Physics Questions

3 In a cylindrical region uniform magnetic field which is perpendicular to the plane of the figure is increasing with time and a conducting rod PQ is placed in the region Then a P will be at higher potential than Q b Q will be at higher potential than P d no omf will be developed

Find the distance of centre of mass of the uniform rod of length into circular arc of radius R from the centre C as shown 3R B 2R A C T R TU D R TR if it is bent

Explain with the help of a labelled circuit diagram how you will find the resistance of a combinatio of three resistors of resistances R R and R3 joined in parallel in the diagram shown below the cell and the ammeter both have negligible resistance The resistors are identical A 4F K

m m The magnitude of normal reaction between the blocks is

1 Consider two npn transistors as shown in figure If 0 Volts corresponds to false and 5 Volts correspond to true then the output at C corresponds to Online April 9 2013 cl sv SV ic 04 ov AO WWW BO WWW 2

tration 10 A heater is designed to operate with a power of 1000 W in a 100 V line It is connected in combination with a resistance R to a 100 V mains as shown in the figure What should be the value of R such that the heater may operate with a power of 62 5 W 1092 100V Heater w R

When radiation of frequency 3 x 1015 Hz incident on a metallic surface having work function 4 eV The minimum velocity of photoelectron is 1 1 72 x 106 ms 1 ayon is 3 10 5 KE Wo4ev 2 3 44 106 ms 1 3 6 88 106 ms 1 4 Zero Vmin 2 6 6x10 KE

19 The current through the 5 resistor is 522 www a 10 A 8 V b 1 A 6 V www 99 4 V c 2 5 A d 0 4 A

A ball is thrown up with a certain velocity at angle 0 to the horizontal The kinetic energy KE of the ball varies with horizontal displacement x as 1 3 KE KE X 2 4 KE N KE t X X

View In English The system is pushed by a force F as shown in figure All surfaces are smooth except between B and C Friction coefficient between B and C is u Minimum value of F to prevent block B from downward slipping is A B m F 2m 1 3 4 36535550 2 2 mg mg mg mg 2m

1 14 Two monochromatic sources of light of same power emit photons of different frequencies 8 and 8 corresponding momenta energies and number of photons emitted per second are P P2 E E and n1 n respectively then wrong statement is P E 3 P E 2 An electron and proton are accelerated to same speed The ratio of de Broglie wavelengths would M P a a 1 n 2 n 10 10 1 8 E n 4 18000

A block is projected up along the line of greatest slop of an inclined plane of angle of inclination 0 0 wher o angle of friction Which of the following friction time graph is correct f gro 04 tint 3 O f f f 2 O El C f 4 0 20 t t

The magnetic field of a cylindrical mag net that has a pole face radius 2 8 cm can be varied sinusoidally between the minimum value 16 8 T and the maxi mum value 17 2 T at a frequency of 50 Hz Cross section of the magnetic field created by the magnet is shown in Fig 3 211 At a radial distance of 2 cm from the axis find the amplitude of the electric field in units ofx 10 mNC induced by the magnetic field variation Fig 3 211 X X X X X X X X X 2 8 cm X X X X X X X

as shown in figure The velocity time will have a shape a a m s and undergoes an acceleration graph from figure L b VI VA

om rest and undergoes an acceleration 131 A particle as shown in figure The velocity time graph from figure will have a shape a c VA a m s a a 1 2 3 4 A b d t

A person is standing in front of a plane mirror at a distance L from mirror and observes image of wall of height H at a distance of 3L behind the person then calculate minimum height of mirror required to see full image of wall in the mirror 1 3 H 3 5 H 2 4 H 3 H 5

A proton and an alpha particle are accelerated through the same potential difference The rati of wavelengths associated with proton and alph particle respectively is 212 1 3 2 5 1 44 1

A series LCR circuit contains a 50 resistance 2H inductane and F capacitance 800 19T T connected across a 220V 50Hz ac source The net reactance of the circuit is 1 2000 2 237 5 3 3750 AY

AB is a surface making an angle of 30 with horizontal A is 6 3 m above the ground while B is 3 8 m above the ground A 35 block slides down from A initially starting from rest Its velocity on reaching B is Ar E 9 30 BE 1 7 ms 2 14 ms 3 7 4 ms 4 4 9 ms 36

First Law of Thermodynamics and Specific Heat Capacity 2018 A sample of 0 1 g of water at 100 C and normal pressure 1 013 x 105 N m2 requires 54 cal of heat energy to convert to steam at 100 C If the volume of the steam produced is 167 1 cc the change in internal energy of the sample is 2 18 Cal 5 2 a 104 3 J c 42 2 J b 208 7 d 84 5J In a thermodynamic system Q repres transferred to or from a system by represents the energy transferred to or by work I Q 0 and W 0 III W 0 and Q 0 II Q 0 and IV W 0 and

