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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 37251. |
Speed of sound in a gas is proportional to |
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Answer» SQUARE ROOT of isotherm cal elasticity |
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| 37252. |
vec(E )_(ax)andvec(E ) _(eq) represent electric field at a point on the axial and equatorial line of a dipole . If points are at a distance r form the centre of the dipole , for r> > a |
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Answer» `vecE_(ax)=vecE_(eq)`  `|vecE_(ax)|=((1)/(4piepsilon_(0)))(2P)/(R^(3))` `|vecE_(eq)|=((1)/(4piepsilon_(0)))(p)/(r^(3))` 
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| 37253. |
What would be the effect of nuclear motion on the radius of the electronic orbit? Would the radius be the same as that of the predicted Bohr orbit By Eq. more or less? |
| Answer» SOLUTION :The RADIUS WOULD be the same | |
| 37254. |
A ray of light is incident grazing the refracting surface of a prism having refracting angle A. It emerges the other refracting surface making an angle theta with the normal to the surface. Prove that the refractive index of the material of the prism is given by mu = [1+ ((cosA + sintheta)/(sinA))^(-2)]^(1//2). |
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Answer» Solution :For grazing incidence on the refracting surface AB of the PRISM, `i_(1) = 90^(@)` [Fig. 2.65]. So, in this case `r_(1) = theta_(c)` (critical angle) `"Now", " "A = r_(1) + r_(\2) or, r_(2) = A - r_(1) = A - theta_(c)` Considering REFRACTION at the second refracting surface, AC `"we get", mu = (sintheta)/(sinr_(2))` `or, " " sintheta = mu sinr_(2) = mu sin(A - theta_(c))` `= mu [sinA costheta_(c) - cosA sintheta_(c)]` `"But" " " sintheta_(c) = (1)/(mu) and costheta_(c) = sqrt(1- (1)/(mu^(2))) = (sqrt(mu^(2)-1))/(mu)` `therefore "" sintheta= mu [sinA* (sqrt(mu^(2) - 1))/(mu) -cos A * (1)/(mu)]` `= sin A sqrt(mu^(2) - 1)` `or, " " sintheta+cosA = sinAsqrt(mu^(2)-1)` `or, " " (sintheta + cosA)/(A) = sqrt(mu^(2) - 1)` `or, "" mu^(2) - 1 = ((sintheta + cos A)/(sinA))^(2)` `or, "" mu^(2) = 1 + ((sintheta + cos A )/(sinA))^(2)` `or, "" mu = [ 1 + ((sintheta + cos A )/(sinA ))^(2)]^(1/2)` |
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| 37255. |
The thermal conductivity of copper is 4 times that of brass. Two rods of copper and brass having same length and cross-section are joined end to end. Free and of copper is at 0^(@)C and free end of brass is 100^(@)C. What is the temperature of junction ? |
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Answer» `20^(@)C` If T is temperature of interface, then `k_(1)(100-T)=4k_(1)(T-0)` `100-T=4T` `rArrT=20^(@)C` Thus correct choice is (a). |
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| 37256. |
Draw the vibration energy of a crystal as a function of frequency (neglecting the zero-point vibrations). Consider two cases: T= Theta//21 and T=Theta//4, where Theta is the Debye temperature. |
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Answer» Solution :In the Debye MODEL `dB_(omega)=A omega^(2), 0LE omegale omega_(m)` Then `3N= int_(0)^(omega_(0))dN_(omega)=(A omega_(m)^(3))/(3)`.(Toltal no.of models is `3N`) Thus `A=(9N)/(omega_(m)^(3))` we GET `U=(9N)/(omega_(m)^(3))int_(0)^(omega_(m))(omega^(2).ħomega)/(e^(-ħ omega//KT-1))d omega` ignoring zero point energy `=9Nħ omega_(m) int_(0)^(1)(x^(3)dx)/(e^(ħ omega_(m)x//kT-1)),x=(omega)/(omega_(m))` `=9 R Theta int_(0)^(1)(x^(3)dx)/(e^(x Theta//T)-1) fo r 0 le x le 1` Thus `(1)/(9R Theta)(dU(x))/(dx)=(x^(3))/(e^(x Theta//T)-1) for 0lexle1` for `T= Theta//2`, this is `(x^(3))/(e^(2x)-1)`, for `T=(Theta)/(4)`, it is `(x^(3))/(e^(4x)-1)` |
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| 37257. |
What is demodulation ? |
| Answer» SOLUTION :Process of detection or demodulation is the inverse of modulation. During Demodulation, audio signal is SEPARATED from modulated signal and fed to the SPEAKER or head-phone which reproduces the ORIGINAL SOUND. | |
| 37258. |
A certain substance decays to 1/32 of its initial activity in 25 days. Calculate its half-life. |
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Answer» 4 days |
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| 37259. |
