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Physics Questions and Answers October 11, 2022

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The upper half of an inclined plane of inclination 0 is perfectly smooth while lower half is rough. A block starting from rest at the top of the plane will again come to rest at the bottom, if the coefficient of friction between the block and lower half of the plane is given by 2 (a) tane (b) 2 tan 0 (c) tan 0 1 (d) tane

10 A carnot engine having an efficiency of as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is (a) 90 J (c) 100 J (b) 99 J (d) 1 J

A barometer that uses water instead of mercury will be (a) shorter. (b) taller. (c) equal in height. (d) inoperable.

An aparticle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of 0.25 Wbm. The wavelength associated with the particle will be (a) 1 (c) 10 (b) 0.1 (d) 0.01

The current gain for a transistor working as commonbase amplifier is 0.96. If the emitter current is 7.2 mA, then the base current is 1996 (a) 0.29 mA (c) 0.39 mA (b) 0.35 mA (d) 0.43 mA

The velocity v of a particle at time t is given by where a, b and c are constant. The b V at tc dimensions of a, b and c are respectively (a) L, T and LT (c) L, LT and T (b) LT, LT and L (d) LT, L and T

A hollow sphere is filled with water. It is hung by a long thread. As the water flows out of a hole at the bottom, the period of oscillation will (a) first increase and then decrease (b) first decrease and then increase (c) go on increasing (d) go on decreasing

An ionization chamber with parallel conducting plates as anode and cathode has 5 x 10 electrons and the same number of singly charged positive ions per cm. The electrons are moving towards the anode with velocity 0.4 ms. The current density from anode to cathode is 4Am. The velocity of positive ions moving towards cathode is (a) 0.4 ms (c) zero

The percentage errors in the measurement of mass and speed are 2 and 3 respectively. The error in kinetic energy obtained by measuring mass and speed will be (a) 12 (c) 8 (b) 10 (d) 2

An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current I along the same direction is shown in fig. Magnitude of force per unit length on the middle wire B is given by 201 d Zoi (a) (b) d Hoi (c) 2nd Hoi (d) 2nd d 90

The largest and the shortest distance of the earth from the sun are r, and r. Its distance from the sun when it is at perpendicular to the majoraxis of the orbit drawn from the sun is (a) 4 (b) (c) (d) rr rr2 r r2 2r r rr rr 3

A galvanometer of 50 ohm resistance has 25 divisions. A current of 4 10 ampere gives a deflection of one per division. To convert this galvanometer into a voltmeter having a range of 25 volts, it should be connected with a resistance of (a) 2450 2 in series (c) 245 2 in series. (b) 2500 2 in series. (d) 2550 2 in series.

A body dropped from top of a tower fall through 40 m during the last two seconds of its fall. The height of tower is (g 10 ms) (a) 60 m (c) 80 m (b) 45 m (d) 50 m

The x and y coordinates of the particle at any time are x 5t 2t and y 10t respectively, where x and y are in meters and t in seconds. The acceleration of the particle at t2s is (a) 5 ms (c)8 ms (b)4 ms (d) 0

If potential (in volts) in a region is expressed as V(x, y, z) 6 xy y 2yz, the electric field (in NC) at point (1, 1, 0) is (a) (6 5j 2k) (b)(2 3) k) (c) (6 9j k) (d) (3 5) 3k)

A series RC circuit is connected to an alternating voltage source. Consider two situations (A) When capacitor is air filled. (B) When capacitor is mica filled. Current through resistor is i and voltage across capacitor is V then (a) V. V (b) i i (c) V V b (d) V

A parallel plate capacitor has a uniform electric field E in the space between the plates. If the distance between the plates is d and area of each plate is A, the energy stored in the capacitor is 2012M, 2011, 2008 (a) EE (b) E Adle (c) E Ad (d) EAd

A conveyor belt is moving at a constant speed of 2ms. A box is gently dropped on it. The coefficient of friction between them is 0.5. The distance that the box will move relative to belt before coming to rest on it taking g 10 ms, is (a) 1.2 m (c) zero (b) 0.6 m (d) 0.4 m

