MCQOPTIONS
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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.
| 4951. |
An electron is moving with a speed of \[{{10}^{8}}\,m/\sec \] perpendicular to a uniform magnetic field of intensity B. Suddenly intensity of the magnetic field is reduced to B/2. The radius of the path becomes from the original value of r [MP PET 1993] |
| A. | No change |
| B. | Reduces to r / 2 |
| C. | Increases to 2r |
| D. | Stops moving |
| Answer» D. Stops moving | |
| 4952. |
A proton of mass m and charge +e is moving in a circular orbit in a magnetic field with energy 1 MeV. What should be the energy of \[\alpha -\]particle (mass = 4m and charge = + 2e), so that it can revolve in the path of same radius [BHU 1997] |
| A. | 1 MeV |
| B. | 4 MeV |
| C. | 2 MeV |
| D. | 0.5 MeV |
| Answer» B. 4 MeV | |
| 4953. |
A proton is moving along Z-axis in a magnetic field. The magnetic field is along X-axis. The proton will experience a force along |
| A. | X-axis |
| B. | Y-axis |
| C. | Z-axis |
| D. | Negative Z-axis |
| Answer» C. Z-axis | |
| 4954. |
A charged particle moves with velocity v in a uniform magnetic field \[\overrightarrow{B}\]. The magnetic force experienced by the particle is [CBSE PMT 1990] |
| A. | Always zero |
| B. | Never zero |
| C. | Zero, if \[\overrightarrow{B}\] and \[\overrightarrow{v\,}\] are perpendicular |
| D. | Zero, if \[\overrightarrow{B}\] and \[\overrightarrow{v\,}\] are parallel |
| Answer» E. | |
| 4955. |
A 2 MeV proton is moving perpendicular to a uniform magnetic field of 2.5 tesla. The force on the proton is [CPMT 1989] |
| A. | \[2.5\times {{10}^{-10}}\,N\] |
| B. | \[7.6\times {{10}^{-11}}\,N\] |
| C. | \[2.5\times {{10}^{-11}}\,N\] |
| D. | \[7.6\times {{10}^{-12}}\,N\] |
| Answer» E. | |
| 4956. |
An electron, moving in a uniform magnetic field of induction of intensity \[\vec{B},\] has its radius directly proportional to [DPMT 2005] |
| A. | Its charge |
| B. | Magnetic field |
| C. | Speed |
| D. | None of these |
| Answer» D. None of these | |
| 4957. |
An electron (mass = \[9.1\times {{10}^{-31}}\] kg; charge = \[1.6\times {{10}^{-19}}\]C) experiences no deflection if subjected to an electric field of \[3.2\times {{10}^{5}}\]V/m, and a magnetic fields of \[2.0\times {{10}^{-3}}\] Wb/m2. Both the fields are normal to the path of electron and to each other. If the electric field is removed, then the electron will revolve in an orbit of radius [BCECE 2005] |
| A. | 45 m |
| B. | 4.5 m |
| C. | 0.45 m |
| D. | 0.045 m |
| Answer» D. 0.045 m | |
| 4958. |
An electric field of 1500 V / m and a magnetic field of 0.40 weber / meter2 act on a moving electron. The minimum uniform speed along a straight line the electron could have is [KCET 2005] |
| A. | 1.6 ´ 1015 m / s |
| B. | 6 ´ 10-16 m / s |
| C. | 3.75 ´ 103 m / s |
| D. | 3.75 ´ 102 m / s |
| Answer» D. 3.75 ´ 102 m / s | |
| 4959. |
An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to [CBSE PMT 2005] |
| A. | \[\frac{B}{v}\] |
| B. | \[\frac{v}{R}\] |
| C. | \[\sqrt{\frac{v}{B}}\] |
| D. | \[\sqrt{\frac{B}{v}}\] |
| Answer» D. \[\sqrt{\frac{B}{v}}\] | |
| 4960. |
The electron in the beam of a television tube move horizontally from south to north. The vertical component of the earth's magnetic field points down. The electron is deflected towards [KCET 2005] |