Energy is constantly fed to a spring oscillator of force constant 225pi^(2)" Nm"^(-1) and attached mass 0.01 kg at a frequency of 50 cycles per s. Will the resonance be achieved ? |
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Answer» Yes = 75 Hz. THUS no resonance. Correct choice is (B). |
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| 37260. |
From Exercise 11 data. Obtain the frequency of revolution of the electron in its circular orbit. Does the answer depend on the speed of the electron ? Explain. |
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Answer» Solution :Given `B=6.5 G=6.5 xx10^(-4)T, V=4.8xx10^(6) m//s, e=1.6xx10^(-19)C` `m_(e)=9.1xx10^(-3) KG` `(nV^(2))/(r )= Q V B rArr (mV)/(r )=q B` If angular VELOCITY of electron is `omega`, then `V=r omega` `(m r(omega))/(r )=qB` `omega =(qB)/(m)` `2pi n=(qB)/(m) rArr n=(qB)/(2 pi m)` Frequency of revolution of electron in orbit `v=(Bq)/(2pi m)=(Be)/(2pi m_(e))=(6.5xx10^(-4)xx1.6xx10^(-19))/(2xx3.14xx9.1xx10^(-31))=18.18xx 10^(6) Hz.` |
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| 37261. |
Attenuation of ground waves is due to (a) Diffraction effect (b) Ratio waves induce currents in the ground because of the polarization |
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Answer» a & B are true |
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| 37262. |
The electrostatic force on a metal sphere of charge 0.4muC due to another identical metal sphere of charge -0.8muC in air is 0.2N. Find the distance between the two spheres and also the force between the same two spheres when they are brought into contact and then replaced in their initial positions. |
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Answer» SOLUTION :(a) We know that `|vecF|=(1/(4piepsi_(0)))((q_(1)q_(2))/x^(2))` i.e., `0.2=(9xx10^(9)xx0.4xx0.8xx10^(-12))/x^(2)` `therefore" "x^(2)=14.4xx10^(-12+9)=14.4xx10^(-3)=0.0144m^(2)` `therefore" "x=0.12mor12cm`. (B) `|vecF_(21)|=|vecF_(12)|=0.2N` repulsive. |
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| 37263. |
Passage : The thermal coefficient of resistivity is given by alpha=(1)/(rho)(d rho)/(dT) where rho is resistivity at a temperature T. alpha is not constant, rather varies as alpha=(-n)/(T), where T is temperature in Kelvin and n is a constant. For carbon alpha=-0.0005K^(-1)and rho=3.5xx10^(-5)(Omega-m)"at"27^(@)C Relation between rho and T using the above information |
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Answer» `RHO PROP T^(N)` |
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| 37264. |
Passage : The thermal coefficient of resistivity is given by alpha=(1)/(rho)(d rho)/(dT) where rho is resistivity at a temperature T. alpha is not constant, rather varies as alpha=(-n)/(T), where T is temperature in Kelvin and n is a constant. For carbon alpha=-0.0005K^(-1)and rho=3.5xx10^(-5)(Omega-m)"at"27^(@)C Find the value of .n. for carbon |
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Answer» 0.15 |
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| 37265. |
An electric dipole is free to move ina uniform electric field. Explain its motion when it is placed. parallel to the field perpendicular to the field. |
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Answer» Solution :When an electric dipole is placed PARALLEL to a UNIFORM electric field.Net force as well as net torque acting on the dipole is zero. Thus, the dipole REMAINS in EQUILIBRIUM and does not MOVE. (b) When dipole is placed perpendicular to the field, a torque `oversetto tau =oversetto p xx oversetto E ` acts on it. Under its influence the dipole executes oscillatory motion about the direction of electric field and finally aligns itself along the direction of electric field. |
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| 37266. |
In alpha- ray scattering, the scattering angle (theta) for impact parameter (b) to become zero is |
| Answer» Answer :C | |
| 37267. |
The capacity of parallel plate condenser is C. When the distance between the plates is halved, its capacity is: |
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Answer» 0.25 |
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| 37268. |
A hollow spherical conductor of radius 1m has a charge of 250mu C then electric intensity at a point distance of 0.5m from the centre of the spherical conductor is |
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Answer» ZERO |
