For the series LCR circuit shown in the figure, what is the resonance frequency and the amplitude of the current at the resonating frequency [Kerala PET 2005]

\[2500\,rad-{{s}^{-1}}\] and \[\frac{5}{\sqrt{2}}A\]

\[2500\,rad-{{s}^{-1}}\] and \[5\sqrt{2}\,A\]

\[2500\,rad-{{s}^{-1}}\] and \[5A\]

\[2500\,rad-{{s}^{-1}}\] and \[\frac{5}{\sqrt{2}}A\]

\[25\,rad-{{s}^{-1}}\] and \[5\sqrt{2}\,A\]

Assertion : Sound travel faster in solids than gases. Reason : Solid possess greater density than gases. [AIIMS 2000]

If assertion is true but reason is false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Water does not wet an oily glass because

Cohesive force of oil>> adhesive force between oil and glass

Cohesive force of oil > cohesive force of water

Cohesive force for water > adhesive force between water and oil molecules

Assertion : If different gases are filled turn by turn at the same pressure in the discharge tube the discharge in them takes place at the same potential. Reason : The discharge depends only on the pressure of discharge tube and not on the ionisation potential of gas.

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : In everyday life the Doppler?s effect is observed readily for sound waves than light waves. Reason : Velocity of light is greater than that of sound. [AIIMS 1995]

If assertion is true but reason is false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : In Young?s experiment, the fringe width for dark fringes is different from that for white fringes. Reason : In Young?s double slit experiment the fringes are performed with a source of white light, then only black and bright fringes are observed. [AIIMS 2001]

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : The focal length of lens does not change when red light is replaced by blue light. Reason : The focal length of lens does not depends on colour of light used.

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

The proton -proton mechanism that accounts for energy production in the sun releases \[26.7\text{ }MeV\]energy for each event. In this process, protons fuse to form an alpha particle \[{{(}^{4}}He)\]. At what rate \[\frac{dm}{dt}\] is hydrogen being consumed in the core of the sun by the p-p cycle? Power of sun is\[3.90\times {{10}^{26}}W\].

\[5.5\times {{10}^{10}}\,kg/s\]

\[6.2\times {{10}^{11}}\,kg/s\]

\[5.5\times {{10}^{10}}\,kg/s\]

In a double slit experiment slits \[{{S}_{1}}\], \[{{S}_{2}}\] is illuminated by a coherent light of wavelength\[\lambda \]. The slits are separated by a distance d. The experimental set up is modified by using plane mirrors as shown in figure. Find the fringe width of interference pattern on the screen.

\[\frac{(2{{D}_{1}}+3{{D}_{2}})\lambda }{d}\]

\[\frac{(3{{D}_{1}}+2{{D}_{2}})\lambda }{d}\]

\[\frac{(2{{D}_{1}}+3{{D}_{2}})\lambda }{d}\]

\[\frac{(3{{D}_{2}}-3{{D}_{1}})\lambda }{d}\]

\[\frac{(3{{D}_{1}}-2{{D}_{2}})\lambda }{2d}\]

Assertion : Cyclotron is a device which is used to accelerate the positive ion. Reason : Cyclotron frequency depends upon the velocity. [AIIMS 1997]

If the assertion and reason both are false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : The division are equally marked on the scale of ac ammeter. Reason : Heat produced is directly proportional to the current.

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

On a stationary sail-boat, air is blown at the sails from a fan attached to the boat. The boat will

Move in a direction opposite to that in which air is blown

Move in the direction in which the air is blown

Assertion : For cooking in a microwave oven, food is always kept in metal containers. Reason : The energy of microwave is easily transferred to the food in metal container.

