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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. |
A solid conducting sphere of radius R is surrounded by a concentric metallic shell of inner radius 2R and outer radius 3R. The shell is earthed. The inner sphere is connected to a switch S by a thin conducting wire through a small hole in the shell. By closing the switch S, the inner sphere is connected to a distant conducting sphere of radius R having charge Q. Find the charge that flows to earth through wire AB. |
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| 2. |
(a) What happens if a bar magnet is cut into two pieces (i) transverse to its length (ii) along its length? (b) What happens if an iron bar magnet is melted? Does it retain its magnetism? (c) A magnetised needle in a uniform magnetic field experiences a torque but no net force. However, an iron nail near a bar magnet experiences a force of attration in addition to a torque, explain. (d) Must every magnetic field configuration have a north pole and a south pole? What about the field due to a toroid? (e) Can you think of magnetic field configuration with three poles? (f) Two identical looking iron bars A and B are given, one of which is definitely known to be magnetised. How would one ascertain whether or not both are magnetised? If only one is magnetised how does one ascertain which one? Use nothing else but the bars A and B. |
| Answer» SOLUTION :No, pole EXISTS only when the SOURCE has some net magnetic moment. There is no pole in toroid. Magnetic field DUE to a toroid `B=mu_(0) n1` | |
| 3. |
A plano-convex lens is made of flint glass, its focal length is |
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Answer» INVERSELY PROPORTIONAL to the WAVELENGTH of light |
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| 4. |
Kirchhoff's law of junctions (first law), Kirchhoff's law of meshes (second law) are respectively based on |
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Answer» CONSERVATION of CHARGE, conservation of ENERGY |
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| 5. |
A second's clock with a iron pendulum is constructed so a to keep correct time at 10^(@)C. Give alpha_("iron")=12xx10^(-6) per""^(@)C. What will be the change in the rate when the temperature rises to 25^(@)C? |
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Answer» Solution :When the pendulum keeps correct TIME, its period of vibration is 2 sec and so it makes `(24xx60xx60)/2=43200` Vibratiions /day If lenth of the pendulum at `10^(@)C` is `l_(10)` and at `25^(@)C` is `l_(25)` `:.l_(25)=l_(10)[1+alpha(25-10)]=l_(10)[1+15alpha]` as `T=2pi sqrt(L//g)` i.e. `T prop sqrt(l)` i.e. `n prop 1/(sqrt(l))`, n is no of vibrations per sec `:.(n_(25))/(n_(10))=sqrt((l_(10))/(l_(24)))=[1+15alpha]^(-1//2)~~1=15/2alpha` `:.n_(25)=n_(10)(1-15/2xx12xx10^(-6))` `=43200[1-0.00009]=43119.2` That is the clock makes (3200-43196.12=3.88 vibratiion loss per day. That is clock losses `3.88xx2=7.76` sec per day). |
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| 6. |
A magnetic needle is placed in a uniform magnetic field. It experienece |
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Answer» Solution :a. In either case, one gets , each with a north and south POLE. b. No force if the field is uniform . The iron nail experiences a nonuniform field to the bar magnet. There is induced magnetic moment in the nail, therefore , it experiences both force and torque. The net force is attractive because the induced south pole (say) in the nail is closer to the north pole of magnet than induced north pole. c. Not necessarily True only if the source of the field has a net NONZERO magnetic moment . This is not so for a toroid or even for a straight infinite conductor. d. Try bring different ends of the closer . A repulsive force in some situation establishesthat both magnetised . If the is always attraction , then one of them is not magnestied . In a bar magnet the intensity of the magnetic field is the strongest at the two ends (poles) and weakest at the central region. This fact MAY be used to determine WHETHER A or B is the magnet . In this case, to see which one of the two bars is a magnet , pick up one, (say,A) and lower one if its ends , first on one of the ends of the other (say, B) and then on the middle of B. If you notice that inthe middle of B, A experiences no force , then B is magnetised If you do not notice any change from the end to the middle of B , then A is magnetised . |
