Basic Physics Questions and Answers

If work done in increasing the size of rectangular soap film with dimensions 8 cm x 3 75 cm to 10 cm x 6 cm is 2 10 J The surface tension of film in newton per meter is 2 1 x 10 2 1 65 x 10 2 3 3 x 10 2 2x 10

9 5VWww 2 7mVww A 430 ID 1101924461 Vous 1101924461 NOTE SCREENSHOT PROHIBITED ID 1101924461 Adder Amplifier out put Voltage 48 8 mV

The commutator x P2 where x and Pare position and momentum operators respectively is d 2ihxP a 2i P b i P c 2ihxP A spin half particle is in the state S 2 The expectation values of 5 5 5 5 are giver

In a thermodynamic process pressure of fixed mass of a gas is changed in such a manner that the gas releases 20 J of heat and 8 J of work is done on the gas If initial internal energy of the gas was 40 J what will be final internal energy 18 J 28 J 52 J 32 J

Light is travelling from kerosene to air Its speed in kerosene is 2 08 x 108 m s Find the critical angle of kerosene air boundary Use nair 1 c 3x108 m s Select one a 43 9 b 40 8 c 50 1 0

If a star has a parallax of 0 015 second of arc and an apparent magnitude of 8 how far away is it and what is its absolute magnitude distance pc absolute magnitude

The specific gravity of glass is 4 28 Its density is equal to Use Density of water 1 0 103 kg m Select one O a 4280 kg m O b 428 kg m c 4280 g m

16 An astronaut orbiting the earth in a circular orbit 1000 km above the surface of earth gently drops a ball out of spaceship The ball will Fall vertically down to the earth 2 2 Will remain stationary at the point of release 3 Will move along with the spaceship 4 Will move randomly in any direction

The incorrect statement among the following is 1 Sunlight is not always required for a solar cell 2 Semiconductors with band gap close to 1 5 eV are ideal material for solar cell fabrication 3 A solar cell works when it is reversed biased 4 I V characteristics for solar cell is drawn in fourth quadrant

Single Correct A If mass M time T and energy E are taken to be fundamental quantity then dimensional formula for length is ME T B EM 21 2 E M 1 2T EZM 1 2T P

d If the fish is stored at ordinary temperatu 10 Three identical buckets were filled with water to the brim In the first one a solid iron ball about the size of a football was dropped In the second bucket a cricket ball and in the third one five glass marbles were dropped In each case some water was spilled The order of the volume of water that spilled is a First bucket Second bucket Third bucket b c d Third bucket Second bucket First bucket Second bucket Third bucket First bucket First bucket Third bucket Second bucket the beginning of civiliza

Question No 11 Single Correct A A A river is flowing from east to west at a speed of 6m min A man on south bank of river capable of swimming 12m min in still water swim across the river in the shortest time he should swim A B D due north due north east due north east with double the speed of river none of the above

1g of water as 100 C occupies a volume 1670cm when it becomes steam at 100 C at one atm The change in internal energy for the process is nearly take L 540 cal g p 1g cc latm 10 N m steam water 1 40 cal 2 540 cal 3 500cal 4 580 cal

4 ppm means 4atoms per 10 6 atoms then ne 4 10 27 4 10 6 only na why they are giving like this please explain A pure semiconductor crystal has 4 x 1027 atoms m It is doped by 4 ppm concentration of pentavalent atom The number of holes per m will be n 10 6 m 10 1 m 3 10 m 3 10 m 3 108 m 3 Solution

4 Two rays of light are incident normally on water Bo the rays pass through glass slabs of different height as shown in the figure Refractive indices of water an glass are 4 3 and 3 2 respectively If c is the speed light in vacuum then the time difference between th rays of light to reach the bottom is A C H 2c H hy h 3c B D H 8H 9c h h 6c

An open glass tube is immersed in mercury in such a way that a length of 8 cm extends above the mercury level The open end of the tube is then closed and sealed and the tube is raised vertically up by additional 46 cm What will be length of the air column above mercury in the tube now Atmospheric pressure 76 cm of Hg 1 38 cm 3 16 cm 2 6 cm 4 22 cm

It is observed that only 0 39 of the original radioactive sample remains undecayed after eight hours Which one of the following is incorrect a the half life of that substance is 1 hour 1 b the mean life of the substance is In 2 hour

