Basic Physics Questions and Answers

2 Look at the following pictures and write a few lines on how the structure shape des each case is used to reduce increase friction grip and the need to do so LO 4 60 a b SP

3 A particle of mass 3 gm moves along the x axis and is attracted towards the origin by a force whose magnitude is numerically equal to to 12 times the instantaneous displacement from the origin The particle is also subjected to a damping force which brings it to the origin in minimum time and whose magnitude is 12 times the instantaneous speed If it is initially at rest at x 10 cm which one of the following equations gives the particle s position at a later time t a 10 40t e 4t b 10 20t e c 10 e t cos 4t d 10 e t sin 4t 2t

A circular copper disc 10 cm in diameter rotates at 1800 revolution per minute about an axis through E its centre and at right angles to disc A uniform field of induction B of 1 Wb mis perpendicular to disc What potential difference is developed between the axis of the disc and the rim 5 a 0 023 V c 23 V b 0 23 V d 230 V

A satellite can be in a geostationary orbit around a planet at a distance r from the centre of the planet If the angular velocity of the planet about its axis doubles a satellite can now be in a geostationary orbit around the planet if its distance from the centre of the planet is D 2 r C A 1 2 B NI r 2 2 r 4 1 3

ing A me axis en the 0 8 m ution ontal place emf a 157 V b 117V c 127V d 137 V 51 A sliding rod AB of resistance R is shown in the figure Here magnetic field B is constant and is out of the paper Parallel wires have no resistance and the rod is moving with constant velocity v The current in the sliding rod AB when switch S is closed at time t 0 is v Bd a c t C R v Bd RIC b d OF v Bd R v Bd t RC eRC 55 whic chan the r evolv a c 56 A me a b c d

d 2 5 1 8 A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil This is because a the magnetic field is constant b the magnetic field is in the same plane as the circular coil and it may or may not vary c the magnetic field has a perpendicular to the plane of the coil component whose magnitude is decreasing suitably d both b and c

18 A stepdown transformer reduces the voltage of a 18 transmission line from 2200 V to 220 V The power delivered by it is 880 W and its efficiency is 88 The input current is 1 4 65 mA 2 0 465 A 3 0 4545 A 4 4 65 A 88 22 25 195 28 440 taf 2200 x ip 13 Her fasil ERT 886 280 1 4 65 mA 2 0 465 A 3 0 4545 A 4 468 A light planet revolving around a very massive star 19

A thin conducting ring is ruptured when it is given a charge q Consider another thin conducting ring radius of which is n times and tensile strength is k times of the former ring How much maximum charge can this second ring be given without rupturing b qn k d Insufficient information a nh c qn k

c into the plane of the paper d out of the plane of the paper 27 A solenoid is connected to a battery so that a stead current flows through it If an iron core is inserted into the solenoid the current will a increase decrease b c remains same d first increase then decrease Which of the following c 32 Th in th pl a c

In the case of linearly polarized light the magnitude of the electric field vector 1 2 3 4 Correct Is parallel to the direction of propagation Does not change with time Increases linearly with time Changes periodically with time 4

Determine the number of photons emitted per second by a laser that emits red light o wavelength 650 nm and has a power output of 2 00 10 W a 6 54 10 5 photons s b 5 23x10 7 photons s c 3 834 10 6 photons s d 9 29 10 4 photons s

43 As shown in the figure a metal rod makes contact 48 with a partial circuit and completes the circuit The circuit area is perpendicular to a magnetic field with B 0 15 T If the resistance of the total circuit is 32 the force needed to move the rod as indicated with a constant speed of 2 ms will be equal to 8 0 15 T into page X a 3 75 10 N c 6 57 x 10 N 50 cm 2ms b 2 75 x 10 N d 4 36 10 N 49 F V P fi a e

9 There is a uniform magnetic field directe perpendicular and into the plane of the paper Am irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper Then a current is induced in the loop in the anti clockwise direction b current is induced in the loop in the clockwis direction c ac is induced in the loop d no current is induced in the loop

The initial amount of carbon 14 is 100 g and the amount of carbon 14 dropped to 1 fter decay process The half life of carbon 14 is 5 730 y Calculate the time taken complete this decay process a 3 8 10 y b 6 0x10 y c 4 0 108 y d 5 0 10 y

