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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 slit beam wide is irradiated normally with microwaves of wavelength 1.0 cm .Then the angular spread of central maximum on either side of incident light is nearly |
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Answer» 1/5 RADIAN |
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| 2. |
Statement I: If a carrier wave is amplitude modulated, the amplitude of its wave changes very slowly. Statement II: Generally, amplitude of wave of a data signal is much less than that of a carrier wave. |
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Answer» Statement I is true, statement II is true, statement II is a CORRECT explanation for statement I. |
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| 3. |
The following combination are concerned with experiments of the characterization and use of a moving coil galvanometer. The series combination of variab resistance R, one 100 Omega resistor and moving coil galvanometer is connected to a mobile phone charger having negligible internal resistance. The zero of the galvanometer lies the centre and the pointer can move 30 division full scale on either side depending on the directin of current. The reading of the galvanometer is 10 divisions and the voltages across the galvanometer and 100 Omega resistor are respectively 12mV and 16 mV. A 24 Omega resistcnce is conneted to a 5 V battery with internal resistance of 1Omega. A 25 Omega resistance is conneted in series with the galvanometer and this combination is used to measur the voltage across the 24 Omega resistance. The number of divisons shown in the galvanometer is |
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Answer» 6 |
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| 4. |
The following combination are concerned with experiments of the characterization and use of a moving coil galvanometer. The series combination of variab resistance R, one 100 Omega resistor and moving coil galvanometer is connected to a mobile phone charger having negligible internal resistance. The zero of the galvanometer lies the centre and the pointer can move 30 division full scale on either side depending on the directin of current. The reading of the galvanometer is 10 divisions and the voltages across the galvanometer and 100 Omega resistor are respectively 12mV and 16 mV. The resistance of the galvanometer is ohm is : |
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Answer» `50OMEGA` |
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| 5. |
The following combination are concerned with experiments of the characterization and use of a moving coil galvanometer. The series combination of variab resistance R, one 100 Omega resistor and moving coil galvanometer is connected to a mobile phone charger having negligible internal resistance. The zero of the galvanometer lies the centre and the pointer can move 30 division full scale on either side depending on the directin of current. The reading of the galvanometer is 10 divisions and the voltages across the galvanometer and 100 Omega resistor are respectively 12mV and 16 mV. The series combination of the galvanometer with a resistnce of R is conneted across an ideal voltage supply of 12 V and this time the galvanometer shows full scale defiention of 30 divisions. The value of R is nealy |
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Answer» `12.5 KOMEGA` |
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| 6. |
On a platform a man is watching two trains one leaving the station the other approaching the station, both with the same velocity 2 m/s and blowing their horn with a frequency 480 Hz. The number of beats heard by the man will be (Velocity of sound in air is 320 m/s) |
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Answer» 6 |
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| 7. |
The diameter of a brass rod is 4 mm and Young's modulus of brass is 9xx10^(10)" N"//"m"^(2). The force required to stretch by 0.1% of its length is : |
| Answer» Answer :C | |
| 8. |
A square loop of length l and resistance R is placed in a magnetic field B which points into the paper and it does not change with time. If the loop moves with velocity 'v', then the induced current and its direction is |
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Answer» Bv/R in anti-CLOCKWISE DIRECTION |
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| 9. |