3 Match List I with List II and select the correct answer using the codes given below the lists List I List II P Photodiode 1 Light into electrical energy Q Zener diode 2 Electrical energy into light R Solar cell 3 Optical signal S LED 4 Voltage regulator Codes P a 2 b 4 c 1 Q R 3 4 1 2 2 3 S 1 3 34 4

21 Arod of length 2m is at temperature of 20 C The temperature is increased to 50 C If permitted expansion without thermal stress is 0 4mm the thermal stress produced is Y 2 10 Pa a 15 10 C 1 5 x 107 N m 2 4 107 N m 3 3 x 107 N m 4 2 107 N m

Q17 The angular velocity of a body changes from one revolution per 25 seconds to one revolution per seconds without applying any torque The ratio of its radius of gyration in two cases is 25 d 25 1 O A OB C O D O Other a 5 1 b 1 5 c 1 1 po

A long wire having linear charge density is moving with constant velocity v along its length At an instant a point charge is at a distance r from the wire and is moving with same speed in opposite direction The net force acting on the charge is given by OD 1 A Hou2 q 2 r EO bjuda q C UMO 0 1 0 4 0 19 do ead 2 r Eo B auiba 19m bus D q 2 ro 1 zero bono lo beib 2 0413 r q

A ray of light is travelling in air falls on a transparent glass slab of refractive index3 If the refracted rays and reflected rays are mutually perpendicular What is angle of incidence 30 45 60 53

The Lagrangian of a particle of mass m moving in a plane is given by L 1 2 m v a xv yv where v and v are velocity components and a is a constant The canonical momenta of the particle are given by y a p mv and p mv my c P mv ay and p mv ax 6 p mv ay and p mv ax d p mv ay and p mv ax

Figure shows a particle of charge q and mass m moving with velocity v along the x axis enters a region of uniform magnetic field Minimum value of v so that the charge q is deflected by an angle 30 is a M M M b B X

46 A block of mass 3m is connected with a string which is wound on pulley of mass m and radius R as shown in the figure If the system is released from rest Then acceleration of the block will be consider pulley as uniform disc 1 g 3 6g 7 3m 2 4 5g g 3

the lengths of the 13 In Fig 11 24 two bars of the same metal are connected The length of the first bar is half of that of the second but the cross sectional area is double What is the temperature of the junction of the bars Ans 20 C 25 C 0 C

Two balle A 2kg and B 4kg move towards each other and after collisio n moves backward If the initial velo cities of A and B were 2m s and 4m s respectively then what could be the ir respective final velocities

Three charges q 1 x 10 C q 2x 10 C 28 and q 3 x 10 C have been placed as shown in figure Then the net electric flux will be maximum for the surface S S A 1 S 2 S 3 Sy 4 Same for all three 14 9 1x 3 question 1 S 2 S 3 S 4

ALLEN The focal lengths of the objective and eye piece 7 of a telescope are respectively 100 cm and 2 cm The moon subtends an angle of 0 5 at the eye If it is looked through the telescope the angle subtended by the moon s image for normal adjustment will be 1 100 3 25 2 50 4 10 A shortsighted person can read a book clearly at faut 100 cm TARINA 1 100 3 25 fuge aun aften of die strat 2 5 gr ff ren an at af 2 50 4 10 Uffe fe ad vta 10 cm

A single phase full bridge inverter bed from 230V DC is connected to load R 10 Q L 0 03 H The inverter is operating in 180 square wave mode The RMS value of fundamental component of output voltage is A 207 10 V C 217 10 V B 407 10 V D 237 10 V

Classr u m us Posi Velo dis B Answer time Rep at t 0 particle is atzero and slope dec becomes 0 and then ve Z Posi rep let us take particle at at een position zero the particle would either have a tve ora ve velo but not zero at t 0 particle has tve Velo rep time at 0 slope of d DT graphiszero the slope initially increases but then decreases at 0 particle is at rest Speed 0

A zener diode having breakdown voltage equal to 10V is used in a voltage regulator circuit shown in figure The current flow the diode is A B C 10 mA 5 mA 15 mA 20002 ww ISV OV 1ks

or more than one choice correct type Questions Consider the condition shown in the figure Pulley is massless and frictionless springs are mass Both the blocks are released with the springs in their natural lengths Choose the correct options MAMAMAY A Maximum elongation in the spring S is B Maximum elongation in the spring S is Th www m 4m m g K m m 4m m g K m m C If m m both the blocks will come to instantaneous rest simultaneously D If K K both the blocks will come to instantaneous rest simultaneously

