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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
A partition wall has two layers of different materials A and B in contact with each other. They have the same thickness but the thermal conductivity of layer A is twice that of layer B. At steady state the temperature difference across the layer B is 50 K, then the corresponding difference across the layer A is |
| A. | 50 K |
| B. | 12.5 K |
| C. | 25 K |
| D. | 60 K |
| Answer» D. 60 K | |
| 152. |
A hydrogen atom (ionisation potential 13.6 eV) makes a transition from third excited state to first excited state. The energy of the photon emitted in the process is |
| A. | 1.89 eV |
| B. | 2.55 eV |
| C. | 12.09 eV |
| D. | 12.75 eV |
| Answer» C. 12.09 eV | |
| 153. |
What kV potential is to be applied on X-ray tube so that minimum wavelength of emitted X-rays may be 1Å (\[h=6.625\times {{10}^{-34}}\]J-sec) [UPSEAT 1999] |
| A. | \[12.42\,kV\] |
| B. | \[12.84kV\] |
| C. | \[11.98kV\] |
| D. | \[10.78kV\] |
| Answer» B. \[12.84kV\] | |
| 154. |
A possible means for making an airplane invisible to radar is to coat the plane with an anti-reflective polymer. Radar waves have a wavelength of 3.00 cm and the index of refraction of the polymer is n=1.50. How thick would you make the coating? |
| A. | 1.50cm |
| B. | 3.00cm |
| C. | 0.50cm |
| D. | None of these |
| Answer» D. None of these | |
| 155. |
For a triode \[{{r}_{p}}=10\]kilo ohm and \[{{g}_{m}}=3\]milli mho. If the load resistance is double of plate resistance, then the value of voltage gain will be [RPMT 1994] |
| A. | 10 |
| B. | 20 |
| C. | 15 |
| D. | 30 |
| Answer» C. 15 | |
| 156. |
A bullet is fired from a gun. The force on the bullet is given by \[F=600-2\times {{10}^{5}}t\], where F is in newtons and t in seconds. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to the bullet [CBSE PMT 1998] |
| A. | 9 Ns |
| B. | Zero |
| C. | 0.9 Ns |
| D. | 1.8 Ns |
| Answer» D. 1.8 Ns | |
| 157. |
In a diode valve, the state of saturation can be obtained easily by [RPET 1998; RPMT 2002] |
| A. | High plate voltage and high filament current |
| B. | Low filament current and high plate voltage |
| C. | Low plate voltage and high cathode temperature |
| D. | High filament current and high plate voltage |
| Answer» C. Low plate voltage and high cathode temperature | |
| 158. |
A combination of two thin lenses with focal lengths \[{{f}_{1}}\] and \[{{f}_{2}}\] respectively forms an image of distant object at distance 60 cm when lenses are in contact. The position of this image shifts by 30 cm towards the combination when two lenses are separated by 10 cm. The corresponding values of \[{{f}_{1}}\] and \[{{f}_{2}}\] are |
| A. | \[30\text{ }cm,\text{ }-60\text{ }cm\] |
| B. | \[20\text{ }cm,\text{ }-30\text{ }cm\] |
| C. | \[15\text{ }cm,\text{ }-20\text{ }cm\] |
| D. | \[12\text{ }cm,\text{ }-15\text{ }cm\] |
| Answer» C. \[15\text{ }cm,\text{ }-20\text{ }cm\] | |
| 159. |
Assertion : Base in a transistor is made very thin as compared to collector and emitter regions. Reason : Due to thin base power gain and voltage gain is obtained by a transistor. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» B. If both assertion and reason are true but reason is not the correct explanation of the assertion. | |
| 160. |
Assertion : When the speed of an electron increases its specific charge decreases. Reason : Specific charge is the ratio of the charge to mass. [AIIMS 2001] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» C. If assertion is true but reason is false. | |