In a radioactive material the activity at time t, is R and at a later time t, it is R. If the decay constant of the material is , then (a) R Re(tt) (c) R R (b) R Re) (d) R Re(tt)

A vertical spring with force constant k is fixed on a table. A ball of mass m at a height h above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance d. The net work done in the process is (a) mg(h d) kd (b) mg(h d) kd (c) mg(hd) kd (d) mg(h d) kd 2

A refrigerator works between 4C and 30C. It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is(Take 1 cal 4.2 joules) (a) 2.365 W (c) 236.5 W (b) 23.65 W (d) 2365 W

In the network shown in the Fig, each resistance is 19. The effective resistance between A and B is (a) (b) (c) 7 Q (d) 1024 10 102 192 B

Light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index of the material of the rod the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence (a) n 2 (c) n 1.1 (b) n 1 (d) n 1.3

What should be the energy of an aparticle to describe a circle of same radius in the same field (a) 2 MeV (c) 0.5 MeV (b) 1 MeV (d) 4 MeV

The ratio of the dimension of Plancks constant and that of the moment of inertia is the dimension of (a) time (b) frequency (c) angular momentum (d) velocity

The photoelectric threshold wavelength of silver is 3250 x 10 m. The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536 10 m is (Given h 4.14 105 eVs and c 3 10 ms ) (a) 0.6 x 10 ms (b) 61 x 10 ms (c) 0.3 x 10 ms 1 (d) 6 x 10 ms

A square loop ABCD carrying a current i, is placed near and coplanar with a long straight conductor XY carrying a current I, the net force on the loop will be Y B C (a) Holi 3 Holi (b) (c) (d) 2 2 liL 3 Holil 2 XI L2 A ( L D L

The surface of planet Earth loses energy to outer space due mostly to (a) conduction. (b) convection. (c) radiation. (d) radioactivity.

If n, n, and n, are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by (a) (b) n3 (c) n n 3 (d) n n n 1

In a region, the potential is represented by V(x, y, z) 6x 8xy 8y 6yz, where V is in volts and x, y, z are in metres. The electric force experienced by a charge of 2 coulomb situated at point (1, 1, 1) is (b) 30 N (a) 65 N (c) 24 N (d) 435 N

A block of mass m is in contact with the cart C as shown in the Figure. m 1007 107 C The coefficient of static friction between the block and the cart is . The acceleration a of the cart that will prevent the block from falling satisfies mg (a) a (b) a (c) a (d) a CL m

Microscopic slush in water tends to make the water (a) more dense. (b) less dense. (c) more slippery. (d) warmer.

An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas (a) Isobaric (b) Isochoric (c) Isothermal (d) Adiabatic

A body of mass 3 kg is under a constant force which causes a displacements in metres in it, given by the relation st, where t is in seconds. Work done by the force in 2 seconds is 2006 (a) J MAS J

The coefficient of performance of a refrigerator is 5. If the inside temperature of freezer is 20C, then the temperature of the surroundings to which it rejects heat is (a) 41C (c) 21C (b) 11C (d) 31C

An electromagnetic radiation of frequency n, wavelength , travelling with velocity v in air enters in a glass slab of refractive index (). The frequency, wavelength and velocity of light in the glass slab will be respectively (a) n, and (b) n, 22 and (c) and 2 (d) , and v V

Put a saucer of water on your table. A process that then occurs is (a) evaporation. (b) condensation. (c) Both. (d) Neither.

Iff, and f, are the focal lengths of a convex lens for violet and red light respectively and F, and F are the focal lengths of concave lens for violet and red light respectively, then we have (a) ff and F F (b) ff and F F (d) ff and F

When relatively slow-moving molecules condense from the air, the temperature of the remaining air tends to (a) remain unchanged. (b) decrease. (c) increase. (d) spread out uniformly.

Compared with radiation from the Sun, terrestrial radiation has a lower (a) wavelength. (b) frequency. (c) Both. (d) Neither.