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

Assertion : Vector product of two vectors is an axial vector Reason : If \[\vec{v}\] = instantaneous velocity, \[\vec{r}\]= radius vector and \[\vec{\omega }\] = angular velocity, then \[\vec{\omega }=\vec{v}\times \vec{r}.\]

If the assertion and reason both are false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

A massive platform of mass M is moving with speed \[v=6m{{s}^{-1}}\]. At. \[t=0,\] a body of mass \[m(m

the body covers a distance 3 m on the platform in the direction of motion of the platform

the body covers a distance 3 m on the platform opposite to the direction of motion of platform before coming to rest

the body covers a distance 6 m on the platform in the direction of motion of the platform

the body covers a distance 6 m on the platform opposite to the direction of motion of platform before coming to rest

Two blocks are placed on a wedge with coefficients of friction being different for two blocks. Choose the correct option (friction is not sufficient to prevent the motion).

if\[{{m}_{1}}={{m}_{2}}\]then normal reaction between the blocks will be zero

if\[{{\mu }_{1}}={{\mu }_{2}}\], then normal reaction between the blocks will be zero

Assertion : In photoelectric effect, on increasing the intensity of light, both the number of electrons emitted and kinetic energy of each of them get increased but photoelectric current remains unchanged. Reason : The photoelectric current depends only on wavelength of light.

If assertion is false but reason is true.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

When N-type of semiconductor is heated [CBSE PMT 1993; DPMT 2000]

Number of electrons increases while that of holes decreases

Number of holes increases while that of electrons decreases

Number of electrons and holes remains same

Number of electrons and holes increases equally

Assertion : To hear distinct beats, difference in frequencies of two sources should be less than 10. Reason : More the number of beats per sec more difficult to hear them.

If assertion is true but reason is false.

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

If assertion is false but reason is true.

If two rods A and B of equal length L, and different areas of cross-section \[{{\operatorname{A}}_{1}}\]and\[{{A}_{2}}\]have one end each at temperature\[{{\operatorname{T}}_{1}}\]and \[{{T}_{2}}\], have equal rates of flow of heat, then

\[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{{{K}_{1}}}{{{K}_{2}}}\]

\[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{{{K}_{2}}}{{{K}_{1}}}\]

Huygen?s principle of secondary wavelets may be used to [KCET 2002]

Find the velocity of light in vacuum

Explain the particle behaviour of light

Find the new position of the wavefront

12583 + Mcqs in Physics in Joint Entrance Exam - Main (JEE Main) Page 7 McqOptions

301.	For the series LCR circuit shown in the figure, what is the resonance frequency and the amplitude of the current at the resonating frequency [Kerala PET 2005]
A.	\[2500\,rad-{{s}^{-1}}\] and \[5\sqrt{2}\,A\]
B.	\[2500\,rad-{{s}^{-1}}\] and \[5A\]
C.	\[2500\,rad-{{s}^{-1}}\] and \[\frac{5}{\sqrt{2}}A\]
D.	\[25\,rad-{{s}^{-1}}\] and \[5\sqrt{2}\,A\]
Answer» C. \[2500\,rad-{{s}^{-1}}\] and \[\frac{5}{\sqrt{2}}A\]

Discussion

302.	Assertion : Sound travel faster in solids than gases. Reason : Solid possess greater density than gases. [AIIMS 2000]
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.

Discussion

303.	The wavelength of X-rays is of the order of [CPMT 1983; MP PMT 1987; KCET 1994; JIPMER 1997]
A.	Centimetre
B.	Micron (10-6 m)
C.	Angstrom (10-10 m)
D.	Metre
Answer» D. Metre

Discussion

304.	Water does not wet an oily glass because
A.	Cohesive force of oil>> adhesive force between oil and glass
B.	Cohesive force of oil > cohesive force of water
C.	Oil repels water
D.	Cohesive force for water > adhesive force between water and oil molecules
Answer» E.

Discussion

305.	Two identical wires of rubber and iron are stretched by the same weight, then the number of atoms in the iron wire will be [DPMT 1999]
A.	Equal to that of rubber
B.	Less than that of the rubber
C.	More than that of the rubber
D.	None of the above
Answer» D. None of the above

Discussion

306.	Assertion : If different gases are filled turn by turn at the same pressure in the discharge tube the discharge in them takes place at the same potential. Reason : The discharge depends only on the pressure of discharge tube and not on the ionisation potential of gas.
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.