| A. | West |
| B. | No deflection |
| C. | East |
| D. | North to south |
| Answer» D. North to south | |
| 4961. |
A very long straight wire carries a current \[I\]. At the instant when a charge \[+Q\] at point \[P\] has velocity \[\overrightarrow{V}\], as shown, the force on the charge is [CBSE PMT 2005] |
| A. | Opposite to OX |
| B. | Along OX |
| C. | Opposite to OY |
| D. | Along OY |
| Answer» E. | |
| 4962. |
A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The time taken by the particle to complete one revolution is [AIEEE 2005] |
| A. | \[\frac{2\pi qB}{m}\] |
| B. | \[\frac{2\pi \,m}{q\,B}\] |
| C. | \[\frac{2\pi \,m\,q}{B}\] |
| D. | \[\frac{2\pi \,{{q}^{2}}B}{m}\] |
| Answer» C. \[\frac{2\pi \,m\,q}{B}\] | |
| 4963. |
In case Hall effect for a strip having charge Q and area of cross-section A, the Lorentz force is [DCE 2004] |
| A. | Directly proportional to Q |
| B. | Inversely proportional to Q |
| C. | Inversely proportional to A |
| D. | Directly proportional to A |
| Answer» B. Inversely proportional to Q | |
| 4964. |
A electron (q = 1.6 ´ 10?19 C) is moving at right angle to the uniform magnetic field 3.534 ´ 10?5 T. The time taken by the electron to complete a circular orbit is [MH CET 2004] |
| A. | 2 ms |
| B. | 4 ms |
| C. | 3 ms |
| D. | 1 ms |
| Answer» E. | |
| 4965. |
Particles having positive charges occasionally come with high velocity from the sky towards the earth. On account of the magnetic field of earth, they would be deflected towards the [NCERT 1977] |
| A. | North |
| B. | South |
| C. | East |
| D. | West |
| Answer» D. West | |
| 4966. |
A very high magnetic field is applied to a stationary charge. Then the charge experiences [DCE 2004] |
| A. | A force in the direction of magnetic field |
| B. | A force perpendicular to the magnetic field |
| C. | A force in an arbitrary direction |
| D. | No force |
| Answer» E. | |
| 4967. |
An electron is projected along the axis of a circular conductor carrying some current. Electron will experience force [DCE 2002] |
| A. | Along the axis |
| B. | Perpendicular to the axis |
| C. | At an angle of 4o with axis |
| D. | No force experienced |
| Answer» E. | |
| 4968. |
An electron moving with a uniform velocity along the positive x-direction enters a magnetic field directed along the positive y-direction. The force on the electron is directed along [UPSEAT 2004] |
| A. | Positive y-direction |
| B. | Negative y-direction |
| C. | Positive z-direction |
| D. | Negative z-direction |
| Answer» E. | |
| 4969. |
An electron, a proton, a deuteron and an alpha particle, each having the same speed are in a region of constant magnetic field perpendicular to the direction of the velocities of the particles. The radius of the circular orbits of these particles are respectively Re, Rp, Rd and Ra. It follows that [UPSEAT 2004] |
| A. | \[{{R}_{e}}={{R}_{p}}\] |
| B. | \[{{R}_{p}}={{R}_{d}}\] |
| C. | \[{{R}_{d}}={{R}_{\alpha }}\] |
| D. | \[{{R}_{p}}={{R}_{\alpha }}\] |
| Answer» D. \[{{R}_{p}}={{R}_{\alpha }}\] | |
| 4970. |
A proton of energy 8 eV is moving in a circular path in a uniform magnetic field. The energy of an alpha particle moving in the same magnetic field and along the same path will be [J & K CET 2004] |
