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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.
| 8201. |
A small source of light is to be suspended directly above the centre of a circular table of radius R. What should be the height of the light source above the table so that the intensity of light is maximum at the edges of the table compared to any other height of the source |
| A. | \[\frac{R}{2}\] |
| B. | \[\frac{R}{\sqrt{2}}\] |
| C. | R |
| D. | \[\sqrt{2}R\] |
| Answer» C. R | |
| 8202. |
The relation between dynamic plate resistance (rp) of a vacuum diode and plate current in the space charge limited region, is |
| A. | \[{{r}_{p}}\propto {{I}_{p}}\] |
| B. | \[{{r}_{p}}\propto I_{p}^{3/2}\] |
| C. | \[{{r}_{p}}\propto \frac{1}{{{I}_{p}}}\] |
| D. | \[{{r}_{p}}\propto \frac{1}{{{({{I}_{p}})}^{1/3}}}\] |
| Answer» E. | |
| 8203. |
A radioactive isotope X with a half-life of \[1.37\times {{10}^{9}}\] years decays to Y which is stable. A sample of rock from the moon was found to contain both the elements X and Y which were in the ratio of 1 : 7. The age of the rock is |
| A. | \[1.96\times {{10}^{8}}\]years |
| B. | \[3.85\times {{10}^{9}}\]years |
| C. | \[4.11\times {{10}^{9}}\]years |
| D. | \[9.59\times {{10}^{9}}\]years |
| Answer» D. \[9.59\times {{10}^{9}}\]years | |
| 8204. |
The eye can detect 5 ´ 104 photons per square metre per sec of green light (l = 5000 Å) while the ear can detect \[{{10}^{-13}}\,(W/{{m}^{2}})\]. The factor by which the eye is more sensitive as a power detector than the ear is close to |
| A. | 5 |
| B. | 10 |
| C. | 106 |
| D. | 15 |
| Answer» B. 10 | |
| 8205. |
A rectangular loop with a sliding connector of length l = 1.0 m is situated in a uniform magnetic field B = 2T perpendicular to the plane of loop. Resistance of connector is r = 2W. Two resistance of 6W and 3W are connected as shown in figure. The external force required to keep the connector moving with a constant velocity v = 2m/s is |
| A. | 6 N |
| B. | 4 N |
| C. | 2 N |
| D. | 1 N |
| Answer» D. 1 N | |
| 8206. |
Three wires of copper, iron and nickel are joined to form three junctions as shown in Fig. When the temperature of junction 1 is kept \[{{50}^{o}}C\] with the other two junctions at \[{{0}^{o}}C\], the sensitive galvanometer gives a deflection of 14 divisions. When the temperature of junction 3 is kept \[{{50}^{o}}C,\]with the other two junctions at \[{{0}^{o}}C,\] the galvanometer gives a deflection of 11 divisions. Then the deflection given by the galvanometer, when temperature of the junction 2 is kept at \[{{50}^{o}}C,\] with the other two junctions at \[{{0}^{o}}C,\] will be |
| A. | 3 div |
| B. | 11 div |
| C. | 14 div |
| D. | 25 div |
| Answer» E. | |
| 8207. |
The displacement due to a wave moving in the positive x-direction is given by \[y=\frac{1}{(1+{{x}^{2}})}\] at time \[t=0\] and by \[y=\frac{1}{[1+{{(x-1)}^{2}}]}\] at \[t=2\] seconds, where x and y are in metres. The velocity of the wave in m/s is |
| A. | 0.5 |
| B. | 1 |
| C. | 2 |
| D. | 4 |
| Answer» B. 1 | |
| 8208. |