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| 7. |
Which one of the following is the unit of electric field intensity? |
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Answer» `"VOLT"//METRE` |
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| 8. |
Using AND ,Not and OR gates desigin a local circuit to evalute ABC+ABC+BAC |
Answer» SOLUTION :
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| 9. |
A child is swinging a swing. He is one metre above the ground at the lower point and 2 metre above the gound at the highest point. The speed of the child at the lowest point of the swing is : (g = 10 ms^(-2)) |
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Answer» `4.5 MS^(-1)` |
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| 10. |
Explain with the help of a labelled diagram, the principle and construction of a cyclotron. Deduce an expression for the cyclotron frequency and show that it does not depend on the speed of the charged particle. |
| Answer» Solution :CONSTRUCTION of a cyclotron : As shown in labelled diagram `D_1 and D_2` are two semi-circular DISC like METAL containers called dees. The straight sections of the dees are open so that the ions can move freely from `D_1 ` to `D_2` and vice-versa. The whole assembly is evacuated to avoid collisions between the ions and the air molecules. A HIGH FREQUENCY oscillating electric field (shown by dot marks in figure) by using an electromagnet. | |
| 11. |
The minimum force required to start pushing a body up a rough (frictional coefficient ) inclined plane is F_(1) while the minimum force needed to prevent it from sliding down is F_(2) if the inclined plane makes an anglethetawith the horizontal such that theta = 2mu then the ratio F_(1)//F_(2) is : |
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Answer» 1 and `F_(2) = mg sin theta-mu mg cos theta` `:.(F_(1))/(F_(2))=(sin theta+mucos theta)/(sin theta-mu cos theta)=(tan theta+mu)/(tan theta- mu)`=`(2mu+mu)/(2mu-mu)=(3mu)/(mu)=3` Thus, (C) is the correct choice 
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| 12. |
Which of the following contains insectivorous plants? |
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Answer» BLADDERWORT and Cuscuta |
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| 13. |
Name the poetic devices used in the poem. |
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Answer» metaphor |
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| 14. |
You are given prisms made of crown glass and flint glass with a wide variety of angles. Suggest a combination of prims which will a. deviate a pencil of white light without much dispersion b. disperse (and displace ) a pencil of white light without much deviation |
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Answer» Solution :Two identical prisms made of the same glass placed with their bases on opposite sides (of the incident white light) and faces touching(or parallel will neither DEVIATE nor DISPERSE, but will mearly produce a parallel displacement of the beam. a . To deviate without dispersion, choose , say the first prism to be crown glass, and take for the second prism a flint glass prism of suitably chosen refracting ANGLE (smaller than that of crown glass prism because the fiint glass prism disperses more ) so that dispersion due to first is nullified by the second. b. To disperse without deviation , increase the angle of flint glass prism (i.,e try flint glass prisms of greater and greater angle ) so that DEVIATIONS due to the two prisms are equal and opposite. (the flint glass has higher refractive index than that of crown glass ). Because of the adjustments involved for so many COLOURS, these are not meant to be precise arrangments for the purpose required. |
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| 15. |
Two particles are projected in air with speed u at angles theta_(1) and theta_(2), (both acute) to the horizontal, respectively. If the height reached by the first particle is greater than that of the second, then which one of the following is correct? |
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Answer» `theta_(1)gttheta_(2)` |
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| 16. |
An electron beam acceleratedby a p.d. of V=100 V enters into a magnetic field perpendicular out the plane of the page. The space occupied by the field is width d=10 cm. A screen is held at right angles to the initial direction of motion of the beam at a distance b=20 cm from the nearer edge of the field. find the distance 'delta' of the point where the beam strikes the screen from the point where it whould strike had there been no field. |
