Saved Bookmarks
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. |
From a rectangular sheet of uniform density a reactangle is cut out as shown in figure. Find new co-ordinate of center of mass w.r.t orign |
|
Answer» `((1)/(12),(b)/(12))` |
|
| 2. |
By combining two words electrons and mechanics we get the word _? |
|
Answer» |
|
| 3. |
Current i flows through a long wire. A square loop made of conducting wire held below the wire in the same vertical plane is released and allowed to fall under gravity. If acceleration of the loop is a, then : |
|
Answer» a current is induced in ANTICLOCKWISE direction and a gt G |
|
| 4. |
A vessel, whose bottom has round holes with diameter of 0.1 mm, is filled with water. The maximum height to which the water can be filled without leakage is (S.T. of water = 75 dynes/cm, g = 1000 cm//s^2) |
|
Answer» 100 cm |
|
| 5. |
Two long parallel conductors cany currents i_(1) = 3A and i_(2) = 3A both are directed into the plane of paper. The magnitude of resultant magnetic field at point 'P, is |
|
Answer» `12muT` |
|
| 6. |
What should be the ratio between the length and radius of the uniform solid cylinder so that its moment of inertia about central axis is the same as that about equatorial axis ? |
|
Answer» `1:SQRT(3)` or `(l^(2))/(R^(2))=(3)/(1)or(l)/(R)=sqrt(3)/(1)` |
|
| 7. |
Consider an evacuated cylindrical chamber of hight h rigid conducting plates at the ends and an insulating curved surgace as shown in the figure. A number of spherical balls madeof a light weight and soft material and coagted with a conducting material are placed on the bottom plate. The balls have a radius rltlth. Nowa high voltage source (HV)is connected across the conducting plates such that th ebottom plate is at+V_(0)and the top plate at-V_(0). Due to their conducting surface the balls will get charged, will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate, where the coefficient of reatitution can be taken to be zero due to the soft nature of the material of the balls. The electric field in the chamber can be considered to be considered to be that of a parallel plate capacitor. Assume tht there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity) The average current in the steady stateregistered by the ammeter in the circuit will be |
|
Answer» PROPORTIONAL to `V_(0)^(2)` |
|
| 8. |
Consider an evacuated cylindrical chamber of hight h rigid conducting plates at the ends and an insulating curved surgace as shown in the figure. A number of spherical balls madeof a light weight and soft material and coagted with a conducting material are placed on the bottom plate. The balls have a radius rltlth. Nowa high voltage source (HV)is connected across the conducting plates such that th ebottom plate is at+V_(0)and the top plate at-V_(0). Due to their conducting surface the balls will get charged, will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate, where the coefficient of reatitution can be taken to be zero due to the soft nature of the material of the balls. The electric field in the chamber can be considered to be considered to be that of a parallel plate capacitor. Assume tht there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity) Which one of the following statements is correct ? |
|
Answer» The balls will execute SIMPLE harmonic motion between the two plates |
|
| 9. |
A rectangular slab of refractive index mu is placed on another slab of refractive index 3. Both the slabs are of the same dimensions. There is a coin at the bottom of the lower slab. What should be the value of musuch that when viewed normally from above, the coin appears to be at the surface of separation of the two slabs? |
|
Answer» SOLUTION :Let thickness of each SLAB be d. According to the QUESTION the apparent depth of the coin = d. `therefore "" d = (d)/(mu) + (d)/(3) or, 1= (1)/(mu) + (1)/(3)` `or, "" (1)/(mu) = (2)/(3)or, mu = (3)/(2) = 1.5` |
|
| 10. |
What does SMSC stands for? |
|
