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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.
| 7551. |
An equilateral triangle wire frame of side L having 3 point charges at its vertices is kept inx-y plane as showm Component of electric field due to the configuration in z direction at (0, 0, L ) is [origin is centroid of triangle ] |
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Answer» ` ( 9sqrt 3 KQ)/(8L^2)` ` r_(PA) = r_(rB) =R _(PC = sqrt ((L/(sqrt3) )^2 +L^2) = (2L)/(sqrt 3)` ` vec E_P = ve cE_(PA) + vec E_(PE) + vec E_(Pc)`  `vecE_(PA) =(Kq)/(r_(PA)^(3))vecrPA =(Kq)/(r^(3) ) (-(1)/(sqrt3) hat j +Lhat k)` ` vec E_(PB) = (Kq)/r^3 (1/2 hat i + 1/(2sqrt 3) hat j + L hat k)` ` vec E_(PC) = (2Kq)/r^3 (- 1/2 hat i + 1/(2sqrt3) hat j + L hat k)` `E_(P(z))=E_(PA(z) +E_(PB(z))+E+(PC_(z)=0` |
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| 7552. |
A circular racetrack of radius 300m is banked at an angle of 15^(@). If the coefficient of friction between the wheels of a race - car and the road is 0.2, what is the (a) optimum speed of the race - car to avoid wear and tear on its tures, and (b) maximum. Permissible speed to avoid slipping ? |
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Answer» Solution :On a banked road, the horizontal component of the NORMAL force and the frictional force contribute to provide centripetal force to KEEP the car moving on a circular turn without SLIPPING. At the OPTIMUM speed, the normal reaction.s component is enough to provide the needed centripetal force, and the frictional force is not needed. The optimum speed `upsilon_(0)` is given by `upsilon_(0)=(Rg tan theta)^(1//2)` Here `R=300 m, theta = 15^(@), g=9.8 ms^(-2)` `upsilon_(0)=(Rg tan theta)^(1//2)=(300xx9.8xx tan15^(@))^(1//2)`. On simplification, `upsilon_(0)28.1 ms^(-1)`. The maximum permissible speed `upsilon_(max)` is given by `v_(max)=sqrt((Rg(tan theta+mu))/((1-mu tan theta)))` `= sqrt((300xx9.8xx(tan 15^(@)+0.2))/((1-0.2 tan 15^(@)))` On simplification `upsilon_(max)=38.1 ms^(-1)`. |
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| 7553. |
In an orbital motion, the angular momentum vector is: |
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Answer» along RADIUS vector `therefore ` Direction of `vecL` is perpendicular to orbital plane. Thus correct choice is (b). |
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| 7554. |
A circular coil AB CD carrying a current / is placed in a uniform magnetic field. If the magnetic force on the segment AB is vecF, the force on the remaining segment BCDA is |
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Answer» `VECF` |
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| 7555. |
An electron enter a region when magnetic field (B) and electric field (E) are mutually perpendicular, then |
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Answer» It will always MOVE in the direction of B |
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| 7556. |
An alternating current of 1.5 mA rms and angular frequency omega = 100 "rad/s" flows through a 10 k Omega resistor and a 0.50 mu F capacitor in series. Calculate the rms voltage across the capacitor and the impedance of the circuit. |
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Answer» |
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| 7557. |
Solar rays are incident at 45^@ on the surface of water (mu = 4/3). The length of the shadow of a pole of length 1.2 m formed at the bottom of the pond is (3.3)/(n) where 'n' is. (If the pole is vertical assuming that 0.2 m of the pole is above the water surface) |
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Answer» 40 |
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| 7558. |
On a long horizontally moving belt ,a child runs to and fro with a speed 9 km h^(-1) with respect to the belt) between his father and mother located 50 m apart. The belt moves with speed of 4 km h^(-1). For an observer on a stationary platform , the speed of the child runing in the direction of motion of the belt is |
| Answer» Answer :D | |
| 7559. |
A cube of side 5 cm substance has its upper surface displaced by 0.65 mm by a tangential force of 0.26 N.The rigidity modulus of the substance is |
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Answer» a)`8 XX 10^2 N/m^2` |
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| 7560. |