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| 17. |
Match list I with list II LIST - I (a) Centrifugal force(b) Centripetal force(c ) Tangential force(d) Angular velocityLIST - II(e ) Along the axis of rotation (f) Towards the centre of rotation(g)Away from the centre of rotation(h) Changes the angular velocity |
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Answer» a-h, B-g, c-f, d-e |
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| 18. |
The equivalent capacity between A and B in the given circuit is (C_1=4 mu F,C_2=12 muF, C_3= 8 muF, C_4= 4 muFC_5 =8 muF) |
| Answer» Answer :C | |
| 19. |
Where was Lencho's house situated? |
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Answer» BOTTOM of the hill |
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| 20. |
1-V characteristics of four devices are shown in figure. Identify devices that can be used for modulation |
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Answer» (i) and (iii) (ii) represents square law diode modulation. (iii) represents CONSTANT current source. (iv) represents PART of it as square law modulation. Thus, for modulation (iii) and some regions of (iv) can be used. |
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| 21. |
The self-inductance of an air-core solenoid is 4.8 mH. If its core is replaced by iron core, then its self-inductance becomes 1.8 H. Find out the relative permeability of iron. |
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Answer» Solution :`L_(AIR)=4.8xx10^(-3)H` `L_(iron)`=1.8H `L_(air)=mu_(0)N^(2)Al=4.8xx10^(-3)H` `THEREFORE``mu_(r)=(L_(iron))/(L_(iron))=(1.8)/(4.8xx10^(-3))`=375 |
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| 22. |
A compass needle of magneticmoment60 Am^(2)pointing geopgraphical north at a place where the horizontal componentof earth fiedlis 40 mu Wbm^(-2)experiences a torque of 1.2 xx10^(-3) Nmthe declination of the place is |
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Answer» `15^(@)` `THEREFORE sin theta =(tau)/(MH)=1/2 therefore theta =30^(@)` |
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| 23. |
A series C–R circuit consists of a capacitance 16 mF and resistance 8Omega. If the input a.c. voltage is (200 V, 50 Hz), Calculate (i) voltage across capacitor and resistor. (ii) Phase by which voltage lags/leads current. |
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Answer» SOLUTION :Current in the circuit `I= (V)/(Z)` When `Z = sqrt(X_(C )^(2)+ R^2), X_(C ) = (1)/(omega C) = (1)/(2 PI v C)` Then TOTAL voltage across capacitor and resistor. `V_(C ) = I X_(C ), V_(R ) = IR`. (II) `tan phi = (X_C)/( R)` [ V lags current] |
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| 24. |
A neutral pion disintegrated during its flight into two gamma quants with equal energies. The angle of divergence of gamma quanta is Theta=60^(@). Find the kinetic energy of the pion and of each gamma quantum. |
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Answer» Solution :No. of nuclei in the FIRST generation= No. of nuclei INITIALLY`=N_(0)` `N_(0)` in the second generation`=N_(0)xx "multiplication FACTOR" =N_(0).k` `N_(0)` in the `3rd` generation `=N_(0).k.k=N_(0)k^(2)` `N_(0)` in the nth generation`=N_(0)k` 
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| 25. |
If X= A xx B and Delta X Delta A and Delta B are maximum absolute error in X ,A and B respectively , then the maximum relative in X is given by |
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Answer» `DeltaX = DeltaA + DeltaB` |
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| 26. |
The maximum electric field at a distance of 10m from an isotropic point source of light is 3.0 Vm^(-1). Calculate (a) the maximum value of magnetic field,(b) average intensity of light at that place and (c ) the power of the source.[c=3xx10^(8)ms^(-1), epsilon_(0)=8.854xx10^(-12)C^(2)N^(-1)m^(-2)] |
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Answer» Solution :`E_(0)=3 V//m, c=3xx10^(8)m//c` `c=(E_(0))/(B_(0))rArr B_(0)=(E_(0))/(c )` `therefore B_(0)=(3)/(3xx10^(8))=1xx10^(-8)T` Average intensity of radiation `I=epsilon_(0)c^(2)E_(RMS)^(2)` `E_(rms)^(2)=(E_(0)^(2))/(2)` `therefore I=(epsilon_(0)cE_(0)^(2))/(2)` `(epsilon_(0)=8.85xx10^(-12)c^(2)//Nm, E_(0)=3 V//m)` `therefore I=(8.85xx10^(-2)xx3xx10^(8))xx(2)/(2)` `=1.195xx10^(-2)W//m^(2)` Now power P = `("energy")/("time")` `=("intensity"xx"area"xx"time")/("time")` `therefore` Power P `=I xx 4PI R^(2) "" [R=10m]` `=1.195xx4xx3.14xx100xx10^(-2)` = 15 WATT. |
