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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
ABCDEF is a regular hexagon of side a. At each vertex A, B and C a point charge +q is fixed and D,E,F a point charge -q is fixed. Intensity of electric field at a point lying on the line joining FC at a distance x away from the centre of hexagon (x gt gt gt gta) is found to be (sqrt(alpha)aq)/(2piepsilon_(0)x^(3)) where alpha is an integer. Find alpha |
Answer» 
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| 2. |
Calculate the radius of a metal sphere kept in air, whichcan hold a charge of 0.25 C, when connected to a power supply of 1 V. |
| Answer» SOLUTION :`2.25xx10^(9)m` | |
| 3. |
Tritium has a half-life of 12.5 y undergoing beta decay. What fraction of a sample of pure tritium will remain undecayed after 25 y. |
| Answer» Solution :By definition of HALF-life, half of the INITIAL sample will remain undecayed after 12.5 y. In the next 12.5 y, ONE-half of these nuclei WOULD have decayed. Hence, one FOURTH of the sample of the initial pure tritium will remain undecayed. | |
| 4. |
If the kinetic energy of an electron in ahydrogen is(e^(2))/(8 pi epsi_(0)r) then its potential energy is..... |
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Answer» `(E^(2))/(4pi epsi_(0)r)` `=-2xx(e^(2))/(8pi epsi_(0)r)` `=-(e^(2))/(4pi epsi_(0)r)` |
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| 5. |
Electron should be accelerated which voltage so that its de-Broglie wavelength will become 0.4 Å. |
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Answer» 9410 V `v=(h^(2))/(2melambda^(2))` `=((6.62xx10^(-34))^(2))/(2xx9.1xx10^(-31)xx1.6xx10^(-19)xx(0.4xx10^(-10))^(2))` |
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| 6. |
Consider the following statements and identify the correct answer. a) In forward bias of p-n diode, the effective barrier potential is (V_B -V). (V_B is barrier potential and V is the applied external voltage) b) In reverse bias of p-n diode, the effective barrier potential is (V_B +V) c) In forward bias, an ideal p-n diode offers zero resistance d) In reverse bias, an ideal p-n diode offers infinite resistance |
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Answer» a, b only are true |
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| 7. |
What happens when a liquid drop is electrified? |
| Answer» Solution :An outward FORCE acts on a charged LIQUID drop. It INCREASES it.s AREA and DECREASES ST. | |
| 8. |
A demodulator circuit contains |
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Answer» A diode |
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| 9. |
At two points P and Q on a screen in Young's double slit experiment, waves from slits S_(1) and S_(2) have a path difference of O and (lambda)/(4) respectively. The ratio of intensities at P and Q will be ...... |
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Answer» `3:2` `=I_(0)cos^(2){K((0)/(2))} "" [ :. r_(2)-r_(1)=0]` `=I_(0)cos^(2)(0)` `I_(P)=I_(0) ""…(1)` `I_(Q)=I_(0)cos^(2){(k(r_(2)-r_(1)))/(2)}` `=I_(0)cos^(2){(2pi)/(lambda)XX(lambda)/(8)} "" [:.r_(2)-r_(1)=(lambda)/(4)]` `=I_(0)cos^(2){(pi)/(4)}` `=I_(0)((1)/(sqrt(2)))^(2)` `I_(Q)=(I_(0))/(2) ""....(2)` `:.(I_(p))/(I_(Q))=(I_(0))/(I_(0)/(2))=(2)/(1)` `:.I_(p)=I_(Q)=2:1` |
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| 10. |
A bob is released from the horizontal position of the inextensible string. If the breaking strength of the string is equal to twice the weight of the bob. Find the. (A) Position where the string breaks. (B) Time after which the bob strikes the ground measured from the instant of breaking of the sting. (C ) Displacement of the bob from its point of breaking to the point of striking. |
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Answer» SOLUTION :`(A)theta=cos^(-1)((2)/(3))`from the vertical (B) `t=sqrt((20R)/(27g)+(16R)/(6G))-sqrt((20R)/(27g))` `(C) (4L)/(3)sqrt((4)/(81)(sqrt23-sqrt5)^(2)+1)` |
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| 11. |
In the above example , if the system moves from Bto A, what is the Change in internal energy ? |
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Answer» 300 J Thus, `DeltaU=DeltaU_(AB)+DeltaU_(BA)=0` or`DeltaU_(BA)=-DeltaU_(AB)=-300J` |
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| 12. |
If the emf of the driving cell be decreased, what will be effect on the position of zero deflection in a potentiometer ? Explain . |
| Answer» SOLUTION :If e.m.f. DECEASES`RARR (V)/(l) `decreases `rArr`positionof zerodeflectionincreases. | |
| 13. |