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| 37269. |
The ratio of the density and pressure of a fixed mass of an ideal gas is "5" at 10°C. Then this ratio at 110°C is |
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Answer» 3.69 |
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| 37270. |
Find the potential difference V_(a)-V_b , between the points a and b shown in each part of the figure. |
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Answer» ` -5.2 V` |
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| 37271. |
The rod A^'B^' moves with a constant velocity v relative to the rod AB (figure). Both rods have the same proper length l_0 and at the ends of each of them clocks are mounted, which are synchronized pariwise: A with B and A^' with B^'. Suppose the moment when the clock B^' gets opposite the clock A is taken for the beginning of the time count in the reference frames fixed to each of the rods. Determine: (a) the readings of the clocks B and B^' at the moment when they are opposite each other, (b) the same for the clocks A and A^'. |
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Answer» Solution :At the instant the picture is taken the coordinates of `A,B,A^',B^'` in the rest frame of AB are `A:(0,0,0,0)` `B:(0,l_0,0,0)` `B^':(0,0,0,0)` `A^':(0_1-l_0sqrt(1-v^2//c^2),0,0)` In this frame the coordinates of `B^'` at other TIMES are `B^': (t, vt, 0, 0)`. So `B^'` is opposite to B at time `t(B)=l_0/v`. In the frame in which `B^'`, `A^'` is at rest the time corresponding this is by Lorentz transformation. `t^0(B^')=(1)/(SQRT(1-v^2/c^2))(l_0/v-(vl_0)/(c^2))=l_0/vsqrt(1-v^2//c^2)` Similarly in the rest frame of A, B, te coordinates of A at other times are `A^':(t, -l_0sqrt(1-v^2/c^2)+vt, 0,0)` `A^'` is opposite to A at time `t(A)=l_0/vsqrt(1-v^2/c^2)` The corresponding time in the frame in which `A^'`, `B^'` are at rest is `t(A^')=gammat(A)=l_0/v` 
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| 37272. |
A packet of weight 'W' dropped from a parachute strikes the ground and comes to rest with retardation equal to twice the acceleration due ot gravity. The force exerted on the grounds is |
| Answer» ANSWER :C | |
| 37273. |
For a photosensitive surface , work function is 3.3 xx 10^(-19) J. Taking plank's constant to be 6.6 xx 10^(-34) Js. Find threshold frequency. |
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Answer» SOLUTION :Here `W_0 = 3.3 xx 10 ^-19 J` `H = 6.6 xx 10^-34 JS` Threshold frequency `v_0 = W_0/h = (3.3 xx 10^-19)/(6.6 xx 10 ^-34) = 5 xx 10^14 Hz` |
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| 37274. |
When radiation with a continuous spectrum is passed through a volume of hydrogen gas whose atoms are all in the ground state, which spectral series will be present in the resulting absorption spectrum? |
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Answer» LYMAN |
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| 37275. |
A point on the rim of a wheel 3 m in diameter has linear velocity of 18 ms^(-1). The angular velocity of the wheel is |
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Answer» `4 RAD s^(-1)` |
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| 37276. |
A thin equiconvex spherical glass lens (mu = 3/2) of radius of curvature 30 cm is placed on the x-axis with its optical centre at x = 40 cm and principal axis coinciding with the x-axis. A light ray given by the equation 39y = -x + 1(and y ale is incident as the lens, in the direction of positive (in cm) X-axis. Then choose the correct alternatively) |
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Answer» The equation of refracted RAY is 3y = x + 1 |
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| 37277. |
By using Coulomb's law, define unit charge. |
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Answer» Solution :In SI, the UNIT of charge is Coulomb. Putting value of `q_(1) = q_(2) = 1C, r =1 m` in `F = k(q_(1)q_(2))/r^(2)`, then `F = 1/(4pi epsilon_(0)) = 9 xx 10^(9)` N Definition of 1 C : 1 C is the charge that when placed at a DISTANCE of 1 m from another charge of the same magnitude in vacuum experiences an ELECTRICAL force of repulsion of magnitude `9 xx 10^9` N. |
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| 37278. |
The earth takes 24h to rotate once about its axis. How much time does the sun take toshift by 1^(@) when viewed from the earth ? |