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| 27. |
Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror and parallel to the second is reflected from the second mirror parallel to the first mirror. The angle between the two mirrors is : |
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Answer» `30^(@)`  So " "`angle M_(1) RS = angle ORO = angle M_(1)OM_(2) = theta` Similarly ""`angleM_(2)QP = angleOQR = angleM_(2)OM_(1) = theta` `THEREFORE "In" Delta ORO, 3theta = 180^(@) , theta = 60^(@)`. |
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| 28. |
A uniform disc of radius R has a hole cut out which has a radius r. The centre of hole is at a distance (R )/(2) from the centre of disc. The position of centre of mass is shifted through a distance x from 'O' find x. If in this question the values of R = 6 m and that if r = 1 m, calculate the valueof shift from 'O' and state whether it is towards left or right of O. |
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Answer» `(R^(2)r)/(2(R^(2)-r^(2))),(3)/(37)m` TOWARDS left of 'O' (t = thickness) Mass of scooped out discc `=pir^(2)trho` Mass of remaining disc `=pi(R^(2)-r^(2))trho` Then, `pi(R^(2)-r^(2))trhoxx X=pir^(2)trho(R)/(2)` or `x=(r^(2)R)/(2(R^(2)-r^(2)))`  Now `x=(r^(2)R)/(2(R^(2)-r^(2)))` Here `r=1m` `R=6m` `THEREFORE x=((1)^(2)xx6)/(2(36-1))=(3)/(35)m` towards left of centre. |
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| 29. |
Is the frequency of oscillation of kinetic energy or potential energy same as the frequency of oscillation of charge ? |
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| 30. |
A flow of liquid is streamline if the Reynold number is : |
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Answer» LESS than 1000 So correct CHOICE is (a). |
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| 31. |
The refractive indices of glass and water are 3/2 and 4/3 respectively. When monochromatic light passes from glass to water, the ratio of wavelength in glass to its wavelength in water is: |
| Answer» ANSWER :C | |
| 32. |
The L-shaped fish tank shown in Fig. is filled with water and is open at the top . Here , d = 70 m . (a) What is the (total) force exerted by the water on face A ? (b) What is the (total) force exerted by the water on face B ? |
| Answer» Solution :(a) `1.17 XX 10^(7) N , (B) 1.33 xx 10^(7) N` | |
| 33. |
Relative permeability mu_r and magnetic susceptibility X_m of a material are related as ___________ . |
| Answer» SOLUTION :`mu_r = 1 + x_(m)` | |
| 34. |
A battery of emf 2 V and internal resistance 0.5 Omega is connected across a resistance of 9.5 Omega. How many electrons pass through a cross-section of the resistance in 1 second ? |
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| 35. |
Why current is a scalar? |
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Answer» Solution :The current I is DEFINED as the SCALAR product of current density and AREA vector in which the charges cross. `I=vecj*vecA` The DOT product of two vector quantity is a scalar form Hence, current is called as a scalar quantity. |
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| 36. |
In (figure9a)a solenoid produce a magnetic field whose stength increases into the plane of the page. An induced emf is established in a conduction loop surrounding the solenoid, and this emf lights bulbs A and B. In figure (b) P and Q are shorted. After the short is inserted |
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Answer» BULB A GOES out bulb B GETS brighter |
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| 37. |
H-polaroid is prepared by |
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Answer» orienting herapathite crystal in the same direction in nitrocellulose |
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| 38. |
Give any two uses microwaves. |
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Answer» Solution :Microwaves are used in 1. Aircraft NAVIGATION, [speed guns to time fast BALLS, tennis SERVES and automobiles). 2. Microwave OVENS. |
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| 39. |
The deceleration experienced by a moving motor boat after its engine is cut off is given by dv/dt =kv^3, where is a constant. Ifv, is the magnitude of the velocity at cut off, the magnitude of velocity at time after the cut off is : |