Name the physical quantity whose S.I. unit is JC^(-1). Is it a scalar or a vector quantit? |
| Answer» SOLUTION :ELECTRIC POTENTIAL , a SCALAR. | |
| 7561. |
The space between the conductors of a spherical capacitor is half filled with a dielectric as shown is Figure. The dielectric constant is K. (a) If a charge is given to the capacitor write the ratio of free charge density on the inner sphere at point A and B. (b) Write the ratio of capacitance with dielectric and without dielectric. |
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Answer» (b) `(1+K)/(2)` |
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| 7562. |
In the circuit shown, the switch is shifted from position 1rightarrow 2 at t=0. The switch was initially in position I since a long time. The graph between charge on capacitor C and time 't' is |
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Answer»
 `V_(0)+2Sigma-2iR-q/C=V_(0)` `1=Sigma/R-q/(2RC)` ALSO `i=(DQ)/(DT)` `:. underset(CSigma)OVERSET(q)int (dq)/((Sigma/R-q/(2RC)))=underset0overset(t)intdt` `ln(Sigma/R-q/(2RC))|_(CSigma)^(q)/((-1/(2RC)))=t` `ln ((2SigmaC-q)/(SigmaC))=-t/(2RC)` `q=2SigmaC-SigmaC_(e)^(-t//2RC)` `q=SigmaC(2-e^(-t//2RC))` |
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| 7563. |
A particle is moving on a circle of radius A .At an instant its speed and tangential acceleration are B and C respectively.Total acceleration of the particle at that instant is |
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Answer» `SQRT(A^2/B^2 +C^2)` |
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| 7564. |
Magnetization for vaccum is ........ |
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Answer» negative |
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| 7565. |
The materials in which electric current flows fairly well are called ? |
| Answer» SOLUTION :CONDUCTORS | |
| 7566. |
In hydrogen atom, an electron makes transition from n = 3 to n = 2 state in time interval of 1.2xx10^(-8) s. Calculate average torque (in Nm) acting on the electron during this transition. |
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Answer» `1.055xx10^(-26)` `=((n_(2)h)/(2pi)-(n_(1)h)/(2pi))/(Deltat)=((n_(2)-n_(1))h)/(2piDeltat)` `=((3-2)xx6.625xx10^(-34))/(2xx3.14xx1.2xx10^(-8))` `=8.79xx10^(-27)` |
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| 7567. |
Which of the following is not a transducer? |
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Answer» loudspeaker |
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| 7568. |
A car travels starting from rest with constant acceleration alpha and reaches a maximum velocity V.It travels with maximum velocity for some time and retards uniformly at the rate of beta and comes to rest.If s is the total distance and t is the total time of journey then t= |
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Answer» Solution :` ` `v=0+alpha1,,t_(1)(V)/(alpha)` `S_(1)=(1)/(2)alphat_(1)^(2)=(v^(2))/(2alpha)` O-V=`betat_(3),t_(3)=(v)/(BETA)` `O^(2)-V^(2)=-2|` `S_(3)=(v_(2))/(2beta)=(1)/(2)betat_(3)^(2)` `t_(2)=(S_(2))/(V)=(S-(S_(1)+S_(3)))/(V)=(S-(v^(2))/(2)((1)/(alpha)+(1)/(beta)))/(V)` `t=t_(1)+t_(2)+t_(3)` `=(v)/(alpha)+(s)/(v)-(v)/(2alpha)-(v)/(2beta)+(v)/(beta) t=(s)/(v)+(v)/(2)((alpha+beta)/(ALPHABETA))` `S_(2)=S-(S_(1)+S_(2))=S-((v^(2))/(2alpha)+(v^(2))/(2alpha))` `=S-(v^(2))/(alpha)`=s-(vt-s) `S_(2)`=2s-vt [`S_(2)`=distance TRAVELLED with constant velocity] |
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| 7569. |
Graph showing the variation of current versus voltage for a material GaAs is shown in figure. Identify the region of (i) negative resistance (ii) where Ohm's law is obeyed. |
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Answer» Solution :Side BANDS (Lower side band and upper side band) are produced due to SUPERPOSITION of low frequency modulating SIGNALS on HIGH frequency carrier waves. Reason: The frequency of lower side band is `omega_(c )-omega_(m)`and of upper side band is `omega_(c )-omega_(m)`. |
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| 7570. |
In net force on a system is zero then |
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Answer» its momentum is CONSERVED |
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| 7571. |