A parallel plate air capacitor has capacitance C. Half of space between the plates is filled with dielectric of dielectric constant K as shown in figure . The new capacitance is C . Then |
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Answer» `C=C[(K)/(K+1)]` `(1)/(C_(AB))=(1)/(((epsilon_(0)KA)/(d//2)))+(1)/(((epsilon_(0)A)/(d//2)))` `IMPLIES (1)/(C_(AB))=(d)/(2epsilon_(0)A)[(1)/(K)+1]` `implies (1)/(C_(AB))=(d)/(2epsilon_(0)A)[(1+K)/(K)]` `implies C_(AB)=(2epsilon_(0)A)/(d)[(K)/(1+K)]=2C[(K)/(1+k)]` `C_(AB)=C((2K)/(1+K))` |
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| 10. |
The variation of potential difference V with length l in case of two potentiometers A and B is as shown in Fig. Which one ofthese two will you prefer for comparing emfs of two primary cells ? |
| Answer» Solution :POTENTIOMETER B is more sensitive because potential gradient for ITIS smaller. Hence, we prefer potentiometer B to compare emfs of two PRIMARY cells. | |
| 11. |
The electric field in a region is radially out ward with magnitude E = Ar. Find the charge contained in a sphere of radius 20 cm. Given A = 100Vm^(-2) |
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Answer» `8.89 XX 10^(-11)C` |
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| 12. |
A red ray and a violet ray passing through a glass slab are incident simultaneously on an interface with air. It is seen that the red ray is refracted but the violet ray is reflected. Explain the reason behind it. |
| Answer» Solution :The refractive INDEX of glass for red light is SMALLER than that of glass for violet light. Since the CRITICAL angle, `theta_(c) = sin^(-1)""(1)/(mu),` so the critical angle of glass for red light is compartively greater. So the angle at which the red and the violet rays are incident, is smaller than the critical angle of red light but greater than the critical angle of violet light. So the red light is refracted and the violet light is totally REFLECTED. | |
| 13. |
A long solenoid of length l=2.0 m , radius r=0.1 m and total number of turns N=1000 is carrying a current i_(0)=20.0A. The axis of the solenoid conicides with the z-axis. (a) State the expression for the magnetic field of the solenoid and calculate its value ? Magnetic field. (b) Obtain the expression for the self - inductance (L) of the solenoid. Calcuate its value. Value of L . ( c) Calculate the energy stored (D) when the solenoid carries this current ? (d) Let the resistance of the solenoid be R. It is connected to a battery of emf e. Obtain the expression for the current (i) in the solenoid. (e) Let the solenoid with resistance R describe in part (d) be strecthed at a constant speed u ( l is increased but B and gamma are constant ). State kirchhoff's second law for this cases. (Note: Do not solve for the current ) (f) Consider a time varying current i=i_(0) cos (omegat) (where i_(0)=20.0A) flowing in the solenoid. Obtain an expression for the electric field due to the current in the solenoid. (Note: Part(e) is not operative, i.e., the solenoidis not being stretched. ) (g) Consider t=pi//2 omega and omega=200//pi rad-s^(-1) in the previous part. Plot the magnitude of the electric field as a function of the radial distance from the solenoid. Also, sketch the electric lines of force. |
Answer» Solution : `N=1000,i_(0)=20A` (a) `vecB=mu_(0)(N)/(l)i_(0)(pmhatk)` `|vecB|=4pixx10^(-3)`Telsa (b) `phi=Li_(0)` BNA`=Li_(0)` `L=(BNA)/(i_(0))=(mu_(0)N^(2)pir^(2))/(l)=2pi^(2)xx10^(-3)H`. (C) ` E=(1)/(2)Li_(0)^(2)=(4pi^(2))/(10)` Joules=3.95J (d) `i=i_(0)(1-e^(-t//tau))` where `tau=(L)/(R),i_(0)=(epsi)/( R)` (e) `epsi-iR-(d)/(dt)(Li)=0` ltbtgt `epsi-iR-L(di)/(dt)-i(dL)/(dt)` `epsi-iR+L(di)/(dt)+i(dL)/(dt)` after time t, `L=(mu_(0)N^(2)pir^(2))/((l+vt))to (dL)/(dt)=-(mu_(0)N^(2)pir^(2)v)/((L+vt)^(2))` ` epsi=iR+(LDI)/(dt)-(mu_(0)N^(2)pir^(2)v)/((L+vt)^(2))` (F) `E_("induced")=intvecE.vec(dl)=-(dphi)/(dt)` `intvecE.vec(dl)=-(dphi)/(dt)` (d `to` Radial distance from axis of solenoid : `r to ` Radius of solenoid ) For `(d lt r)` `E.2pid=-pid^(2)(DB)/(dt)` `=pid^(2) mu_(0)(N)/(l)(di)/(dt)` `E.2pid=pid^(2) mu_(0) (N)/(l)i_(0)omega sin(omegat)` `E=(mu_(0)Ni_(0)omegad sin(omegat))/(2l)` For `d ge r ` `E. 2pid=-pi^(2)(dB)/(dt)` `E=(mu_(0)Ni_(0)omegar^(2))/(2dl) sin(omegat)` (g)  `t=(pi)/(2W)` `E=(mu_(0)Ni_(0)omegad)/(2l)d lt r` `E=(mu_(0)Ni_(0)omegar^(2))/(2dl) d ge r ` Lines of force 
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| 14. |
