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When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell the saturation current and cut off voltage are 12mA and 0.5v . If the same source is palced at 0.4 m away from the same photoelectric cell , then the saturation current , now will be ……………………….
Education is a part of Life
In a circuit for finding the resistance of a galvanometer by half deflection method , a 6v battery and a high resistance of 11 kῼ are used . The figure of merit of galvanometer is 60𝜇A/division . In the absence of shunt resistance the galvanometer produces a deflection of 𝜃=9 divisions when current flows in the circuit . The value of the shunt resistance that can cause the deflection of 𝜃/2 is closed to ………………..
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Two thin symmetrical lens of different nature have equal radii of curvature of all faces R=20 cm . The lenses are put close together and immersed in water . The focal length of system is 24cm . The difference between refractive indies of the two lenses is ………………………..x1/9 . Refractive index of wirer is 4/3
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A uniform solid cylinder of mass M and radius R is placed on a rough horizontal board of same mass , which in turn is placed on a smooth surface . The coefficient of friction between the board and the cylinder is 𝜇=0.3 . If the board starts acceleration with constant acceleration a , as shown in the figure , then the maximum value of a , so that the cylinder performs pure rolling is ……………… m/𝑠^2 , g = 10 m/𝑠^2
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In the system shown all the surfaces are frictionless while pulley and string are massless. Mass of block A is 3m and that of block B is m . If the acceleration of block B with respect to ground after system is released from rest is ‘a’ then the value of ‘10a’ is (take g= 10 , 5√2= 7.0 )
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A students performs an experiment to determine the young’s modulus of a wire , exactly 2m long buy Searle’s method . In a particular reading ,the student measures the extension in the length of the wire to be 0.8 mm with an uncertainty of ±0.05 mm at a load of exactly 1.0 kg the student also measures the diameter of the wire to be 0.4mm with an uncertainty of ± 0.01mm. Take g = 10.0 m𝑠^(−2) . The young’s modulus obtained from the reading is A) (2.0 ±0.3) x 〖10〗^11 N𝑚^(−2) B) (2.0 ±0.2) x 〖10〗^11 N𝑚^(−2) C) (2.0 ±0.1) x 〖10〗^11 N𝑚^(−2) D) (2.0 ±0.05) x 〖10〗^11 N𝑚^(−2)
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In young’s double slit experiment , the distance between the slits varies with time as d(t) = 2𝑑_𝑜 + 𝑑_𝑜sin𝜔𝑡 where 𝑑_𝑜 and 𝜔 are positive constants . The difference between the largest and the smallest fringe width obtained over time is ( D = distance between slits and screen ≫d & λ=𝑤𝑎𝑣𝑒𝑙𝑒𝑛𝑡ℎ 𝑜𝑓 𝑙𝑖𝑔ℎ𝑡 𝑢𝑠𝑒𝑑 ) A ) 𝐷λ/(2𝑑_𝑜 ) B) 𝐷λ/(3𝑑_𝑜 ) c) 2𝐷λ/(3𝑑_𝑜 ) D) 𝐷λ/(6𝑑_𝑜 )
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A pane electromagnetic wave travelling along the positive x-direction has a wavelength of 3mm . The variation in the electric field occurs in the y – direction with an amplitude 66 V/m . The equations for the electric and magnetic fields as a function of x and t are respectively . 𝐸_𝑦 = 66 cos 𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) , 𝐵_𝑧 = 1.1x 〖10〗^(−7) cos 𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) 𝐸_𝑦 =11 cos 2𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) , 𝐵_𝑦 = 11x 〖10〗^(−7) cos 2𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) 𝐸_𝑥 = 66 cos 𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) , 𝐵_𝑥 = 2.2 x 〖10〗^(−7) cos 𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) 𝐸_𝑦 = 66 cos 2𝜋 x 〖10〗^11(t - 𝑥/𝑐 ) , 𝐵_𝑧 = 2.2 x 〖10〗^(−7) cos 2𝜋 x 〖10〗^11(t - 𝑥/𝑐 )
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Assertion : A current I flows along the length of an infinitely long straight and thin walled pipe . Then the magnetic field at any point inside the pipe is zero Reason : ∮1▒〖(𝐵.) ⃗(𝑑𝑙.) ⃗ 〗 = 〖𝜇" " 〗_𝑜 I Read the assertion and reason carefully to mark the correct option out of the options given below : Both assertion and reason are true and the reason is the correct explanation of the assertion Both assertion and reason are true but reason is not the correct explanation of the assertion Assertion is true but reason is false Assertion and reason both are false