| A. | 4 eV |
| B. | 2 eV |
| C. | 8 eV |
| D. | 6 eV |
| Answer» D. 6 eV | |
| 4971. |
In the given figure, the electron enters into the magnetic field. It deflects in ...... direction [Orissa PMT 2004] |
| A. | + ve X direction |
| B. | ? ve X direction |
| C. | + ve Y direction |
| D. | ? ve Y direction |
| Answer» E. | |
| 4972. |
The cyclotron frequency of an electron grating in a magnetic field of 1 T is approximately [AIIMS 2004] |
| A. | 28 MHz |
| B. | 280 MHz |
| C. | 2.8 GHz |
| D. | 28 GHz |
| Answer» E. | |
| 4973. |
Electrons move at right angles to a magnetic field of \[1.5\times {{10}^{-2}}\]Tesla with a speed of \[6\times {{10}^{7}}m/s.\]If the specific charge of the electron is \[1.7\times {{10}^{11}}\]C/kg. The radius of the circular path will be [BHU 2003] |
| A. | 2.9 cm |
| B. | 3.9 cm |
| C. | 2.35 cm |
| D. | 3 cm |
| Answer» D. 3 cm | |
| 4974. |
An electron and a proton have equal kinetic energies. They enter in a magnetic field perpendicularly, Then [UPSEAT 2003] |
| A. | Both will follow a circular path with same radius |
| B. | Both will follow a helical path |
| C. | Both will follow a parabolic path |
| D. | All the statements are false |
| Answer» E. | |
| 4975. |
An electron is travelling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion will be [AIIMS 2003] |
| A. | Straight line along the x-direction |
| B. | A circle in the xz-plane |
| C. | A circle in the yz-plane |
| D. | A circle in the xy-plane |
| Answer» C. A circle in the yz-plane | |
| 4976. |
If the direction of the initial velocity of the charged particle is neither along nor perpendicular to that of the magnetic field, then the orbit will be [MP PET 1993] |
| A. | A straight line |
| B. | An ellipse |
| C. | A circle |
| D. | A helix |
| Answer» D. A helix | |
| 4977. |
A proton moving with a constant velocity passes through a region of space without any change in its velocity. If \[\overrightarrow{E}\] and \[\overrightarrow{B}\] represent the electric and magnetic fields respectively, then this region of space may have [IIT-JEE 1985; AMU 1995; AFMC 2001; Roorkee 2000; AMU (Med.) 2000] |
| A. | \[E=0,\,B=0\] |
| B. | \[E=0,\,B\ne 0\] |
| C. | \[E\ne 0,\,B=0\] |
| D. | \[E\ne 0,\,B\ne 0\] |
| Answer» B. \[E=0,\,B\ne 0\] | |
| 4978. |
A particle is moving in the vertical plane. It is attached at one end of a string of length \[\lambda \] whose other end is fixed. The velocity at the lowest point is \[u\]. The tension in the string is \[\vec{T}\] and velocity of the particle is \[\vec{v}\] at any position. Then, which of the following quantity will remain constant. |
| A. | \[\vec{T}.\vec{v}\] |
| B. | kinetic energy |
| C. | Gravitational potential energy |
| D. | \[\vec{T}\times \vec{v}\] |
| Answer» B. kinetic energy | |
| 4979. |
A simple pendulum consisting of a mass \[M\] attached to a string of length L is released from rest at an angle \[a\]. A pin is located at a distance \[l\] below the pivot point. When the pendulum swings down, the string hits the pin as shown in the figure. The maximum angle \[\theta \] which the string makes with the vertical after hitting the pin is |
| A. | \[{{\cos }^{1}}\left[ \frac{L\,\cos a+l}{L+l} \right]\] |
