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An auditorium has volume of 105m3 and surface area of absorption 2 x 104m2.Its average absorption coefficient is 0.2 .The reverberation time of the auditorium in seconds is

If c is velocity of light in fre space,the time taken by the light to travel a distance x in a medium of refractive index μ is given by:

A sound wave passing through an ideal gas at NTP produces a pressure change of 0.001 dyne/cm2 during adiabatic compression. The corresponding change in temperature (γ=1.5 for the gas and atmospheric pressure is 1.013 x106 dynes/cm2) is

A wire of length 44cm is bent into a circle and a current of 9.8A is passed through it.The intensity of magnetic induction at the centre of the circle is

A bullet of mass 10 g is fired horizontally with a velocity 1000ms-1 from a rifle situated at a height 50 m above the ground. If the bullet reaches the ground with a velocity 500ms-1, the work done against air resistance in the trajectory of the bullet is : (g=10ms-2)

When an air bubble of radius r rises from the bottom to the surface of a lake. Its radius becomes 5r/4 (the pressure of the atmosphere is equal to the 10 m height to water column). If the temperature is constant and the surface tension is neglected the depth of the lake is

Which of the following Statements is not correct when a junction diode is in forward bias ?

In an n-type semiconductor, the Fermi energy level lies

Three condensers 1μF,2μF and 3μF are connected in series to a p.d of 330volt.The PD across the plates of 3μF is

Two unknown resistance X and Y are connected to left and right gaps of a meter bridge and the balancing point is obtained at 80 cm from left. When a 10Ω resistance is connected in parallel to X, the balance point is 50 cm from left. The values of X and Y respectively are

A liquid of mass M and specific heat S is at temperature 2t. If another liquid of thermal capacity 1.5 times at a temperature of t/3 is added to it,the resultant temperature will be

A proton is projected with a velocity 107ms-1 ,at right angles to a uniform magnetic field of induction 100mT.The time(in seconds)taken by the proton to traverse 900 arc is:(Mass of proton=1.65x10-27kg and charge of proton = 1.6x10-19C

In Young's double slit experiment,first slit has width four times the width of the second slit, the ratio of the maximum intensity to the minimum intensity in the interference fringe system is :

A bomb is dropped from an aircraft travelling horizontally at 150m/s at a height of 490m. The horizontal distance travelled by the bomb before it hits the ground is (in metre):

A galvanometer of resistance 20Ω is to be shunted so that only 1% of the current passes through it. Shunt connected is

The magnitude of maximum acceleration is π times that of maximum velocity of a simple harmonic oscillator. The time period of the oscillator in seconds is

A given mass of a gas is compressed isothermally until its pressure is doubled. It is then allowed to expand adiabatically until its original volume is restored and its pressure is then found to be 0.75 of its initial pressure.The ratio of the specific heats of the gas is approximately

Two charges of 50μC and 100μC are separated by a distance of 0.6m.The intensity of electric field at a point midway between them is

In Ramsden eyepiece, the two planoconvex lenses each of focal length / are separated by a distance 12 cm. The equivalent focal length (in cm) of the eyepiece is

Two condensers of capacities 4 μF and 5 μF are joined in series. The potential difference across 5 μF is 10 V then the potential difference across 4 μF condenser is:

A galvanometer of resistance 100Ω gives full scale deflection with 5mA current.To convert it into a 5 volt range voltmeter,the value of resistance connected in series is

Power radiated by a black body at temperature T1 is P and it radiates maximum energy at a wavelength λ1.If the temperature of the black body is changed from T1toT2,it radiates maximum energy at a wavelength λ1/2.The power radiated at T2 is

Two concentric circular coils A and B have radii 25cm and 15cm and carry currents 10A and 15A respectively.A has 24 turns and B has 18 turns.The direction of currents are in opposite order.The magnetic induction at the common centre of the coil is

A charged particle of mass 3 x 10-6 held stationary in spacing in an electric field of strength 106 NC-1 directed vertically downwards. The charge on the particle is :

A car of mass 400 kg and travelling at 72 kmph crashes into a truck of mass 4000 kg and travelling at 9 kmph, in the same direction. The car/bounces back at a speed of 18 kmph.The speed of truck after the impact is