Discussion

307.	Assertion : In everyday life the Doppler?s effect is observed readily for sound waves than light waves. Reason : Velocity of light is greater than that of sound. [AIIMS 1995]
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.

Discussion

308.	Assertion : In Young?s experiment, the fringe width for dark fringes is different from that for white fringes. Reason : In Young?s double slit experiment the fringes are performed with a source of white light, then only black and bright fringes are observed. [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» E. If assertion is false but reason is true.

Discussion

309.	A brass disc fits simply in a hole of a steel plate. The disc from the hole can be loosened if the system [UPSEAT 2001]
A.	First heated then cooled
B.	First cooled then heated
C.	Is heated
D.	Is cooled
Answer» E.

Discussion

310.	A mass M is suspended from a spring of negligible mass. The spring is pulled a little and then released so that the mass executes simple harmonic oscillations with a time period T. If the mass is increased by m then the time period becomes \[\left( \frac{5}{4}T \right)\]. The ratio of \[T\frac{p}{p-1}\] is [CPMT 1991]
A.	9/16
B.	25/16
C.	4/5
D.	5/4
Answer» B. 25/16

Discussion

311.	The self-induced e.m.f. in a 0.1 H coil when the current in it is changing at the rate of 200 ampere/second is [DPMT 2002]
A.	\[8\times {{10}^{-4}}\,V\]
B.	\[8\times {{10}^{-5}}\,V\]
C.	\[20\,V\]
D.	\[125\,V\]
Answer» D. \[125\,V\]

Discussion

312.	Assertion : The focal length of lens does not change when red light is replaced by blue light. Reason : The focal length of lens does not depends on colour of light used.
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.

Discussion

313.	In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of photoelectrons will become
A.	Double
B.	Half
C.	Four time
D.	No change
Answer» E.

Discussion

314.	A particle has displacement of 12 m towards east and 5 m towards north then 6 m vertically upward. The sum of these displacements is [AIIMS 1998]
A.	12
B.	10.04 m
C.	14.31 m
D.	None of these
Answer» D. None of these

Discussion

315.	The proton -proton mechanism that accounts for energy production in the sun releases \[26.7\text{ }MeV\]energy for each event. In this process, protons fuse to form an alpha particle \[{{(}^{4}}He)\]. At what rate \[\frac{dm}{dt}\] is hydrogen being consumed in the core of the sun by the p-p cycle? Power of sun is\[3.90\times {{10}^{26}}W\].
A.	\[1.6\times {{10}^{10}}kg/s\]
B.	\[2.3\times {{10}^{9}}kg/s\]
C.	\[6.2\times {{10}^{11}}\,kg/s\]
D.	\[5.5\times {{10}^{10}}\,kg/s\]
Answer» D. \[5.5\times {{10}^{10}}\,kg/s\]

Discussion

316.	Triple point of water is [CPMT 2002]
A.	273.16°F
B.	273.16 K
C.	273.16°C
D.	273.16 R
Answer» C. 273.16°C

Discussion

317.	If prism angle \[\alpha =1{}^\circ ,\ \mu =1.54,\]distance between screen and prism \[(b)=0.7\,m,\] distance between prism and source \[a=0.3\,m,\ \lambda =180\pi \ nm\] then in Fresnal biprism find the value of \[\beta \] (fringe width) [RPMT 2002]
A.	\[{{10}^{-4}}m\]
B.	\[{{10}^{-3}}mm\]
C.	\[{{10}^{-4}}\times \pi m\]
D.	\[\pi \times {{10}^{-3}}m\]
Answer» B. \[{{10}^{-3}}mm\]