The meehanism behind nut and bolt arrangement also works for screw gauge. In case of nut and bolt mechanism, with rotation of bolt, it has translational movement also. In one complete rotation of bolt, tip of bolt moves by a linear distance equal to linear distance between two consecutive threads on the screw, known as pitch in case of screw gauge, the circular scale is divided in several parths. The ratio of pitch and total number of divisions on circular scale is known as least count. Spherometer is a device used to measure very small distances such as radius of curvature and thicness of thin plate. The screw gauge can be used to meaure diameter of a spherical sample. A screw gauge has 100 divisions on head scale and in 8 rotations distance covered is 8 mm. A screw gauge has which of the following characteristics ? |
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Answer» pitch only |
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| 7572. |
What do you mean by the term remote sensing ? |
| Answer» SOLUTION :Remote SENSING is any method of obtaining information about an object / AREA from a distance without having physical CONTACT. | |
| 7573. |
The meehanism behind nut and bolt arrangement also works for screw gauge. In case of nut and bolt mechanism, with rotation of bolt, it has translational movement also. In one complete rotation of bolt, tip of bolt moves by a linear distance equal to linear distance between two consecutive threads on the screw, known as pitch in case of screw gauge, the circular scale is divided in several parths. The ratio of pitch and total number of divisions on circular scale is known as least count. Spherometer is a device used to measure very small distances such as radius of curvature and thicness of thin plate. The screw gauge can be used to meaure diameter of a spherical sample. A screw gauge has 100 divisions on head scale and in 8 rotations distance covered is 8 mm. Least count of given screw gauge is |
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Answer» 0.08 mm |
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| 7574. |
An alternating voltage is connected to a box with some unknown circuital arrangement. The applied voltage and current through the circuit are measured as (v = 80 sin omega t) volt and (i = 1.6sin(omega t + 45^0) ampere: Is the circuit in the box largely capacitive or in ductive? |
| Answer» SOLUTION :CAPACITIVE | |
| 7575. |
The current when cells in series is i=_____and when in parallel is i=________ |
| Answer» SOLUTION :`[(NE)/(R+nr)]` and `[(mE)/(mR+r)]` | |
| 7576. |
An alternating voltage is connected to a box with some unknown circuital arrangement. The applied voltage and current through the circuit are measured as (v = 80 sin omega t) volt and (i = 1.6sin(omega t + 45^0) ampere : Is the circuit in the box at resonance? |
| Answer» SOLUTION :No HINT : CURRENT and VOLTAGE are not in the same PHASE. | |
| 7577. |
Which ratio below best defines the efficiency of simple machines ? |
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Answer» `"useful work OUTPUT "/"work input"XX100%` |
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| 7578. |
A very large plank P of some unknown mass is being moved with velocity v_(0)hati under application of an external force (not shown in figure). Simultaneously a block B of mass m placed on the plank is also moving with velocity v_(0)hatk. All these velocities are with respect to ground frame and at t=0. Coefficient of frictioin between the plank and the block mu. Choose the correct option(s). |
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Answer» Kinetic friction force acting on the block at `t=0` is `-mumghatk` `P_(f_(k))=mu mg [(hati)/(sqrt(2))-(hatk)/(sqrt(2))].(v_(0)hatk)` `=-(mu mg v_(0))/(sqrt(2))` `(dQ)/(dt)=mumgv_(0)2/(sqrt(2))=sqrt(2) mu mg v_(0)` |
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| 7579. |
Using Eqs. Demonstrate that if in the intertial reference frame Kthere is only electricor only magnetic field. In any other interial frame K' both electric and magneticfiedlswill coxist simutaneously, with E' _|_ B'. |
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Answer» Solution :Suppose, thereis only electric fied `vec(E)`, in `K`. THENIN `K'`, consideringnonrelativistic velocity `vec(v), vec(E') = vec(E), vec(B) = (vec(v) XX vec(E))/(c^(2))`, So, `vec(E') vec(B') = 0` In the relatiistic case, `{:(vec(E')_(||)=vec(E)_(||)),(E'_(bot)=(vec(E_(bot)))/(sqrt(1-v^(2)//c^(2)))):}}{:(vecB'_(||)=vec(B)_(||)=0),(vec(B')_(bot)=(-vec(v)xxvec(E)//c^(2))/(sqrt(1-v^(2)//c^(2)))):}` Now,`vec(E').vec(B') = vec(E'_(|\|)). vec(B'_(|\|)) + vec(E'_(_|_)). vec(B'_(_|_)) = 0`, since `E'_(_|_).'B'_(_|_) =-vec(E_(_|_)). (vec(v) xx vec(E))//(1 - v^(2)//c^(2)) = vec(E_(_|_)).(vec(v) xx vec(E_(_|_))//(1 - (v^(2))/(c^(2))) = 0'` |