The focal length of objective lens of astronomical telescope is 50 cm and tube length is 55 cm when final image is obtained at infinity The angular magnification of telescope will be O 11 O 10 O45 60

Q23 A circular disc of mass M and radius R is rotating with an angular velocity w about an axis passing through its centre and perpendicular to the plane of the disc A small point like part of mass m detaches from the rim of the disc and continues to move with same angular speed The angular velocity of remaining disc just after detaching will become a b M 2m M m M 2m M m d M 2m c M M m 0 0 M 2m M m e w 0

A 3 x 3 matrix has eigenvalues 0 2 i and 2 i Which one of the following statements is correct a The matrix is Hermitian b The matrix is unitary c The inverse of the matrix exists d The determinant of the matrix is zero The 1 2

If a circular hole of radius R 2 is removed from semicircular disc as shown find the moment of inertia about AB of the remaining body Use mass of semicircular disc as m before removal A 5mR 32 B 3mR 32 C B R 3mR 32 D mR 32

Identify the correct statement regarding power MOSFET You can select multiple correct answers MOSFET is a unipolar voltage controlled three terminal device The MOSFET has higher switching losses than that of a BJT The gate circuit impedance of MOSFET is higher than that of a BJT MOSFET is a bipolar current controlled two terminal device

Obtain the approximate force in MN required to punch a 20 mm diameter hole in a plate that is 50 mm thick Use shear strength as 350 MN m and 22 7 6 10 m

The maximum value of anode current which it must attain during turn on process to maintain conduction when gate pulse is removed The minimum value of anode current which it must attain during turn on process to O maintain conduction when gate pulse is removed Identify the correct statements about fast recovery diode You can select multiple correct answers Current rating vary from 1 A to several thousand amperes Voltage rating is maximum up to 100v The diode with low reverse recovery time Used in line frequency rectifiers Select correct statements for gate triggering You can select multiple correct answers

Two particles having position vectors 31 51 m and 2 51 31 m at t 0 are moving with velocities V 41 33 m s and V ai 73 m s For what value of a they collide at t 2 sec Block 1 sits on top of block 2 Both of them have a mass of 1 kg The coefficients of friction

The mass of a density bottle is 35 g when empty 79 g when filled with water and 63 g when filled with alcohol Find the relative density of alcohol

For the circuit shown power consumed is 3kw and the power factor is 0 75 Fir a Impedance of circuit b Resistance of coil B of coil A c Inductance R 592 00000000 A L 0 02H oooooooo B 240 V 50 Hz

d linear momentum c acceleration The three vectors whose resultant is zero mus colinear co planar b nonlinear d co axial the following examples given below which but it is not a vector quantity greate 10 m te a p

Correct true statement regarding IGBT Has HIGH INPUT IMPEDANCE AS MOSFET AND HAS High ON STATE POWER LOSS AS IN BJT h O Has HIGH INPUT IMPEDANCE AS MOSFET AND HAS LOW ON STATE POWER LOSS AS IN BJT O Has Low INPUT IMPEDANCE AS MOSFET AND HAS LOW ON STATE POWER LOSS AS IN BJT Has Low INPUT IMPEDANCE AS MOSFET AND HAS High ON STATE POWER LOSS AS IN BJT

A fresh dry cell of 1 5 volt and two resistors of 10 k each are connected in series An analog voltmeter measures a voltage of 0 5 volt across each of the resistors A 100 F capacitor is fully charged using the same source The same voltmeter is now used to measure the voltage across it The initial value of the current and the time in which the voltmeter reading falls to 0 5 volt are respectively A 60 A 11s B 120 A 15s C 150 A 15s D 150 A 1 1 s

air bubble in sphere having 4 cm diameter appears 1 cm from surface nearest to eye when looked along diameter If all stance of bubble from refracting surface is A B D 1 2 cm 3 2 cm 2 8 cm 1 6 cm

c vector is translated parall d vector is rotated Minimum number of unequal coplanar vectors required whose vector sum can be equal to zero is a two b four c three d any of the above roduces the same effect as

In figure shown car A is travelling due north and car B is traveling due east They collide and stick to each other Here 1 2 3 4 shows possible direction of motion of cars Which is most likely B 1 2 2 4 W

1 7 10 A clock hung on a wall has marks instead of numerals on its dial On the adjoining wall there is a plane mirror and the image of the clock in the mirror indicates the time 7 40 Then the time on the clock is Question Type Single Correct Type 2 4 20 English 3 5 40 Review Q