Explore topic-wise MCQs in Joint Entrance Exam - Main (JEE Main).

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.

1451.

An oxide coated filament is useful in vacuum tubes because essentially                                 [SCRA 1994]

A. It has high melting point
B. It can withstand high temperatures
C. It has good machanical strength
D. It can emit electrons at relatively lower temperatures
Answer» E.
1452.

A wedged shaped air film having an angle of 40 second is illuminated by a monochromatic light and the fringes are observed vertically down through a microscope. The fringe separation between two consecutive bright fringes is 0.12 cm. The wavelength of light is:

A. \[~5545\overset{o}{\mathop{A}}\,\]
B. \[6025\overset{o}{\mathop{A}}\,\]
C. \[4925\overset{o}{\mathop{A}}\,\]
D. \[~4655\overset{o}{\mathop{A}}\,\]
Answer» E.
1453.

The unit of Young?s modulus is [Pb. PET 2001]

A. \[N{{m}^{2}}\]
B. \[N{{m}^{-2}}\]
C. Nm
D. \[N{{m}^{-1}}\]
Answer» C. Nm
1454.

In an experiment to determine the focal length (f) of a concave mirror by the u - v method, a student places the object pin A on the principal axis at a distance x from the pole P. The student looks at the pin and its inverted image from a distance keeping his/her eye in line with PA. When the student shifts his/her eye towards left, the image appears to the right of the object pin. Then,

A. \[x<f\]
B. \[f<x<2f\]
C. \[x=-2f\]
D. \[x>2f\]
Answer» C. \[x=-2f\]
1455.

Two masses m1 and m2 are suspended together by a massless spring of constant K. When the masses are in equilibrium, m1 is removed without disturbing the system. The amplitude of oscillations is                     [J & K CET 2005]

A. \[\frac{{{m}_{1}}g}{K}\]
B. \[\frac{{{m}_{2}}g}{K}\]
C. \[\frac{({{m}_{1}}+{{m}_{2}})g}{K}\]
D. \[\frac{({{m}_{1}}-{{m}_{2}})g}{K}\]
Answer» B. \[\frac{{{m}_{2}}g}{K}\]
1456.

A man is watching two trains, one leaving and the other coming in with equal speeds of 4m/ sec. If they sound their whistles, each of frequency 240 Hz, the number of beats heard by the man (velocity of sound in air = 320 m/sec) will be equal to

A. 6
B. 3
C. 0
D. 12
Answer» B. 3
1457.

A spring executes SHM with mass of 10kg attached to it. The force constant of spring is 10N/m.If at any instant its velocity is 40cm/sec, the displacement will be (where amplitude is 0.5m)                                              [RPMT 2004]

A. 0.09 m
B. 0.3 m
C. 0.03 m
D. 0.9 m
Answer» C. 0.03 m
1458.

Assertion             :       The force with which one plate of a parallel plate capacitor is attracted towards the other plate is equal to square of surface density per e per unit area.             Reason     :   The electric field due to one charged plate of the capacitor at the location of the other is equal to surface density per e.

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» E. If assertion is false but reason is true.
1459.

Hydrogen atom excites energy level from fundamental state to n = 3. Number of spectrum lines according to Bohr, is

A. 4
B. 3
C. 1
D. 2
Answer» C. 1
1460.

When an electron in hydrogen atom is excited, from its 4th to 5th stationary orbit, the change in angular momentum of electron is (Plancks constant: \[h=6.6\times {{10}^{-34}}J\text{-s}\]

A. \[4.16\times {{10}^{-34}}\,J\text{-}s\]
B. \[3.32\times {{10}^{-34}}\,J\text{-}s\]
C. \[1.05\times {{10}^{-34}}\,J\text{-}s\]
D. \[2.08\times {{10}^{-34}}\,J\text{-}s\]
Answer» D. \[2.08\times {{10}^{-34}}\,J\text{-}s\]
1461.

