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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. |
The resistivity of a wire |
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Answer» VARIES with its LENGTH |
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| 2. |
When a plane mirror is rotated through a certain angle theta how the reflected ray turns ? |
| Answer» SOLUTION :DOUBLE, `2THETA` | |
| 3. |
White light is incident normally on a plane parallel thin film of µ=1.5. Find the minimum thickness of the film for which light of lamda=4000 Å is absent from the reflected light |
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Answer» |
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| 4. |
A physical quantity Q is found to depend on observables x, y and z, obeying relation Q=(x^(3)y^(2))/(z). The percentage error in the measurements of x, y and z are 1%, 2% and 4% respectively. What is percentage error inthe quantityQ ? |
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Answer» `4%` |
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| 5. |
The momentum of a body is p. and its K.E. is E. If its momentum, becomes 2p its K.E. will be |
| Answer» Solution :`E=(p^(2))/(2M)` when p is doubled then E becomed=s 4 TIMES. | |
| 6. |
If both the mass and radius of earth decrease by 1% the value of acceleration due to gravity will decrease by nearly: |
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Answer» `1% ` `therefore (g.)/(g)-1=1.01-1 RARR (g.-g)/(g)=0.01` or`(g.-g)/(g)xx100=1%` So the correct CHOICE is (a). |
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| 7. |
A rod of 10 cm length is moving perpendicular to uniform magnetic field of intensity 5 xx 10^(-4) "Wb/m"^2. If the acceleration of the rod is 5 "m/s"^2, then the rate of increase of induced emf is …. |
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Answer» `2.5XX10^(-4) Vs^(-1)` `THEREFORE (d|epsilon|)/(DT)=B(dv)/(dt)l` =Bal `=5xx10^(-4)xx5xx0.1` `=2.5xx10^(-4) "Vs"^(-1)` |
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| 8. |
What is Huygens' principle? |
| Answer» SOLUTION :According to Huygens principle, each point of the WAVEFRONT is the source FO SECONDARY wavelets emanating from these points spreading out in all direactions with the speed of the wave. These are called as secondary wavelets. | |
| 9. |
10 cm long wire is placed horizontally on the surface of water and is gently pulled up with a force 2 xx 10^-2 N to keep the wire in equilibrium. The surface tension in N/m is, |
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Answer» 0.002 |
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| 10. |
What is amplitude modulation ? |
| Answer» Solution :Amplitude MODULATION is a type of modulation in which the amplitude of a radio frequency CARRIER wave is varied by an AMOUNT that is PROPORTIONAL to the amplitude of a baseband or basic information carrying signal at a frequency equal to that of the modulating baseband signal . The frequency of the MODULATED wave is the same as that of the carrier wave. | |
| 11. |
H^(+),He^(+) and O^(++) all having same kinetic energy while they pass through a region in which there is a uniform magnetic field perpendicular to their velocities. The masses of H^(+),He^(+) and O^(++) are 1, 4 and 16 a.m.u respectively then, |
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Answer» `H^(+)` is DEFLECTED most |
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| 12. |
Explain the use of p-n diode as half wave rectifier. |
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Answer» Solution :p-n junction as HALF wave rectifier The circuit for using junction diode as half wave rectifier is as shown below in figure (a) .  During first half of a.c.one of the ends of SECONDARY say A ,becomes positive and diode operates under forward bias and the current flows through LOAD R. During second half, A becomes negative and diode operates under negative bias. Practically no current flows through the load. THUS half of the cycle of a.c. is rectified and we get UNIDIRECTIONAL current as shown in fig. (b). |
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| 13. |
A diverging mirror is : |
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Answer» a PLANE mirror |
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| 14. |
a container filled with glycerine of density σ becomes constant after sometime. The viscous force acting on the ball in the final stage is |
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Answer» `MG ((sigma )/(RHO))` `=mg (1- (Th)/(mg))=mg (1- (v sigmag)/(v rhog))` `=mg (1- (sigma)/(rho))` |
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| 15. |
In the shown figure, AC and BD are straight conductors and CED and AFB are semicircular conductors with radii r and 4r, respectively. The entire setup is lying in the same plane. If i is current entering at A what fraction of i will flow in the ACEDB such that resultant magnetic field at O is zero |
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Answer» `i/5` |
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| 16. |