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| 7580. |
Steady current flows in a metallic conductor of nonuniform cross section. Which of the following quantities is a constant along the conductor? |
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Answer» CURRENT |
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| 7581. |
The dependence of binding energy per nucleon, B_Non the mass number A, is represented by |
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Answer»
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| 7582. |
A body has maximum range R_(1) when projected up the inclined plane. The same body when projected down the inclined plane, it has maximum range R_(2). Find its maximum horizontal inclined plane in the line of the greatest slope. |
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Answer» Solution :As derived earlier, For upward projection, `R_("max") =(v_(0)^(2))/(g(1+sinbeta))= R_(1)""....(i)` For downward projection, `R_("max") =(v_(0)^(2))/(g(1-sin beta)) = R_(2)""......(iii)` For a projection on horizontal surface substituting `beta = 0` Then, we have `R_("max") = (v_(0)^(2))/(g) = R("SAY")"".......(iii)` To establish a relation between R, `R_(1)` and `R_(2)` we need to eliminate `sin beta` ADDING `(1)/(R_(1))`from eq. (i) with`(1)/(R_(2))` from eq (ii) we have `(2)/(R) = (1)/(R_(1)) + (1)/(R_(2))` Then `R= (2R_(1)R_(2))/(R_(1)+R_(2))` |
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| 7583. |
A big block of mass M is placed on a horizontal surface. Two cubes each of mass m are attached with ideal string-pulley system as shown in figure. On ecube falls in the groove drilled into the block as shown. Assuming all the surfaces are smooth and system is released from rest, find instantaneous power developed by gravity. (consider M=2m). Assume that the system starts moving from rest at time t = 0 . |
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Answer» |
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| 7584. |
A variable air capacitor used in radio tuning circuit is made of N semi-cireuler plates each of radius Rand positioned a distance d from its neighboring plates. A second set of similar plates is enmeshed with its plates half-way between those of first set. Second set of plates can rotate as a complete |
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Answer» `(Nepsilon_0(pi-theta)R^2)/d` |
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| 7585. |
Capacitors C_(1)(10 mu F) and C_(2) (20 mu F)are connected in series across a 3 kV supply, as shown. Whatis the charge on the capacitor C_(1) ? |
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Answer» 45000 `mu`C |
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| 7586. |
In a common base transistor amplifier the input resistance is 200 ohm and output resistance is 20,000 ohms. If alpha = 0.95 Then power gain is |
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Answer» 50 |
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| 7587. |
A hollow cylinder ( rho= 2.2 xx 10^(-8)Omega -m) of length 3 m has inner and outer diameters are 2 mm and 4 mm respectively. The resistance of the cylinder is |
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Answer» `0.35 XX 10^(-3)Omega ` |
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| 7588. |
In a common base transistor amplifier the input resistance is 200 ohm and output resistance is 20,000 ohms. If alpha = 0.95 Then voltage gain is |
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Answer» 50 VOLTAGE gain `A_v = alpha (R_0)/(R_i)` `=0.95xx(20,000)/200=95` |
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| 7589. |
The present day abundances (in moles) of the isotopes U^(238)andU^(235) are in the atio of 128 : 1. They have half lives of 4.5xx10^(9) years and 7xx10^(8) years respectively. If age of earth in (49X)/(76)xx10^(7) years, then calculate X (Assume equal moles of each isotope existed at the time of formation of the earth) |
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Answer» |
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| 7590. |
