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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.
| 8101. |
A racing car moving towards a cliff, sounds its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If \[v\] is the velocity of sound, then the velocity of the car is [KCET 2002; CBSE PMT 2004] |
| A. | \[v/\sqrt{2}\] |
| B. | \[v/2\] |
| C. | \[v/3\] |
| D. | \[v/4\] |
| Answer» D. \[v/4\] | |
| 8102. |
In the following star circuit diagram (figure), the equivalent resistance between the points A and H will be |
| A. | 1.944 r |
| B. | 0.973 r |
| C. | 0.486 r |
| D. | 0.243 r |
| Answer» C. 0.486 r | |
| 8103. |
An infinite number of identical capacitors each of capacitance \[1\mu F\] are connected as in adjoining figure. Then the equivalent capacitance between \[A\] and \[B\] is [EAMCET 1990] |
| A. | \[1\mu F\] |
| B. | \[2\mu F\] |
| C. | \[\frac{1}{2}\mu F\] |
| D. | \[\infty \] |
| Answer» C. \[\frac{1}{2}\mu F\] | |
| 8104. |
A lamp emits monochromatic green light uniformly in all directions. The lamp is 3% efficient in converting electrical power to electromagnetic waves and consumes 100W of power. The amplitude of the electric field associated with the electromagnetic radiation at a distance of 10m from the lamp will be |
| A. | 1.34 V/m |
| B. | 2.68 V/m |
| C. | 5.36 V/m |
| D. | 9.37 V/m |
| Answer» B. 2.68 V/m | |
| 8105. |
A small plane mirror placed at the centre of a spherical screen of radius R. A beam of light is falling on the mirror. If the mirror makes n revolution. per second, the speed of light on the screen after reflection from the mirror will be |
| A. | 4pnR |
| B. | 2pnR |
| C. | \[\frac{nR}{2\pi }\] |
| D. | \[\frac{nR}{4\pi }\] |
| Answer» B. 2pnR | |
| 8106. |
Two radioactive materials \[{{X}_{1}}\] and \[{{X}_{2}}\] have decay constants \[10\lambda \] and \[\lambda \] respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of \[{{X}_{1}}\] to that of \[{{X}_{2}}\] will be \[1/e\] after a time [IIT-JEE (Screening) 2000] |
| A. | \[1/(10\lambda )\] |
| B. | \[1/(11\lambda )\] |
| C. | \[11/(10\lambda )\] |
| D. | \[1/(9\lambda )\] |
| Answer» E. | |
| 8107. |
A simple pendulum with bob of mass m and conducting wire of length L swings under gravity through an angle \[2\theta \]. The earth?s magnetic field component in the direction perpendicular to swing is B. Maximum potential difference induced across the pendulum is [MP PET 2005] |
| A. | \[2BL\sin \left( \frac{\theta }{2} \right){{(gL)}^{1/2}}\] |
| B. | \[BL\sin \left( \frac{\theta }{2} \right)(gL)\] |
| C. | \[BL\sin \left( \frac{\theta }{2} \right){{(gL)}^{3/2}}\] |
| D. | \[BL\sin \left( \frac{\theta }{2} \right){{(gL)}^{2}}\] |
| Answer» B. \[BL\sin \left( \frac{\theta }{2} \right)(gL)\] | |
| 8108. |
In Melde's experiment, the string vibrates in 4 loops when a 50 gram weight is placed in the pan of weight 15 gram. To make the string to vibrates in 6 loops the weight that has to be removed from the pan is [MH CET 2004] |
| A. | 0.0007 kg wt |
| B. | 0.0021 kg wt |
| C. | 0.036 kg wt |
| D. | 0.0029 kg wt |
| Answer» D. 0.0029 kg wt | |
| 8109. |
Following figure shows cross-sections through three long conductors of the same length and material, with square cross-section of edge lengths as shown. Conductor B will fit snugly within conductor A, and conductor C will fit snugly within conductor B. Relationship between their end to end resistance is |
| A. | RA = RB = RC |
| B. | RA > RB > RC |
| C. | RA < RB < R |