An initially parallel cylindrical beam travels in a medium of refractive index mu(I) = mu_(0) + mu_(2)I, where mu_(0) and mu_(2) are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. The speed of light in the medium is : |
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Answer» maximum on the axis of the beam `mu (I) = mu_(1) + mu_(2) I` So is maximum along the axis of CYLINDER i.e. refractive INDEX `mu` is maximum along the axis. `rArr` velocity is minimum along the axis of bam. |
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| 14. |
Two capillary tubes of radii 0.2 cm and 0.4 cm are dipped in the same liquid. The ratio of heights through which liquid will rise in the tube is |
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| 15. |
An initially parallel cylindrical beam travels in a medium of refractive index mu(I) = mu_(0) + mu_(2)I, where mu_(0) and mu_(2) are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. The initial shape of the wavefront of the beam is : |
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Answer» PLANAR 
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| 17. |
In an interference the intensity of two interfering waves are I and 4I respectively. They produce intensity at two point A and B with phase angle of (pi)/(2) and pi it respectively. Then differation in between them is ...... |
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Answer» I Here `I_(1)=I` and `I_(2) =4I, phi_(1)=(pi)/(2), phi_(2)= pi` On point `A I_(A)=I+4I+2 sqrt(4I^(2)) "cos" (pi)/(2)` On point `B I_(B)=I+4I+2 sqrt(4I^(2)) "cos" pi` `=5I-4I` =I Now `I_(A)-I_(B)=5I-I=4I` |
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| 18. |
A charged particle with velocityvec(upsilon) = x hati+y hatjmoves in a magnetic field vecB = y hati+x hatj . Magnitude of the force acting on the particle is F. The correct option for F is a) No force will act on particle if x = y b) Force will act along y-axis if y lt x c) Force is proportional to (x^2-y^2) if x gt y d) Force is proportional to (x^2 + y^2) if ygtx |
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Answer» a and b are true |
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| 19. |
Consider a sphere of radius R made of glass of refractive index mu. A small object moves along the diameter with a constant velocity u. Find the velocity of the image as seen by an observer outside when the object passes through center. |
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Answer» using a convex mirror of focal length less than 0.25 m |
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| 20. |
The output of a two input AND gate is one, only when its |
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Answer» EITHER INPUT is one |
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| 21. |
Figureshows two point sources S_1 and S_2that emit sound of wavelength lamda = 3.00 m. The emissions are isotropic and in phase, and the separation between the sources is d = 16.0 m. At any point P on the x axis, the wave from S_1 and the wave from S_2 interfere.When P is very far away ( x ~~ 0) , what are (a) the phase difference between the arriving waves from S_1 and S_2 and (b) the type of interference they produce? Now move point P along the x axis toward S_1. (c ) Does the phase difference between the waves increase or decrease? At what distance x do the waves have a phase difference of (d) 0.50lamda,( e) 1.00lamda, and (f) 1.50lamda? |
| Answer» SOLUTION :No PHASE DIFFERENCE , (b) CONSTRUCTIVE INTERFERENCE , (c ) increase , (d) 84.6 m , (c ) 41.2m , (f) 26.2 m | |
| 22. |
An initially parallel cylindrical beam travels in a medium of refractive index mu(I) = mu_(0) + mu_(2)I, where mu_(0) and mu_(2) are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius. As the beam enters the medium, it will : |
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Answer» travel as a CYLINDRICAL beam |
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| 23. |
The flow of positive charge, in one direction, is equivalent tothe flow of an equal |
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Answer» NEGATIVE CHARGE in the same direction |
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| 24. |
Calculate the force of attraction per unit length between two long straight conductors 10 cm apart, each carrying 5A, when they are at (i) 0^(@) (ii) 90^(@) (iii) 60^(@) inclinationi to each other. [Hint: DeltaF=(mu_(0)I_(1)I_(2)costheta)/(2pid) |
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| 25. |
What is common in Ustilago, Neurospora and Agaricus ? |
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Answer» All are edible |
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| 26. |