Discussion

318.	A uniform rope of length l lies on a table. If the coefficient of friction is \[\mu \], then the maximum length \[{{l}_{1}}\] of the part of this rope which can overhang from the edge of the table without sliding down is [DPMT 2001]
A.	\[\frac{l}{\mu }\]
B.	\[\frac{l}{\mu +l}\]
C.	\[\frac{\mu l}{1+\mu }\]
D.	\[\frac{\mu l}{\mu -1}\]
Answer» D. \[\frac{\mu l}{\mu -1}\]

Discussion

319.	An oscillator circuit consists of an inductance of 0.5mH and a capacitor of 20\[\mu F\]. The resonant frequency of the circuit is nearly [Kerala PET 2002]
A.	15.92 Hz
B.	159.2 Hz
C.	1592 Hz
D.	15910 Hz
Answer» D. 15910 Hz

Discussion

320.	An object 2.5 cm high is placed at a distance of 10 cm from a concave mirror of radius of curvature 30 cm The size of the image is [BVP 2003]
A.	9.2 cm
B.	10.5 cm
C.	5.6 cm
D.	7.5 cm
Answer» E.

Discussion

321.	In a double slit experiment slits \[{{S}_{1}}\], \[{{S}_{2}}\] is illuminated by a coherent light of wavelength\[\lambda \]. The slits are separated by a distance d. The experimental set up is modified by using plane mirrors as shown in figure. Find the fringe width of interference pattern on the screen.
A.	\[\frac{(3{{D}_{1}}+2{{D}_{2}})\lambda }{d}\]
B.	\[\frac{(2{{D}_{1}}+3{{D}_{2}})\lambda }{d}\]
C.	\[\frac{(3{{D}_{2}}-3{{D}_{1}})\lambda }{d}\]
D.	\[\frac{(3{{D}_{1}}-2{{D}_{2}})\lambda }{2d}\]
Answer» B. \[\frac{(2{{D}_{1}}+3{{D}_{2}})\lambda }{d}\]

Discussion

322.	If eight identical drops are joined to form a bigger drop, the potential on bigger as compared to that on smaller drop will be [RPMT 2002]
A.	Double
B.	Four times
C.	Eight times
D.	One time
Answer» C. Eight times

Discussion

323.	The bob of a simple pendulum of mass m and total energy E will have maximum linear momentum equal to
A.	\[\sqrt{\frac{2E}{m}}\]
B.	\[\sqrt{2mE}\]
C.	\[2mE\]
D.	\[m{{E}^{2}}\]
Answer» C. \[2mE\]

Discussion

324.	The elastic limit for a gas
A.	Exists
B.	Exists only at absolute zero
C.	Exists for a perfect gas
D.	Does not exist
Answer» B. Exists only at absolute zero

Discussion

325.	In Young?s double slit experiment, the intensity of light coming from the first slit is double the intensity from the second slit. The ratio of the maximum intensity to the minimum intensity on the interference fringe pattern observed is [KCET 2002]
A.	34
B.	40
C.	25
D.	38
Answer» B. 40

Discussion

326.	The average e.m.f. induced in a coil in which the current changes from 2 ampere to 4 ampere in 0.05 second is 8 volt. What is the self-inductance of the coil? [NCERT 1984; CPMT 1997; MP PMT 1999, 2003; UPSEAT 2000; RPMT 2000; Pb. PMT 2002; RPET 2003; DPMT 2005]
A.	0.1 H
B.	0.2 H
C.	0.4 H
D.	0.8 H
Answer» C. 0.4 H

Discussion

327.	Assertion : Cyclotron is a device which is used to accelerate the positive ion. Reason : Cyclotron frequency depends upon the velocity. [AIIMS 1997]
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.

Discussion

328.	Assertion : The division are equally marked on the scale of ac ammeter. Reason : Heat produced is directly proportional to the current.
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.