| D. | Information is not sufficient |
| Answer» B. RA > RB > RC | |
| 8110. |
To form a composite \[16\mu F,\ 1000V\] capacitor from a supply of identical capacitors marked \[8\mu F,\ 250V\], we require a minimum number of capacitors [MP PET 1996; AIIMS 2000] |
| A. | 40 |
| B. | 32 |
| C. | 8 |
| D. | 2 |
| Answer» C. 8 | |
| 8111. |
A convex lens of focal length 30 cm and a concave lens of 10 cm focal length are placed so as to have the same axis. If a parallel beam of light falling on convex lens leaves concave lens as a parallel beam, then the distance between two lenses will be |
| A. | 40 cm |
| B. | 30 cm |
| C. | 20 cm |
| D. | 10 cm |
| Answer» D. 10 cm | |
| 8112. |
Amplification factor of a triode is 10. When the plate potential is 200 volt and grid potential is ? 4 volt, then the plate current of 4mA is observed. If plate potential is changed to 160 volt and grid potential is kept at ? 7 volt, then the plate current will be |
| A. | 1.69 mA |
| B. | 3.95 mA |
| C. | 2.87 |
| D. | 7.02 mA |
| Answer» B. 3.95 mA | |
| 8113. |
Half-life of a radioactive substance is 20 minutes. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately [AIIMS 2000] |
| A. | 10 min |
| B. | 20 min |
| C. | 30 min |
| D. | 40 min |
| Answer» C. 30 min | |
| 8114. |
A conducting ring of radius 1 meter is placed in an uniform magnetic field B of 0.01Telsa oscillating with frequency 100Hz with its plane at right angles to B. What will be the induced electric field [AIIMS 2005] |
| A. | \[\pi \,volt/m\] |
| B. | \[2\,volt/m\] |
| C. | \[10\,volt/m\] |
| D. | \[62\,volt/m\] |
| Answer» C. \[10\,volt/m\] | |
| 8115. |
An organ pipe is closed at one end has fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a normal person can hear is : [AIIMS 2004] |
| A. | 14 |
| B. | 13 |
| C. | 6 |
| D. | 9 |
| Answer» D. 9 | |
| 8116. |
12 cells each having same emf are connected in series with some cells wrongly connected. The arrangement is connected in series with an ammeter and two cells which are in series. Current is 3 A when cells and battery aid each other and is 2 A when cells and battery oppose each other. The number of cells wrongly connected is |
| A. | 4 |
| B. | 1 |
| C. | 3 |
| D. | 2 |
| Answer» C. 3 | |
| 8117. |
Five identical plates each of area A are joined as shown in the figure. The distance between the plates is d. The plates are connected to a potential difference of \[V\ volts\]. The charge on plates 1 and 4 will be [IIT 1984] |
| A. | \[\frac{{{\varepsilon }_{0}}AV}{d}.\frac{2{{\varepsilon }_{0}}AV}{d}\] |
| B. | \[\frac{{{\varepsilon }_{0}}AV}{d}.\frac{2{{\varepsilon }_{0}}AV}{d}\] |
| C. | \[\,\frac{{{\varepsilon }_{0}}AV}{d}.\frac{-2{{\varepsilon }_{0}}AV}{d}\] |
| D. | \[\frac{-{{\varepsilon }_{0}}AV}{d}.\frac{-2{{\varepsilon }_{0}}AV}{d}\] |
| Answer» D. \[\frac{-{{\varepsilon }_{0}}AV}{d}.\frac{-2{{\varepsilon }_{0}}AV}{d}\] | |
| 8118. |
A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometre from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of [CBSE PMT 2004] |
| A. | 0.5 m |
| B. | 5 m |
| C. | 5 mm |
| D. | 5 cm |
| Answer» D. 5 cm | |
| 8119. |
For a triode m = 64 and gm =1600 m mho. It is used as an amplifier and an input signal of 1V (rms) is applied. The signal power in the load of 40 kW will be |
| A. | 23.5 mW |
| B. | 48.7 mW |
| C. | 25.6 mW |
| D. | None of these |
| Answer» D. None of these | |
| 8120. |