The third line of Balmer series of an ion equivalent to hydrogen atom has wavelength of 108.5 nm. The ground state energy of an electron of this ion will be

A. 3.4 eV
B. 13.6 eV
C. 54.4 eV
D. 122.4 eV
Answer» D. 122.4 eV
1462.

The unit of reactance is [MP PET 2003]

A. (a) Ohm
B. Volt
C. Mho
D. Newton
Answer» B. Volt
1463.

A container contains hot water at \[{{100}^{o}}C\]. If in time \[{{T}_{1}}\] temperature falls to \[{{80}^{o}}C\] and in time \[{{T}_{2}}\] temperature falls to \[{{60}^{o}}C\] from \[{{80}^{o}}C\], then

A. \[{{T}_{1}}={{T}_{2}}\]
B. \[{{T}_{1}}>{{T}_{2}}\]
C. \[{{T}_{1}}<{{T}_{2}}\]
D. None
Answer» D. None
1464.

A body takes 5 minute to cool from \[80{}^\circ C\] to \[50{}^\circ C\]. How much time it will take to cool from \[60{}^\circ C\] to \[30{}^\circ C\], if room temperature is \[20{}^\circ C\].

A. 40 minute
B. 9 minute
C. 30 minute
D. 20 minute
Answer» C. 30 minute
1465.

Assertion             :       The capacity of a given conductor remains same even if charge is varied on it.             Reason     :   Capacitance depends upon nearly medium as well as size and shape of conductor.

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.
1466.

The density of steel at \[0 {}^\circ C\]is 8.0 g/cc. At what temperature is density lesser by 0.1%? Coefficient of linear expansion of steel is \[1{{0}^{-5}} /{}^\circ C\].

A. \[37.2{}^\circ C\]
B. \[33.3{}^\circ C\]
C. \[55.4{}^\circ C\]
D. \[40.2{}^\circ C\]
Answer» C. \[55.4{}^\circ C\]
1467.

The coefficient of linear expansion of brass and steel are \[{{\alpha }_{1}}\] and \[{{\alpha }_{2}}\]. If we take a brass rod of length \[{{l}_{1}}\] and steel rod of length \[{{l}_{2}}\] at 0°C, their difference in length \[({{l}_{2}}-{{l}_{1}})\] will remain the same at a temperature if        [EAMCET (Med.) 1995]

A. \[{{\alpha }_{1}}{{l}_{2}}={{\alpha }_{2}}{{l}_{1}}\]
B. \[{{\alpha }_{1}}l_{2}^{2}={{\alpha }_{2}}l_{1}^{2}\]
C. \[\alpha _{1}^{2}{{l}_{1}}=\alpha _{2}^{2}{{l}_{2}}\]
D. \[{{\alpha }_{1}}{{l}_{1}}={{\alpha }_{2}}{{l}_{2}}\]
Answer» E.
1468.

Assertion          :           In circular motion, work done by centripetal force is zero.             Reason            :           In circular motion centripetal force is perpendicular to the displacement.

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.
1469.

A man projects a coin upwards from the gate of a uniformly moving train. The path of coin for the man will be

A. Parabolic
B. Inclined straight line
C. Vertical straight line
D. Horizontal straight line
Answer» D. Horizontal straight line
1470.

r and r? denote the angles inside an equilateral prism, as usual, in degrees. Consider that during some time interval from \[t=0\] to \[t=t,\,r'\] varies with time as \[r'=10+{{t}^{2}}.\] During this time r will vary as: (Assume that r and r? are in degree):

A. \[50-{{t}^{2}}\]
B. \[50+{{t}^{2}}\]
C. \[60-{{t}^{2}}\]
D. \[60+{{t}^{2}}\]
Answer» B. \[50+{{t}^{2}}\]
1471.

A bomb is dropped from an aeroplane moving horizontally at constant speed. When air resistance is taken into consideration, the bomb

A. Falls to earth exactly below the aeroplane
B. Fall to earth behind the aeroplane
C. Falls to earth ahead of the aeroplane
D. Flies with the aeroplane
Answer» C. Falls to earth ahead of the aeroplane
1472.

