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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.
| 44151. |
Even though an electric field E exerts a force qE on a charged particle yet the electric field of an EM wave does not contribute to the radiation pressure (but transfers energy). Explain. |
| Answer» Solution :Electric field of electromagnetic waves is an oscillating field and so the electric FORCE caused by it on CHARGED particle. This electric force averaged over an integral number of cycles is ZERO SINCE its direction changes EVERY half cycle. Hence electric field is not responsible for radiation pressure. | |
| 44152. |
At a place, the horizontal component of earth's magnetic field is B and angle of dip is 60^@. What is the value of horizontal component of earth's magnetic field at equator? |
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Answer» Solution :`B_(H)=B_(E) cos delta` `B=B_(E)cos 60^(@)impliesB_(E)=2B` Aq equator `delta=0^(@)` `:.B_(H)=2Bcos0^(@)=2B` [Alternativ\ely, Award full one MARK, if student doesn't the value `(=2B)` of `B_(E)` while finding the value of horizontal component of equator, and just WRITES and formula only.] |
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| 44153. |
Find the capacitance of a capacitor in which the space between the plates is partly filled with a dielectric (Fig. 25.5) |
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Answer» Solution :Here we have two capacitors connected in parallel, with capacitances `C_(1)=(espi_(0)S_(1))/(d)=(epsi_(0)S(l_(0)-L))/(dl_(0))` and `C_(2)=(EPSI epsi_(0)S_(2))/(d)=(epsi epsi_(a) Sl)/(dl_(0))` |
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| 44154. |
A chrage 'q' is placed at the centre of a cube of side 'l' . What is the electric flux passing through each face of the cube? |
| Answer» Solution :As PER Gauss. law electric flux PASSING through ENTIRE cube is `(q)/(in_0) `. As the cube has 6 FACES and charge q is situated symmetrically, flux passing through each face = ` (q)/(6in _0)` | |
| 44155. |
Explain the change in the band with the temperatureof the intrinsic semiconductor by drawing figure. |
Answer» Solution :An intrinsic semiconductor will behave like an INSULATOR at T = 0K as SHOWN in figure (a).  At T = 0K temperature all the electrons are bound in the valence band and they are not in CONDUCTION band so electrons cannot flow, as a result it behave as insulators. These thermally exicted electrons at `T gt 0K`, partially occupy the conduction band which is shown in figure.  Solid dots indicates electrons while empty dot indicates holes in the figure. As shown in the figure, four electrons getting energy from valence band and have gone into conduction band so four holes shown in valence band. |
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| 44156. |
Amplitude of electric and magnetic field are related C = ____. |
| Answer» SOLUTION :`[(E_0)/B_0]` | |
| 44157. |
The time of oscillation of a small drop of liquid under surface tension depends upon density rho. Radius r and surface tension s, as T alpha rho^(a) s^(b) r^(e). Then the descending order of a, b and c is |
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Answer» a `GT B gt C` |
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| 44158. |
A : Number of air molecules in a room in winter is morethanthe number of molecules in the same room in summer. R : At a given pressure and volume, the number of moleculesof a given massof a gasisdirectly proportional to the absolute temperature. |
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Answer» If bothAssertion & Reason are TRUE and the reason is the correct explanation of the assertion, then Mark (1) |
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| 44159. |
Which basic mode of communication is used in satellite communication? What type of wave propagation is used in this mode? Write, given reason, the frequency range used in this mode of propagation. |
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Answer» Solution :The basic MODE of COMMUNICATION used in satellite communication is point -to o point mode. SPACE wave propagation is used in satellite communication. In space wave propagation, the RANGE of frequency is between 54 MHz to 4.26 GHz since both the ground wave and sky wave propagation fail at such high FREQUENCIES. |
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| 44160. |
Two radioactive substances X and Y initially contain equal number of atoms. Their half-lives are 1 hour and 2 hours respectively. Calculate the ratio of their rates of disintegration after four hours. |