When a neutron is disintegrated to give a beta-particle, |
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Answer» a neutrino ALONE is emitted `""_(0)n^(1)=""_(1)p^(1)+""_(-1)beta^(0)+vecv` |
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| 7591. |
A ball of mass 10 gm dropped from a height of 5 m hits the floor and rebounds to a height of 1.25 m. If the ball is in contact with the ground for 0.1s, the force exerted by the ground on the ball is (g = 10 m/s^(2)) |
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Answer» 0.5 N |
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| 7592. |
Who discoveredthe nucleus ? |
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Answer» Thomson |
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| 7593. |
Two light sources are called coherent if both of them |
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Answer» have the same amplitude of vibrations |
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| 7594. |
A train is moving at 30 m/s in still air. The frequency of the locomotive whistle is 500 Hz and the speed of sound is 345 m/s.what would be the apparent wavelengths in front of and behind the locomotive if a wind of speed 10 m/s were blowing in the same direction as that in which the locomotive is travelling? |
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Answer» `0.63m , 0.75 m` |
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| 7595. |
A metallic wire is folded to form a square loop a side 'a'. It carries a current 'i' and is kept perpendicular to a uniform magnetic field. If the shape of the loop is changed from square to a circle withoul changing the length of the wire and current, the amount of work done in doing so is |
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Answer» Solution :W = Find P.E - initial P.E `W=-M_(F)B-(-M_(i)B)` `W=iB(A_(i)-A_(f))W=iBa^(2)[1-4/pi]` |
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| 7596. |
The kinetic energy and potential energy of a particle executing simple harmonic motion will be equal when its displacement is : (amplitude = a) : |
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Answer» `(a)/(2)` `(1)/(2)momega^(2)(r^(2)-y^(2))=(1)/(2)m omega^(2)y^(2)`. `implies""y=( r )/(sqrt(2))=(a)/(sqrt(2))`. So correct CHOICE is (B). |
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| 7597. |
The potential at the centre of a uniformly charged circular disc of radius 3 cm is 460V. What is the total charge on the disc? |
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Answer» SOLUTION :Data supplied, V=460 volts `r=3 xx 10^(-2)m` Potential (V) `=(sigma r)/(2epsi_(0))` `sigma =(2epsi_(0)V)/(r)" But ",sigma=(q)/(pir^(2))` `q/(pi r^(2))=(2epsi_(0)V)/(r)` `q= (2PI epsi_(0) Vr)` `=2 xx 3.14 xx 8.854 xx 10^(-12) xx 460 xx 3 xx 10^(-2)` =0.7673nC  Surface charge density of disc `sigma(("say"))` Consider a ring of radius x and thickness dx. Charge of this ring `=2pi xdx sigma` Potential at the centre due to this ring `=(1)/(4pi epsi_(0)) (2pi x sigma dx)/(x)=(sigma)/(2epsi_(0)) dx` Whole disc (potential) `=sigma/(2epsi_(0)) UNDERSET(0)overset(x)int dx=(sigma)/(2epsi_(0)) r` |
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| 7598. |
The amount of heat energy radiated by a metal at temperature T is E. When the temperature is increased to 3T, energy radiated is |
| Answer» Answer :A | |
| 7599. |
Which of the following statements are true A) The resistance of intrinsic semiconductors decreases with the increase of temperature B) Doping pure silicon with trivalent impurities gives P - type semi conductors C) The majority carries in N-type semiconductors are holes D) Ap-n junction can act as a diode |
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Answer» A and B are TRUE |
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| 7600. |
In the figure shown, light waves A and B both of wavelength lambda are initially in phase and travelling rightward as incident by the two rays. Wave A is reflected from four parallel surfaces but ends up travelling in original direction. The possible value(s) of distance L in terms of wavelength lambda in figure which put A and B exactly out of phase with each other after all the reflected is/are |
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Answer» `LAMBDA//2` |
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