Answer» Short messaging SERVICE CENTER |
|
| 11. |
If a hemispherical body is placed in a uniform electric field E then the flux linked with the curved surface is |
|
Answer» `2piR^(2)E` |
|
| 12. |
Assertion (A) : Zener diode works on the principle of breakdown voltage. Reason (R) : Current increases suddenly after breakdown voltage. |
| Answer» Solution :Zener diodes are special PURPOSE diode used as VOLTAGE regulator. They are used in reverse bias in breakdown voltage region and work on the principle that below breakdown voltage they behave as insulator but at and above breakdown voltage they START DRAWING a large current. | |
| 13. |
A black body at high temperature TK radiates energy at the rate "EW/ m"^(2). When the temperature falls to ((T)/(2)) K, the radiated energy will be : |
|
Answer» SOLUTION :`(E_(2))/(E_(1))=((T_(2))/(T_(1)))^(4)""rArr(E_(2))/(E_(1))=((T//2)/(T))^(2)` `rArrE_(2)=(E)/(16)` Thus correct CHOICE is (d). |
|
| 14. |
In Young's double slit experiment, using monochromatic light of wavelength lamda, the intensity of light at a point on the screen where path difference is lamda is K units. The intensity of light at a point where path difference is lamda/3 is |
|
Answer» 4K `I = 4I_(0) cos^(2)(PHI)/2` where `I_(0)` is the intensity of either wave and `phi` is the phase difference between two waves. Phase difference, `phi = (2pi)/(lamda) xx` Path difference When path difference is `lamda` then `phi = (2pi)/(lamda) xx lamda = 2pi` `:. I = 4I_(0) cos^(2) ((2pi)/2) = 4I_(0) cos^(2) (pi) = 4I_(0) = K` ...(1) When path difference is `(lamda)/3` , then `phi = (2pi)/(lamda) xx (lamda)/3 = (2pi)/3` `:. I = 4I_(0) cos^(2) ((2pi)/(3)) = K/4`[Using (i)] |
|
| 15. |
The motion of a gas molecule which determines the temperature in |
|
Answer» TRANSLATORY |
|
| 16. |
According to classical physics, the kinetic energy K of an electron revolve in orbit of radius r is ........ |
|
Answer» `(1)/(8piin_(0)).(Ze^(2))/(R)` CENTRIPETAL force = Coulombian force `(MV^(2))/(r)=(1)/(4piin_(0)).((Ze)(e))/(r^(2))` `:.(1)/(2)mv^(2)=(1)/(8piin_(0)).(Ze^(2))/(r)` `:.K=(1)/(8piin_(0)).(Ze^(2))/(r)` |
|
| 17. |
A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet . The ratio of intensities of illumination at the centre and at points on the circumference of the table will be |
| Answer» ANSWER :C | |
| 18. |
(a) An electric dipole of dipole moment vecp is placed in a uniform electric field vecE at an angle theta with it. Derive the expression for torque (vec(tau)) acting on it. Find the orientation of the dipole relative to the electric field for which torque on it is (i) maximum, and (ii) half of maximum. (b) Two point charges q_(1)=+1muC and q_(2)=+4muC are placed 2 m apart in air. At what distance from q_(1) along the line joining the two charges, will the net electric field be zero ? |
|
Answer» As shown in here, forces qE and qE act on the two charges in mutually opposite directions. CONSEQUENTLY, net translational force on dipole is ZERO and there is no translatory motion of dipole. However, as the two forces act at two different points NON- linearly, they constitute a couple whose torque is given by : torque `tau = (qE)`. Normal distance between the forces `=qE2asintheta=pEsintheta` The torque has a tendency to align the dipole along the direction of electric field. Thus, according to right hand rule `vectau=vecpxxvecE` (iii) If `theta` = 90° i.e., dipole is set perpendicular to the direction of electric field E, then torque `tau` = pE sin 90° = pE = maximum. (ii) When torque is ONE half of maximum value, torque `tau.=(pE)/2=pEsintheta.rArrsintheta.=1/2` or `theta=30^(@)` (b) Let charges `q_(1)=+1muC` and `q_(2)=pm4muC` be placed at points A and B respectively separated by a distance AB = 2 min air. Let net electric field `vecE` be zero at a point C situated at a distance x m from `q_(1)` or (2-x) m from `q_(2)`. Then `abs(vecE_(A)+vecE_(B))=vec0` or `abs(vecE_(A))=abs(vecE_(B))` `rArr1/(4piepsi_(0))(q_(1))/(x^(2))=1/(4piepsi_(0))(q_(2))/((2-x)^(2))` `rArr(x/(2-x))=sqrt((q_(1))/(q_(2)))=sqrt((1muC)/(4muC))=1/2rArrx=2/3m` 