| B. | \[{{\cos }^{1}}\left[ \frac{L\,\cos a+l}{L-l} \right]\] |
| C. | \[{{\cos }^{1}}\left[ \frac{L\,\cos a-l}{L-l} \right]\] |
| D. | \[{{\cos }^{1}}\left[ \frac{L\,\cos a-l}{L+l} \right]\] |
| Answer» D. \[{{\cos }^{1}}\left[ \frac{L\,\cos a-l}{L+l} \right]\] | |
| 4980. |
A particle of mass m moves along a circular path of radius r with centripetal acceleration \[{{a}_{n}}\] changing with time t as \[{{a}_{n}}=k{{t}^{2}}\], where k is-a positive constant. The average power developed by all the forces acting on the particle during the first \[{{t}_{0}}\] seconds is |
| A. | \[mkr{{t}_{0}}\] |
| B. | \[\frac{mkr{{t}_{0}}^{2}}{2}\] |
| C. | \[\frac{mkr{{t}_{0}}^{{}}}{2}\] |
| D. | \[\frac{mkr{{t}_{0}}^{{}}}{4}\] |
| Answer» C. \[\frac{mkr{{t}_{0}}^{{}}}{2}\] | |
| 4981. |
A mass m starting from A reaches B of a frictionless track. On reaching B, it pushes the track with a force equal to x times its weight, then the applicable relation is |
| A. | \[h=\frac{(x+5)}{2}r\] |
| B. | \[h=\frac{x}{2}r\] |
| C. | \[h=r\] |
| D. | \[h=\left( \frac{x+1}{2} \right)r\] |
| Answer» B. \[h=\frac{x}{2}r\] | |
| 4982. |
A particle located in a one-dimensional potential field has its potential energy function as \[U(x)\,\frac{a}{{{x}^{4}}}-\frac{b}{{{x}^{2}}}\], where a and b are positive constants. The position of equilibrium x corresponds to |
| A. | \[\frac{b}{2a}\] |
| B. | \[\sqrt{\frac{2a}{b}}\] |
| C. | \[\sqrt{\frac{2a}{a}}\] |
| D. | \[\frac{a}{2a}\] |
| Answer» C. \[\sqrt{\frac{2a}{a}}\] | |
| 4983. |
A particle of mass \[m\] moves with a variable velocity \[v\], which changes with distance covered \[x\] along a straight line as \[v=k\sqrt{x}\], where A: is a positive constant. The work done by all the forces acting on the particle, during the first \[t\] seconds is |
| A. | \[\frac{m{{k}^{4}}}{{{t}^{2}}}\] |
| B. | \[\frac{m{{k}^{4}}{{t}^{2}}}{4}\] |
| C. | \[\frac{m{{k}^{4}}{{t}^{2}}}{8}\] |
| D. | \[\frac{m{{k}^{4}}{{t}^{2}}}{16}\] |
| Answer» D. \[\frac{m{{k}^{4}}{{t}^{2}}}{16}\] | |
| 4984. |
When a person stands on a weighing balance, workingon the principle of Hooke's law, it shows a reading of 60 kg after a long time and the spring gets compressed by2.5 cm. If the person jumps on the balance from a height of 10 cm, the maximum reading of the balance will be |
| A. | 60 kg |
| B. | 120kg |
| C. | 180 kg |
| D. | 240kg |
| Answer» E. | |
| 4985. |
A particle of mass 0.1 kg is subjected to a force which varies with distance as shown in the figure. If it starts its journey from rest at \[x=0\], its velocity at \[x=12\] m is |
| A. | \[0\,m/s\] |
| B. | \[20\sqrt{2}m/s\] |
| C. | \[20\sqrt{3}m/s\] |
| D. | \[40\,m/s\] |
| Answer» E. | |
| 4986. |
A particle is released from the top of two inclined rough surfaces of height '\[h\]' each. The angle of inclination of the two planes are \[30{}^\circ \] and \[60{}^\circ \] respectively. All other factors (e.g. coefficient of friction, mass of block etc.) are same in both the cases. Let \[{{K}_{1}}\] and \[{{K}_{2}}\] be the kinetic energies of the particle at the bottom of the plane in two cases. Then |
| A. | \[{{K}_{1}}={{K}_{2}}\] |
| B. | \[{{K}_{1}}>{{K}_{2}}\] |
| C. | \[{{K}_{1}}<{{K}_{2}}\] |
| D. | data insufficient |