| 161. |
Unit of energy is [NCERT 1974; CPMT 1975] |
| A. | \[J/\sec \] |
| B. | \[Watt-day\] |
| C. | \[Kilowatt\] |
| D. | \[gm\text{-}cm/{{\sec }^{2}}\] |
| Answer» C. \[Kilowatt\] | |
| 162. |
In figure, Young's double slit experiment Q is the position of the first bright fringe on the right side of O. P is the\[{{11}^{th}}\]fringe on the other side, as measured from Q. If\[\lambda =6000\overset{o}{\mathop{A}}\,\], then \[{{S}_{1}}B\]will be equal to |
| A. | \[6\times {{10}^{-6}}m\] |
| B. | \[6.6\times {{10}^{-6}}m\] |
| C. | \[3.318\times {{10}^{-7}}m\] |
| D. | \[3.144\times {{10}^{-7}}m\] |
| Answer» B. \[6.6\times {{10}^{-6}}m\] | |
| 163. |
A beam of light consisting of two wavelength \[6500\,\overset{o}{\mathop{A}}\,\] and \[5200\,\overset{o}{\mathop{A}}\,\]is used to obtain interference fringes in a young's double slit experiment. The distance between the slits is 2.0 mm and the distance between the plane of the slits and the screen is 120 cm. What is the least distance from the central maximum where the bright fringes due to both the wave length coincide? |
| A. | 0.156 cm |
| B. | 0.152 cm |
| C. | 0.17 cm |
| D. | 0.16 cm |
| Answer» B. 0.152 cm | |
| 164. |
An object of length 6 cm is placed on the principle axis of a concave mirror of focal length f at a distance of 4f. The length of the image will be [MP PET 2003] |
| A. | 2 cm |
| B. | 12 cm |
| C. | 4 cm |
| D. | 1.2 cm |
| Answer» B. 12 cm | |
| 165. |
If the voltage of X-ray tube is doubled, the intensity of X-rays will become [RPMT 2003] |
| A. | Half |
| B. | Unchanged |
| C. | Double |
| D. | Four times |
| Answer» C. Double | |
| 166. |
In X-ray experiment Ka, Kb denotes [DCE 2005] |
| A. | Characteristic |
| B. | Continuous wavelength |
| C. | a, b-emissions respectively |
| D. | None of these |
| Answer» B. Continuous wavelength | |
| 167. |
By corpuscular theory of light, the phenomenon which can be explained is |
| A. | Refraction |
| B. | Interference |
| C. | Diffraction |
| D. | Polarisation |
| Answer» B. Interference | |
| 168. |
If\[{{n}_{1}}\],\[{{n}_{2}}\]and \[{{n}_{3}}\] are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by |
| A. | \[\frac{1}{n}=\frac{1}{{{n}_{1}}}+\frac{1}{{{n}_{2}}}+\frac{1}{{{n}_{3}}}\] |
| B. | \[\frac{1}{\sqrt{n}}=\frac{1}{\sqrt{{{n}_{1}}}}+\frac{1}{\sqrt{{{n}_{2}}}}+\frac{1}{\sqrt{{{n}_{3}}}}\] |
| C. | \[\sqrt{n}=\sqrt{{{n}_{1}}}+\sqrt{{{n}_{2}}}+\sqrt{{{n}_{3}}}\] |
| D. | \[n={{n}_{1}}+{{n}_{2}}+{{n}_{3}}\] |
| Answer» B. \[\frac{1}{\sqrt{n}}=\frac{1}{\sqrt{{{n}_{1}}}}+\frac{1}{\sqrt{{{n}_{2}}}}+\frac{1}{\sqrt{{{n}_{3}}}}\] | |
| 169. |
Density of rubber is d. A thick rubber cord of length L and cross-section area A undergoes elongation under its own weight on suspending it. This elongation is proportional to |
| A. | dL |
| B. | Ad/L |
| C. | \[Ad/{{L}^{2}}\] |
| D. | \[d{{L}^{2}}\] |
| Answer» E. | |
| 170. |
Two trains are moving towards each other with speeds of 20m/s and 15 m/s relative to the ground. The first train sounds a whistle of frequency 600 Hz. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is 340 m/s) |
| A. | 600 Hz |
| B. | 585 Hz |
| C. | 645 Hz |
| D. | 666 Hz |
| Answer» E. | |
| 171. |
If a battery of \[5\,V\] is connected across a plate of the semiconductor of area \[2\times {{10}^{-4}}\text{ }{{m}^{2}}\] and of thickness \[1.2\times {{10}^{-3}}m,\] then the current flowing through the plate is |