|
|
| 19. |
Two bodies A and B of definite shape are placed near one another. Electrostaitc attraction is found between the bodies, then |
|
Answer» Both bodies MUST be POSITIVELY CHARGED |
|
| 20. |
Assuming earth to be an isolated conducting sphere of radius 6400 km, what is capacitance of earth ? |
| Answer» SOLUTION :CAPACITANCE of EARTH `C=4piepsilon_0r`Here,`4piepsilon_0=1/(9xx10^9)r=6400km=6.4xx10^6mC=(6.4xx10^6)/(9xx10^9)=0.711xx10^-3F=711muF.` | |
| 21. |
The variations of potential energy (U) with position x for three simple harmonic oscillators A, B and C are shown in figure. The oscillators have same mass. The time period of oscillation is greatest for |
|
Answer» A |
|
| 22. |
A conducting wire of 2m length is used to form a circular loop. If it carries a current of 2A, its magnetic moment will be ______ Am^(2). |
|
Answer» SOLUTION :`l=2pir` `-r=l/(2pi)=2/(2pi)=1/pi` `thereforem=IA` = `Ixxpir^(2)` = `2xxpixx1/pi^(2)` = `2/piAm^(2)` |
|
| 23. |
Resistance of tungsten wire at 150^@C is 133Omegha.Its resistance temperature co.efficient is 0.0045^@C.The resistance of this wire at 500^@C will be : |
|
Answer» `180Omega` |
|
| 24. |
(A): As the drift velocity increases the current flowing through the conductor decreases. (R): The current flowing through a conductor is inversily proportional to the drift velocity. |
|
Answer» Both 'A' and 'R' are true and 'R' is the correct EXPLANATION of 'A' |
|
| 25. |
What is the phase relation between current and voltage in a series LCR circuit in which X_(L)ltX_(C)? |
| Answer» Solution :`phi=tan^(-1)((X_(C)-X_(L))/(R))` | |
| 26. |
Four similar prisms of angle of prism are arranged. Which of the following arrangements give no net angular deviation? |
|
Answer» |
|
| 28. |
In the adjoning figure, the potential difference across the 4.5 muF capacitor is |
|
Answer» 4 V |
|
| 29. |
The photoelectric cut-off voltage in a certain experiment 1.5 V. What is the maximum kinetic energy of photoelectrons emitted ? |
|
Answer» Solution :Here `V_(0) = 1.5` V `K_(max) = eV_(0) = 1.5 eV` `= 1.5 xx 1.6 xx 10^(-19) J` `K_(max) = 2.4 xx 10^(-19)J` |
|
| 30. |
The difference between the apparent frequency of a source of sound as perceived by the observer during its approach and recession is 2% of the frequency of the source. If the speed of sound in air is 300 ms^(-1), the velocity of the source is |
|
Answer» 12 m/s |
|
| 31. |
STATEMENT-1: In electric circuits, wires carrying currents in opposite directions are often twisted together. because STATEMENT-2: The magnetic field in the surrounding space of a twisted wire system is not precisely zero because the wires are not in the same location in space. |
|
Answer» Statement-1 is TRUE , Statement-2 is True , Statement-2 is a CORRECT EXPLANATION for Statement-1. |
|
| 32. |
The magnetic moment ofthe system will be |
|
Answer» `SQRT(3)ma`  `=sqrt(2M^(2)a^(2)+2m^(2)xx1/2)` `sqrt(3)` ma |
|
| 33. |
The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor are: |
|
Answer» `21xx10^3overset+- 10%` |
|
| 34. |
A radioactive decay can form an isotope of the original nucleus with the emission of particles |
|
Answer» one `alpha` and four `BETA` |
|
| 35. |
A radio can tune over the frequency range of a portion of MW broadcast band: (800 kHz to 1200 kHz). If its LC circuit has an effective inductance of 200muH, what must be the range of its variable capacitor?(Hint: For tuning, the natural frequency i.e., the frequency of free oscillations of the LC circuit should be equal to the frequency of the radio wave.] |
| Answer» SOLUTION :`C_1 = 198, C_2 = 88 PF` | |
| 36. |
A person with a normal near point (25 cm) using a compound microscope with objective of focal length 8.0 mm and an eyeplece of focal length 2.5 cm can bring an object placed at 2.0 mm from the objective in sharp focus. What is the separation between the two lenses ? Calculate the magnifying power of the microscope. |
