A to Z Exams

In a parallel plate air capacitor of capacitance 4 farad, if the lower half of air space is filled with a material of dielectric constant 3 its capacitance changes to

The wavelength of blue light in air is 45000A if the refractive index for blue light is 1.55 in glass what will be the wavelength of blue light in glass(c=3x108m/s)its frequency is

A mass of 12 kg at rest explodes into two pieces of masses 4 kg and 8 kg which move in opposite directions. If the velocity of 8 kg piece is 6 m/s, then the kinetic energy of the other piece is (in joule):

A parallel plate capacitor has a capacitance of 10 micro farads without dielectric. A dielectric of dielectric constant 2 is used to fill exactly half the thickness between the plates. The capacitance in micro farads,now 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 trains are approaching each other on parallel tracks with same velocity.The whistle sound produced by one train is heard by a passenger in another train.If actual frequency of whistle is 620Hz and apparent increase its frequency is 100Hz,the velocity of one of the two trains is(Velocity of sound in air=335ms-1)

When two capacitors are joined in series the resultant capacity is 2.4 μF and when the same two are joined in parallel the resultant capacity is 10μF.their individual capacities are

Two strings x and y on a Veena playing the same note are slightly out of tune and produce 6 beats per second. The tension in x is slightly decreased and it is found tha the beats fall to 3 per second. If the original frequency of x is 324 Hz, the frequency of y is

The area of the coil in moving coil galvanometer is 80 cm2 and its has 200 turns. The magnetic induction of the radial field is 0.2T and the couple per unit twist of the suspension wire is 2 x 10-6Nm per degree. If the deflection is 40,the current passing through it is

In a transistor if IC/IE and IC/IB=β.If α varies between 20/21 and 100/101,then the value of β lies between

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

In a p-n junction the depletion region is 400nm wide and electric field of 5x105Vm-1 exists in it. The minimum energy of a conduction electron, which can diffuse from n-side to the p-side is

An electrical meter of internal resistance 20Ω gives full scale deflection when one milliampere current flows through it.The maximum current that can be measured by using three resistors of resistance 12Ω each,in milliamperes is

In an experiment of photoelectric emission, for incident light of 4000A0, stopping potential is 2V. If the wavelength of incident light is made 3000A0, then the stopping potential will be

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:

With a standard rectangular bar magnet of length (l), breadth (b; b < < l) and magnetic moment M, the time period of the magnet in a vibration magnetometer is 4 s. If the magnet is cut normal to its length into four equal pieces, the time period (in seconds) with one of the pieces is :

If two identical bar magnets, each of length l, pole strength m and magnetic moment  M are placed perpendicular to each other with their unlike poles in contact, the magnetic moment of the combination is :

Charge 20,30,-40 and 50 μC are at the corners of a square of 10cm. The field at the point of intersection of the diagonals is

A stone is projected vertically up to reach maximum height h, The ratio of its kinetic energy to its potential energy, at a height (4/5) h, will be :

A motor car approaching a cliff with a velocity of 90 kmph sounds the horn and the echo is heard after 20 seconds.Assuming the velocity of sound in air to be 332m/s,the distance between the car and cliff when the horn is sounded is

One mole of a gas occupies 100 ml at 50 mm pressure.The volume of 2 mole of the gas at 100 mm pressure and same temperature is

A cylindrical resonance tube open at both ends has a fundamental frequency “f’ in air.If half of the length is dipped vertically in water,the fundamental frequency of the air column will be

Two organ (open) pipes of lengths 50 cm and 51 cm produce 6 beats/s. Then the speed of sound is nearly

A transistor having a β equal to 80 has a change in base current of 250μA,then the change in collector current is :

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

A long string with a charge of λ per unit length passes through an imaginary cube of edge a. The maximum flux of the electric field through the cube will be

The total mechanical energy of a harmonic oscillator of A=1m and force constant 200 N/m is 150J.Then

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

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

In Young's double slit experiment, the 10th maximum of wavelength λ1 is at a distance of y1 from the central maximum. When the wavelength of the source is changed to λ2, 5th maximum is at a distance of y2 from its central maximum. then the ratio of y1 / y2 is

Two long straight conductors are held parallel to each other at a distance 0.3m.If the conductors carry currents 2A and 8A in opposite directions,the distance of the neutral point from the conductor carrying smaller current is

The distances between the objective and the eye lens of an astronomical telescope when adjusted for parallel light is 100cm.The measured value of the magnification is 19.The focal length of objective and eye piece are

The natural frequency of an I.-C circuit is 1,25,000 cycle/s. Then the capacitor C is replaced by another capacitor with a dielectric medium of dielectric constant K. In this case, the frequency decreases by 25 kHz. The value of K is