One of the refracting surface of a prism of refractive index \[\sqrt{2}\] is silvered. The angle of the prism is equal to the critical angle of a medium of refractive index 2. A ray of light incident in the silvered surface passes through the prism and retraces its path after reflection at the silvered face. Then the angle of incidence on the un silvered surface is

A. \[{{0}^{o}}\]
B. \[{{30}^{o}}\]
C. \[{{45}^{o}}\]
D. \[{{60}^{o}}\]
Answer» D. \[{{60}^{o}}\]
1473.

In Newton's experiment of cooling, the water equivalent of two similar calorimeters is 10 gm each. They are filled with 350 gm of water and 300 gm of a liquid (equal volumes) separately. The time taken by water and liquid to cool from \[{{70}^{o}}C\] to \[{{60}^{o}}C\] is 3 min and 95 sec respectively. The specific heat of the liquid will be

A. \[0.3\,Cal\text{/}gm\times {}^\circ C\]
B. \[0.6\,Cal\text{/}gm\times {}^\circ C\]
C. \[0.6\,Cal\text{/}gm\times {}^\circ C\]
D. \[0.8\,Cal\text{/}gm\times {}^\circ C\]
Answer» D. \[0.8\,Cal\text{/}gm\times {}^\circ C\]
1474.

The molar heat capacity of a certain substance varies with temperature according to the given equation, \[C=27.2+(4\times {{10}^{-3}})T.\] The heat necessary to change the temperature of 2 mol. of the substance from 300K to 700K is

A. \[3.46\times {{10}^{4}}J\]
B. \[2.33\times {{10}^{3}}J\]
C. \[12\times {{10}^{5}}\]
D. \[2.33\times {{10}^{4}}J\]
Answer» E.
1475.

A system changes from the state \[({{P}_{1}},\,\,\,{{V}_{1}})\] to \[({{P}_{2}},\,\,\,{{V}_{2}})\] as shown in the figure below. What is the work done by the system?

A. \[7.5\times {{10}^{5}}\] joule
B. \[7.5\times {{10}^{5}}\] ergs
C. \[12\times {{10}^{5}}\] joule
D. \[6\times {{10}^{5}}\] joule
Answer» D. \[6\times {{10}^{5}}\] joule
1476.

Assertion             :       Efficiency of a Carnot engine increase on reducing the temperature of sink. Reason                 :       The efficiency of a Carnot engine is defined as ratio of net mechanical work done per cycle by the gas to the amount of heat energy absorbed per cycle from the source.

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.
1477.

Light rays from a very distant source travel along the \[+x\] direction. Two identical thin lenses with focal length \[f>0\] and their optical axis along x, sit, one at \[x=0\] and the other at \[x=d

A. \[d+\frac{f(f-d)}{2f-d}\]
B. \[d-\frac{f(f-d)}{d}\]
C. \[d+\frac{f(f-d)}{2(f+d)}\]
D. \[d+\frac{{{f}^{2}}}{2(f-d)}\]
Answer» B. \[d-\frac{f(f-d)}{d}\]
1478.

A convex lens forms a real image three times larger than the object on a screen. Object and screen are moved until the image becomes twice the size of the object. If the shift of the object is 6 cm. The shift of screen is:

A. 36 cm
B. 72 cm
C. 18 cm
D. 9 cm
Answer» B. 72 cm
1479.

A plano-convex lens of focal length 10 cm is silvered at its plane face. The distance d at which an object must be placed in order to get its image on itself is:

A. 5 cm
B. 20 cm
C. 10 cm
D. 2.5 cm
Answer» D. 2.5 cm
1480.

A particle moves under the effect of a force \[F~=Cx\]from x = 0 to \[x={{x}_{1}}\]. The work done in the process is                         [CPMT 1982; DCE 2002;Orissa JEE 2005]

A. \[Cx_{1}^{2}\]
B. \[\frac{1}{2}Cx_{1}^{2}\]
C. \[C{{x}_{1}}\]
D. Zero
Answer» C. \[C{{x}_{1}}\]
1481.

10 gm of ice at 0°C is mixed with 100 gm of water at 50°C. What is the resultant temperature of mixture                [AFMC 2005]

A. 31.2°C
B. 32.8°C
C. 36.7°C
D. 38.2°C
Answer» E.
1482.

A particle moves in a circle of radius 25 cm at two revolutions per second. The acceleration of the particle in \[m/{{s}^{2}}\] is     [MNR 1991; UPSEAT 2000;                                     DPMT 1999; RPET 2003; Pb. PET 2004]

A. \[{{\pi }^{2}}\]
B. \[8{{\pi }^{2}}\]
C. \[4{{\pi }^{2}}\]
D. \[2{{\pi }^{2}}\]
Answer» D. \[2{{\pi }^{2}}\]
1483.

A cell is connected between two points of a uniformly thick circular conductor. The magnetic field at the centre of the loop will be                                                                  [MP PMT 1994]

