) T₁ < T < T₂
(B) T₁ > T > T₂
(C) T₁ = T₂ = T
(D) T₁ >T > T₂
Option a – T₁
A liquid rises to a height of 1.8 cm in a glass capillary ‘A’. Another glass capillary ‘B’ having a diameter of 90% of capillary ‘A’ is immersed in the same liquid. The rise of liquid in capillary ‘B’ is :
(A) 1.4 cm
(B) 1.8 cm
(C) 2.0 cm
(D) 2.2 cm
Option c – 2.0 cm
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