6 A wheel with 20 metallic spokes each of length 0 8 m long is rotated with a speed of 120 revolution per minute in a plane normal to the horizontal component of earth magnetic field H at a place If H 0 4 x 10 T at the place then induced emf between the axle and the rim of the wheel is a 2 3 x 10 V b 3 1 x 10 V c 2 9 x 10 V d 1 61 x 10 V

to a uniform held of 0 4 gauss second The A coil of is held perpendicular The coil is turned through 180 in average induced emf is a 0 02 V b 0 04 V c 14 V d 0 08 V A long solenoid with 10 turns per cm has a small loop of area 3 cm placed inside normal to the axis of the solenoid If the current carried by the solenoid changes steadily from 2 A to 4 A in 0 2 s what is the induced voltage in the loop while the current is changing a 4 2 x 10 v c 7 3 x 10 V 10 b 4 V c e b 2 8 x 10 d 3 8 x 10 V V at a constant rate of 1 mm s The induced emf when the radius is 2 cm is a 2 V b V T d 2 V 12 An air cored solenoid with length 20 cm area of 17 A square loop of side 12 cm and resistance 0 60 2 is cross section 20 cm and number of turns 400 carries a current 2 A The current is suddenly switched off within 10 s The average back emf induced across the ends of the open switch in the circuit is ignore the variation in magnetic field near the ends of the c 3V d 5V placed vertically in the east west plane A uniform magnetic field of 0 10 T is set up across the plane in north east direction The magnetic field is decreased to zero in 0 6 s at a steady rate The magnitude of current during this time interval is a 1 42 10 A solenoid a 2 V c 3 41 x 10 A b 2 67 10 A d 4 21 10 A b le HV 16 A circular coil of radius 8 cm 400 turns and resistance 2 2 is placed with its plane perpendicular to the horizontal component of the earth s magnetic field It is rotated about its vertical diameter through 180 in 0 30s Horizontal component of earth magnetic field at the place is 3 x 10 T The magnitude of current induced in the coil is approximately a 4 10 A c 8 10 A b 8 x 10 A d 1 92 10 A 13 The magnetic flux through a coil perpendicular to its 18 A rectangular coil of 100 turns and size 0 1 mx 0 05 m plane and directed into paper is varying according to the relation 2 4t 6 mWb The emf induced in the loop at t 4 s is is placed perpendicular to a magnetic field of 0 1 T If the field drops to 0 05 T in 0 05 second the magnitude of the e m f induced in the coil is a 2 b 3 c 0 5 d 6 a 0 12 V b 2 4 V c 0 02 V d 1 2 V 14 A long solenoid S has turns per metre with 19 A uniform magnetic field B points vertically up diameter a At the centre of this coil we place a smaller coil of N turns and diameter b b a If the current in the solenoid increases linearly with time then the emf will be induced in the smaller coil Which of the following is the correct graph showing le verses t if current varies as a function of mr C and is slowly changed in magnitude but not in direction The rate of change of the magnetic field is a A conducting ring of radius r and resistance R is held perpendicular to the magnetic field and is totally inside it The induced current in the ring is a zero b ra c d 20 A magnetic field B is confined to a region r S a and points out of the paper the z axis r 0 being the centre of the circular region A charged ring charge q of radius b b a and mass m lies in the x y plane with its centre at the origin The ring is free to rotate and is at rest The magnetic field is brought to zero in time At The angular velocity to of the ring after the field vanishes is 9 Ba 2mb 2mb qBa 15 A conducting circular loop is placed in a uniform magnetic field B 0 025 T with its plane perpendicular to the loop The radius of the loop is a c 2rB R b d 9 Ba 2mb 9 Ba 2mb T R

c 3 41 x 10 A d 4 21 x 10 A A rectangular coil of 100 turns and size 0 1 mx 0 05 m is placed perpendicular to a magnetic field of 0 1 T If the field drops to 0 05 T in 0 05 second the magnitude of the e m f induced in the coil is a 2 b 3 c 0 5 d 6

A potentiometer circuit is set up as shown The potenti gradient across the potentiometer wire is k volt cm an the ammeter present in the circuit reads 1 0 A when th two way key is switched off The balance points whe the key between the terminals i 1 and 2 ii 1 and 3 plugged in are found to be at lengths 1 em and la cr respectively The magnitudes of the resistors R and in ohm are then equal respectively to A DA www R wwwww X 1 k 12 1 and kl 2 kly and k l2 4 3 k l2 1 and kl 4 kl and kl B

24 The direction of induced current in the coils A ar B in the situation shown in the figure is B S a p to q in coil A and x to y in coil B b q to p in coil A and x to y in coil B c p to q in coil A and y to x in coil B d q to p in coil A and y to x in coil B

OB enb Note If L C and R denote the inductar capacitance and resistance respectively dimensional formula for C LR is A ML T I C M L2 T6 F B M L 7 10 D M L 7 10 7