| A. | \[0.32\,mA\] |
| B. | \[0.64\,mA\] |
| C. | \[1.28\,mA\] |
| D. | \[2.56\,mA\] |
| Answer» D. \[2.56\,mA\] | |
| 172. |
In a stationary wave all the particles [KCET 2002] |
| A. | On either side of a node vibrate in same phase |
| B. | In the region between two nodes vibrate in same phase |
| C. | In the region between two antinodes vibrate in same phase |
| D. | Of the medium vibrate in same phase |
| Answer» C. In the region between two antinodes vibrate in same phase | |
| 173. |
In stationary waves [RPMT 1998; JIPMER 2002] |
| A. | Energy is uniformly distributed |
| B. | Energy is minimum at nodes and maximum at antinodes |
| C. | Energy is maximum at nodes and minimum at antinodes |
| D. | Alternating maximum and minimum energy producing at nodes and antinodes |
| Answer» C. Energy is maximum at nodes and minimum at antinodes | |
| 174. |
Three moles of an ideal monoatomic gas perform a cycle shown in figure. The gas temperatures in different states are \[{{T}_{1}}=200K,{{T}_{2}}=400K,{{T}_{3}}=1600K\] and \[{{T}_{4}}=800K.\] The work done by the gas during the cycle is (Take \[R=25/3\text{ }J/mol\text{-}K\]) |
| A. | 5 kJ |
| B. | 25 kJ |
| C. | 15 kJ |
| D. | 20 kJ |
| Answer» D. 20 kJ | |
| 175. |
In P-N junction, the barrier potential offers resistance to [AMU 1995, 96] |
| A. | Free electrons in N region and holes in P region |
| B. | Free electrons in P region and holes in N region |
| C. | Only free electrons in N region |
| D. | Only holes in P region |
| Answer» B. Free electrons in P region and holes in N region | |
| 176. |
For a cyclic process \[A\to B\to C\to A,\] the following information is given Path \[\Delta Q\](Heat supplied) \[\Delta U\] (Increase in internal energy) Work done by system on surrounding \[A\to B\] 600 J 200 J 400 J \[B\to C\] - 100 J 100 J - 200 J \[C\to A\] - 100 J - 300 J 200 J Calculate the heat of the cycle and efficiency of cycle. |
| A. | 400 J, 100% |
| B. | 600 J, 66.67% |
| C. | 400 J, 66.67% |
| D. | 600 J, 100% |
| Answer» D. 600 J, 100% | |
| 177. |
The displacement \[\times \] of a particle is given by \[x=a{{e}^{-\alpha t}}+b{{e}^{\beta t}}\] with \[a,\,b,\,\alpha \] and \[\beta \] as constants. With increase in time, the associated velocity |
| A. | increases |
| B. | decreases |
| C. | increases and decreases |
| D. | decreases and increases |
| Answer» B. decreases | |
| 178. |
A body starts from rest with uniform acceleration a, its velocity after n seconds is \[\upsilon \]. The displacement of the body in last 3 seconds is: |
| A. | \[\frac{\upsilon (6n-9)}{2n}\] |
| B. | \[\frac{2\upsilon (6n-9)}{n}\] |
| C. | \[\frac{2\upsilon (2n+1)}{n}\] |
| D. | \[\frac{2\upsilon (n-1)}{n}\] |
| Answer» B. \[\frac{2\upsilon (6n-9)}{n}\] | |
| 179. |
What is the amplitude of simple harmonic motion at resonance in the ideal case of zero damping? |
| A. | Zero |
| B. | -1 |
| C. | 1 |
| D. | Infinite |
| Answer» E. | |
| 180. |
A metallic sphere having radius 0.08 m and mass m = 10 kg is heated to a temperature of \[227{}^\circ C\] and suspended inside a box whose walls are at a temperature of \[27{}^\circ C\]. The maximum rate at which its temperature will fall, is (Take \[e=1,\] Stefan's constant \[\sigma =5.8\times {{10}^{-8}}W{{m}^{-2}}{{K}^{-4}}\] and specific heat of the metal \[s=90\,cal/kg/\deg ,\,J=4.2\] joules/calorie) |
| A. | \[{{0.055}^{o}}C/s\] |
| B. | \[{{0.066}^{o}}C/s\] |