36 a What is the potential of point a with respect to point b in figure when switch S is open V 18 0 V 6 00 S 3 00 www a www S b 6 00 uF 3 00 uF fo Which point a or b is at the higher potential c What is the final potential of point b with respect to ground when switch S is closed d How much charge flows through switch S when it is closed

A point object is located at a distance of 100 m from a screen A lens of focal length 23 cm mounted on a movable frictionless stand is kept between the source and the screen The stand is attached to a spring of natural length 50 cm and spring constant 800 N m as shown Mass of the stand with lens is 2 kg How much impulse P should be imparted to the stand so that a real image of the ob is formed on the screen after a fixed time gap Also find this time gap Neglect widt the stand P ooooooo 50 cm 100 cm Stre

the values of two resistances are and R 10 0 0 1 The when they are connected in parallel In an experiment R 5 0 0 2 total resistance is a 3 3 7 c 3 4 7 b 3 3 5 d 2 5 7

Q 16 4 1 01 13 A particle is projected in a region where an electric field E E with a velocity from the origin at times t 0 If m is the mass of the particle and q is the charge of the particle then the momentum vector of the article when its x coordinate becomes is neglect gravitational effect

n e C 48 A uniform horizontal rod of length 40 cm and mass 1 2 kg is supported by two identical wires as shown in figure 15 E9 Where should a mass of 4 8 kg be placed on the rod so that the same tuning fork may excite the wire on left into its fundamental vibrations and that on right into its first overtone Take g 10 m s2 2 800 308 40 cm Figure 15 E9

1 A particle with total energy E is moving in a potential energy region U x Motion of the particle is restricted to the region when 1 U x E 2 U x E 3 U x 0 4 U X E

6 In the EM wave the amplitude of magnetising field H and the amplitude of electric field E at any place are related as 1 H Eo 3 H Eo Ho 2 Ho E C 4 H E Eo

19 Three conducting infinite plates are given having charge density o 20 and 4o respectively Electric field at point p is given by 1 20 Co 2 760 Co 20 40 18 76 3 20 26 46 26 Fe 460 36 46 26 226 4 70 80

A thin cir ying direction is lying in the x y plane with its centre at the origin A uniform magnetic field of strength B B 27 31 sk tesla is applied in the region The ring can rotate about the axis AA only and AA is in x y plane neglect effect of gravity B B A C Bolo rads m 5ml B 2 The magnitude of initial angular acceleration of the ring is A 2B 1 r 31 21 rads2 B D zero P m O 450 AL rads2

tion 25 A small block of mass m is attached to three springs with respective stiffness constants k k and ks see fig Find the period of oscillations if the block is slightly pressed against the spring with stiffness constant k Will your answer be the same if the block be pressed against the spring with stiffness 000000 constant k 90

Example 10 39 Light source of wavelength 400 nm used in Lloyd s mirror lies 1 mm above the plane mirror Find the distance of first minima above the mirror Distance of the screen from the plane of the sources is 2 m

9 Two masses M and M connected by means of a string which is made to pass over light smooth pulley are in equilibrium on a fixed smooth wedge as shown in figure If 0 60 and a 30 the ratio of M to M is M 50 a Lo M

D A straight wire of finite length carrying current subtends an angle of 60 at point P as shown The magnetic field at Pis ey 1 Hol 2 3TX 3 l P 60 2 Hol 2TX Ko

c S2 and 53 19 When sunlight is scattered by atmospheric atoms and molecules the amount of scattering of light of wavelength 440 nm is A The amount of scattering for the light of wavelength 660 nm is approximately c 1 5A A b 2 25A d 0 66A

A 4 00 uF capacitor and a 6 00 uF capacitor are connected in parallel across a 660 V supply line a Find the charge on each capacitor and the voltage across each b The charged capacitors are disconnected from the line and from each other and then reconnected to each other with terminals of unlike sign together Find the final charge on each and the voltage across each

1 A cylindrical log of wood floats vertically in water with one fourth of its length out of water The density of wood is A 0 25 g cc B 0 5 g cc D 1 g cc C 0 75 g cc

An automobile travelling with a speed of 60km h can brake to stop within a distance of 20m If the car is going twice as fast i e 120km h the stopping distance will be 1 20m 2 40m 3 60m 4 80m

A sphere of diameter r is cut from a solid sphere of radius r such that the centre of mass of remaining part be at maximum distance from orginal centre then this distance is 2 1 1 1 20 1 3 2 1135235 5 1 27 3 r 14 A 365 4 none of these

Q TUR4 r be the charge density distribution for a solid sphere of radius R and total charge Q For a point P inside the sphere at distance r from the centre of sphere the magnitude of electric field is AIEEE 2009 4 144 Let p r 1 4 2 2 Qr 4 R4 3 Qr 3 R4 4 0