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Answer» SOLUTION :Time taken for `360^(@)` SHIFT = 2th time taken for `1^(@)` shift = `(24)/(360h) ` =4 min |
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| 37279. |
A parallel plate capacitor is charged with a battery and then separated from it. Now if the distance between its two plates is increased, what will be the changes in electric charge, potential difference and capacitance respectively ? |
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Answer» remains constant, decreases, decreases Hence, ACCORDING to V = Ed, V Increases andfrom ` C = (epsilon_(0)A)/(d)` C decreases as d increases. |
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| 37280. |
An alternating voltage given by V =140 sin 314 t isconnected across a pure resistor of 50 Omega find : (i)the frequency of the source. (ii) The rms current through the resistor. |
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Answer» Solution :(i) `2pi v = omega` `rArr 2pi v = 314 rad s^(-1)` `rArr v = 50 Hz` (II) `I_(rms) = (V_(rms))/(R )` Where `V_(rms) = (V_(0))/(sqrt(2))` `I_(rms) = (140)/(sqrt(2) xx 50) = 1.98 ~~ 2A` |
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| 37281. |
यदि x और Y दो ऐसे समुच्चय हैं, ताकि x में 21 अवयव Y में 32 अवयव और x तथा Y में उभयनिष्ठ अवयव 11 हैं, तो n(XuuY)= |
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Answer» 64 |
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| 37282. |
The electric field (E),current density (J) and conductivity (sigma) of a conductor are related as : |
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Answer» `sigma=E/J` |
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| 37283. |
A metal disc of radius 200cm is rotated at a constant angular speed of 60 "rad" s^(-1) in a plane at right angle to an external field of magnetic induction 0.05 Wbm^(-2). Find the e.m.f. induced between the centre and a point on the rim. |
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Answer» |
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| 37284. |
The magnetic moment vectors mu_(s) and mu_(l) associated with the intrinsic spin angular momentum S and orbital angular momentum l, respectively, of an electron are predicted by quantum theory (and verified experimentally to a high accuracy) to be given by : overset(to)(mu_(s) ) = -((e)/(m)) S, overset(to)(mu_(l)) = - ((e)/( 2m)) overset(to)(l) Which of these relations is in accordance with the result expected classically ? Outline the derivation of the classical result. |
Answer» Solution :ACCORDING to CLASSICAL physics due to orbital motion of electron around the NUCLEUS, it has orbital angular momentum `overset(to) (l) ` and orbital magnetic moment `overset(to) (mu_(l ) )`, related by following relation.  According to quantum physics, alongwith orbital motion, electron also has spinning , motion around its AXIS. Due to such motion, electron has spin magnetic moment `overset(to) (mu_(s) )` which is given by following relation. `overset(to) (mu_(s ) ) = - ((e)/( m) ) overset(to) (S) ""...(2)` where `overset(to) (S) = ` spin angular momentum of electron. Above relation is verified experimentally, which shows a great success of quantum theory. |
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| 37286. |
A perfectly black body emits total energy of 5 xx 10^2 joules in 50 minutes. If its area is 10 m^2 its emissive power at the temperature is |
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Answer» a)0.16 `w/m^2` |
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| 37287. |
A condenser of capacity 5O'|1F is charged to 10-volts. Its energy is equal to: |
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Answer» `2.3xx10^-3"JOULE"` |
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| 37288. |
Discuss the natural phenomena occured due to Sunlight. |
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Answer» Solution :The interplay of light with things around us gives rise to SEVERAL beautiful PHENOMENA. The spectacle of colour that we SEE around us all the time is possible only due to sunlight. The blue of the SKY, white clouds, the red hue at sunrise and sunset, the rainbow, the brilliant colours of some pearls, SHELLS and wings of birds are just a few of the natural wonders we are used to. |
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| 37289. |