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Answer» Solution :Rate of disintegration `(R)=(dN)/(dt)=lambdaN=Nxx0.693/T` `THEREFORE` The ratio of rates of disintegration , `R_1/R_2=(N_1/N_2)T_2/T_1` Here, `T_1`= 1 hour : `T_2` =2 hours `N_0` is same for both the RADIO ACTIVE substances. In four hours, X completes 4 half-lives as its half-life is 1 hour. The ramaining NUMBER of atoms of X, `N_1=N_0/2^n=N_0/2^4=N_0/16`. Y completes 2 half-lives in four hours as its half-life is 2 hours. The number of atoms of Y remaining , `N_2=N_0/2^2=N_0/4` `therefore R_1/R_2=N_0/16xx4/N_0(2/1)=1/2`. |
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| 44161. |
A cricket fielder can throw the cricbmket ball with a speed v_0. If the throws the ball while running wirth speed u at an angle theta to the horizontal, |
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Answer» the effective angle to the horizontal at which the ball is projected in air as SEEN by a spectator is `TAN^(-1)((v_0 sin theta)/(v_0 cos theta + u))` |
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| 44162. |
A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I_(1) at a distance d from the donductor as shown in figure. The loop will experience |
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Answer» a NET repulsive FORCE force away from the conductor |
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| 44163. |
Two long, thin, parallel conductorsare keptvery closeto each other , without touching . One carries a current I,and the otherhas chargelambdaper unitlength. An electron movingparallelto the conductorsis undeflected.Let c bethe velocityof lightand v be the velocity of electron, then |
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Answer» `v = (lambdac^(2))/(I)` ` E = lamda/( 2 pi in_(0)x)` ( to the RIGHT ) . and magneticfield, B ` (mu_(0)I)/(2 pi x)` FORNO deflection, ` E = VB = orv= E/B ` ` or v=lamda/(2 pi in_(0)) xx (2 pi x)/(mu 0 I) = ( lamda)/I 1/(in_(0) mu_(0))= (lamdac^(2))/(I)` 
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| 44164. |
Define internal field emission or field ionization . |
| Answer» SOLUTION :The PROCESS of emission of electrons DUE to the ruptured of banks infrom the lattice due to strong electric field is KNOW as INTERNAL field emission or field ionization. | |
| 44165. |
The apparent frequency of a note is 200 Hz. When a listener is moving with a velocity of 40 ms^(-1) towards a stationary source. When he moves away from the same source with the same speed, the apparent frequency of the same note is 160 Hz. The velocity of sound in air in m//s is |
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Answer» 360 160 ` = (v_(s) - 40)/(v_(s)) xx n` Dividing ` (200)/(160) = (v_(s) + 40)/(v_(s)- 40) ` this gives `v_(s) = 360 ms^(-1)` correct choice is (a) . |
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| 44166. |
What should we never despise anyone for? |
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Answer» Poverty |
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| 44167. |
. A small circular ring of radius R is placed in Y-Z plane with its centre at (-a , 0, 0). Another small circular ring of same radius Ris placed in X-Z plane with its centre at (0, -a , 0). Calculate the magnitude and direction of net magnetic field at the origin (0, 0, 0), if both the rings carry current I. The direction of current in the first loop and the second loop is clockwise and anticlockwise respectively, when seen from the origin. |
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Answer» |
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| 44168. |
In various phenomena, radiation either possess wave nature or quantum (particle) nature. What we call this behavior. |
| Answer» SOLUTION :DUAL NATURE. | |
| 44169. |
State the reason, why are GaAs and Si preferred materials for fabrication in solar cells. |
| Answer» Solution :Because their energy band gap is NEARLY 1.5eV ie., almost same as that corresponding to MAXIMA in SOLAR RADIATION spectrum and absorption coefficient is RELATIVELY high. | |
| 44170. |
The numerical aperture for a human eye is of the order of |
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Answer» 1 |
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| 44171. |
Two similar conducting balls having charges + q and - q are placed at a separation d from each other in air. The radius of each ball is r and the separation between their centres is d (d gt gtr ). Calculate the capacitance of the two ball system |
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Answer» `4 pi epsilon_(0)`r |
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| 44172. |
The light reflected by plane mirror may form a real images . |
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Answer» If the rays incident on the mirror are diverging |
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| 44173. |
let B be the magnetic field at a point between the two conductors, at a distance x from the axis. Let B_(2) be the magnetic field at a point outside conductor, at a distance 2x from the axis |