A hollow sphere is filled with water through a small hole in it. It is then hung by a long thread and made to oscillate. As the water slowly flows out of the hole at the bottom, the period of oscillation will [MP PMT 1994; KCET 1994; RPET 1996; AFMC 2000; CBSE PMT 2000; CPMT 2001; AIEEE 2005] |
| A. | Continuously decrease |
| B. | Continuously increase |
| C. | First decrease and then increase to original value |
| D. | First increase and then decrease to original value |
| Answer» E. | |
| 8209. |
A wire of resistor R is bent into a circular ring of radius r. Equivalent resistance between two points X and Y on its circumference, when angle XOY is a, can be given by |
| A. | \[\frac{R\alpha }{4{{\pi }^{2}}}(2\pi -\alpha )\] |
| B. | \[\frac{R}{2\pi }(2\pi -\alpha )\] |
| C. | R (2p ? a) |
| D. | \[\frac{4\pi }{R\alpha }(2\pi -\alpha )\] |
| Answer» B. \[\frac{R}{2\pi }(2\pi -\alpha )\] | |
| 8210. |
The linear portions of the characteristic curves of a triode valve give the following readings [Roorkee 1985] \[{{V}_{g}}\](volt) 0 ? 2 ? 4 ? 6 \[{{I}_{p}}(mA)\] for \[{{V}_{p}}=150\] volts 15 12.5 10 7.5 \[{{I}_{p}}(mA)\] for \[{{V}_{p}}=120\] volts 10 7.5 5 2.5 The plate resistance is |
| A. | 2000 ohms |
| B. | 4000 ohms |
| C. | 8000 ohms |
| D. | 6000 ohms |
| Answer» E. | |
| 8211. |
If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately [MNR 1987] |
| A. | 60% |
| B. | 65% |
| C. | 70% |
| D. | 75% |
| Answer» C. 70% | |
| 8212. |
Two loudspeakers L1 and L2 driven by a common oscillator and amplifier, are arranged as shown. The frequency of the oscillator is gradually increased from zero and the detector at D records a series of maxima and minima. If the speed of sound is 330 ms?1 then the frequency at which the first maximum is observed is |
| A. | 165 Hz |
| B. | 330 Hz |
| C. | 496 Hz |
| D. | 660 Hz |
| Answer» C. 496 Hz | |
| 8213. |
A particle of mass m is attached to three identical springs A, B and C each of force constant k a shown in figure. If the particle of mass m is pushed slightly against the spring A and released then the time period of oscillations is |
| A. | \[2\pi \sqrt{\frac{2m}{k}}\] |
| B. | \[2\pi \sqrt{\frac{m}{2k}}\] |
| C. | \[2\pi \sqrt{\frac{m}{k}}\] |
| D. | \[2\pi \sqrt{\frac{m}{3k}}\] |
| Answer» C. \[2\pi \sqrt{\frac{m}{k}}\] | |
| 8214. |
Length of a hollow tube is 5m, it?s outer diameter is 10 cm and thickness of it?s wall is 5 mm. If resistivity of the material of the tube is 1.7 ´ 10?8 W´m then resistance of tube will be |
| A. | 5.6 ´ 10?5 W |
| B. | 2 ´ 10?5 W |
| C. | 4 ´ 10?5 W |
| D. | None of these |
| Answer» B. 2 ´ 10?5 W | |
| 8215. |
A piece of cloud having area \[25\times {{10}^{6}}{{m}^{2}}\] and electric potential of \[{{10}^{5}}\] volts. If the height of cloud is \[0.75\,km\], then energy of electric field between earth and cloud will be [RPET 1997] |
| A. | \[250\,J\] |
| B. | \[750\,J\] |
| C. | \[1225J\] |
| D. | \[1475J\] |
| Answer» E. | |
| 8216. |
In a single slit diffraction of light of wavelength l by a slit of width e, the size of the central maximum on a screen at a distance b is |
| A. | \[2b\lambda +e\] |
| B. | \[\frac{2b\lambda }{e}\] |
| C. | \[\frac{2b\lambda }{e}+e\] |
| D. | \[\frac{2b\lambda }{e}-e\] |
| Answer» D. \[\frac{2b\lambda }{e}-e\] | |
| 8217. |