A conducting bar pulled with a constant speed v in a smooth conducting rail. The region has a steady magnetic field of induction B as shown in the figure. If the speed of the bar is doubled then the rate of heat dissipation will be |
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Answer» CONSTANT |
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| 27. |
Three charges are placed along x-axis at x = - a x = 0 and x = a as shown in the figure. The potential energy of the system is |
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Answer» `-( (1)/(4 pi epsilon_(0)) ) (q^(2))/(a)` |
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| 28. |
A resistance of 50 Omega is to be prepared using a wire of cross-sectional area 10^(-8) m^(2) and conductivity 2.2 xx 10^(6) siemens/metre. The length of the wire required is |
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Answer» 22.5 m |
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| 29. |
If 'G' is the resistance of the galvanometer, then its voltage sensitivity (S_(v)) and current sensitivity (S) are related as |
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Answer» `S_(V)=GS_(i)` |
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| 30. |
A terrestrial telescope consists of three convex lenses in row whose focal lengths are 100 cm, 5 cm and 10 cm respectively (i) Calculate the total magnification in normal adjustment (ii) What would the nature of the final image ? |
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| 31. |
In the above question find the force required to move the rod with constant vlocity v, and also find the power delivered by the external agent. |
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Answer» Solution :The force needed to keep the velocity CONSTANT `F_(ext)=ilB=(B^(2)l^(2)v)/(R+r)` Power due to external force `=(B^(2)l^(2)v^(2))/(R+r)=(EPSI^(2))/(R+r)=i^(2)(R+r)` Note that the power DELIVERED by the external agent is joule heating in the CIRCUIT. That means magnetic field helps in converting the mechanical energy into joule heating. |
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| 32. |
In a p-n junction in an unbiased condition |
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Answer» the POTENTIAL is the same everywhere. |
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| 33. |
What is the torsional couple due to? |
| Answer» Solution :The torisonal couple is due to the CLASTICITY possessed by the PHOSPHOR bronze RIBBON from which the COIL is suspended. | |
| 34. |
A particle is moving eastward with a velocity of 5 m/s. In 10 seconds, the velocity changes to 5 m/s northward. The average acceleration in this time is |
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Answer» `0.5 m s^-2 N W` |
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| 35. |
An L-C circuit contains a 0.60 H inductor and a 25muF capacitor is 3.0xx10^(-5)C? |
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| 36. |
(a)Define electric flux . Write its S.I. unit. (b) Using Gauss's law , prove that electric field at a point due to a uniformly charged infinite plane sheet is independent of the distance from it.(c )How is the field directed if (i)the sheet is positively charged , (ii)negatively charged ? |
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Answer» Solution :(a)Electric flux is defined as the NUMBER of electric field lines passing through an area normal to the surface. Alternatively, Surface INTEGRAL of the electric field is defined as the electric flux through a closed surface `phi=ointvecE*vecds` SI unit : `(N.m^(2))/(C)`or volt . metre (b)  Outward flux through the Gaussian surface , is `2EA=sigmaA//epsilon_(0)` `thereforeE=sigma//2epsilon_(0)` In vector FORM , `VECE=(sigma)/(2epsilon_(0))hatn` where `hatn` is a unit vector normal to the plane , away from it . Hence electric field is independent of the distance from the sheet. (c )For positively charged sheet theelectric field is directed away from the sheet. For negatively charged sheet the electric field is directed towards the plane of sheet. For positively charged sheet the electric field is directed towards the plane of sheet. |
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| 37. |
The half life of ""_(38) Sr^(90) isotope is 28 years. What is the rate of disintegration of 15 mg of this isotope? (Given Avogadro No =6.023 xx 10^(23) ) |
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Answer» Solution :`T_(1//2) = 28` years `= 28 XX 365 xx 24 xx 3600` `T_(1//2) = 8.83 xx 10^(8)` SECONDS `90g Sr_(38)^(90)` contains `6.0.23 xx 10^(23)` atoms `N = (6.023 xx 10^(23) xx 15 xx 10^(-3))/(90) = 1.004 xx 10^(20)` atoms `lambda = (0.693)/(T_(1//2)) = (0.693)/(8.83 xx 10^(8)) = 0.07848 xx 10^(-8)` `lambda = 7.85 xx 10^(-10)` Rateof disintegration `R = lambda N` `R = 7.85 xx 10^(-10) xx 1.004 xx 10^(20)` `R = 7.8814 xx 10^(10)B Q` |