A tension of 22 N is applied to a copper wire of cross-sectional area 0.02 cm2 Young’s modulus of copper is 1.1x1011 N/m2and Poisson’s ratio 0.32. The decrease in cross sectional area will be

An n-p-n transistor power amplifier in C-E configuration gives :

A light ray of wavelength λ is passing through a pin hole of diameter D and the effect is observed on a screen placed at a distance L from the pin hole. The approximations of geometrical optics are applicable if

In Sun, the important source of energy is

A parallel plate capacitor has a capacity 80x10-6 when air is present between the plates.The volume between the plates is then completely filled with a dielectric slab of dielectric constant 20. The capacitor is now connected to a battery of 30 V by wires. The dielelctric slab is then removed. Then, the charge that passes now through the wire is

A train is travelling at 120kmph and blows a whistle of frequency 1000Hz.The frequency of the note heard by a stationary observer if the train is approaching him and moving away from him are(Velocity of sound in air=330ms-1)nearly

A steady current is set up in a metallic wire of non-uniform cross-section. Then the drift velocity related the area of cross-section (A) as

Thomson coefficient of a conductor is 10μV/K.The two ends of it are kept at 500C and 600C respectively.Amount of heat absorbed by the conductor when a charge of 10C flows through it is

Two concentric circular coils A and B have radii 25cm and 15cm and carry currents 10A and 15A respectively.A has 24 turns and B has 18 turns.The direction of currents are in opposite order.The magnetic induction at the common centre of the coil is

A 2μF condenser is charged to 500 V and then the plates are joined through a resistance in joule is

Two identical piano wires have a fundamental frequency of 600 c/s when kept under the same tension. What fractional increase in the tension of one wire will lead to the occurrence of 6 beats per second when both wires vibrate simultaneously

A machine gun fires 360 bullets per minute. Each bullet moves with a velocity of 600ms-1, If the power of the gun is 5.4kw, the mass of each bullet is,

The de Broglie wavelength of an electron moving with a velocity of 1.5x108m/s is equal to that of a photon. The ratio of kinetic energy of the electron to that of the photon (C=3x108m/s)

X-rays of energy 50 KeV are scattered from a carbon target. The scattered rays are detected at 900 from the incident beam. the percentage change in wave length approximately [mo=9.0x10-31kg, c=3x108 m/sec] is

An open pipe resonates to a frequency f1 and a closed pipe resonates to a frequency f2.if they are joined together to form a longer tube, then it will resonate to a frequency of (neglect end corrections and consider fundamental frequencies)

A body is thrown horizontally from the top of a tower of 5 m height. It touches the ground at a distance of 10m from the foot of the tower. The initial velocity of the body is: (g = 10ms-2)

A source producing sound of frequency 170 Hz is approaching a stationary observer with a velocity of 17 ms-1. The apparent change in the wavelength of sound heard by the observer is: (speed of sound in air=340ms-1)

At least how many thermal neutrons should be available to start a fission reaction

Two tuning forks of frequencies 250 and 256 Hz produce beats.If maximum is produced now,thus the minimum time after which minimum is produced at that same place

Light wave of frequency 4x1014Hz and λ=5x10-7m passes through a medium.The refractive index μ then the focal length of lens is

An observer is moving away from a sound source of frequency 100Hz. If the observer is moving with a velocity 49m/s and the speed of sound in air is 330m/s. The observed frequency is:

Two wires of same material and same length have their resistances in the ratio 5:7.The ratio of the masses of the wires is

Two charges each of 100 micro coulomb are separated in a medium of relative permittivity 2 by a distance of 5cm.The force between them is

A fire engine with its bell ringing with a frequency of 200 Hz is moving with a velocity of 54 kmph towards an observer at rest near a hut on fire. The apparent frequency of sound heard by the observer is (velocity of sound in air = 300ms-1)

A body is thrown vertically upward with an initial velocity u reaches maximum height in 6 sec.The ratio of distance travelled by the body in the first and seventh second is :

Two charges 2C and 6C are separated by a finite distance. If a charge of -4C is added to each of them, the initial force of 12 x 103 N will change to

The energy stored in a sphere of 10cm radius when the sphere is charged to a potential of 300 volt is

An electron beam moving with a speed of 2x107ms-1 enters a magnetic field of induction 3x10-3T, directed perpendicular to its direction of motion. The intensity of electric field applied so that the electron beam is undeflected due to the magnetic field is