The distance of the moon from earth is \[3.8\times {{10}^{5}}km.\] The eye is most sensitive to light of wavelength 5500 Å. The separation of two points on the moon that can be resolved by a 500 cm telescope will be [AMU (Med.) 2002] |
| A. | 51 m |
| B. | 60 m |
| C. | 70 m |
| D. | All the above |
| Answer» B. 60 m | |
| 8218. |
The plate current ip in a triode valve is given \[{{i}_{p}}=K{{({{V}_{p}}+\mu \,{{V}_{g}})}^{3/2}}\] where ip is in milliampere and Vp and Vg are in volt. If rp = 104 ohm, and \[{{g}_{m}}=5\times {{10}^{-3}}mho,\] then for \[{{i}_{p}}=8\,mA\] and \[{{V}_{p}}=300\,volt,\] what is the value of K and grid cut off voltage [Roorkee 1992] |
| A. | ? 6V, (30)3/2 |
| B. | \[-\,6V,\,{{(1/30)}^{3/2}}\] |
| C. | + 6V, (30)3/2 |
| D. | + 6V, (1/30)3/2 |
| Answer» C. + 6V, (30)3/2 | |
| 8219. |
The half life of radioactive Radon is 3.8 days. The time at the end of which \[1/{{20}^{th}}\]of the Radon sample will remain undecayed is (Given\[{{\log }_{10}}e=0.4343\]) [IIT 1981] |
| A. | 3.8 days |
| B. | 16.5 days |
| C. | 33 days |
| D. | 76 days |
| Answer» C. 33 days | |
| 8220. |
Two metallic plates A and B, each of area 5 ´ 10?4m2 are placed parallel to each other at a separation of 1 cm. Plate B carries a positive charge of 33.7 pc. A monochromatic beam of light, with photons of energy 5 eV each, starts falling on plate A at t = 0, so that 1016 photons fall on it per square meter per second. Assume that one photoelectron is emitted for every 106 incident photons. Also assume that all the emitted photoelectrons are collected by plate B and the work function of plate A remains constant at the value 2 eV. Electric field between the plates at the end of 10 seconds is |
| A. | 2 ´ 103 N/C |
| B. | 103 N/C |
| C. | 5 ´ 103 N/C |
| D. | Zero |
| Answer» B. 103 N/C | |
| 8221. |
The temperature of hot junction of a thermo-couple changes from \[{{80}^{o}}C\] to \[{{100}^{o}}C.\] The percentage change in thermoelectric power is |
| A. | 8% |
| B. | 10% |
| C. | 20% |
| D. | 25% |
| Answer» E. | |
| 8222. |
A highly conducting ring of radius R is perpendicular to and concentric with the axis of a long solenoid as shown in fig. The ring has a narrow gap of width d in its circumference. The solenoid has cross sectional area A and a uniform internal field of magnitude B0. Now beginning at t = 0, the solenoid current is steadily increased to so that the field magnitude at any time t is given by B(t) = B0 + at where \[\alpha >0\]. Assuming that no charge can flow across the gap, the end of ring which has excess of positive charge and the magnitude of induced e.m.f. in the ring are respectively |
| A. | X, Aa |
| B. | X pR2a |
| C. | Y, pA2a |
| D. | Y, pR2a |
| Answer» B. X pR2a | |
| 8223. |
A man standing in front of a mountain beats a drum at regular intervals. The rate of drumming is generally increased and he finds that the echo is not heard distinctly when the rate becomes 40 per minute. He then moves nearer to the mountain by 90 m and finds that echo is again not heard when the drumming rate becomes 60 per minute. The distance between the mountain and the initial position of the man is |
| A. | 205 m |
| B. | 300 m |
| C. | 180 m |