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| 38. |
A solid conducting sphere having a charge 'Q' is surrounded by an uncharged concentric conducting hollow spherical shell. Let the P.D between the surface of the solid sphere and that of the outer surface of the hollow shell be V. If the shell is now given a charge of -3Q. The new PD between the same two surfaces is |
| Answer» ANSWER :A | |
| 39. |
A charged particle (charge q, mass m) has velocity vo at origin in +x direction. In space there is a uniform magnetic field B in-z direction. Find the y coordinate of particle when it crosses y axis. |
| Answer» SOLUTION :`(2mv_0)/(QB)` | |
| 40. |
The pair of equations x + 2y + 5 = 0 and −3x − 6y + 1 = 0 has |
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Answer» UNIQUE solution |
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| 41. |
A thick wire of radius r=5 mm carries a steady current I=10 A. An electron leaves its surface perpendicularly with velocity v_(0)=10^(6) m//s. Find the maximum distance from the surface of the wire before it turns back. |
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| 42. |
For a reaction to occur spontaneously : |
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Answer» `Delta S` Mustbe negative `Delta F=-ve` `Delta G=DeltaH-TDELTAS` `DeltaH-TDeltaS=-Ve` OR `-DeltaH +TDeltaS =+Ve` |
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| 43. |
The magnetic flux linked with a coil, in weber, is given by the equation: The induced e.mn.f. in the coil in the fourth second will be |
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Answer» 145 V |
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| 44. |
Statement - 1 : Sky wave signals are used for long distance radio communication . These signals are in general, less stable than of ionosphere varies form hour to hour , day to day and and season to season. |
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Answer» Statement -1 is true , Statement -2 is true , Statement -2 is the correct explanation of Statement -1. |
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| 45. |
Geostationary satellite appears unstable in space above a place in the soil of the earth.Is it true? |
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| 46. |
A transverse wave is represented by the equation y = y_(0) sin " "(2pi)/(lambda) (vt- x) For what value of lambda is the particle velocity? |
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Answer» `lambda = pi y_(0)` here `V_(MAX) = 2V` `y_(0) OMEGA = 2v` `y_(0).2 pi v"" rArr "" (v)/(V) = pi y_(0)`. or `"" lambda = pi y_(0)` CORRECT choice is (a). |
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| 47. |
A particle is projected from the origin in X-Y plane. Acceleration of particle in Y direction is a. If equation of path of the particle is y = ax-bx^(2), then find initial velocity of the particle. |
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Answer» Solution :`y=ax- BX^(2) "" y= X tan theta= (alpha x^(2))/(2 u cos^(2) theta)` `tan theta= a and (alpha)/(2U cos^(2) theta)=b u= sqrt((alpha(1+a^(2)))/(2B)` |
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| 48. |
Explain the working of an endoscope. |
| Answer» Solution :An endoscope is an instrument used by DOCTORS which has a bundle of OPTICAL fibres that are used to see inside a patient.s BODY. Endoscopes work on thephenomenon of total internal reflection. The optical fibres are inserted in to the body through mouth, nose or a special hole MADE in the body. Even operation could be CARRIED out with the endoscope cable which has | |
| 49. |
(A): The electric bulbs glows immediately when switch is on. (R): The drift velocity of electrons in a metallic wire is very high. |
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Answer» Both 'A' and 'R' are TRUE and 'R' is the CORRECT explanation of 'A' |
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| 50. |
Itis now established that protonsand neutronsare themselves built out of more elementary units called quarks a proton and a neutron consist ofthree quarks each. Two types of quarks , the so called 'up' quark, (denoted by U) of charge + (2//3) e and the 'down' quark (denoted by d) of charge (-1//3) etogether with electronsbuild up ordinary matter. Suggest a possible quark composition of a protonand neutron |
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Answer» <P> SOLUTION :p,UUD, N,UDD |
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