Emissions of beta -rays in radioactive decay results in the change of |
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Answer» both MASS and CHARGE |
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| 15. |
What does the ammeter A read in the circuit shown in figure? What if the positions of the cell and the ammeter are interchanged? |
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Answer» |
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| 16. |
The temperature of coffee in a cup with time is most likelygiven by then curve in the figure. |
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Answer»
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| 17. |
A block of mass 10 kg is placed on the rough horizontal surface. A pulling force F is acting on the block which makes an angle theta above the horizontal. If coefficient of friction between block and surface is 4/3 then minimum value of force required to just move the block is (g = 10 m/s^2) |
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Answer» 80 N |
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| 18. |
यदि a=bq+r तो म०स० (a,b) = म०स० (.........) |
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Answer» B,r |
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| 19. |
A closly wound coil of 1000 turns and cross-swctional area of 200 cm^2 carries a current of 10 mA. The magnetic moment of the coil is : |
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Answer» 0.2 `Am^2` |
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| 20. |
Two coherent waves of light produce |
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Answer» CONSTRUCTIVE interference if the phase difference between then is `90^(@)` |
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| 21. |
In the transmission of a.c. power through transmission lines, when the voltage is stepped up n times, the power loss in transmission ………. |
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Answer» INCREASES n TIMES but `I=V/Z` `therefore P=V^2/Z^2R` If the VOLTAGE is stepped up n times then, we get, `P_1=n^2(V^2/Z^2)R` `therefore P_1/P=n^2` |
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| 22. |
A man runs at a speed of 4 ms to overtake a standing bus. When he is 6m behind the door (a ) the bus moves forward and continues moving with constant acceleration of 1.2 m/s^2. The time after which the man is able to catch the bus is : |
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Answer» 4.4s |
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| 23. |
What is the value of electric field and potential at a point midway between two equal like charges ? |
| Answer» Solution :The electric field is ZERO at this POINT. But potential is TWICE the VALUE of potential DUE to single charge at that point. | |
| 24. |
Conductance is the _____of resistance and its SI units is _____. |
| Answer» SOLUTION :RECIPROCAL , SIEMEN | |
| 25. |
What was done to the bodies of revolutionaries? |
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Answer» CHOPPED off and burnt |
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| 26. |
A slender homogeneous rod of length 2L floats partly immersed in water, being supported by a string fastened to one of its ends, as shown in the figure. The specific gravity of the rod is 0.36. The length of the rod that extends out of the water is (KL)/(10) Find the value of K. |
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Answer» |
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| 27. |
A particle is moving three times as fast as anelectron. The ratio of the de Broglie wavelength of the particle to that of the electron is 1.813 xx 10^(-4). The mass of the particle is (Mass of electron = 9.1xx10^(-31) kg ) |
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Answer» `1.67xx10^(-27)` kg `lambda=h/p=h/(mv)` or `m=h/(lambdav)` Given : `v/v_e=3, lambda/lambda_e=1.813xx10^(-4)` Mass of the particle , `m=m_e(v_e/v)(lambda_e/lambda)` Substituting the VALUES , we GET `m=(9.1xx10^(-31) kg) xx (1/3) xx(1/(1.813xx10^(-4)))` `RARR m=1.67xx10^(-27)` kg |
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| 28. |
An engine whistling at a constant frequency n_(0) and moving with a constant velocity goes past a stationery observer. As the engine crosses him, the frequency of the sound heard by him changes by a factor f. The actual difference in the frequencies of the sound heard by him before and after the engine crosses him is |