A particle free to move along the x-axis has potential energy given by U(x) = K(1-〖 𝑒〗^(−𝑥^2 )) for −∞ ≤x≤ +∞ where k is a positive constant of appropriate dimensions . Then At point away from the origin ,the particle is in unstable equilibrium For any finite non zero value of x , there is a force directed away from the origin If its total mechanical energy is k/2 , then kinetic energy at the origin is k For small displacements from x=0 the motion is simple harmonic
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Two rigid boxes containing different ideal gases are placed on a table . Box A contains one mole of nitrogen at temperature 𝑇_𝑜 , while box B contains one mole of helium at temperature 7/3 𝑇_𝑜 . The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature (ignore the heat capacity of boxes and heat exchange will happen only between boxes ) . Then the final temperature of the gases in terms of 𝑇_𝑜 is 7/3 𝑇_𝑜 3/2 𝑇_𝑜 5/2 𝑇_𝑜 3/7 𝑇_𝑜
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Two moles of ideal helium gas are in a rubber balloon at 30°C . The balloon is fully expandable and can be assumed to required no energy in its expansion . The temperature of the gas in the balloon is slowly changed to 35℃ . The amount of heat required in raising the temperature is nearly (take R=8.31 j/mol.K ) 62 J 104J 125J 208J
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Water rises to a height of 10cm in a capillary tube and mercury falls to a depth of 3.42 cm in the same capillary tube . If the density of mercury is 13.6 g/cc and the angle of contact of mercury and water are 135° and 0° respectively , the ratio of surface tension of water to mercury is : A) 1: 0.15 B) 1:3 C) 1: 6.5 D) 1.5: 1
SOLUTION WILL BE UPLOADED
A planet of radius R has an acceleration due to gravity of 𝑔_𝑠 on its surface . A deep smooth tunnel is dug on this planet , radially inward , to reach a point P located at a distance of 𝑅/2 from the centre of the planet . Assume that the planet has uniform density . the kinetic energy required to be given to a small body of mass m , projected radially outward from P , sop that it gains a maximum altitude equal to the thrice the radius of the planet from its surface is equal to 63/16m𝑔_𝑠R 3/8m𝑔_𝑠R 9/8m𝑔_𝑠R 21/8m𝑔_𝑠R
NXT INDIA ROHAN SIR SOLUTION WILL UPLOADED
particle is moving parallel to x-axis as shown in the figure such that all instants the y – component of its position vector is constant and equal to ‘b ‘ . The angular velocity of the particle p about origin at the given instant is A) 𝑉/𝑏 cos𝜃 B) 𝑉/𝑏 sin𝜃 C) 𝑉/𝑏 sin^2𝜃 D) vb
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A system of two bodies of masses ‘m’ and M being interconnected by a spring of stiffness k , in its natural length , moves towards a rigid wall on a smooth horizontal surface as shown in figure with a K.E. system ‘E’ . If the body M sticks to the wall after the collision , the maximum compression of the springs will be : A) √(𝑚𝐸/𝑀𝑘) B) √(2𝑚𝐸/(𝑀+𝑚)𝑘) C) √((2(𝑚+𝑀)𝐸)/𝑘(𝑚) ) D) √(2𝑀𝐸/(𝑀+𝑚)𝑘)
An object is placed on the surface of a smooth inclined plane of inclination 𝜃 . It takes time t to reach the bottom . If the same object is allowed to slide down a rough inclined plane of same inclination 𝜃 , so as to move the same distance , it takes time ‘nt’ to reach the bottom where n is a number greater than 1 . The coefficient of friction 𝜇 𝑖𝑠 𝑔𝑖𝑣𝑒𝑛 𝑏𝑦 : 𝜇 = tan𝜃 (1 - 1/𝑛^2 ) 𝜇 = cot𝜃 (1 - 1/𝑛^2 ) 𝜇 = tan𝜃 〖"(1 - " 1/𝑛^2 ")" 〗^(1/2) 𝜇 = cot𝜃 〖"(1 − " 1/𝑛^2 ")" 〗^(1/2)
ROHAN SIR
A sphere of mass 𝑚_1=2kg collides with a sphere of mass 𝑚_2=2kg which is at rest . Mass 𝑚_1 , after the collision will move at right angle to the joining centers of two spheres at the time of collision , assuming colliding surfaces are smooth , if the coefficient of restitution is
A sphere of mass 𝑚_1=2kg collides with a sphere of mass 𝑚_2=2kg which is at rest . Mass 𝑚_1 , after the collision will move at right angle to the joining centers of two spheres at the time of collision , assuming colliding surfaces are smooth , if the coefficient of restitution is