A body of mass m has its position x at a time t, expressed by the equation :x=3t^(3//2)+2t-(1)/(2). The instantaneous force F on the body is proportional to |
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Answer» `t^(3//2)` |
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| 37290. |
A sample of an ideal gas is heated doubling its absolute temperature . Which of the following statements best describes the result of heating the gas? |
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Answer» The root-mean-SQUARE speed of GAS molecules doubles. |
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| 37291. |
What is electromagnetic wave theory of light? |
| Answer» Solution :Maxwell(1864) PROVED that light is an electromagnetic wave which is TRANSVERSE in nature CARRYING electromagnetic ENERGY. He could also show that no medium is necessary for the propagation of electromagnetic waves. All the phenomenon of lightcould be successfully EXPLAINED by this theroy. | |
| 37292. |
A : A reflecting type of telescope is preferred over refracting type in astronomy. R : A reflecting type of telescope is free from chromatic aberration and spherical aberration. |
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Answer» If both Assertion & Reason are true and the reason is the CORRECT explanation of the assertion, then MARK (1). |
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| 37293. |
Draw a labelled diagram using zener diode for constant voltage power supply. |
Answer» SOLUTION :ZENER DIODE as CONSTANT voltage power SUPPLY. 
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| 37294. |
A whistle whose air column is open at both ends has a fundamental frequency of 5100 Hz. If the speed of sound in air is 340 ms^(-1), the length of the whistle, in cm, is |
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Answer» `5//3` FUNDAMENTAL frequency, `v=v/(2L)` where v is the speed of sound in air. or `L =v/(2v)` SUBSTITUTING the given values , we get `L = 340/(2 xx 5100) = 1/30 m = 10/3 m` |
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| 37295. |
Car tyres are made of rubber and not of iron because |
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Answer» Rubber is CHEAPER than iron |
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| 37296. |
What is potentiometer ? Why it is named so, |
| Answer» SOLUTION :Because it is USED to MEASURE POTENTIAL DIFFERENCE. | |
| 37297. |
PassageII We have two parallel plate capacitors P and Q having same capacitance C_(0). P is connected to a battery of potential difference V and it remains connected to the battery even after the charging is over. Q is also connected to a battery of the same potential difference V but after the charging gets over, it is disconnected from the battery. Answer the following questions: If dielectric slab of dielectric constant 5 is inserted in between the paltes of Q so that the entire space is occupied by the dielectric and if U is the energy stored before the insertion of dielectric then stored energy after the dielectric slab is introduced is |
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Answer» U |
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| 37298. |
PassageII We have two parallel plate capacitors P and Q having same capacitance C_(0). P is connected to a battery of potential difference V and it remains connected to the battery even after the charging is over. Q is also connected to a battery of the same potential difference V but after the charging gets over, it is disconnected from the battery. Answer the following questions: If a dielectric slab of dielectric constant 5 is inserted in between the plates of P so that the entire space is occupied by the dielectric and if U is the energy stored before the insertion of dielectric then stored energyafter the dielectric slab is introduced is |
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Answer» U |
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| 37299. |
By which type of supply capacitor works ? |
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Answer» A .C. SUPPLY |
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| 37300. |
I know I should fall if tried to fly who spoke this line. |
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Answer» LITTLE kite |
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