A. Zero
B. \[\frac{{{\mu }_{0}}}{2a}({{i}_{1}}-{{i}_{2}})\]
C. \[\frac{{{\mu }_{0}}}{2a}({{i}_{1}}+{{i}_{2}})\]
D. \[\frac{{{\mu }_{0}}}{a}({{i}_{1}}+{{i}_{2}})\] (Here \[{{i}_{1}}\] and \[{{i}_{2}}\] are the currents flowing in the two parts of the circular conductor of radius ?a? and \[{{\mu }_{0}}\] has the usual meaning)
Answer» B. \[\frac{{{\mu }_{0}}}{2a}({{i}_{1}}-{{i}_{2}})\]
1484.

If the two ends P and N of a P-N diode junction are joined by a wire                                        [MP PMT 2002]

A. There will not be a steady current in the circuit
B. There will be a steady current from N side to P side
C. There will be a steady current from P side to N side
D. There may not be a current depending upon the resistance of the connecting wire
Answer» B. There will be a steady current from N side to P side
1485.

In damped oscillations, the amplitude of oscillations is reduced to one-third of its initial value \[{{a}_{0}}\] at the end of 100 oscillations. When the oscillator completes 200 oscillations, its amplitude must be

A. \[{{a}_{0}}/2\]
B. \[{{a}_{0}}/4\]
C. \[{{a}_{0}}/6\]
D. \[{{a}_{0}}/9\]
Answer» E.
1486.

If the temperature increases, the modulus of elasticity

A. Decreases
B. Increases
C. Remains constant
D. Becomes zero
Answer» B. Increases
1487.

A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2.  the weight of the block is         [AIEEE 2003]

A. 2 N
B. 20 N
C. 50 N
D. 100 N
Answer» B. 20 N
1488.

Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively. Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively. For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface. [Take \[\sigma \times \,4\pi {{R}^{2}}\,\times \,{{300}^{4}}=\,\beta J{{s}^{-1}}\]] The temperature of A (a perfect black body) is \[{{T}_{A}}=300K\] and temperature of H is \[{{T}_{0}}=OK\]. For H take \[{{e}_{H}}=0.5\] and \[t=0.5\]. For this situation mark out the correct statement(s).

A. The rate at which A loses the energy is \[\beta J{{s}^{-1}}\]
B. The rate at which spherical surface containing P receives the energy is \[\frac{\beta }{2}J{{s}^{-1}}\].
C. The rate at which spherical surface containing Q receives the energy is \[\beta \,J/{{s}^{-1}}\]
D. All of the above
Answer» E.
1489.

Direction: Consider a spherical body A of radius R which placed concentrically in a hollow enclosure H, of radius 4R as shown in the figure. The temperature of the body A and H are \[{{T}_{A}}\] and \[{{T}_{H}},\] respectively. Emissivity, transitivity and reflectivity of two bodies A and H are \[\text{(}{{e}_{A}},\text{ }{{e}_{H}})\text{ (}{{t}_{A}},\text{ }{{t}_{H}}\text{)}\] and \[({{r}_{A}},\text{ }{{r}_{H}})\] respectively. For answering following questions assume no absorption of the thermal energy by the space in-between the body and enclosure as well as outside the enclosure and all radiations to be emitted and absorbed normal to the surface. [Take \[\sigma \times \,4\pi {{R}^{2}}\,\times \,{{300}^{4}}=\,\beta J{{s}^{-1}}\]] In above question, if body A has \[{{e}_{A}}=0.5,\] \[{{r}_{A}}=0.5\] and for H, \[{{e}_{H}}=0.5,\] \[r=0.5,\] then mark out the correct statement.

A. The rate at which A loses the energy is
B. The rate at which the spherical surface containing P receives the energy is zero
C. The rate at which the spherical surface containing Q receives the energy is\[\beta \].
D. All of the above
Answer» E.
1490.

Assuming the sun to be a spherical body of radius R at a temperature of TK, evaluate the total radiant power, incident on earth, at a distance from the sun. Where r0 is the radius of the earth and a is Stefans constant.