| C. | \[{{0.044}^{o}}C/s\] |
| D. | \[{{0.033}^{o}}C/s\] |
| Answer» C. \[{{0.044}^{o}}C/s\] | |
| 181. |
In a water-fall the water falls from a height of 100 m. If the entire K.E. of water is converted into heat, the rise in temperature of water will be [MP PMT 2001] |
| A. | 0.23°C |
| B. | 0.46°C |
| C. | 2.3°C |
| D. | 0.023°C |
| Answer» B. 0.46°C | |
| 182. |
A string is stretched between fixed points separated by 75.0 cm. It is observed to have resonant frequencies of 420 Hz and 315 Hz. There are no other resonant frequencies between these two. Then, the lowest resonant frequency for this string is |
| A. | 105 Hz |
| B. | 1.05 Hz |
| C. | 1050 Hz |
| D. | 10.5 Hz |
| Answer» B. 1.05 Hz | |
| 183. |
Two tuning forks A and B vibrating simultaneously produce 5 beats. Frequency of B is 512. It is seen that if one arm of A is filed, then the number of beats increases. Frequency of A will be [MP PMT 1991] |
| A. | 502 |
| B. | 507 |
| C. | 517 |
| D. | 522 |
| Answer» D. 522 | |
| 184. |
A thin steel ring of inner diameter 40 cm and cross- sectional area \[1 m{{m}^{2}}\], is heated until it easily slides on a rigid cylinder of diameter 40.05 cm. [For steel,\[\alpha =1{{0}^{-5}}/{}^\circ C, Y= 200 GPa\]] When the ring cools down, the tension in the ring will be: |
| A. | 1000 N |
| B. | 500 N |
| C. | 250 N |
| D. | 100 N |
| Answer» D. 100 N | |
| 185. |
The potential difference applied to an X-ray tube is 5kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is [IIT-JEE (Screening) 2002] |
| A. | \[2\times {{10}^{16}}\] |
| B. | \[5\times {{10}^{16}}\] |
| C. | \[1\times {{10}^{17}}\] |
| D. | \[4\times {{10}^{15}}\] |
| Answer» B. \[5\times {{10}^{16}}\] | |
| 186. |
A block connected to a spring oscillates vertically. A damping force\[{{F}_{d}}\] , acts on the block by the surrounding medium. Given as \[{{F}_{d}}=-bVb\] is a positive constant which depends on : |
| A. | viscosity of the medium |
| B. | size of the block |
| C. | shape of the block |
| D. | All of these |
| Answer» E. | |
| 187. |
In a Young's double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is : |
| A. | 9.75 mm |
| B. | 15.6 mm |
| C. | 1.56 mm |
| D. | 7.8 mm |
| Answer» E. | |
| 188. |
If the tension on a wire is removed at once, then |
| A. | It will break |
| B. | Its temperature will reduce |
| C. | There will be no change in its temperature |
| D. | Its temperature increases |
| Answer» E. | |
| 189. |
Assertion : In S.H.M., the motion is ?to and fro? and periodic. Reason : Velocity of the particle \[(v)=\omega \sqrt{{{k}^{2}}-{{x}^{2}}}\] (where x is the displacement and k is amplitude) [AIIMS 2002] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» C. If assertion is true but reason is false. | |
| 190. |
The temperature of an ideal gas is kept constant as it expands. The gas does external work. During this process, the internal energy of the gas |
| A. | Decreases |
| B. | Increases |
| C. | Remains constant |
| D. | Depends on the molecular motion |
| Answer» D. Depends on the molecular motion | |
| 191. |
Which of the following is not thermodynamical function |
| A. | Enthalpy |
| B. | Work done |
| C. | Gibb's energy |
| D. | Internal energy |
| Answer» C. Gibb's energy | |
| 192. |
An ideal Black-body at room temperature is thrown into a furnace. It is observed that |
| A. | initially it is the darkest body and at later times the brightest |
| B. | it is the darkest body at all times |