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Answer» `B_(1)=B_(2)` `B_(1)=B_(2)` |
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| 44174. |
As shown in the following figure, take A and B input waveforms. Sketch the output waveform obtained from AND gate. |
Answer» SOLUTION :
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| 44175. |
A closely wound solenoid of 800 turns and area of cross section 2.5xx10^(-4)m^(2) carries a current of 3.0A. What is its associated magnetic moment ? |
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Answer» 0.5 J/T |
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| 44176. |
Which type of semiconductor is obtained by mixing arsenic with silicon ? |
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Answer» N |
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| 44177. |
Meaning of the word Hurtle... |
| Answer» Answer :D | |
| 44178. |
STATEMENT-1: Current is passed through a metallic wire, heating it red. When cold water is poured on half of its portion, then rest of the half portion becomes more hot. because STATEMENT-2: Resistance decreases due to decrease in temperature and then current through wire increases |
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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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| 44179. |
When a low flying air craft passes over head we some times notice a slight shaking of the picture on our TV screen. This is due to |
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Answer» diffraction of the signal RECEIVED from the antenna |
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| 44180. |
What vector must be added to the sum of two vectors 2 hati - hat j + 3 hat k and 3 hati -2 hat j - 2 hat k so that the resultant is a unit vector along Z axis |
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Answer» `5 hati + HAT k` |
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| 44181. |
If one of two identical slits producing interference in Young's experiment is covered with glass, so that the light intensity passing through it is reduced 50 50%, find the ratio of the maximum and minimum intensity of the fringe in the interference pattern. (b) What kind of fringes do you expect to observe if white light is used instead of monochromatic light ? |
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Answer» Solution :(a) Let INTENSITY of light passing through first slit be `I_(1)=I`. So the intensity of light passing through second slit covered with glass `I_(2)=50%` of I=0.5I. `therefore`MAXIMUM intensity of interference PATTERN `I_(max)=I_(1)+I_(2)+2sqrt(I_(1)I_(2))=I+0.5I+2sqrt(I*(0.5I))=(1.5+sqrt(2))I` and minimum intensity of interference pattern `I_("min")=I_(1)+I_(2)-2sqrt(I_(1)I_(2))=I+0.5I-2sqrt(I*(0.5I))=(1.5-sqrt(2))I` `implies(I_(max))/(I_("min"))=(1.5+sqrt(2))/(1.5-sqrt(2))=(1.5+1.414)/(1.5-1.414)=(2.914)/(0.086)=33.9:1` (B) N/A. |
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| 44182. |
One magnet is moved towards a coil, first speedily and then slowly. Then amount of electric charge induced would be _____ |
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Answer» equal in both the cases. |
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| 44183. |
वृताकार पथ पर तीन धावक एक ही स्थान से दौड़ना प्रारम्भ करते है, तो एक चक्कर लगाने में क्रमश: 2 घंटे, 4 घंटे और 6 घटे लगते हैं तो तीनों को प्रा रंभिक बिंदु पर पुनः मिलने में कितना समय लगेगा? |
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Answer» 8 घंटे |
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| 44184. |
The following observations were recorded on a platinum resistance thermometer: Resistance at melting point of ice = 3.70 ohm, resistance of boiling point of water at normal pressure Omega and resistance at t”^(@)C = 5.29 ohm. Calculate (i) Temperature coefficient of resistance of platinum, (ii) Value of temperature t |
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Answer» SOLUTION :(i) TEMPERATURE coefficient of resistance is givenby `aplha=(R_100-R_0)/(R_0xx100)=(4.71-3.70)/(3.70xx100)` `(1.01)/(370)=2.73xx10^(-3)PER"^(C )` For temperature t we have `t=100"^(@)Cxx(R_1-R_0)/(R_100-R_0)` `100^(@)Cxx(5.29-3.70)/(4.71-3.70)=100^(@)Cxx(1.59)/(1.01)=157.4"^(@)C` |
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| 44185. |
Consider a wire carrying a steady current, I placed in a uniform magnetic field vecB perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do no work. This implies that, |
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Answer» motion of charges inside the CONDUCTOR is unaffected by `vecB` since they do not absorb energy. `F=IlBsintheta` `theta=90^(@)" "(becauseIvecl_|_vecB)` `thereforeF=IlB` According to Fleming.s left hand rule the direction of magnetic force is perpendicular to magnetic field. So, work done by magnetic force on ions are zero. So, options (B), (D) are true. |