| D. | 270 m |
| Answer» E. | |
| 8224. |
Three masses 700g, 500g, and 400g are suspended at the end of a spring a shown and are in equilibrium. When the 700g mass is removed, the system oscillates with a period of 3 seconds, when the 500 gm mass is also removed, it will oscillate with a period of |
| A. | 1 s |
| B. | 2 s |
| C. | 3 s |
| D. | \[\sqrt{\frac{12}{5}}\,s\] |
| Answer» C. 3 s | |
| 8225. |
The figure shows a system of two concentric spheres of radii r1 and r2 and kept at temperatures T1 and T2, respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to [AIEEE 2005] |
| A. | \[\frac{{{r}_{1}}\,{{r}_{2}}}{({{r}_{1}}-{{r}_{2}})}\] |
| B. | \[({{r}_{2}}-{{r}_{1}})\] |
| C. | \[({{r}_{2}}-{{r}_{1}})({{r}_{1}}\,{{r}_{2}})\] |
| D. | In \[\left( \frac{{{r}_{2}}}{{{r}_{1}}} \right)\] |
| Answer» B. \[({{r}_{2}}-{{r}_{1}})\] | |
| 8226. |
In the circuit shown here, the readings of the ammeter and voltmeter are [Kerala PMT 2002] |
| A. | 6 A, 60 V |
| B. | 0.6 A, 6 V |
| C. | 6/11 A, 60/11 V |
| D. | 11/6 A, 11/60 V |
| Answer» D. 11/6 A, 11/60 V | |
| 8227. |
A point charge of 40 stat coulomb is placed 2 cm in front of an earthed metallic plane plate of large size. Then the force of attraction on the point charge is |
| A. | 100 dynes |
| B. | 160 dynes |
| C. | 1600 dynes |
| D. | 400 dynes |
| Answer» B. 160 dynes | |
| 8228. |
A circular disc is placed in front of a narrow source. When the point of observation is 2 m from the disc, then it covers first HPZ. The intensity at this point is I. When the point of observation is 25 cm from the disc then intensity will be |
| A. | \[{{\left( \frac{{{R}_{6}}}{{{R}_{2}}} \right)}^{2}}I\] |
| B. | \[{{\left( \frac{{{R}_{7}}}{{{R}_{2}}} \right)}^{2}}I\] |
| C. | \[{{\left( \frac{{{R}_{8}}}{{{R}_{2}}} \right)}^{2}}I\] |
| D. | \[{{\left( \frac{{{R}_{9}}}{{{R}_{2}}} \right)}^{2}}I\] |
| Answer» E. | |
| 8229. |
The average distance between the earth and moon is \[38.6\times {{10}^{4}}\]km. The minimum separation between the two points on the surface of the moon that can be resolved by a telescope whose objective lens has a diameter of 5 m with \[\lambda =6000\ {AA}\] is [MP PMT 1993] |
| A. | 5.65 m |
| B. | 28.25 m |
| C. | 11.30 m |
| D. | 56.51 m |
| Answer» E. | |
| 8230. |
A nucleus with mass number 220 initially at rest emits an a-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the a-particle [IIT JEE (Screening) 2003] |
| A. | 4.4 MeV |
| B. | 5.4 MeV |
| C. | 5.6 MeV |
| D. | 6.5 MeV |
| Answer» C. 5.6 MeV | |
| 8231. |
In a photocell bichromatic light of wavelength 2475 Å and 6000 Å are incident on cathode whose work function is 4.8 eV. If a uniform magnetic field of 3 ´ 10?5 Tesla exists parallel to the plate, the radius of the path describe by the photoelectron will be (mass of electron = 9 ´ 10?31 kg) |
| A. | 1 cm |
| B. | 5 cm |
| C. | 10 cm |
| D. | 25 cm |
| Answer» C. 10 cm | |
| 8232. |
The north and south poles of two identical magnets approach a coil, containing a condenser, with equal speeds from opposite sides. Then |
| A. | Plate 1 will be negative and plate 2 positive |
| B. | Plate 1 will be positive and plate 2 negative |
| C. | Both the plates will be positive |