A stationary particle explodes into two particles of masses m, and m, which move in opposite directions with velocities v, and v. The ratio of their kinetic energies EE, is (a) m,vmv, (c) m,m, (b) mm, (d) 1

A high-temperature source radiates relatively (a) short wavelengths. (b) long wavelengths. (c) low frequencies of radiation. (d) None of these.

The equation of a simple harmonic wave is given by 3 sin y 2(50t x) Where x and y are in meters and t is in seconds. The ratio of maximum particle velocity to the wave velocity is (a) 2 (b) (c) 3 (d) n

In a mixture of hydrogen, oxygen, and nitrogen gases at a given temperature, the fastest molecules on average are those of (a) hydrogen. (c) nitrogen. (b) oxygen. (d) All have same average speed.

A simple harmonic oscillator has an amplitude A and time period T. The time required by it to travel from x A to x A2 is (a) T6 (c) T3 (b) T4 (d) T2

A wire carrying current I has the shape as shown in adjoining figure. Linear parts of the wire are very long and parallel to Xaxis while semicircular portion of radius R is lying in YZ plane. Magnetic field at point O is (a) B( x 2k) 4 R Ho 1 (b) B 4 R (c) B(n 2k) (d) B (n 2k) 4 R Ho 1 4 R (n 2k) Z

When a metallic surface is illuminated with radiation of wavelength 2, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 22, the stopping potential is. The threshold wavelength for the metallic surface is V (a) 42 (b) 52 (c) (d) 32

As entropy in a system increases, energy in the system (a) becomes more ordered. (b) becomes less ordered. (c) reaches equilibrium. (d) moves toward destruction.

Heat engines, such as a jet engine, are more efficient when run at (a) high temperatures. (b) constant temperatures. (c) low temperatures. (d) a constant rate.

A rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 weberm. The coil carries a current of 2A. If the plane of the coil is inclined at an angle of 30 with the direction of the field, the torque required to keep the coil in stable equilibrium will be (a) 0.20

The momentum of a photon of energy 1 MeV in kg ms, will be (a) 7 1024 (c) 5 x 102 (b) 1022 (d) 0.33 x 106

The lowest possible temperature is absolute zero, at (a) 0 kelvin. (b) ?273C. (c) Both are the same. (d) None of these.

A car moving with a speed of 40 kmh can be stopped by applying brakes at least after 2 m. If the same car is moving with a speed of 80 kmh, what is the minimum stopping distance (a) 8 m (c) 4 m (b) 6 m (d) 2 m

Regelation occurs due to waters (a) high specific heat. (b) open-structured ice crystals. (c) high rate of expansion. (d) slight tendency to freeze when its temperature is lowered.

Boiling and freezing occur when water is subjected to (a) decreased temperatures. (b) decreased atmospheric pressure. (c) increased temperatures. (d) increased atmospheric pressure.

Two spherical bodies of mass M and 5 M and radii R and 2 R released in free space with initial separation between their centres equal to 12 R. If they attract each other due to gravitational force only, then the distance covered by the smaller body before collision is (a) 4.5 R (c) 1.5 R (b) 7.5 R (d) 2.5 R

A galvanometer of resistance 20 2 gives full scale deflection with a current of 0.004 A. To convert it into an ammeter of range 1 A, the required shunt resistance should be (a) 0.38 (c) 0.08 (b) 0.21 (d) 0.0592

If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is (a) 0 (c) 45 (b) 90 (d) 180

A source of sound S emitting waves of frequency 100 Hz and an observor O are located at some distance from each other. The source is moving with a speed of 19.4 ms at an angle of 60 with the source observer line as shown in the figure. The observor is at rest. The apparent frequency observed by the observer is (velocity of sound in air 330 ms )

An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, the value of n is. 2011M (a) 3 (c) 5 (b) 4 (d) 2