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| 44186. |
A sphericalball contract in volume by 0.5%,when subject to a normal uniform pressure Calculate the volume strain producd in sperical ball |
| Answer» Solution :Volume STRAIN =`(DELTAV)/(v)=(0.05)/(100)=5XX10^(-4)` | |
| 44187. |
In Division Germer Experiment, when electron strikes the Ni crystal, which one of the following is produced ? |
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Answer» X-rays |
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| 44188. |
Which of the following statement is correct . |
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Answer» A charged particle enters a region of uniform magnetic field at an angle `85^(@)` to magnetic lines of FORCE. The PATH of the particle is a circle . |
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| 44189. |
The maximum number of possible interference maxima for slit separation equal to twice the wavelength in Young.s double slit experiment is |
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Answer» INFINITE |
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| 44190. |
Three identical spheres lie at rest along a line on a smooth horizontal surface. The separation between any two adjacent spheres is L. The first sphere is moving with a velocity u towards the second sphere at time t = 0. The coefficient of restitution for a collision between any two blocks is 1/3The correct statement is |
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Answer» The third sphere will start moving at `t=(5L)/(2U)` |
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| 44191. |
Determine the magnitude of the total magnetic field at point C if d=0.10m. |
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Answer» `2.4xx10^(-5)` T |
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| 44192. |
A long straight conductor carrying current is placed near a current carrying circular loop as in the figure. ( ## EXP_SPS_PHY_XII_C04_E04_023_Q01 .png" width="80%">: If B_1, is the field of the ring and B_2, the field due to straight conductor what will be the direction of B_1 And B_2 at O. |
| Answer» SOLUTION :`(B_1)`, into the PLANE and `(B_2)`, out of the plane. | |
| 44193. |
Who wrote the "A letter to God"? |
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Answer» G.L. Fuentes |
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| 44194. |
For a CE transistoramplifier, the audio signal voltage across the collector resistance of 4.0kOmega is 4.0V. suppose the current amplification factor of the transistor is 100. What should be the value of R_(B) in series with supply of 2.0 V if the de base current has to be 10 times the signal current. Also calculate the dc drop across the V_(BB) collector resistance. |
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Answer» Solution :The output as voltage is 4.0V. So the ac collector currnet `I_(C)=4.0//4000=1.0mA`. The SIGNAL current through the BASE is therefore given by `i_(B)=i_(C)//beta=1.0mA//100=0.010mA`. The dc base current has to be `10xx0.010=0.10mA`. ASLO `R_(B)=(V_(BB)-V_(BE))//I_(B)`, Assuming `V_(BE)=0.6V` `R_(B)=(2.0-0.6)//0.10=14kOmega` The dc collector current `I_(C)=100xx0.10=10mA` |
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| 44195. |
The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, its new resistance will be: |
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Answer» `(R)/(N^(2))` |
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| 44196. |
A charge's isplaced at the center of a cube what is the electric flux passing through the cube ? |
| Answer» SOLUTION :phi_E =q/epsilon_0 | |
| 44197. |
A presbyopic patient has near point as 30 cm and far point as 40 cm . The dioptric power for the corrective lens for seeing distant objects is |
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Answer» 40 D |
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| 44198. |
The nuclear model of atom was proposed by: |
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Answer» J.J Thomson |
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| 44199. |
The radius of curvature of the path of a charged particle moving under a uniform , normal magnetic field is directly proportional to |
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Answer» <P>the charge on the particle |
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| 44200. |
What was the objective of alpha-particle scattering experiment ? |
| Answer» Solution :Rutherford marked `alpha-particle` scattered in different DIRECTIONS were detected by an `alpha-particles` in AIR is LIMITED to about 5 CM. | |