| D. | Both the plates will be negative |
| Answer» C. Both the plates will be positive | |
| 8233. |
The same mass of copper is drawn into two wires 1 mm and 2 mm thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio |
| A. | 2 : 1 |
| B. | 1 : 16 |
| C. | 4 : 1 |
| D. | 16 : 1 |
| Answer» E. | |
| 8234. |
One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance \[{{x}_{0}}\] from the black. The spring is then compressed by \[2{{x}_{0}}\] and released. The time taken to strike the wall is |
| A. | \[\frac{1}{6}\pi \sqrt{\frac{k}{m}}\] |
| B. | \[\sqrt{\frac{k}{m}}\] |
| C. | \[\frac{2\pi }{3}\sqrt{\frac{m}{k}}\] |
| D. | \[\frac{\pi }{4}\sqrt{\frac{k}{m}}\] |
| Answer» D. \[\frac{\pi }{4}\sqrt{\frac{k}{m}}\] | |
| 8235. |
The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are T2 and T1 (T2 > T1). The rate of heat transfer through the slab, in a steady state is \[\left( \frac{A({{T}_{2}}-{{T}_{1}})K}{x} \right)f\], with ¦ which equal to [AIEEE 2004] |
| A. | 1 |
| B. | \[\frac{1}{2}\] |
| C. | \[\frac{2}{3}\] |
| D. | \[\frac{1}{3}\] |
| Answer» E. | |
| 8236. |
A battery of internal resistance 4W is connected to the network of resistances as shown. In order to give the maximum power to the network, the value of R (in \[\Omega \]) should be [IIT 1995] |
| A. | 4/9 |
| B. | 8/9 |
| C. | 2 |
| D. | 18 |
| Answer» D. 18 | |
| 8237. |
Two point charges \[+q\] and \[-q\] are held fixed at \[(-d,\,0)\] and \[(d,\,0)\] respectively of a \[(X,\,Y)\] coordinate system. Then [IIT 1995] |
| A. | E at all points on the \[Y-\]axis is along \[\hat{i}\] |
| B. | The electric field \[\overrightarrow{E}\] at all points on the \[X-\]axis has the same direction |
| C. | Dipole moment is \[2qd\] directed along \[\hat{i}\] |
| D. | Work has to be done in bringing a test charge from infinity to the origin |
| Answer» B. The electric field \[\overrightarrow{E}\] at all points on the \[X-\]axis has the same direction | |
| 8238. |
An astronaut is looking down on earth's surface from a space shuttle at an altitude of \[400\,km.\] Assuming that the astronaut's pupil diameter is \[5\,mm\] and the wavelength of visible light is \[500\,nm.\] The astronaut will be able to resolve linear object of the size of about [AIIMS 2003] |
| A. | 0.5 m |
| B. | \[5\,m\] |
| C. | 50 m |
| D. | 500 m |
| Answer» D. 500 m | |
| 8239. |
The shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate |
| A. | OR |
| B. | AND |
| C. | NAND |
| D. | None of these |
| Answer» C. NAND | |
| 8240. |
In X-ray tube when the accelerating voltage V is halved, the difference between the wavelength of Ka line and minimum wavelength of continuous X-ray spectrum |
| A. | Remains constant |
| B. | Becomes more than two times |
| C. | Becomes half |
| D. | Becomes less than two times |
| Answer» E. | |
| 8241. |
A conducting ring is placed around the core of an electromagnet as shown in fig. When key K is pressed, the ring |
| A. | Remain stationary |
| B. | Is attracted towards the electromagnet |
| C. | Jumps out of the core |
| D. | None of the above |
| Answer» D. None of the above | |
| 8242. |