A thin conducting ring of radius R is given a charge Q. The electric field at the centre O of the ring due to the charge on the part AKB of the ring is E. The electric field at the centre due to the charge on the part ACDB of the ring is (a) E along KO (c) E along KO O K B D (b) E along OK (d) 3 E along OK

The time it takes for a pendulum swinging to and fro refers to its (a) frequency. (b) period. (c) wavelength. (d) amplitude

A particle moves along a circle of radius (2) m with constant tangential acceleration. If the velocity of the particle is 80 ms at the end of the second revolution after motion has begun, the tangential acceleration is (a) 40 ms ms (c) 640 (b) 40 ms (d) 160 ms

You swing to and fro on a playground swing. If you stand rather than sit, the time for a to-and-fro swing is (a) lengthened. (b) shortened. (c) unchanged.

A monoatomic gas at a pressure P, having a volume V expands isothermally to a volume 2V and then adiabatically to a volume 16V. The final pressure of the gas is (take y ) (a) 64P P (c) 64 (b) 32P (d) 16P

A wire has a resistance of 3.102 at 30C and a resistance 4.502 at 100C. The temperature coefficient of resistance of the wire (a) 0.0064C (c) 0.0025C (b) 0.0034C (d) 0.0012C

If C, be the velocity of sound in air and C be the r.m.s velocity, then (a) C

A bomb of mass 1 kg is thrown vertically upwards with a speed of 100 ms. After 5 seconds it explodes into two fragments. One fragment of mass 400 gm is found to go down with a speed of 25 ms. What will happen to the second fragment just after the explosion (g 10 ms) (a) It will go upward with speed 40 ms (b) It will go upward with speed 100 ms

The periodic waves of intensities I, and I, pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is 2 (a) II (c)(1 2 (b) () (d) 2(1, I)

A body is executing S.H.M. When the displacements from the mean position are 4cm and 5 cm, the corresponding velocities of the body are 10 cm per sec and 8 cm per sec. Then the time period of the body is (a) 2 sec (b) 2 sec (c) sec (d) (32)sec

Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that O is their common point for the two. The wires carry I, and I currents respectively. Point P is lying at distance d from O along a direction perpendicular to the plane containing the wires. The magnetic field at the point P will

A current loop in a magnetic field (a) can be in equilibrium in one orientation (b) can be in equilibrium in two orientations, both the equilibrium states are unstable (c) can be in equilibrium in two orientations, one stable while the other is unstable (d) experiences a torque whether the field is uniform or nonuniform in all orientations

A Energy levels A, B, C of a certain atom correspond to increasing values of energy i.e., E

wt wt If vectors A coswt sin w t and B cos 2 sin are functions of time, then the value of t at which they are orthogonal to each other is (a) t (b) t TT 2w TT 3 (c) t 0 (d) t 4w

A remote sensing satellite of earth revolves in a circular orbit at a height of 0.25 10 m above the surface of earth. If earths radius is 6.38 10 m and g 9.8 ms, then the orbital speed of the satellite is (a) 8.56 km s 1 (b) 9.13 km s (d) 7.76 km s (c) 6.67 km s

Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohrs atomic model (a) 1.9 eV (c) 13.6 eV (b) 11.1 eV (d) 0.65 eV

A body of 3 kg moves in the XY plane under the action of a force given by 6t 4t. Assuming that the body is at rest at time t 0, the velocity of the body at t 3s is (a) 6 6 (c) 18 12 (b) 18 6) (d) 12 18

Find the speed of a wave by multiplying its frequency by its (a) period. (b) wavelength. (c) amplitude. (d) None of these.