A light bulb and an open coil inductor are connected to an ac source through a key as shown in Fig. The switch is closed and after sometime, an iron rod is inserted into the interior of the inductor. The glow of the light bulb (a) increases, (b) decreases, (c) is unchanged, as the iron rod is inserted. Give your answer with reasons. |
| Answer» SOLUTION :As the iron rod is inserted, the magnetic field inside the coil magnetizes the iron INCREASING the magnetic field inside it. Hence, the inductance of the coil increases. Consequently, the INDUCTIVE reactance of the coil increases. As a result, a larger fraction of the applied ac voltage appears across the inductor, leaving less voltage across the BULB. Therefore, the glow of the light bulb decreases. | |
| 17. |
Choose the correct statement of the following A: In solids valence band may be empty or may be partially filled with electrons. B: In solids conduction band may be empty or may be partially filled with electrons. |
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Answer» A is true, B is FALSE |
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| 18. |
If a pair of equation is inconsistent , then the lines will be – |
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Answer» Intersecting |
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| 19. |
A uniform rod AB of length L and mass m is uniformly charged with a charge Q and it is freely suspended from end A as shown in figure. An electric E is suddenly switched on in the horizontal direction due to which rod get turned by a maximum angle 90^(@). The magnitude of E is how many number of times of (Mg)/(Q) |
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Answer» |
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| 20. |
A piece of metal and a piece of non-conducting stone are dropped from same height, will they reach the earth in sometime ? |
| Answer» Solution :Both the pieces fall through the magnetic field of the EARTH. Eddy CURRENTS are set up inside the METAL piece while it is not so case of STONE. | |
| 21. |
STATEMENT-1: A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to friction between the block and the surface after moving a certain distance. The surface is now tilted to an angle of 30^(@) with the horizontal and the same block is made to go up on the surface with the same initial velocity v. The decrease in the mechanical energy in the second situation is smaller than that in the first situation. because STATEMENT-2: The coefficient of friction between the block and the surface decreases with the increase in angle of inclination. |
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Answer» Statement-1 is True, Statement-2 is True, Statement-2 is a correct EXPLANATION for statement-1. |
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| 22. |
A metal ball hits a wall and does not rebound, where as a rubber ball of the same mass on hitting the wall with the same velocity rebounds back. It can be concluded that: |
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Answer» The initial momentum of METAL ball is greater than initial momentum of RUBBER |
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| 23. |
A charged particle with velocity barv =xhati+ y hatj moves in a magnetic field barB = 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 < x c) Force is proportional to (x^(2)-y^(2)) if x > y d) Force is proportional to (x^(2) + y^(2)) if y > x |
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Answer» a and B are true |
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| 24. |
In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular path of radius R using a magnetic field B. If V and B arc kept constant the ratio (("charge on the ion")/("mass of the ion")) will be proportional to |
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Answer» `1//R^(2)` |
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| 25. |
If yellow light emitted by sodium lamp in Young's double slit experiment is replaced by monochromatic blue value of light of the same intensity then.... |
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Answer» fringe width will DECREASE `:. barX prop lambdaand lambda_(B) gt LAMBDA` `:. barX_(b) gt barX_(y)` `:.` Fringe width will decrease. |
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| 26. |
A convex lens made up of glass of refractive index 1.5 is dipped, in turn, in (i) a medium of refractive index 1.65, (ii) a medium of refractive index 1.33. (a) Will it behave as a converging or a diverging lens in the two cases ? (b) How will its focal length change in the two media ? |
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Answer» Solution :Let FOCAL LENGTH of given convex lens in air `f_("air") =f` (say) , refractive index of glass `n_g = 1.5` (a) (i) When the lens is dipped in a medium of refractive index `n_m = 1.65` , the lens will start BEHAVING as a diverging lens because `n_m gtn_g`. (ii) However, when the lens is dipped in a medium of refractive index n.m = 1.33, the lens will continue to behave as a converging lens because `n_(m)^(.) lt n_(g)`. (b) We know that focal length of a lens in a medium `f_(m)`is given by: `f_(m) = (n_(m)(n_(g)-1))/(n_(g)-n_(m))f`, where f= focal length of the lens in air. (i) When glass lens (`n_(g) = 1.5`) is dipped in 1ST medium (`n_m = 1.65`), then `f_(m) = (1.65(1.5-1))/(1.5-1.65).f = (1.65 xx 0.5)/(-0.15).f = -5.5 f` (ii) When glass lens (`n_(g)=1.5`) is dipped in 2ND medium `(n_(m)^(.) = 1.33)`then `f_(m)^(.) = (1.33(1.5-1))/(1.5 -1.33).f = (1.33 xx 0.5)/(0.17)f. = 3.91 f` |