A radioactive nucleus undergoes a-emission to form a stable element. What will be the recoil velocity of the daughter nucleus if V is the velocity of a-emission and A is the atomic mass of radioactive nucleus [DCE 2000; AIIMS 2004] |
| A. | \[\frac{4V}{A-4}\] |
| B. | \[\frac{2V}{A-4}\] |
| C. | \[\frac{4V}{A+4}\] |
| D. | \[\frac{2V}{A+4}\] |
| Answer» B. \[\frac{2V}{A-4}\] | |
| 8121. |
The current in a LR circuit builds up to \[\frac{3}{4}\]th of its steady state value in \[4s\]. The time constant of this circuit is [Roorkee 2000] |
| A. | \[\frac{1}{\ln 2}s\] |
| B. | \[\frac{2}{\ln 2}s\] |
| C. | \[\frac{3}{\ln 2}s\] |
| D. | \[\frac{4}{\ln 2}s\] |
| Answer» C. \[\frac{3}{\ln 2}s\] | |
| 8122. |
A tuning fork of frequency 340Hz is vibrated just above the tube of 120 cm height. Water is poured slowly in the tube. What is the minimum height of water necessary for the resonance (speed of sound in the air = 340 m/sec) [CBSE PMT 1999; UPSEAT 1999] |
| A. | 15 cm |
| B. | 25 cm |
| C. | 30 cm |
| D. | 45 cm |
| Answer» E. | |
| 8123. |
Current through wire XY of circuit shown is |
| A. | 1 A |
| B. | 4 A |
| C. | 2 A |
| D. | 3 A |
| Answer» D. 3 A | |
| 8124. |
In the grid circuit of a triode a signal \[E=2\sqrt{2}\cos \omega t\] is applied. If m = 14 and rp =10 kW then root mean square current flowing through \[{{R}_{L}}=12\,k\Omega \] will be |
| A. | 1.27 mA |
| B. | 10 mA |
| C. | 1.5 mA |
| D. | 12.4 mA |
| Answer» B. 10 mA | |
| 8125. |
The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is [Roorkee 1999] |
| A. | 2000 |
| B. | 3000 |
| C. | 4000 |
| D. | 5000 |
| Answer» E. | |
| 8126. |
For ensuring dissipation of same energy in all three resistors \[({{R}_{1}},\,{{R}_{2}},\,{{R}_{3}})\] connected as shown in figure, their values must be related as ] [AIIMS 2005] |
| A. | \[{{R}_{1}}={{R}_{2}}={{R}_{3}}\] |
| B. | \[{{R}_{2}}={{R}_{3}}\]and \[{{R}_{1}}=4{{R}_{2}}\] |
| C. | \[{{R}_{2}}={{R}_{3}}\]and \[{{R}_{1}}=\frac{1}{4}{{R}_{2}}\] |
| D. | \[{{R}_{1}}={{R}_{2}}+{{R}_{3}}\] |
| Answer» D. \[{{R}_{1}}={{R}_{2}}+{{R}_{3}}\] | |
| 8127. |
There are three sources of sound of equal intensity with frequencies 400, 401 and 402 vib/sec. The number of beats heard per second is [MNR 1980; J & K CET 2005] |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» C. 2 | |
| 8128. |
In the circuit shown in figure reading of voltmeter is V1 when only S1 is closed, reading of voltmeter is V2 when only S2 is closed and reading of voltmeter is V3 when both S1 and S2 are closed. Then |
| A. | V3 > V2 > V1 |
| B. | V2 > V1 > V3 |
| C. | V3 > V1 > V2 |
| D. | V1 > V2 > V3 |
| Answer» C. V3 > V1 > V2 | |
| 8129. |
A parallel plate capacitor is charged to a potential difference of 50 V. It is discharged through a resistance. After 1 second, the potential difference between plates becomes 40 V. Then [Roorkee 1999] |
| A. | Fraction of stored energy after 1 second is 16/25 |
| B. | Potential difference between the plates after 2 seconds will be 32 V |
| C. | Potential difference between the plates after 2 seconds will be 20 V |
| D. | Fraction of stored energy after 1 second is 4/5 |
| Answer» 1 , 2. Potential difference between the plates after 2 seconds will be 32 V | |
| 8130. |
A parallel plate capacitor of plate separation 2 mm is connected in an electric circuit having source voltage 400 V. if the plate area is 60 cm2, then the value of displacement current for \[{{10}^{-6}}\,\sec \] will be |
| A. | 1.062 amp |
| B. | \[1.062\times {{10}^{-2}}\]amp |
| C. | \[1.062\times {{10}^{-3}}\]amp |
| D. | \[1.062\times {{10}^{-4}}\]amp |