A black body radiates energy at the rate of E watt/m2 at a high temperature T K. When the temperature is reduced to (T/2) K, the radiant energy 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 source and an observer move away from each other, each with a velocity of 10 m/s. with respect to ground If the observer find the frequency of sound coming from tile source as 1950 Hz, the original frequency of the source is: (assume velocity of sound in air = 340 m/s)

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

In Resonance Column experiment with a closed pipe, the first, second and third reso-nance lengths L1, L2, L3 respectively beat the relationship

A train is moving towards north with a speed of 180 kilometers per hour.If the vertical component of the earths magnetic field is 0.2x10-4T,the emf induced in the axle of length 1.5 m is

The velocity of propagation of sound is 330 m/s, in air. If the third harmonic of the fundamental that can be exerted in an open ended tube is 450 Hz, the length of the tube is :

16 tuning forks are arranged in increasing order of frequency.Any two consecutive tuning forks when sounded together produce 8 beats per second.If the frequency of the last tuning fork is twice that of the first the frequency of the last tuning fork is

The relation between the coefficient of real expansion (γr) and coefficient of apparent expansion (γa) of a liquid and the coefficient of linear expansion (αg) of the material of the container is

Temperature of cold junction in a thermo- couple is 100C and neutral temperature is 2700C, then the temperature of inversion is

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,

In a hall a person receives direct sound from a source 120m away. He also receives waves from the same source which reach him after being reflected from the 25m high ceiling at a point midway between them. The two waves interfere constructively for wavelengths (in metre) of

Consider the following statements A and B and identify the correct answer :(A) : In an elastic collision, if a body suffers a head on collision with another of same mass atrest, the first body comes to rest while the other starts moving with the velocity of the first one.(B) : Two bodies of equal mass suffering a head on elastic collision merely exchanges their velcities :

An iron block of sides 50 cm x 8 cm x 15 cm has to be pushed along the floor. The force required will be minimum when the surface in contact with ground is:

If 4 moles of an Ideal monoatomic gas at temperature 400 K is mixed with 2 moles of another ideal monoatomic gas at temperature 700 K, the temperature of the mixture 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)

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

In an experiment on photoelectric emission from a metallic surface, wavelength of incident light is 2xl0-7 m and stopping potential is 2.5 V. The threshold frequency of the metal (in Hz)   approximately   (charge  of electron e= 1.6 x 10-19 C  Planck's constant h = 6.67 x 10-34 J-s)

A man slides down on a telegraphic pole with  an acceleration equal to one-fourth of acceleration due to gravity. The frictional force between man and pole is equal to in terms of man's weight w

Which of the following statements is not true in the case of 1 Huygen's eye piece

A body of weight "64N" is pushed with just enough force to start it moving across a horizontal floor and the same force continues to act afterwards, if the coefficients of static and dynamic friction are 0.6 and 0.4 respectively, the acceleration of the body is: (acceleration due to gravity = g)

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

When an air column of length ‘l’ open at both ends vibrates in its fundamental note, the wavelength is given by

8 beats are produced when two tuning forks A,B are made to vibrate together.The number of beats decreases to 5 beats/s when prongs of B are filed.If natural frequency of A is 282 Hz,the frequency of B before and after filling is

A varying current in a coil changes from 10 A to zero in 0.5 seconds. If the average emf induced in the coil is 220 volts, the self-inductance of the coil is:

In a thermo couple the cold junction is at 300C.The temperature of inversion is found to be 5400C,Then the neutral temperature is

The plates of a parallel plate capacitor are charged upto 200 volts. A dielectric slab of thickness 4 mm is inserted between its plates. Then, to maintain the same potential difference between the plates of the capacitor, the distance between the plates is increased by 3.2 mm. The dielectric constant of the dielectric slab is :

Assertion (A): Propagation of light through an optical fibre is due to total internal reflection taking place at the core-clad interface.Reason (R): Refractive index of the material of the core of the optical fibre is greater than that of air.

The Poisson's ratio of a material is 0.4. If a force is applied to a wire of this material, there is a decrease of cross-sectional area by 2%. The percentage increase in its length is:

A simple microscope is rated 5x for a normal relaxed eye.what will be its magnifying power for a far sighted man whose near point is 40 cm.