| Answer» D. data insufficient | |
| 4987. |
The force exerted by a compression device is given by \[F(x)=kx\,(x-l)\,for\,0\le x\le l\], where \[l\] is the maximum possible compression, \[x\] is the compression and is a constant. The work required to compress the device by a distance \[d\]will be maximum when: |
| A. | \[d=\frac{l}{4}\] |
| B. | \[d=\frac{l}{\sqrt{2}}\] |
| C. | \[d=\frac{l}{2}\] |
| D. | \[d=l\] |
| Answer» E. | |
| 4988. |
The block of mass \[M\] moving on a frictionless horizontal surface collides with a spring of spring constant \[k\] and compresses it by length \[L\]. The maximum momentum of the block after collision is |
| A. | \[\frac{M{{L}^{2}}}{k}\] |
| B. | zero |
| C. | \[\frac{k{{L}^{2}}}{2M}\] |
| D. | \[\sqrt{Mk}L\] |
| Answer» E. | |
| 4989. |
When a rubber-band is stretched by a distance\[x\], it exerts a restoring force of magnitude \[F=ax+b{{x}^{2}}\], where a and b are constants. The work done in stretching the unstretched rubber band by \[L\] is, |
| A. | \[\frac{a{{L}^{2}}}{2}+\frac{b{{L}^{3}}}{3}\] |
| B. | \[\frac{1}{2}\left( \frac{a{{L}^{2}}}{2}+\frac{b{{L}^{3}}}{3} \right)\] |
| C. | \[a{{L}^{2}}+b{{L}^{3}}\] |
| D. | \[\frac{1}{2}(a{{L}^{2}}+a{{L}^{3}})\] |
| Answer» B. \[\frac{1}{2}\left( \frac{a{{L}^{2}}}{2}+\frac{b{{L}^{3}}}{3} \right)\] | |
| 4990. |
Find the maximum compression in the spring, if the lower block is shifted to rightwards with Acceleration \['a'\] All the surfaces are smooth: |
| A. | \[\frac{ma}{2k}\] |
| B. | \[\frac{2ma}{k}\] |
| C. | \[\frac{ma}{k}\] |
| D. | \[\frac{4ma}{k}\] |
| Answer» C. \[\frac{ma}{k}\] | |
| 4991. |
The kinetic energy of a particle moving along a straight line increases uniformly with respect to the distance travelled by it. The force acting on the particle is (\[v\] is the speed of particle at any time) |
| A. | constant |
| B. | proportional to \[v\] |
| C. | proportional to \[{{v}^{2}}\] |
| D. | inversely proportional to \[v\] |
| Answer» B. proportional to \[v\] | |
| 4992. |
A spring is compressed between two toy carts of masses \[{{m}_{1}}\]and\[{{m}_{2}}\]. When the toy carts are released, the spring exerts on each toy cart equal and opposite forces for the same small time \[t\]. If the coefficients of friction \[\mu \] between the ground and the toy carts are equal, then the magnitude of displacements of the toy carts are in the ratio |
| A. | \[\frac{{{S}_{1}}}{{{S}_{2}}}=\frac{{{m}_{2}}}{{{m}_{2}}}\] |
| B. | \[\frac{{{S}_{1}}}{{{S}_{2}}}=\frac{{{m}_{1}}}{{{m}_{2}}}\] |
| C. | \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{2}}}{{{m}_{1}}} \right)}^{2}}\] |
| D. | \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{1}}}{{{m}_{2}}} \right)}^{2}}\] |
| Answer» D. \[\frac{{{S}_{1}}}{{{S}_{2}}}={{\left( \frac{{{m}_{1}}}{{{m}_{2}}} \right)}^{2}}\] | |
| 4993. |
A string is under tension so that its length is increased by \[1/n\] times its original length. The ratio of fundamental frequency of longitudinal vibrations and transverse vibrations will be |
| A. | \[1:n\] |
| B. | \[{{n}^{2}}:1\] |
| C. | \[\sqrt{n}:1\] |
| D. | \[n:1\] |
| Answer» D. \[n:1\] | |
| 4994. |
When beats are produced by two progressive waves of nearly the same frequency, which one of the following is correct? |