A wire of cross sectional area A is stretched horizontally between two clamps located at a distance 1 metres from each other A weight W kg is suspended from the mid point of the wire If the verticle distance through which the mid point of the wire moves down be x 1 then the strain produced in the wire is OS me 1 x 4 2 x 2 t 3 x 1 4 2 x 1 19 A co ant force F is an niform alactic

J The magnetic flux through a coil perpendicular to its 18 plane and directed into paper is varying according to the relation 2 4t 6 mWb The emf induced in the loop at f 4 s is a 0 12 V b 2 4 V c 0 02 V d 1 2 V

5 A circular disc of radius 0 2 m is placed in a uniform Wb m in such magnetic field of induction way that its axis makes an angle of 60 with The magnetic flux linked with the disc is b 0 06 Wb a 0 02 Wb c 0 08 Wb d 0 01 Wb FARADAY S LAW OF INDUCTI

a c 2 The north pole of a bar magnet is rapidly introduced into a solenoid at one end say A Which of 38 A cir the following statements correctly depicts the phenomenon taking place a No induced emf is developed b The end A of the solenoid behaves like a south pole magn produ a b c The end A of the solenoid behaves like north c pole d The end A of the solenoid acquires positive stential d

c 2qV d 2 A coil of area 0 4 m has 100 turns A magnetic field of 0 04 Wb m is acting normal to the coil surface If this magnetic field is reduced to zero in 0 01 s then the induced emf in the coil is a 160 V c 270 V b 250 V d 320 V

Two vectors in which one has magnitude twice that of the other act on a particle Find the angle between them if their resultant is perpendicular to the first vector

ypical small flashlight contains two batteries each ving an emf of 1 50 V connected in series with a bulb ving a resistance of 14 2 Submit Request Answer Part C The resistance of real batteries increases as they run down If the initial internal resistance is negligible what is the combined intern resistance of both batteries when the power to the bulb has decreased to half its initial value Assume that the resistance of the bu constant Actually it will change somewhat when the current through the filament changes because this changes the temperature c filament and hence the resistivity of the filament wire W Express your answer using two significant figures VAX 1

c An air cored solenoid with length 20 cm area of 17 cross section 20 cm and number of turns 400 carries a current 2 A The current is suddenly switched off within 10 s The average back emf induced across the ends of the open switch in the circuit is ignore the variation in magnetic field near the ends of the solenoid c 3V d 5V 2V b 4 V

99 Two batteries V and V are connected to three resistors as shown below M Vi www a 7 mA c 20 mA 1 If V 2V and V 0 V the current I 3 mA If V 0 V and V 4V the current I 4mA Now if V 1 10 V and V 10 V the current will be 2 V b 15 mA d 25 mA

An open ended U tube of uniform cross sectional area contains water density 1 0 gram centimeter standing initially 20 centimeters from the bottom in each arm An immiscible liquid of density 4 0grams centimeter is added to one arm until a layer 5 centimeters high forms as shown in the figure above What is the ratio h h of the heights of the liquid in the two arms A 3 1 B 5 2 C 2 1 D 3 2

Both capacitors are initially uncharged and then connected as shown and switch is closed What is the potential difference across the 3uF capacitor A 30V B 10V 2uF H 9V 19V C 25V SE D None of these 3C

2011 E A directly proportional to R but inversely proportional to v B directly proportional to both radius R and velocity v C inversely proportional to both radius R and velocity v D inversely proportional to R but directly proportional to velocity v 37 A cubical block of side a and density p slides over a fixed inclined plane with constant velocity y There is a thin film of viscous fluid of thickness t between the plane and the block Then the coefficient of viscosity of the thin film will be A 3pagt 5v B 4pagt 5v C Pagt D none of these 50 JEE Physics ALLEN 38 There is a Imm thick layer of glycerine between a flat plate of area 100 cm a big fixed plate If the

Let A be a 3 x 3 diagonalizable matrix with eigenvalues A 1 with corresponding eigenvector v 2 and A 2 with corresponding 191 eigenvectors v 0 and V3 22 Then P 1 APD with 22 VOTONO TOO 1 5 D 2 2 1 1 P 0 0 0 0 2 01 200 0 21 2 2 and 11

We repeat the experiment from the video but this time we connect the wires in parallel rather than in series Which wire will now dissipat the most heat View Available Hint s O Both wires will dissipate the same amount of heat O The Nichrome wire resistance 2 7 12 O The copper wire resistance 0 1 2

21 A narrow but tall cabin is falling freely near the earth s surface Inside the cabin two small stones A and B are released from rest relative to the cabin Initially A is much above the centre of mass and B much below the centre of mass of the cabin A close observation of the motion of A and B will reveal that a both A and B continue to be exactly at rest relative to the cabin b A moves slowly upward and B moves slowly downward relative to the cabin c both A and B fall to the bottom of the cabin with constant acceleration due to gravity d A and B move slightly towards each other vertically