Discussion

329.	A spherical drop of mercury having a potential of 2.5 V is obtained as a result of merging 125 droplets. The potential of constituent droplets would be [Orissa JEE 2003]
A.	1.0 V
B.	0.5 V
C.	0.2 V
D.	0.1 V
Answer» E.

Discussion

330.	On a stationary sail-boat, air is blown at the sails from a fan attached to the boat. The boat will
A.	Remain stationary
B.	Spin around
C.	Move in a direction opposite to that in which air is blown
D.	Move in the direction in which the air is blown
Answer» B. Spin around

Discussion

331.	The block of mass M moving on the frictionless horizontal surface collides with the spring of spring constant k and compresses it by length L. The maximum momentum of the block after collision is
A.	\[\frac{k{{L}^{2}}}{2M}\]
B.	\[\sqrt{Mk}L\]
C.	\[\frac{M{{L}^{2}}}{k}\]
D.	zero
Answer» C. \[\frac{M{{L}^{2}}}{k}\]

Discussion

332.	Latent heat of 1gm of steam is 536 cal/gm, then its value in joule/kg is [RPMT 1999]
A.	\[2.25\times {{10}^{6}}\]
B.	\[2.25\times {{10}^{3}}\]
C.	2.25
D.	None
Answer» B. \[2.25\times {{10}^{3}}\]

Discussion

333.	Assertion : For cooking in a microwave oven, food is always kept in metal containers. Reason : The energy of microwave is easily transferred to the food in metal container.
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.

Discussion

334.	The process by which ac is converted into dc is known as [RPMT 1997]
A.	Purification
B.	Amplification
C.	Rectification
D.	Current amplification
Answer» D. Current amplification

Discussion

335.	Assertion : Vector product of two vectors is an axial vector Reason : If \[\vec{v}\] = instantaneous velocity, \[\vec{r}\]= radius vector and \[\vec{\omega }\] = angular velocity, then \[\vec{\omega }=\vec{v}\times \vec{r}.\]
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.

Discussion

336.	A 100 mH coil carries a current of 1 ampere. Energy stored in its magnetic field is [CBSE PMT 1992; KCET 1998]
A.	0.5 J
B.	1 J
C.	0.05 J
D.	0.1 J
Answer» D. 0.1 J

Discussion

337.	A massive platform of mass M is moving with speed \[v=6m{{s}^{-1}}\]. At. \[t=0,\] a body of mass \[m(m<
A.	the body covers a distance 3 m on the platform in the direction of motion of the platform
B.	the body covers a distance 3 m on the platform opposite to the direction of motion of platform before coming to rest
C.	the body covers a distance 6 m on the platform in the direction of motion of the platform
D.	the body covers a distance 6 m on the platform opposite to the direction of motion of platform before coming to rest
Answer» E.

Discussion

338.	If \[{{n}_{e}}\] and \[{{n}_{h}}\] are the number of electrons and holes in a semiconductor heavily doped with phosphorus, then [MP PMT 2000]
A.	\[{{n}_{e}}>>{{n}_{h}}\]
B.	\[{{n}_{e}}<<{{n}_{h}}\]
C.	\[{{n}_{e}}\le {{n}_{h}}\]
D.	\[{{n}_{e}}={{n}_{h}}\]
Answer» B. \[{{n}_{e}}<<{{n}_{h}}\]

Discussion

339.	Two blocks are placed on a wedge with coefficients of friction being different for two blocks. Choose the correct option (friction is not sufficient to prevent the motion).
A.	if\[{{m}_{1}}<{{m}_{2}}\], then normal reaction between blocks will be non-zero
B.	if\[{{m}_{1}}={{m}_{2}}\]then normal reaction between the blocks will be zero
C.	if\[{{\mu }_{1}}={{\mu }_{2}}\], then normal reaction between the blocks will be zero
D.	None of the above
Answer» D. None of the above

Discussion

340.	Assertion : In photoelectric effect, on increasing the intensity of light, both the number of electrons emitted and kinetic energy of each of them get increased but photoelectric current remains unchanged. Reason : The photoelectric current depends only on wavelength of light.
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.