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| 27. |
The refractive index of a medium is 1.8. A bubble lies in this medium at an apparent depth of 10 cm. The real depth of the bubble is |
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Answer» `10/1.8`cm |
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| 28. |
The energy emitted per second by a black body at 1227^(@)C is E. If the temperature of the black body is increased to 2727^(@)C, the energy emitted per second in terms of E is : |
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Answer» E |
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| 29. |
यदि कोई वस्तु समय के साथ अपनी स्थिति में परिवर्तन करता है तो वह वस्तु कहलाता है - |
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Answer» बल में |
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| 30. |
When current changes from + 2A to -2A in 0.05 S, an emf of 8V is induced in the coil. The self inductance of the coil is |
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Answer» 0.2H |
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| 31. |
(a) Write the expression for the force, vecF, acting on a charged particle of charge 'q', moving with a velocity vecV in the presence of both electric field vecE and magnetic field vecB. Obtain the condition under which the particle moves undeflected through the fields. (b) A rectangular loop of size lxxb carrying a steady current I is placed in a uniform magnetic field vecB. Prove that the torque vectau acting on the loop is given by vectau=vecmxxvecB," where "vecm is the magnetic moment of the loop. |
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Answer» Solution :(a) The direction of `VECE,vecv and vecB` are such that `vecE bot vecv, vecE bot vecB and vec v` is not PARALLEL or anti-parallel to `vecB.` Force on charge due to electric field `vecE, vecF = q vecE.` Force on charge due to magnetic field `vecB, vecF = q vecv xx vecB` If PARTICLE moves undeflected then magnitude of both the forces are equal i.e. `|q, vec E|= |q vecVxx vecB |` `rArr" "qE=qvB sin 90^(@)""rArr""qE-qvBrArrv=(B)/(E)` (b) `vectau = NI vecAxxvec A= vecMxxvecB` `"where "vecM=NIvecA` is magnetic moment of LOOP. The unit of magnetic moment in S.I. system is AMPERE `xx"metre"^(2)(Am^(2))`. 
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| 32. |
The magnetic susceptibility (x) of a paramagnetic material changes with absolute temperature (T) as |
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Answer» `X PROP T` |
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| 33. |
A blocks of mass 'M' is pressedagainsta wall with a horizontal force F. Then it will slide down if the wall is smooth frictional force may balance the weight if the wall is rough Normal reaction is equalto weight of theblock Normalreaction is zeroif the wallis smooth |
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Answer» a &B are CORRECT |
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| 34. |
1200 turns of copper wire are wound onto a cardboard cylinder 60 cm 160 long and 5 cm diameter. What is the inductance of the coil? |
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Answer» |
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| 35. |
Paragraph A hiker stands on edge of a cliff 490 m above the ground and throws a stone horizontally with an initial speed of 15ms^(-1). Take g=9.8ms^(-2). Neglect air resistance.Take the point of projection as the origin of coordinate system, x-axis is horizontal direction, y-axis vertically upwards. What is the coordinates in metres of the point where the stone hits the ground? |
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Answer» (0, 490) |
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| 36. |
lamda_(1) and lamda_(2) are used to illuminate the slits, beta_(1) and beta_(2) are the corresponding fringe widths. The wavelength lamda_(1) cm produce photoelectric effect when incident on a metal. But the wavelength lamda_(2) cannot produce photoelectric effect. the correct relation between beta_(1) and beta_(2) is : |
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Answer» `beta_(1)ltbeta_(2)` Hence, `beta_(1) lt beta_(2)` |
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| 37. |
Paragraph A hiker stands on edge of a cliff 490 m above the ground and throws a stone horizontally with an initial speed of 15ms^(-1). Take g=9.8ms^(-2). Neglect air resistance.Take the point of projection as the origin of coordinate system, x-axis is horizontal direction, y-axis vertically upwards. Withwhat speed the stone hits the ground? |
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Answer» `15MS^(-1)` |
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| 38. |
A cylindrical vessel of 28 cm diameter contains 20 g of nitrogen compressed by a piston supporting a weight of 75 kg. The temperature of the gas is 17^@C. What work will the gas do, if it is heated to a temperature of 250^@C? What amount of heat should be supplied to it? What distance will the weight be raised? The process should be assumed isobaric, the heating of the vessel and the external pressure should be neglected. |