The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied (a) Length 100 cm, diameter 1 mm (b) Length 200 cm, diameter 2 mm (c) Length 300 cm, diameter 3 mm (d) Length 50 cm, diameter 0.5 mm

Three point charges q, q and q are placed at points (x 0, y a, z0), (x 0, y 0, z 0) and (x a, y 0, z 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are (a) 2qa along the line joini points (x 0, y 0, z 0) and (x a, y a, z 0) (b) qa along the line joining points (x 0, y 0, z

A varying current in a coil changes from 10A to zero in 0.5 sec. If the average e.m.f induced in the coil is 220V, the selfinductance of the coil is (a) 5 H (c) 11 H (b) 6 H (d) 12 H

If radius of the Al nucleus is taken to be R Al then the radius of 33Te nucleus is nearly 53 2015 (a) RAI (b) RA1 1 (c) (d) 53 13 RA1 RA1

The power obtained in a reactor using U5 disintegration is 1000 kW. The mass decay of U per hour is 235 (a) 10 microgram (c) 40 microgram (b) 20 microgram (d) 1 microgram

In an electromagnetic wave in free space the root mean square value of the electric field is E 6Vm. The peak value of the magnetic field is (a) 2.83 x 10 T rms (c) 4.23 x 108 T (b) 0.70 10 T (d) 1.41 x 10 T

A thermodynamic system undergoes cyclic process ABCDA as shown in fig. The work done by the system in the cycle is (a) P.V Povo (c) 2 (d) Zero 0 P 3Po 2P Pol B D Vo 2Vo V (b) 2P V 0

A force F acting on an object varies with distance x as shown here. The force is in N and x in m. The work done by the force in moving the object from x 0 to x 6 m is F(N) 321 (a) 18.0 J (c) 9.0 J 0 1234567 (b) 13.5 J (d) 4.5 J x(m)

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 is (a) 0.5 (c) 1.0 (b) 0.8 (d) 0.2 2

One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face forms an image 12 cm behind the silvered face. The refractive index of the glass is (a) 0.4 (c) 1.2 (b) 0.8 (d) 1.6

The charge flowing through a resistance R varies with time t as Q at bt, where a and b are positive constants. The total heat produced in R is aR (a) 5853585 6b aR 3b 2b aR b

The angular velocity and the amplitude of a simple pendulum is and a respectively. At a displacement x from the mean position if its kinetic energy is T and potential energy is V, then the ratio of T to Vis (axw) (a) xw xw (b) (c). (d) (axw) (ax) x x (ax)
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The period of a 10-Hz wave is (a)1/10 s. (b) 1.0 s. (c) 10 s. (d) None of these.

Compared with the sound you hear from the siren of a stationary fire engine, its sound when it approaches you has an increased (a) speed. (b) frequency. (c) Both of these. (d) Neither of these.

The vibrations in a longitudinal wave move in a direction (a) along and parallel to the wave. (b) perpendicular to the wave. (c) Both of these. (d) Neither of these.

The loudness of a sound is most closely related to its (a) frequency. (b) period. (c) wavelength. (d) amplitude.

The compressions and rarefactions in sound normally travel (a) in the same direction. (b) in opposite directions. (c) at right angles to each other. (d) None of these.

During the time an aircraft produces a sonic boom, the aircraft is (a) breaking the sound barrier. (b) pulling out of a subsonic dive. (c) flying faster than sound. (d) All of these.

A long straight wire carries a certain current and weber at a m produces a magnetic field of 2 10 perpendicular distance of 5 cm from the wire. An electron situated at 5 cm from the wire moves with a velocity 10 ms towards the wire along perpendicular to it. The force experienced by the electron will be (charge on electron 1.6 10 C) (a) Zero (c)

The work functions for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einsteins equation, the metals which will emit photoelectrons for a radiation of wavelength 4100 isare (a) none (b) A only (c) A and B only (d) all three metals

A car accelerates from rest at a constant rate a for some time, after which it decelerates at a constant rate and comes to rest. If the total time elapsed is t, then the maximum velocity acquired by the car is (a) () t (b) (aB) t (c). (aB)t a (d)

The length of the wire between two ends of a sonometer is 100 cm. What should be the positions of two bridges below the wire so that the three segments of the wire have their fundamental frequencies in the ratio of 135 1500 2000 (a) cm, cm 23 23 1500 500 (b) cm, cm 23 23 1500 300 (c) cm, cm 23 1500 23 23 300 (d) cm, 23 cm