Discussion

341.	\[22\,g\] of \[C{{O}_{2}}\] at \[{{27}^{o}}C\] is mixed with \[16\,g\] of \[{{O}_{2}}\] at \[37{}^\circ C\]. The temperature of the mixture is
A.	\[32{}^\circ C\]
B.	\[27{}^\circ C\]
C.	\[37{}^\circ C\]
D.	\[30.5{}^\circ C\]
Answer» B. \[27{}^\circ C\]

Discussion

342.	Which one of the following is not used to reduce friction [Kerala (Engg.) 2001]
A.	Oil
B.	Ball bearings
C.	Sand
D.	Graphite
Answer» D. Graphite

Discussion

343.	The potential energy of a certain spring when stretched through a distance ?S? is 10 joule. The amount of work (in joule) that must be done on this spring to stretch it through an additional distance ?S? will be [MNR 1991; CPMT 2002; UPSEAT 2000; Pb. PET 2004]
A.	30
B.	40
C.	10
D.	20
Answer» B. 40

Discussion

344.	When N-type of semiconductor is heated [CBSE PMT 1993; DPMT 2000]
A.	Number of electrons increases while that of holes decreases
B.	Number of holes increases while that of electrons decreases
C.	Number of electrons and holes remains same
D.	Number of electrons and holes increases equally
Answer» E.

Discussion

345.	Assertion : To hear distinct beats, difference in frequencies of two sources should be less than 10. Reason : More the number of beats per sec more difficult to hear them.
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.

Discussion

346.	A potential barrier of \[0.50\,V\] exists across a p-n junction. If the depletion region is \[5.0\times {{10}^{-7}}m\]wide, the intensity of the electric field in this region is
A.	\[1.0\times {{10}^{6}}\,V/m\]
B.	\[1.0\times {{10}^{5}}\,V/m\]
C.	\[2.0\times {{10}^{5}}\,V/m\]
D.	\[2.0\times {{10}^{6}}\,V/m\]
Answer» B. \[1.0\times {{10}^{5}}\,V/m\]

Discussion

347.	If two rods A and B of equal length L, and different areas of cross-section \[{{\operatorname{A}}_{1}}\]and\[{{A}_{2}}\]have one end each at temperature\[{{\operatorname{T}}_{1}}\]and \[{{T}_{2}}\], have equal rates of flow of heat, then
A.	\[{{A}_{1}}={{A}_{2}}\]
B.	\[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{{{K}_{1}}}{{{K}_{2}}}\]
C.	\[\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{{{K}_{2}}}{{{K}_{1}}}\]
D.	\[{{K}_{1}}={{K}_{2}}\]
Answer» D. \[{{K}_{1}}={{K}_{2}}\]

Discussion

348.	A light of wavelength\[5890\,\,{AA}\]falls normally on a thin air film. The minimum thickness of the film such that the film appears dark in reflected light [Pb. PMT 2003]
A.	\[2.945\times {{10}^{-7}}m\]
B.	\[3.945\times {{10}^{-7}}m\]
C.	\[4.95\times {{10}^{-7}}m\]
D.	\[1.945\times {{10}^{-7}}m\]
Answer» B. \[3.945\times {{10}^{-7}}m\]

Discussion

349.	An e.m.f. of 12 volt is produced in a coil when the current in it changes at the rate of 45 amp/minute. The inductance of the coil is [MP PET 2000]
A.	0.25 henry
B.	1.5 henry
C.	9.6 henry
D.	16.0 henry
Answer» E.

Discussion

350.	Huygen?s principle of secondary wavelets may be used to [KCET 2002]
A.	Find the velocity of light in vacuum
B.	Explain the particle behaviour of light
C.	Find the new position of the wavefront
D.	Explain photoelectric effect
Answer» D. Explain photoelectric effect

Discussion

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