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Answer» |
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| 39. |
Paragraph A hiker stands on edge of a cliff 490 m above the ground and throws a stone horizontally with an initial speed of 15ms^(-1). Take g=9.8ms^(-2). Neglect air resistance.Take the point of projection as the origin of coordinate system, x-axis is horizontal direction, y-axis vertically upwards. What is the equation of trajectory? |
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Answer» `y= -(4.9)/(225) X^(2)` |
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| 40. |
What is Photodiode ? |
Answer» Solution :Photodiode is a p-n junction having photosensitive semiconducting material and is based on the principal of electric conduction from light.  Photo diode is reversed biased as shown in the FIGURE and when light is made to fall, the valence electrons absorb this energy and jump to conduction band leaving a hole in the valence band, so additional electron hole pairs are created in both p and n regions. Thus there is small change in majority CARRIER CONCENTRATION and large change in minority carrier concentration. So the reverse current is increased to a large value due to additional minority carriers. Hence with the increase in intensity of incident light the current increases LINEARLY till it becomes saturated. |
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| 41. |
The power factor of the circuit is 1//sqrt(2). The capacitance of the circuit is equal to |
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Answer» `400muF` |
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| 42. |
Newtanian mechanics regarded that space existed "___________". |
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Answer» with REFERENCE to objects |
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| 43. |
A stone is thrown vertically upward with a speed of 10.0 ms^(-1) from the edge of a cliff 65 m high.What will be its speed just before hitting the bottom? |
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Answer» 3.14 m/s |
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| 44. |
A lens of glass is immersed in water, what will be its effect on the power of the lens ? |
| Answer» Solution :On immersing a GLASS LENS into WATER, its power is reduced. | |
| 45. |
Figure shows two idential capacitors, C_1 and C_2, each of 1mu F capacitance connected to a battery of 6 V. Initially switch 'S' is closed. After sometime 'S' is left open and dielectric slabs of dielectric constant K = 3 are inserted to fill completely the space between the plates of the two capacitors. How will the (i) charge and (ii) potential difference between the plates of the capacitors be affected after the slabs are inserted? |
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Answer» Solution :Initially,when the switch S is closed in the arrangment shown, we have `C_1 = C_2 =1 muF, V_1 =V_2 = 6 V and Q_1 = Q_2 = CV = 6muF` When the switch S is left open, the capacitor `C_1` is still connected to the battery but capacitor `C_2` is now disconnected from the battery. On inserting dielectric SLABS of dielectric constant K = 3, so as to fill completely the space between the plates of two CAPACITORS,their CAPACITY changes to `C._1 = C._2 = KC_1 or KC_2 = 3 xx 1 muF = 3 muF` (i) As capacitor `C_1` is still connected to the battery, its new voltage `V._1 = V_1 =6 V` and new charge `Q._1 = C._1 V._1 = 3muF xx 6 V = 18 muC` (II) As capacitor `C_2` is now disconnected from the battery, its new charge `Q._2= Q_2 = 6muC` and new potential difference across its plates `V._2 = (Q._2)/(C._2) = (6muC)/(3 muF) = 2V`. |
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| 46. |
If a function f is defined from A to B and a function g is defined from C to D then fog is defined if |
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Answer» A=B |
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| 47. |
The number of turns of an a.c. generator is 5000 and the area of the coil is 0.25 m^(2). The coil is rotated at the rate of 100 c.p.s, in a magnetic field of 0.2 Wb m^(-2). The peak value of the emf generated is nearly |
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Answer» 786 kV |
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| 48. |
Define electron volt. Express it value in joule. |
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Answer» Solution :It is the KINETIC ENERGY gained by an ELECTRON when it is accelerated through a potential difference of 1 volt. `1 eV = 1.6 xx 10^(-19) J` `1 MeV = 1.6 xx 10^(-13) J` |
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| 49. |
In a region of space having a spherically symmetric distribution of charge, the electric flux enclosed by a concentric spherical Gaussian surface, varies with radius r as phi=(phi_0r^3)/R^3 for r le R phi=phi_0 for r > R where R and phi_0are constants. The volume charge density in the region is given as |
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Answer» `(3phi_0epsilon_0r^2)/(4piepsilon_0R^5)` for `R LE R , 0` for r GT R |
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