A sonometer consists of two wires of same material whose radii are in the ratio2:3.The tension in thick wire is 4 times the tension in thin wire.If V is velocity of transverse were in thin wire,then the velocity of transverse wave in thick wire is

Δλ is the difference between the wave length of kα line and the minimum wavelength of the continuous X-ray spectrum when the X-ray tube is operated at a voltage V. If the operating voltage is changed to v/3 , then the above difference is Δλ'. Then :

Two positive charges q1=4x10-6C and q2=9x10-6C are placed 10cm apart in air.The position of a third charge to be placed between them,such that there will be no resultant force on it is

The emf of a Cu-Fe thermocouple varies with the temperature T of the hot junction, the cold junction being at 100C, as Vinμv=14T-0.02T2.Determinate the neutral temperature and the of inversion.

A motor of power P0 is used to deliver water at a certain rate through a given horizontal pipe. To increase the rate of flow of water through the same pipe n times, the power of the motor is increased to P1 The ratio of P1 to P0 is

A car moving with a speed of 72kmph towards a hill.Car blows horn at a distance of 1800m from the hill.If echo is heard after 10s,the speed of sound (in ms-1) is

Two tuning forks A and B produce 6 beats per second when sounded together. When B is slightly loaded with wax the beats are reduced to 4 per second. If the frequency of A is 512 Hz the frequency of B is

A prism of refractive index μ and angle A is placed in the minimum deviation position. If the angle of minimum deviation Is A, then the value of A in terms of μ is

In order to double the frequency of the fundamental note emitted by a stretched string, the length is reduced to 3/4th of the original length and the tension is changed. The factor by which the tension is to be changed is:

The coil in a MCG has an area of 4cm2 and 500 turns.The intensity of magnetic induction is 2T.when a current of 10-4A is passed through it,the deflection is 200.The couple per unit twist is(N-m)

If the work done in stretching a wire by 1mm is 2J,the work necessary for stretching another wire of same material but with double radius of cross-section and half the length by 1mm(in joule) is:

The frequency of the sound of a car horn as recorded by an observer towards whom the car is moving differs from the horn by 10%. Assuming the velocity of sound in air to be 330ms-1, the velocity of the car is

Two tuning forks of frequencies 250 and 256 Hz produce beats. If maximum is produced now, thus the minimum time after which minimum is produced at that same place

A stretched wire of some length under a tension is vibrating with its fundamental frequency. Its length is decreased by 45% and tension is increased by 21%.Now its fundamental frequency

A bar magnet of magnetic moment M and moment of inertia I is freely suspended such that the magnetic axial line is in the direction of magnetic meridian. If the magnet is displaced by a very small angle (θ), the angular acceleration is (Magnetic induction of earth's horizontal field = BH)

The frequency of the sound of a car horn as recorded by an observer towards whom the car is moving differs from the frequency of the horn by 10%.Assuming the velocity of sound in air to be 330ms-1,the velocity of the car is

If vibrating tuning fork of frequency 255Hz is moving with a velocity 4 ms-1 towards the wall the number of beats heard per second is (speed of found in air = 340 ms-1)

The equation connecting thermo emf with the temperature difference between the junctions 't' of a thermocouple, whose cold junction is maintained at 00C, is given by e = 2040 t - 6.2 t2. The neutral and inversion temperatures of the thermocouple in C .ire respectively and nearly equal to:

A body of mass m is suspended to an ideal spring of force constant k. The expected change in the position of the body due to an additional force F acting vertically downwards is

Two ions having masses in the ratio 1:1 and charges 1 : 2 are projected into uniform magnetic field perpendicular to the field with speeds in the ratio 2:3. The ratio of the radii of circular paths along with the two particles move is

The dark lines in the solar spectrum are due to:

A beam of charged particles of charge 'q' and mass m are accelerated from rest through a potential difference of 100 volts. They pass through crossed electric and magnetic fields which together produce null deflection. If these electronic and magnetic fields are respectively 15xl03 volts/m and 5weber/m2, then 'q/m' has a value, in coulomb/kg, equal to :

A small square loop of wire of side l is placed inside a large square loop of side L(L>>1). If the loops are coplanar and their centres coincide, the mutual induction of the system is directlv proportional to :