|
Answer» Solution :Angular MAGNIFICATION of the eye piece for IMAGE at 25 cm `=(1+(D)/(f))=1+(25)/(2.5)=11` for objective, `u=-0.9cm, f=0.8cm` `(1)/(UPSILON)-(1)/(u)=(1)/(f)` `(1)/(upsilon)=(1)/(0.8)-(1)/(0.9)=(9-8)/(7.2)=(1)/(7.2)` `rArr upsilon =7.2cm.` for eye piece, `upsilon = -25CM, f_(0)=25cm` Again `(1)/(upsilon)-(1)/(u)=(1)/(f)` `(-1)/(u)=(1)/(f)-(1)/(v)=(1)/(2.5)-(1)/(-25)=(11)/(25)` `u=-(25)/(11)=-2.27cm` `therefore` Distance between objective and eye piece `=v+|u|=7.2+2.27=9.47cm` MAGNIFYING power of microscope `=(7.2)/(0.9)xx(-25)/((-25)/(1))=88` |
|
| 37. |
A man stands in a lift going downward with uniform velocity. He experiences a loss of weight at the start but not when lift is in uniform motion. Explain Why? |
|
Answer» Solution :The apparent weight W' when lift is going down with ACCELERATION 'a' is GIVEN by W' = m (g-a). Iniially, when the lift is in acceleration at start a = 0 and HENCE, W' |
|
| 38. |
A moving coil galvanometer of resistance G gives full scale deflection for a certain current. The shunt resistance required to convert it to measure a current n times the initial current is about |
|
Answer» `(n-1)G` |
|
| 39. |
The electric field in a certain region of space is (5 hat(i) + 4 hat(j) - hat(k)) xx 10^(5) N//C. Calculate electric flux due to this field over an area of (2 hat(i) - hat(j)) xx 10^(-2) m^(2). |
|
Answer» `6XX10^(2) NC^(-1) m^(2)` |
|
| 40. |
The space between two large plane surfaces is 2.5 cm and it is filled with glycerine. What force is required to drag a very thin plate 1 m^2 in area, between the surfaces at a speed of 1m/s ? (The plate is at a distance of 1 cm from one of the surfaces. ) (eta=0.75Ns//m^2) |
| Answer» ANSWER :D | |
| 41. |
(a). Use the method in part (b) of the previous problem of calculate the electrostatic self energy of a uniformly charegd sphere of radius R having charge Q. (b). Divide the above sphere (mentally) into two regions-spherical concentric part having radius (R)/(2) and the remaining annular part (between (R)/(2) and R). Denote the point charges in sphere of radius R//2 by q_(1),q_(2),q_(3) .. . .etc. The charges in annular part be denoted by Q_(1),Q_(2),Q_(3) . . . etc. Calculate the electrostatic interaction energy for all pairs like [(Q_(i),Q_(j))+(q_(i)+q_(j))]. |
|
Answer» (B). `(147)/(320)(Q^(2))/(4pi epsi_(0)R)` |
|
| 42. |
Relation between voltage sensitivity (sigma_(v)) and current sensitivity (sigma_(i)) of a moving coil galvanometer is ______ |
|
Answer» `sigma_(i)/G=sigma_(v)` `thereforesigma_(i)=theta/(i*G)*G` `thereforesigma_(i)=sigma_(v)*G` `thereforesigma_(i)/G=sigma_(v)` |
|
| 43. |
A device which converts d.c.into a.c.is called |
|
Answer» Rectifier |
|
| 44. |
If the forward voltage in a diode is increased the width of the depletion region |
|
Answer» increases |
|
| 45. |
The voltage gain of an amplifier state is 100. The gain expressed in db is |
|
Answer» 100 |
|
| 46. |
A pith ball of mass 9 xx 10^(-5) kg carries a charge of 5 mu C. What must be charge in another pith ball placed directly 2 cm above the given pith ball such that they are held in equilibrium ? |
|
Answer» `3.2 xx 10^(-11)C` |
|
| 47. |
Which of the following type of radiation has maximum wavelength? |
|
Answer» BLUE light |
|
| 48. |
In a single-slit diffraction pattern the angular width of the central maxima is-___ of the angular width of subsequent maxima. |
| Answer» SOLUTION :TWICE (or DOUBLE) | |
| 49. |
Choose the most appropriate answer. In the nuclear reaction presented above, the other particles might be |
|
Answer» An alpha PARTICLE, which consists of TWO protons and two neutrons |
|
| 50. |
A thin rod of length l and mass m isturned at mid-point O at angle of 60°. The moment of inertia of the rod about an axis passing through O and perpendicular to the plane of the rod will be |
|
Answer» `ML^(2)//3` M.I. of the system=`2xx(m/2)((l//2)^(2))/3=(ml^(2))/12` |
|