| C. | it cannot be distinguished at all times |
| D. | initially it is the darkest body and at later times it cannot be distinguished |
| Answer» B. it is the darkest body at all times | |
| 193. |
The following diagram indicates the energy levels of a certain atom when the system moves from 2E level to E, a photon of wavelength \[\lambda \] is emitted. The wavelength of photon produced during its transition from \[\frac{4E}{3}\] level to E is |
| A. | \[\lambda /3\] |
| B. | \[3\lambda /4\] |
| C. | \[4\lambda /3\] |
| D. | \[3\lambda \] |
| Answer» E. | |
| 194. |
Assertion : Transverse waves travel through air in an organ pipe. Reason : Air possesses only volume elasticity. |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» F. | |
| 195. |
Why the current does not rise immediately in a circuit containing inductance [EAMCET 1994] |
| A. | Because of induced emf |
| B. | Because of high voltage drop |
| C. | Because of low power consumption |
| D. | Because of Joule heating |
| Answer» B. Because of high voltage drop | |
| 196. |
Assertion : A hollow metallic closed container maintained at a uniform temperature can act as a source of black body radiation. Reason : All metals acts as a black body [AIIMS 1996] |
| A. | If both assertion and reason are true and the reason is the correct explanation of the assertion. |
| B. | If both assertion and reason are true but reason is not the correct explanation of the assertion. |
| C. | If assertion is true but reason is false. |
| D. | If the assertion and reason both are false. |
| E. | If assertion is false but reason is true. |
| Answer» D. If the assertion and reason both are false. | |
| 197. |
Unit of magnetic moment is [MP PET 1989] |
| A. | \[Ampere-metr{{e}^{2}}\] |
| B. | \[Ampere-metre\] |
| C. | \[Weber-metr{{e}^{2}}\] |
| D. | \[Weber/metre\] |
| Answer» B. \[Ampere-metre\] | |
| 198. |
A body can be negatively charged by [CPMT 1972; AIIMS 1998] |
| A. | Giving excess of electrons to it |
| B. | Removing some electrons from it |
| C. | Giving some protons to it |
| D. | Removing some neutrons from it |
| Answer» B. Removing some electrons from it | |
| 199. |
Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are \[{{\operatorname{K}}_{1}} and {{K}_{2}}\]. The thermal conductivity of the composite rod will be : |
| A. | \[\frac{3({{K}_{1}}+{{K}_{2}})}{2}\] |
| B. | \[{{K}_{1}}+{{K}_{2}}\] |
| C. | \[2\left( {{K}_{1}}+{{K}_{2}} \right)\] |
| D. | \[\frac{{{K}_{1}}+{{K}_{2}}}{2}\] |
| Answer» E. | |
| 200. |
An alternating e.m.f. of frequency \[v\,\left( =\frac{1}{2\pi \sqrt{LC}} \right)\] is applied to a series LCR circuit. For this frequency of the applied e.m.f. [Roorkee 1999] |
| A. | The circuit is at resonance and its impedance is made up only of a reactive part |
| B. | The current in the circuit is in phase with the applied e.m.f. and the voltage across R equals this applied emf |
| C. | The sum of the p.d.?s across the inductance and capacitance equals the applied e.m.f. which is \[{{180}^{o}}\] ahead of phase of the current in the circuit |
| D. | The quality factor of the circuit is \[\omega L/R\] or \[1/\omega CR\] and this is a measure of the voltage magnification (produced by the circuit at resonance) as well as the sharpness of resonance of the circuit |
| Answer» C. The sum of the p.d.?s across the inductance and capacitance equals the applied e.m.f. which is \[{{180}^{o}}\] ahead of phase of the current in the circuit | |