| A. | The particles vibrate simple harmonically, with the frequency equal to the difference in the component frequencies. |
| B. | The amplitude of vibration at any point changes simple harmonically with a frequency equal to the difference in the frequencies of the two waves. |
| C. | The frequency of beats depends upon the position, where the observer is. |
| D. | The frequency of beats changes as the time progresses. |
| Answer» C. The frequency of beats depends upon the position, where the observer is. | |
| 4995. |
A source of sound of frequency\[{{f}_{1}}\] is placed on the ground. A detector placed at a height is released from rest on this source. The observed frequency\[{{f}_{{}}}(Hz)\] is plotted against time \[t\](sec). The speed of sound in air is 300 m/s. Find\[{{f}_{1}}\]\[(g=10m/{{s}^{2}})\] |
| A. | \[0.5\times {{10}^{3}}Hz\] |
| B. | \[1\times {{10}^{3}}Hz\] |
| C. | \[0.25\times {{10}^{3}}\] |
| D. | \[0.25\times {{10}^{3}}Hz\] |
| Answer» C. \[0.25\times {{10}^{3}}\] | |
| 4996. |
Two pulses in a stretched string whose centres are initially 8 cm apart are moving towards each other as shown in the figure. The speed of each pulse is 2 cm/s. After 2 seconds, the total energy of the pulses will be |
| A. | Zero |
| B. | Purely kinetic |
| C. | Purely potential |
| D. | Partly kinetic and partly potential |
| Answer» C. Purely potential | |
| 4997. |
A stone is hung in air from a wire which is stretched over a sonometer. The bridges of the sonometer are \[L\] cm apart when the wire is in unison with a tuning fork of frequency\[N\]. When the stone is completely immersed in water, the length between the bridges is \[l\] cm for re-establishing unison, the specific gravity of the material of the stone is |
| A. | \[\frac{{{L}^{2}}}{{{L}^{2}}+{{l}^{2}}}\] |
| B. | \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] |
| C. | \[\frac{{{L}^{2}}}{{{L}^{2}}-{{t}^{2}}}\] |
| D. | \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] |
| Answer» D. \[\frac{{{L}^{2}}-{{l}^{2}}}{{{L}^{2}}}\] | |
| 4998. |
Two sources \[{{S}_{1}}\] and \[{{S}_{2}}\] of same frequency\[f\]emits sound. The sources are moving as shown with speed \[u\] each. A stationary observer hears that sound. The beat frequency is (\[v\] = velocity of sound) |
| A. | \[\frac{2{{u}^{2}}f}{{{v}^{2}}-{{u}^{2}}}\] |
| B. | \[\frac{2{{v}^{2}}f}{{{v}^{2}}-{{u}^{2}}}\] |
| C. | \[\frac{2\,u\,vf}{{{v}^{2}}-{{u}^{2}}}\] |
| D. | \[\frac{2u}{v}f\] |
| Answer» D. \[\frac{2u}{v}f\] | |
| 4999. |
An open pipe is in resonance in its \[{{2}^{nd}}\] 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 |
| 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. \[n=5,\,\,{{f}_{2}}=\frac{3}{4}{{f}_{1}}\] | |
| 5000. |
How long will it take sound waves to travel a distance between points \[A\] and \[B\] if the air temperature between them varies linearly from \[{{T}_{1}}\] to\[{{T}_{2}}\]? (The velocity of sound in air at temperature T is given by \[v=\alpha \sqrt{t}\], where a is \[a\] constant) |
| A. | \[\frac{2l}{\alpha \sqrt{{{T}_{1}}{{T}_{2}}}}\] |
| B. | \[\alpha l\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\] |
| C. | \[\sqrt{{{T}_{1}}+{{T}_{2}}}.\alpha l\] |
| D. | \[\frac{2l}{\alpha (\sqrt{{{T}_{2}}+\sqrt{{{T}_{1}}}})}\] |
| Answer» E. | |