In a full wave rectifier output is taken across a load resistor of 800ohm.If the resistance of diode in forward biased condition is 200 ohm,the efficiency of reflection of rectification of ac power into dc power is

A source of sound vibrating with a frequency 510Hz is in between a stationary observer and a fort wall, if source is moving towards observer with velocity 3m/s, the number of beats produced by the observer is (velocity of sound in air is 340m/s)

A wire of length 1m and negligible mass is fixed at one end ,and a sphere attached to it at the other end.The sphere is projected horizontally with velocity√90ms-1 and it describes a vertical circle. The elongation in the wire when the sphere is at the top position is e.Now the elongation in the wire when the sphere is at bottom position is(g=10ms-2),the stress in the wire at bottom position is within elastic limit)

The two lenses of an achromatic doublet should have

A. ball of mass m moving with a velocity V*collides head on elastically with another of the same mass m but moving with a - V (in the opposite direction). After the collision :

In a meterbridge experiment,the balance length is 40cm.the resistance in the gap opposite to this length of wire is 8 ohm.The resistance in the other gap is

A certain block weights 15N in air. But it weighs only 12N when completely immersed in water. When immersed in another liquid, it weighs 13N. The ratio of relative density of the block and the liquid

A coil has 1,000 turns and 500cm2 as its area.The plane of the coil is placed at right angles to a magnetic induction field of 2x10-5web/m2.The coil is rotated through 1800 in 0.2 seconds.The average emf induced in the coil,in milli volts,is

A pipe having an internal diameter ‘D’ is connected to anther pipe of same size. water flows into the second pope through ‘n’ holes, each of diameter ‘d’. If the water in the first pipe has speed ‘V’, the speed of water leaving the second pipe is

The volume of a cinema theatre is 100mx60mx20m and total acoustic absorption in it is 6800metric sabine.The reverberation time in that theatre is

If the cold junction is held at 00C, the same thermo emf V of a thermocouple varies as V = 10 x 10 6t - * x 10 bt2, where t is the 40 temperature of the hot junction in 0C. The neutral temperature and the maximum value of thermo emf are respectively:

A car travels the first half of a distance between two places a speed of 30 km/hr and the second half of the distance a 50km/hr. The average speed of the car for the whole journey is

In Millikans oil drop experiment, an oil drop of radius r charge q falls under the gravity with a terminal velocity Vg and moves up with a terminal velocity Ve in the uniform vertical electric field of intensity E. If η is coefficient of viscosity of air, the charge of oil drop is

A capacitor of 8 μF is charged to a potential of 1000V. The energy stored in the capacitor is

A small amplitude progressive wave in a stretched string has a velocity of 10ms-1 and frequency of 100Hz.What is the phase differences, in radians between two points 5cm apart in the string?

The ratio of surface areas of the two spheres is 9:16.They are put in contact and a charge of 7μC is given to the system and they are separated. Then the intensity of the electric field at a distance of 100m from the centre of smaller sphere is

The velocity of a listener who is moving away from a stationary source of sound such that the listener notices 5% apparent decrease in frequency of sound is(Velocity of sound in air=340ms-1)

Two vibrating tuning forks produce vibrations at the tympanic of an observer represented by y1=4sin(260 πt) and y2=4sin(256 πt).The number of beats heard by the observer in one minute is

Two spheres of radii 12 cm and 16 cm have equal charge. The ratio tstored in the condenser is

When a vibrating tuning fork is placed on a sound box of a sonometer, 8 beats per second are heard when the length of the sonometer wire is kept at 101 cm or 100 cm. Then the frequency of the tuning fork is (consider that the tension in the wire is kept constant)

The coils A and B having the radii in the ratio 1:2 carrying currents in the ratio 5:1 and have the number of turns in the ratio 1:5.The ratio of magnetic inductions at their centres is

The pole strength of a 12 cm long bar magnet is 2.0 A-m. The magnetic induction at a point 10 cm away from the centre of the magnet on the axial line is (μ0/4∏=10-7Hm-1)

The crictical angle for light going from a medium in which wavelength is 4000A0 to medium in which wavelength is 6000A0

Two point charges are separated by 3 cm of air and 3 cm of a dielectric of relative permittivity 4.The equivalent air separation between them is (as far as their coulombic interaction is concerned)

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