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

A force is experienced by cathode rays when they pass through uniform electric field

A solid wooden block resting on a frictionless surface is hit by a bullet. The bullet gets embedded. During this process:

One junction of thermo couple is at 00C and the other junction is heated .Maximum current in the thermo couple is observed when hot junction is at 2400C.The temperature of the hot junction at which the direction of current reverses is

A long horizontal rigidly supported wire carries ia=96A.Directly above it and parallel to it at a distance, another wire of 0.144N weight per meter carrying a current ib=24A, in a direction opposite to that of ia is placed. If the upper wire is to float in air due to magnetic repulsion, then tits distance (in mm) from the lower wire is:

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

The couple acting on a magnet of length 10 cm placed in a uniform magnetic field of intensity 40 N/Am such that the axis of the magnet makes 450 with the field direction is √2/10 Nm. The pole strength of the magnet in Weber is :

The half life of Ra226 is 1620 years. Then the number of atoms decay in one second in 1 gm of radium (Avogadro number = 6.023x1023)

The following phenomenon which is not explained by Huygens construction of wave front is

Along the x-axis, three charges q/2 , -q and q/2 are placed at x = 0, x = a and x = 2a respectively. The resultant electric potential at a point P located at a distance r from the charge -q ( a << r ) is ( εo is the permittivity of free space )

A ball is projected vertically down with an initial velocity from a height of 20 m on to a horizontal floor. During the impact it loses 50% of the energy and rebounds to the same height, the initial velocity of its projection is :

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 train is travelling at 120 Kmph 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 =330 ms-1)nearly

An ideal transformer has 400 turns in the primary and 200 turns in the secondary. If the primary connected to a 12V battery, then the secondary voltage is

Two tuning forks have frequencies 200 Hz and x. When they are sounded together 4 beats/sec heard. The value of x is

Consider the following statements A and B and identify the correct answers given below :A : Peltier coefficient is numerically equal to the potential difference across the junctions of the thermocouple through which current is flowing.B : According to Thomson, energy is neither absorbed nor evolved at the junction of a thermocouple but is observed or evolved only along the lengths of both the conductors.

A thin magnetic iron rod of lenght 30cm is suspended in a uniform magnetic filed.Its time period of oscillation is $s.It is broken into three equal parts.The time period in seconds of oscialltion of one part when suspended in the same magnetic filed is:

A tangent galvanometer properly adjusted gives a deflection of 300 when a certain current is passed through it. When the current is changed, then it gives a deflection of 450. The ratio of the current in the two cases is:

The fundamental frequency of a sonometer wire is 200 Hz when a body whose relative density 4 is suspended at the end of wire.The fundamental frequency of the same wire when the suspended body is made to immerse in water 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

A 100 PFcapacitor is charged to a potential difference of 24V.It is connected to an uncharged capacitor 20PF.what will be the new potential difference across 100PF capacitor

Four bulbs each marked 40 W. 250 V are connected in series with 250 V source. The total power output is

The lengths of two wires made of same material are 2m and 1m. Their radii are 1mm and 2mm. The ratio of their specific resistances is

Capacitance of a capacitor becomes 7/6 times its original value if a dielectric slab of thickness,t=2/3d is introduced in between the plates.d is the separation between the plates.The dielectric constant of the di-electric slab is

A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in a uniform magnetic field of induction 2 tesla.If the magnetic field is perpendicular to the length of the wire,the force acting on the wire

When a wave travels in a medium the particles displacement is given by the equation y(x,t) = 0.03 sin π(2t - 0.01 x) where y and x are in metres and t in seconds. The wavelength of the wave is :

A metal string is fixed between rigid supports. It is initially at negligible tension. Its youngs modulus is ‘Y’ density is ρ and coefficient of linear expansion is α. It is now cooled through a temperature ‘t’ transverse waves will move along it with a speed.

Two wires A and B are of lengths 40 cm and 30 cm, A is bent into a circle of radius r and B into an arc of radius r. A current i1 passed.through A and i2 through B. To have the same magnetic inductions at the centre, the ratio of    i1  :   i2  is

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

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 2 kg stone tied at the end of a string of 1 m length, is whirled along a vertical circle at a constant speed of 4 m/s. The tension in the string has a value of 52 N when the stone is :

A coil of 50 turns has dimension 10 x 10 cm. It is roated at the rate of 5 rps in a uniform magnetic field of flux density 0.7T. The maximum emf included in it is

An iron load of 2kg is suspended in air from the free end of a sonometer wire of length 1m.A tuning fork of frequency 256Hz is in resonance with 1/√14 times the length of the sonometer wire.If the load is immersed in water,the length of the wire in meter that will be in resonance with the same tuning fork is (specific gravity of iron=8)

A step down transformer has a supply line voltage of 2200V in to 220V. The primary coil has 5000 turns. The efficiency and power transmitted by the transformer are 90% and 8 kilowatt respectively. Then the number of turns in the secondary is

The weight of a man in a lift moving upwards is 608 N while the weight of the same man in the lift moving downwards, with the same acceleration is 368 N. His normal weight in N is:

There are two holes one each along the opposite sides of a wide rectangular tank. The cross section of each hole is 0.01 m2and the vertical distance between the holes is one meter. The tank is filled with water. The net force on the tank in newton when the water flows out of the holes is: ( Density of water = 1000 kg/m3 )

Work done to increase the temperature of one mole of an ideal gas by 300C, if it is expanding under the condition V∝T2/3 is, (R =8.314 J/mole/0 K)