| Answer» C. \[1.062\times {{10}^{-3}}\]amp | |
| 8131. |
A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be [MP PET 1989; RPMT 1998] |
| A. | 1 kW |
| B. | 5 kW |
| C. | 10 kW |
| D. | 20 kW |
| Answer» C. 10 kW | |
| 8132. |
For a substance the average life for a-emission is 1620 years and for b emission is 405 years. After how much time the 1/4 of the material remains after a and b emission [RPET 1999] |
| A. | 1500 years |
| B. | 300 years |
| C. | 449 years |
| D. | 810 years |
| Answer» D. 810 years | |
| 8133. |
Water of volume 2 litre in a container is heated with a coil of 1 kW at 27 oC. The lid of the container is open and energy dissipates at rate of 160 J/s. In how much time temperature will rise from 27oC to 77oC [Given specific heat of water is 4.2 kJ/kg] [IIT-JEE (Screening) 2005] |
| A. | 8 min 20 s |
| B. | 6 min 2 s |
| C. | 7 min |
| D. | 14 min |
| Answer» B. 6 min 2 s | |
| 8134. |
The network shown in the figure is a part of a complete circuit. If at a certain instant the current i is 5 A and is decreasing at the rate of \[{{10}^{3}}A/s\] then \[{{V}_{A}}-{{V}_{B}}\] is |
| A. | 5 V |
| B. | 10 V |
| C. | 15 V |
| D. | 20 V |
| Answer» D. 20 V | |
| 8135. |
Three waves of equal frequency having amplitudes 10 mm, 4 mm and 7 mm arrive at a given point with successive phase difference of \[\frac{\pi }{2}\]. The amplitude of the resulting wave in mm is given by [AIIMS 1995] |
| A. | 7 |
| B. | 6 |
| C. | 5 |
| D. | 4 |
| Answer» D. 4 | |
| 8136. |
In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was fraction equal to |
| A. | 1 / 8 |
| B. | 1 / 6 |
| C. | 1 / 10 |
| D. | 1 / 4 |
| Answer» B. 1 / 6 | |
| 8137. |
nnCapacitance of a capacitor made by a thin metal foil is \[2\mu F\]. If the foil is folded with paper of thickness\[0.15mm\], dielectric constant of paper is 2.5 and width of paper is\[400mm\], then length of foil will be [RPET 1997] |
| A. | \[0.34\ m\] |
| B. | \[1.33\ m\] |
| C. | \[13.4\ m\] |
| D. | \[33.9\ m\] |
| Answer» E. | |
| 8138. |
The ratio of the intensity at the centre of a bright fringe to the intensity at a point one-quarter of the distance between two fringe from the centre is |
| A. | 2 |
| B. | 1/2 |
| C. | 4 |
| D. | 16 |
| Answer» B. 1/2 | |
| 8139. |
The focal length of an objective of a telescope is 3 metre and diameter 15 cm. Assuming for a normal eye, the diameter of the pupil is 3 mm for its complete use, the focal length of eye piece must be [MP PET 1989] |
| A. | 6 cm |
| B. | 6.3 cm |
| C. | 20 cm |
| D. | 60 cm |
| Answer» B. 6.3 cm | |
| 8140. |
The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then [IIT 1999; UPSEAT 2003] |
| A. | X and Y have the same decay rate initially |
| B. | X and Y decay at the same rate always |
| C. | Y will decay at a faster rate than X |
| D. | X will decay at a faster rate than Y |
| Answer» D. X will decay at a faster rate than Y | |
| 8141. |
The figure shows three circuits with identical batteries, inductors, and resistors. Rank the circuits according to the current through the battery (i) just after the switch is closed and (ii) a long time later, greatest first |
| A. | (i) \[{{i}_{2}}>{{i}_{3}}>{{i}_{1}}\,\,({{i}_{1}}=0)\] (ii) \[{{i}_{2}}>{{i}_{3}}>{{i}_{1}}\] |
| B. | (i) \[{{i}_{2}}<{{i}_{3}}<{{i}_{1}}\,\,({{i}_{1}}\ne 0)\] (ii) \[{{i}_{2}}>{{i}_{3}}>{{i}_{1}}\] |
| C. | (i) \[{{i}_{2}}={{i}_{3}}={{i}_{1}}\,\,({{i}_{1}}=0)\] (ii) \[{{i}_{2}}<{{i}_{3}}<{{i}_{1}}\] |
| D. | (i) \[{{i}_{2}}={{i}_{3}}>{{i}_{1}}\,\,({{i}_{1}}\ne 0)\] (ii) \[{{i}_{2}}>{{i}_{3}}>{{i}_{1}}\] |