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Answer» `(1)/(2)n_(0)(1-F^(2))` |
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| 29. |
A ball is thrown vertically upwards from the top of a tower. Velocity at a point 'h'm vertically below the point of projection is twice the downward velocity at a point 'h'm vertically above the point of projection. The maximum height reached by the ball above the top of the tower is |
| Answer» ANSWER :D | |
| 30. |
A voltage amplifier operated from a 12 volt battery has a collector load 6 kOmega .Calculate the maximum collector current in the circuit. |
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Answer» Solution :Maximum collector current flows when whole battery voltage is dropped ACROSS collector load.Thus max.Collector current. `("Battery voltage")/("Collector load")=(12 "Volt")/(6 K OMEGA)=2MA` |
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| 31. |
A submarine cable consisting of a wire 3 mm in diameter and insulated with 3 mm of guttapercha (permittivity=4.26) is placed in water. Calculate the capacitance of 1 km of the cable in micro farads. [Hint: Consider the submarine cable as a cylindral capacitor of inner radius 1.55 mm and outer radius of 4.5 mm.] |
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Answer» |
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| 32. |
Why are Manganin and Constantan used in making resistance coils? |
| Answer» Solution :The temperature COEFFICIENTS of resistance of Manganin and Constantan are very SMALL and their RESISTIVITY very HIGH. Therefore these materials are used in making resistance COILS. | |
| 33. |
In an LC circuit, resistance of the circuit is negligible. If time period of oscillation is T then : (i) at what time is the energy stored completely electrical |
| Answer» SOLUTION :(i) t = 0, T/2, 3T/2,....... | |
| 34. |
If the earth does not have an atmosphere , would the average surface temperature be higher or lower than what it is now ? |
| Answer» Solution :The AVERAGE surface temperature will be LOWER DUE to the ABSENSE of green house effect. | |
| 35. |
Draw a ray diagram for the formation of image of a distant object by an astronomical telescope in normal adjustment position. Deduce the expression for its magnifying power. |
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Answer» Solution :Magnifying power (or ANGULAR magnification) of an astronomical telescope is defined as the ratio of the angle SUBTENDED by the final image at eye (`beta`) to the angle subtended by object directly (`alpha`) at eye. As the object lies at very LARGE distance, angle subtended by the object at Q (the optical centre of objective) may be CONSIDERED as almost the same as the angle subtended by the object at the eye. Therefore, Angular magnification `m = beta/alpha` As angles `alpha`and `beta` , are small, therefore, `alpha = tanalpha` and `beta = tan beta` In `triangleA.B.C_(2)`, `tanbeta_(2)(A.B.)/(C_(2)B.)` and in `triangleA.B.C_(1), tan alpha =(A.B.)/(C_(1)B.)` `m=-f_(0)/f_(e)` Here -ve sign indicates that the final image is an inverted image. From the above relation it is clear that for higher magnifying power, the focal length `f_0` of the objective lens should be as high as possible and the focal length `f_e` of the eyepiece should be least possible. |
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| 36. |
The colour code of a carbon resistor is Brown-Red-Brown-Gold. What is its resistance ? |
| Answer» SOLUTION :`120 OMEGA 5%.` | |
| 37. |
In the figure below, PQRS denotes the path followed by a ray of light as it travels through three media insuccession. The absolute refractive indices of the media are mu_(1) ,mu_(2)and mu_(3)respectively. (The line segment RS' inthe figure is parallel to PQ). |
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Answer» `mu_(1) gt mu_(2) gtmu_(3)` |
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| 38. |
Two men, one far-sighted and one short-sighted one, see objects through their spectacles of his short-sighted friend, he found that he could see distinctly puts on the spectacles of his short-sighted friend, he found that he found that he could see distinctly onlyinfinitely far objects. At what minimum distance would the shortsighted man be able to read small type if he wore the spectacles of far-sighted man? |
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Answer» |
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| 39. |