The Vernier scale of a Vernier caliper has 50 divis divisions of main scale division If each main scale division is least count is 0 0 05 mm O 0 45 mm 0 0 1 mm O 0 2 mm

It is comfortable than reading in dim light Which of the following is the most reasonably bright light is more reason for this effect appropriate a Contraction of ciliary muscles reduces astigmatism b Contraction of pupil in bright light reduces spherical aberration c In bright light image formed on retina has more intensity than that in dim light d This is purely a psychological effect bright light merely stimulates some more visual neurons that are normally dormant

R R Two ve charge each of magnitude q are situated at 2r 4 distance apart A ve charge q is lying at the centre between them The potenual energy of the system is U If the two nearest charges are mutually interchanged and the potential energy becomes U then 1 1 3 2 1 9 3 9 1 4 3 1 An uncharged U U will be 3 3K R1 R Q 3k G 3 12 sphere 4 KCB 2K R R k fan fef GUI af f d feel si at feefars 1 1 3 3 9 1 ch 1 2 3 4 2 9 49 28 2 1 9 4 3 1 y Kq

A converging lens of focal length fis used to cast an image of an object as shown in the figure The upper half of the lens is now covered by an opaque coating Which of the following statements is most appropriate a Upper half of the image is brighter than its lower half b Lower half of the image is brighter than its upper half c Entire portion of the image appears with uniformly reduced brightness d Entire portion of the image appears with reduced brightness but to predict intensity distribution more information is required Object S

Resistance RH is a fundamental constant with dimensions of resistance If h is Planck s constant and e the electron charge then the dimension of RH is the same as a c h 2 h b d 0 20

Sometimes it is convenient to construct a system of units so that all quantities can be expressed in terms of only one physical quantity In one such system dimensions of differe quantities are given in terms of a quantity X as follows position position X speed X acceleration X liner momentum X9 force X Then This question has multiple correct options A B C D a p 2 P q r P q r a P q r B

If the r m s velocity of the molecules of a gas in a container be doubled than pressure of gas will X Become 4 times of its previous value B Becomes 2 times of its previous value C Remains same CRO

91 An isolated sphere of radius R contains uniform volume distribution of positive charge Which of the curves shown below correctly illustrates the dependence of the magnitude of the electric field of the sphere as a function of the distance r from its centre e Electric field magnitude Electric field magnitude a I c III O R R r T Electric field magnitude IV 0 Electric field magnitude b II d IV R OR I I

23 If the speed v of the bob in a simple pendulum is plotted against the tangential acceleration a the correct graph will be represented by 14 t II C a I c III I st III V V b II d IV IV

30 At 23 C a pipe open at both ends resonates at a frequency of 450 Hz At what frequency does the same pipe resonate on a hot day when the speed of sound is 4 percent higher than it would be at 23 C a 446 Hz b 454 Hz c 468 Hz d 459 Hz 31 In a Young s double slit set un light from a locor

6 3 Two events A and B occur at places separated by 10 km B occurring 5 s after A a Find the velocity of a frame in which these events occur at the same place b What is the time interval between the events in this frame

95 A constant amount of an ideal gas undergoes the cyclic process ABCA in the PV diagram shown below P kPa 500 200 A 2 B V m The path BC is an isothermal The work done by the gas during one complete cycle beginning and ending at A is nearly a 600 kJ c 300 kJ b 300 kJ d 600 kJ

25 Two bulbs of identical volumes connected by a small capillary are initially filled with an ideal gas at temperature T Bulb 2 is heated to maintain a temperature 2T while bulb 1 remains at temperature T Assume throughout that the heat conduction by the capillary is negligible Then the ratio of final mass of the gas in bulb 2 to the initial mass of the gas in the same bulb is close to a c 12 13 b 2 3 d 1

determination of young s modulus of a metal wire but forgets to put the labels figure The quantities on X and Y axes may be respectively i Weight hung and length increased ii Stress applied and length increased iii Stress applied and strain developed iv Length increased and the weight hung uch dar n uzurual quich Aukur PA 34 MT yg uh ur Real Acad 1 X GIR Y GET UR ferui 3421 zt Achat ric A i iii iv B ii iii iv

5 Light of wavelength is incident on a slit First minima of the diffraction pattern is found to lie at a distance of 6 mm from the central maximum on a screen placed at a distance of 2 m from the slit If slit width is 0 2 mm then wavelength of the light used will be a 4000 A b 6000 A c 7000 A d 7400 A