A. \[4\pi r_{0}^{2}\,{{R}^{2}}\,\sigma {{T}^{4}}/\,{{r}^{2}}\]
B. \[\pi r_{0}^{2}\,{{R}^{2}}\,\sigma {{T}^{4}}/\,{{r}^{2}}\]
C. \[r_{0}^{2}\,{{R}^{2}}\,\sigma {{T}^{4}}/4\pi \,{{r}^{2}}\]
D. \[{{R}^{2}}\,\sigma {{T}^{4}}/\,{{r}^{2}}\]
Answer» C. \[r_{0}^{2}\,{{R}^{2}}\,\sigma {{T}^{4}}/4\pi \,{{r}^{2}}\]
1491.

A pendulum has time period T. If it is taken on to another planet having acceleration due to gravity half and mass 9 times that of the earth then its time period on the other planet will be                                  [CMEET Bihar 1995]

A. \[\sqrt{T}\]
B. T
C. \[{{T}^{1/3}}\]
D. \[\sqrt{2}\]T
Answer» E.
1492.

A simple pendulum is executing simple harmonic motion with a time period T. If the length of the pendulum is increased by 21%, the percentage increase in the time period of the pendulum of increased length is [BHU 1994, 96; Pb. PMT 1995; AFMC 2001; AIIMS 2001; AIEEE 2003]

A. 10%
B. 21%
C. 30%
D. 50%
Answer» B. 21%
1493.

In a simple pendulum, the period of oscillation T is related to length of the pendulum l as             [EAMCET (Med.) 1995]

A. \[\frac{l}{T}=\]constant
B. \[\]\[\frac{{{l}^{2}}}{T}=\]constant
C. \[\frac{l}{{{T}^{2}}}=\]constant
D. \[\frac{{{l}^{2}}}{{{T}^{2}}}=\]constant
Answer» D. \[\frac{{{l}^{2}}}{{{T}^{2}}}=\]constant
1494.

The shortest wavelength of X-rays emitted from an X-ray tube depends on the  [MP PMT 1987; CPMT 1988, 92; IIT 1982]

A. Current in the tube
B. Voltage applied to the tube
C. Nature of gas in the tube
D. Atomic number of target material
Answer» C. Nature of gas in the tube
1495.

The bob of a simple pendulum of mass m and total energy E will have maximum linear momentum equal to                                                                                          [MP PMT 1986]

A. \[\sqrt{\frac{2E}{m}}\]
B. \[\sqrt{2mE}\]
C. \[2mE\]
D. \[m{{E}^{2}}\]
Answer» C. \[2mE\]
1496.

The length of the second pendulum on the surface of earth is 1 m. The length of seconds pendulum on the surface of moon, where g is 1/6th value of g on the surface of earth, is [CPMT 1971]

A. 1 / 6 m
B. 6 m
C. 1 / 36 m
D. 36 m
Answer» B. 6 m
1497.

A heavy uniform chain lies on a horizontal table-top. If the coefficient of friction between the chain and table surface is 0.25, then the maximum fraction of length of the chain, that can hang over one edge of the table is            [CBSE PMT 1990]

A. 20%
B. 25%
C. 35%
D. 15%
Answer» B. 25%
1498.

A second's pendulum is placed in a space laboratory orbiting around the earth at a height 3R, where R is the radius of the earth. The time period of the pendulum is [CPMT 1989; RPMT 1995]

A. Zero
B. \[2\sqrt{3}\,sec\]
C. 4 sec
D. Infinite
Answer» E.
1499.

A, B, C and D are four different physical quantities having different dimensions. None of them is dimensionless. But we know that the equation \[AD=C\text{ }In\text{ (}BD\text{)}\]holds true. Then which of the combination is not a meaningful quantity?

A. \[\frac{C}{BD}-\frac{A{{D}^{2}}}{C}\]
B. \[{{A}^{2}}-{{B}^{2}}{{C}^{2}}\]
C. \[\frac{A}{B}-C\]
D. \[\frac{(A-C)}{D}\]
Answer» E.
1500.

Assertion             :       Light is produced in gases in the process of electric discharge through them at high pressure. Reason                 :       At high pressure electrons of gaseous atoms collide and reach and excited state.

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» E. If assertion is false but reason is true.