A coil of wire of resistance \[50\,\Omega \] is embedded in a block of ice. If a potential difference of 210 V is applied across the coil, the amount of ice melted per second will be |
| A. | 4.12 gm |
| B. | 4.12 kg |
| C. | 3.68 kg |
| D. | 2.625 gm |
| Answer» E. | |
| 8243. |
A sphere and a cube of same material and same volume are heated upto same temperature and allowed to cool in the same surroundings. The ratio of the amounts of radiations emitted will be |
| A. | 1 : 1 |
| B. | \[\frac{4\pi }{3}\,\,:\,\,1\] |
| C. | \[{{\left( \frac{\pi }{6} \right)}^{1/3}}:\,\,1\] |
| D. | \[\frac{1}{2}\,{{\left( \frac{4\pi }{3} \right)}^{2/3}}:\,\,1\] |
| Answer» D. \[\frac{1}{2}\,{{\left( \frac{4\pi }{3} \right)}^{2/3}}:\,\,1\] | |
| 8244. |
A plano-convex lens when silvered in the plane side behaves like a concave mirror of focal length 30cm. However, when silvered on the convex side it behaves like a concave mirror of focal length 10 cm. Then the refractive index of its material will be [BHU 1997; UPSEAT 1995] |
| A. | 3.0 |
| B. | 2.0 |
| C. | 2.5 |
| D. | 1.5 |
| Answer» E. | |
| 8245. |
The combination of gates shown below produces |
| A. | AND gate |
| B. | XOR gate |
| C. | NOR gate |
| D. | NAND gate |
| Answer» E. | |
| 8246. |
The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilate, they produce gamma-rays of wavelength(s) [UPSEAT 2002] |
| A. | 0.012 Å |
| B. | 0.024 Å |
| C. | 0.012 Å to ¥ |
| D. | 0.024 Å to ¥ |
| Answer» B. 0.024 Å | |
| 8247. |
The minimum intensity of light to be detected by human eye is \[{{10}^{-10}}W/{{m}^{2}}\]. The number of photons of wavelength \[5.6\times {{10}^{-7}}m\] entering the eye, with pupil area \[{{10}^{-6}}{{m}^{2}}\], per second for vision will be nearly |
| A. | 100 |
| B. | 200 |
| C. | 300 |
| D. | 400 |
| Answer» D. 400 | |
| 8248. |
Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction \[B={{B}_{0}}{{e}^{-t}}\] is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to |
| A. | \[\frac{B_{0}^{2}\pi {{r}^{2}}}{R}\] |
| B. | \[\frac{{{B}_{0}}10{{r}^{3}}}{R}\] |
| C. | \[\frac{B_{0}^{2}{{\pi }^{2}}{{r}^{4}}R}{5}\] |
| D. | \[\frac{B_{0}^{2}{{\pi }^{2}}{{r}^{4}}}{R}\] |
| Answer» E. | |
| 8249. |
An open pipe is in resonance in its 2nd harmonic with tuning fork of frequency\[{{f}_{1}}\]. Now it is closed at one end. If the frequency of the tuning fork is increased slowly from \[{{f}_{1}}\] then again a resonance is obtained with a frequency\[{{f}_{2}}\]. If in this case the pipe vibrates \[{{n}^{th}}\] harmonics then [IIT-JEE (Screening) 2005] |
| A. | \[n=3,\] \[{{f}_{2}}=\frac{3}{4}{{f}_{1}}\] |
| B. | \[n=3,\] \[{{f}_{2}}=\frac{5}{4}{{f}_{1}}\] |
| C. | \[n=5,\] \[{{f}_{2}}=\frac{5}{4}{{f}_{1}}\] |
| D. | \[n=5,\] \[{{f}_{2}}=\frac{3}{4}{{f}_{1}}\] |
| Answer» D. \[n=5,\] \[{{f}_{2}}=\frac{3}{4}{{f}_{1}}\] | |
| 8250. |
The resistance of a wire of iron is 10 ohms and temp. coefficient of resistivity is \[5\times {{10}^{-3}}/{}^\circ C\]. At \[20{}^\circ C\] it carries 30 milliamperes of current. Keeping constant potential difference between its ends, the temperature of the wire is raised to \[120{}^\circ C\]. The current in milliamperes that flows in the wire is [MP PMT 1994] |
| A. | 20 |
| B. | 15 |
| C. | 10 |
| D. | 40 |
| Answer» B. 15 | |