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Answer» `(v_0)/(2)` `[1/2v^2]_(v_0)^(v)=kt` or `(1)/(2v^2)-(1)/(2v_(0)^(2))=kt` or `v_(0)^(2)-v^(2)=2kt v^(2)v_(0)^(2)` `v^(2)=(v_(0)^(2))/(2ktv_(0)^(2)+1)` or `v=(v_0)/(sqrt(2ktv_(0)^(2)+1)` |
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| 40. |
The total energy ofa particle of mass 0.1 kg performing SHM is 0.2 J . Find its maximum speed and period if the amplitude is 2cm. |
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Answer» Solution :Data : m= 0.1 kg, E = 0.2 J , A = 2 cm = ` 2XX 10^(-2)` m (i) The TOTAL ENERGY of the particle. ` E = KE_(max) = 1/2mv^(2) _(max)` `v_(max) = sqrt((2E)/m) = sqrt((2xx0.2)/(0.1)= 2 m//s` (ii) ` omega = (2PI)/T = omegaA = v_(max) = 2 m//s` ` (2piA)/T= 2m//s` The period of SHM of the particle . ` T= (2piA)/2 = piA = 3.142 xx 2xx 10^(-2) = 0.06284 s` |
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| 41. |
A: To increase resolving power of a telescope, the diameter of objective should be large. R: Resolving power of a telescope is given by (D)/(1.22 lambda) |
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Answer» Both ASSERTION and reason are true and the reason is correct EXPLANATION of the assertion. |
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| 42. |
Distinguish between Nanoscience and Nanotechnology. |
Answer» SOLUTION :
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| 43. |
Define the term retentivity or remanence. |
| Answer» Solution :Retaining the magnetism even after the removal of the MAGNETISING FIELD is CALLED RETENTIVITY. | |
| 44. |
The branch which deals with, design,/development and application of electron devices what we call ? |
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| 45. |
A laser beam is used for locating distant objects because it. |
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Answer» Has SMALL ANGULAR speed |
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| 46. |
High precision optical instruments uses prisms instead of mirror to reflect light Name the phenomena used for reflecting light using prism. |
| Answer» SOLUTION :TOTAL intemal REFLECTION | |
| 47. |
A thin-walled. Spherical conducting shell S of radius R is given charge Q. The same amount of charge is also placed at its centre C. Which of the following statements are correct ? |
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Answer» On the outer surface of S, the charge density is `(Q)/(2pi R^(2))` |
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| 48. |
A capacitor has some dielectric between its plates and the capacitor is connected to a DC source. The battery is now disconnected and then the dielectric is removed. State whether the capacitance, the energy stored in it, electric field, charge stored and the voltage will increase, decrease or remain constant. |
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Answer» Solution :Capacitance of CAPACITOR with dielectric constant K, `C = (K in_(0)A)/(d)` where K is positive and its value is greater then 1. So by removing dielectric slab and keeping A and d constant capacitance C of capacitor will decrease. When banery and dielectric slab from capacitor is removed the CHARGE remains the same. As the energy in capacitor`U = (q^(2))/(2C)` when capacitance C is decreased by removing dielectric slab but q is the same HENCE in `U prop (1)/(C)` C is decreased so U will increase. By equation `C= (qQ)/(V)` , q is constant and C decreases and V should increase. Now d is constant and V INCREASES henceaccording to `E = (V)/(d)` E is increases . |
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| 49. |
A person is listening to two trains one approaching him while the other moving from him. The speed of both the trains is 5 m/s, If both trains give off whistle frequency of 280 Hz then the observer will hear......no of beats. (Velocity of sound = 350 m/s) |
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Answer» 6 |
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| 50. |
An open knife edge of mass M is dropped from a height h on a wooden floor. If the blade penetrates adistances into the wood, the average resistance offered by the wood to the blade is :- |
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Answer» Mg Work done =(F-Mg) s=kinetic ENERGY Velocity of FALL = `sqrt(2gh)` `therefore (F-mg)s =1/2 M(sqrt(2gh))^2` or `(F-Mg)s=1/2 M XX 2gh` or `F=(Mgh)/s + Mg =Mg(1+h/s)` |
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