| Answer» B. (i) \[{{i}_{2}}<{{i}_{3}}<{{i}_{1}}\,\,({{i}_{1}}\ne 0)\] (ii) \[{{i}_{2}}>{{i}_{3}}>{{i}_{1}}\] | |
| 8142. |
In the following circuit, 5 W resistor develops 45 J/s due to current flowing through it. The power developed per second across 12 W resistor is [AMU (Engg.) 1999] |
| A. | 16 W |
| B. | 192 W |
| C. | 36 W |
| D. | 64 W |
| Answer» C. 36 W | |
| 8143. |
The displacement of a particle in string stretched in X direction is represented by y. Among the following expressions for y, those describing wave motions are [IIT 1987] |
| A. | \[\cos kx\sin \omega \,t\] |
| B. | \[{{k}^{2}}{{x}^{2}}-{{\omega }^{2}}{{t}^{2}}\] |
| C. | \[\cos (kx+\omega \,t)\] |
| D. | \[\cos ({{k}^{2}}{{x}^{2}}-{{\omega }^{2}}{{t}^{2}})\] |
| Answer» D. \[\cos ({{k}^{2}}{{x}^{2}}-{{\omega }^{2}}{{t}^{2}})\] | |
| 8144. |
Consider the circuits shown in the figure. Both the circuits are taking same current from battery but current through R in the second circuit is \[\frac{1}{10}\]th of current through R in the first circuit. If R is 11 W, the value of R1 |
| A. | 9.9 W |
| B. | 11 W |
| C. | 8.8 W |
| D. | 7.7 W |
| Answer» B. 11 W | |
| 8145. |
A dielectric slab of thickness \[d\] is inserted in a parallel plate capacitor whose negative plate is at \[x=0\] and positive plate is at \[x=3d\]. The slab is equidistant from the plates. The capacitor is given some charge. As one goes from 0 to \[3d\] [IIT-JEE 1998] |
| A. | The magnitude of the electric field remains the same |
| B. | The direction of the electric field remains the same |
| C. | The electric potential increases continuously |
| D. | The electric potential increases at first, then decreases and again increases |
| Answer» C. The electric potential increases continuously | |
| 8146. |
The diameter of moon is \[3.5\times {{10}^{3}}\]km and its distance from the earth is \[3.8\times {{10}^{5}}\]km. If it is seen through a telescope whose focal length for objective and eye lens are 4 m and 10 cm respectively, then the angle subtended by the moon on the eye will be approximately [NCERT 1982; CPMT 1991] |
| A. | 15o |
| B. | 20o |
| C. | 30o |
| D. | 35o |
| Answer» C. 30o | |
| 8147. |
A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current |
| A. | 6.25 V |
| B. | 0.16 V |
| C. | 15.2 V |
| D. | None of these |
| Answer» B. 0.16 V | |
| 8148. |
A freshly prepared radioactive sample of half- life 1 hour emits radiations that are 128 times as intense as the permissible safe limit. The minimum time after which this sample can be safely used is [KCET 1996] |
| A. | 14 hours |
| B. | 7 hours |
| C. | 128 hours |
| D. | 256 hours |
| Answer» C. 128 hours | |
| 8149. |
What is the mutual inductance of a two-loop system as shown with centre separation l |
| A. | \[\frac{{{\mu }_{0}}\pi {{a}^{4}}}{8{{l}^{3}}}\] |
| B. | \[\frac{{{\mu }_{0}}\pi {{a}^{4}}}{4{{l}^{3}}}\] |
| C. | \[\frac{{{\mu }_{0}}\pi {{a}^{4}}}{6{{l}^{3}}}\] |
| D. | \[\frac{{{\mu }_{0}}\pi {{a}^{4}}}{2{{l}^{3}}}\] |
| Answer» E. | |
| 8150. |
The thermo e.m.f. of a thermocouple varies with the temperature \[\theta \] of the hot junction as \[E=a\theta +b{{\theta }^{2}}\] in volts where the ratio a/b is \[{{700}^{o}}C.\] If the cold junction is kept at \[{{0}^{o}}C,\] then the neutral temperature is [AIEEE 2004] |
| A. | \[{{700}^{o}}C\] |
| B. | \[{{350}^{o}}C\] |
| C. | \[{{1400}^{o}}C\] |
| D. | No neutral temperature is possible for this thermocouple |
| Answer» E. | |