Three charges of respective values 2 C 2 2 C and 2 C are arranged along a straight line as shown in the figure Calculate the total electric field intensity due to all three charges at the point P P 1864 10 2 C 1m 2 2 C 1m 2LLC

A beam of electrons after being accelerated through a potential difference of 100 volts enters into a uniform magnetic field which is perpendicular to the plane of paper and directed outwards The width of the region OM in which magnetic field is present is 2cm Till magnetic field is not switched on the electron beam moves straight forward and produces a bright spot at a point C on the fluorescent screen 6cm from the PQ which is at a distance 2 edge of the magnetic field When the magnetic field is switched on the spot shifts to a point A along the path ONA Find the displacement CA of the spot if the induction of the magnetic field B 1 5 x 10 3 Tesla 0 N M C

A tube filled with water rotating with angular velocity w Find equation of curve so formed 5 cm 10 cm 5 cm Ans V 2x

kk w wt Q Figure 10 23 b shows light reflected from a transparent medium say water As before the dots and arrows indicate that both polarisations are present in the incident and refracted waves We have drawn a situation in which the reflected wave travels at right angles to the refracted wave The oscillating electrons in the water produce the reflected wave These move in the two directions transverse to the radiation from wave in the medium i e the refracted wave The arrows are parallel to the direction of the reflected wave Motion in this direction does not contribute to the reflected wave As the figure shows the reflected light is therefore linearly polarised perpendicular to the plane of the figure represented by dots This can be checked by looking at the reflected light through an analyser The transmitted intensity will be zero when the axis of the analyser is in the plane of the figure i e the plane of incidence When unpolarised light is incident on the boundary between two transparent media the reflected light is polarised with its electric vector perpendicular to the plane of incidence when the refracted and reflected rays make a right angle with each other Thus we have seen that when reflected wave is perpendicular to the refracted wave the reflected wave is a totally polarised wave The angle of incidence in this case is called Brewster s angle and is denoted by ig We can see that i is related to the refractive index of the denser medium Since we have i r 2 we get from Snell s law R R 90 siniB sinr siniB sin 2 iB

2 A wire is bent in the form of an equilateral triangle of side 100cm and carries a current of 2A It is placed in a magnetic field of induction 2 0T directed perpendicular into the plane of paper The direction and magnitude of magnetic force acting on each side of the triangle will be X X X X X X X x B X X 1 2 N normal to the side towards centre of the triangle 2 2 N normal to the side away from the centre of the triangle 3 4 N normal to the side towards centre of the triangle 4 4 N normal to the side away from the centre of the triangle

Comprehension l Two trains A and B are moving with speeds 20 m s and 30 m s respectively in the same direction on the same straight track with B ahead of A The engines are at the front ends The engine of train A blows a long whistle Assume that the sound of the whistle is composed of components varying in frequency from f 800 Hz to f 1120 Hz as shown in the figure The spread in the frequency Thighest frequency lowest frequency is thus 320 Hz The speed of sound in still air is 340 m s J The speed of sound of the whistle is A 340 m s for passengers in A and 310 m s for passengers in B B 360 m s for passengers in A and 310 m s for passengers in B C 310 m s for passengers in A and 360 m s for passengers in B D 340 m s for passengers in both the trains The distribution of the sound intensity of the whistle as observed by the passengers in train A is best represented by 2007 7 A C Intensity Intensity f Frequency f2 Frequency B D Intensity Intensity Intensity f pro f2 Frequency 1120 f Frequency f2 Frequency 2007

B A tank with a square base of area 2 m is divided into two compartments by a vertical partition in the middle There is a small hinged door of face area 20 cm at the bottom of the partition Water is filled in one compartment and an acid of relative density 1 53 x 10 kg m 3 in the other both to a height of 4 m The force necessary to keep the door closed is Take g 10 m s d 80 N c 40 N a 10 N b 20 N

c 340 N d 6800 N A steel tape measures the length of copper rod as 90 00 cm when both are at 10 C the calibration temperature for the tape What would the tape read for the length of the rod when both are at 30 C given steel 1 2 x 10 5C and ac 1 7 x 10 5PC a 89 00 cm b 90 21 cm d 90 01 cm c 89 90 cm The density of a substance decreases from

4 Initially spring is in its natural length Now a block of mass 0 25 kg is kept as shown Find out maximum force by system on floor when block of mass 0 25 kg oscillates with amplitude psMmo01 1 2 cm and angular frequency 20 rad s 1 22 50 N m m 0 25kg 000000000000 M 2 kg 2 23 75 N

3 An a particle is moving with the velocity v ul u in a uniform magnetic field B Bk Magnetic force on a particle is 2 euB i j 4 2euB i j 1 2euB i j euB 1 1 3

Out of the three conducting identical plates middle flat is given charge 3 C and other two plates are not having any charge If switch S is closed Find the charge passing through switch S in C 0 3