A stiff wire. is bent into a circular loop of diameter D. It is clamped by knife edges at two pointsopposite to each other. A transverse wand is sent around the loop by means of a small vibrator which acts close to one clamp. The resonance frequency (fundamental mode) of the loop in terms of wave speed V and diameter D is |
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Answer» `v/D` |
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| 40. |
How many air molecules are in a room at temperature 23.8^@ C and standard pressure if the dimensions of the room are 3.66 m xx3.66 m xx2.43 m? |
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Answer» 1330 |
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| 41. |
A : The work done by friction on an object during pure rolling motion is zero.R : In pure rolling motion, there is relative motion at the point of contact. |
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Answer» If both Assertion & Reason are true and the reason is the correct explanation of the assertion, |
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| 42. |
Which of the following electromagnetic radiations has the smallest wavelength ? |
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Answer» Microwaves |
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| 43. |
An a.c.source is connected to a capacitor of capacitance C. Find the expression for current flowing through it. |
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Answer» Solution : Let an alternating voltage V = `V_(m) sin omega t` be applied across a pure capacitor C. Then instantaneous value of CHARGE on a PLATE of the capacitor is: `q =CV = CV_(m) sin omega t` Current FLOWING through the capaictor `I = (dq)/(dt) = CV_(m) omega cos omega t = V_(m)/(1//Comega). sin (omega t + pi/2)`  `=I_(m) sin (omega t + pi/2)` Expression for current clearly shows that for a pure capacitive a.c. circuit the current leads the voltage by a PHASE angle `pi/2` |
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| 44. |
The focal length of a convex lens of refractive index: 1.5 is 'f' when it is placed in air. When it is immersed in a liquid it behaves as a converging lens and its focal length becomes xf (x > 1). The refractive index of the liquid is |
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Answer» `GT 3//2` |
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| 46. |
A small bulb is placed at the bottom of a tank containing water to a depth of 80cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33 (consider the bulb to be a point source . ) |
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Answer» Solution :n = 1.33`"" THEREFORE n = (1)/(sin i_(e))` `therefore sin i_(e) = (1)/(n) = (1)/(1.33)"" therefore = 48^(@) 45.` OP= 80 cm From the figure, tan `i_(e) == (PQ)/(OP)` PQ - OP `tan i_(e)80 + tan 48^(@) 45. - 91.22 ` cm `therefore ` Area of the SURFACE of water= `PI (PQ)^(2) = 3.14 (91.22)^(2) = 2.61m^(2)` |
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| 47. |
How many AM broadcast stations can be accommodated in a 100 kHz bandwidth if the highest modulating frequency of carrier is 5 kHz. ? |
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Answer» Solution :Any station being modulated by a 5 kHz SIGNAL will produce an upper side frequency 5 kHz above its CARRIER and a lower side frequency 5 kHz below its carrier, thereby requiring a bandwidth of 10 kHz. Thus, Number of stations accommodated `("Total bandwidth")/("Band width PER station")= (100)/(10)= 10` |
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| 48. |
Suppose the loop in Exercise 6.4 is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that the field decreases from its initial value of 0.3 T at the rate of 0.02 T s^(-1). If the cut is joined |
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Answer» Solution :Here ν = 0.5 Hz, N =100, A = 0.1 `m^2`and B = 0.01 T. Employing Eq. Eq. (6.21) `epsi_0 = NBA (2pi V)` `=100xx 0.01xx0.1xx2xx3.14xx0.5` `=0.314V` The MAXIMUM voltage is 0.314 V We urge you to explore such alternative POSSIBILITIES for power generation. |
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| 49. |
A coin is kept at distance of 10 cm from the centre of a circular turn table. If mu =0.8, the frequency of rotation at which the coin just begins to slip is |
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Answer» 62.8 RPM |
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