Assertion : When the lift moves with uniform velocity the man in the lift will feel weightlessness. Reason : In downward accelerated motion of lift, apparent weight of a body decreases.

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 body cools in a surrounding which is at a constant temperature of \[{{\theta }_{0}}\]. Assume that it obeys Newton's law of cooling. Its temperature\[\theta \]is plotted against time t. Tangents are drawn to the curve at the points\[P\left( \theta ={{\theta }_{2}} \right)\]and\[Q\left( \theta ={{\theta }_{1}} \right)\]. These tangents meet the time axis at angle of\[{{\phi }_{2}}\] and \[{{\phi }_{1}}\], as shown, then

\[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{1}}}{{{\theta }_{2}}}\]

\[\frac{\tan {{\phi }_{2}}}{\tan {{\phi }_{1}}}=\frac{{{\theta }_{1}}-{{\theta }_{0}}}{{{\theta }_{2}}-{{\theta }_{0}}}\]

\[\frac{\tan {{\phi }_{2}}}{\tan {{\phi }_{1}}}=\frac{{{\theta }_{2}}-{{\theta }_{0}}}{{{\theta }_{1}}-{{\theta }_{0}}}\]

\[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{1}}}{{{\theta }_{2}}}\]

\[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{2}}}{{{\theta }_{1}}}\]

The YDSE apparatus is as shown in Fig. The condition for point P to be a dark fringe is

\[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=\frac{(2n-1)\lambda }{2}\]

\[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=n\lambda \]

\[({{l}_{1}}-{{l}_{2}})+({{l}_{3}}-{{l}_{4}})=\frac{(2n-1)}{2}\lambda \]

\[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=\frac{(2n-1)\lambda }{2}\]

\[({{l}_{1}}-{{l}_{2}})+({{l}_{4}}-{{l}_{3}})=\frac{(2n-1)\lambda }{2}\]

What is the effect on Fresnel?s biprism experiment when the use of white light is made [RPMT 1998]

Diffraction pattern is spread more

Central fringe is white and all are coloured

Consider the three waves \[{{z}_{1}},{{z}_{2}}\] and \[{{z}_{3}}\] as \[{{z}_{1}}=A\sin (kx-\omega \,t)\], \[{{z}_{2}}=A\sin (kx+\omega \,t)\] and \[{{z}_{3}}=A\sin (ky-\omega \,t)\]. Which of the following represents a standing wave [DCE 2004]

\[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}\]

Stopping potential for photoelectrons

Depends upon the intensity of the incident light

Does not depend on the frequency of the incident light

Does not depend upon the nature of the cathode material

Depends on both the frequency of the incident light and nature of the cathode material

Depends upon the intensity of the incident light

When NPN transistor is used as an amplifier

electrons move from base to emitter

holes move from emitter to base

electrons move from collector to base

holes move from base to emitter

A block rests on a horizontal table which is executing SHM in the horizontal plane with an amplitude 'a'. If the coefficient of friction is \['\mu '\], then the block just starts to slip when the frequency of oscillation is

\[\frac{1}{2\pi }\sqrt{\frac{\mu g}{a}}\]

\[2\pi \sqrt{\frac{a}{\mu g}}\]

When a body is taken from the equator to the poles, its weight [EAMCET 1978]

Increases at N-pole and decreases at S-pole

In extrinsic semiconductors [EAMCET (Engg.) 1999]

The gap between conduction band and valence band will be 100 eV and more

The conduction band and valence band overlap

The gap between conduction band and valence band is more than 16 eV

The gap between conduction band and valence band is near about 1 eV

The gap between conduction band and valence band will be 100 eV and more

A mass m is suspended separately by two different springs of spring constant K1 and K2 gives the time-period \[{{t}_{1}}\] and \[{{t}_{2}}\]respectively. If same mass m is connected by both springs as shown in figure then time-period t is given by the relation [CBSE PMT 2002]

\[t=\frac{{{t}_{1}}.{{t}_{2}}}{{{t}_{1}}+{{t}_{2}}}\]

\[{{t}^{2}}={{t}_{1}}^{2}+{{t}_{2}}^{2}\]

\[{{t}^{-2}}={{t}_{1}}^{-2}+{{t}_{2}}^{-2}\]

A particle of mass m oscillates with a potential energy\[U={{U}_{0}}+\alpha \,\,{{x}^{2}}\], where \[{{U}_{0}}\] and a are constants and x is the displacement of particle from equilibrium position. The time period of oscillation is

\[\pi \sqrt{\frac{2m}{\alpha }}\]

\[2\pi \sqrt{\frac{m}{\alpha }}\]

\[2\pi \sqrt{\frac{m}{2\alpha }}\]

\[\pi \sqrt{\frac{2m}{\alpha }}\]

\[2\pi \sqrt{\frac{m}{{{\alpha }^{2}}}}\]

Universal time is based on [SCRA 1989]

Rotation of the earth on its axis

Earth's orbital motion around the earth

For moving ball of cricket, the correct statement about de-Broglie wavelength is

It is not applicable for such big particle

A pendulum clock keeps correct time at \[0{}^\circ C\]. Its mean coefficient of linear expansions is a\[{{\alpha }^{o}}{{C}^{-1}}\]. The loss in seconds per day by the clock if the temperature rises by \[t{}^\circ C\] is

\[\frac{\frac{1}{2}\alpha \,t\times 86400}{{{\left( 1+\frac{\alpha \,t}{2} \right)}^{2}}}\]

\[\frac{\frac{1}{2}\alpha t\times 864000}{1-\frac{\alpha \,t}{2}}\]

\[\frac{1}{2}\alpha \,t\times 86400\]

\[\frac{\frac{1}{2}\alpha \,t\times 86400}{{{\left( 1+\frac{\alpha \,t}{2} \right)}^{2}}}\]

\[\frac{\frac{1}{2}\alpha \,t\times 86400}{1+\frac{\alpha \,t}{2}}\]

A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance [AFMC 1996; AIIMS 2000; Pb. PET 2000]

First increases then decreases to zero

Assertion : When radius of circular loop carrying current is doubled, its magnetic moment becomes four times. Reason : Magnetic moment depends on area of the loop.

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.

The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the [AIEEE 2003]

Variation of scattering mechanism with temperature

Variation of the number of charge carriers with temperature

12583 + Mcqs in Physics in Joint Entrance Exam - Main (JEE Main) Page 2 McqOptions

51.	Two identical piano wires kept under the same tension T have a fundamental frequency of 600 Hz. The fractional increase in the tension of one of the wires which will lead to occurrence of 6 beats/s when both the wires oscillate together would be
A.	0.02
B.	0.03
C.	0.04
D.	0.01
Answer» B. 0.03

Discussion

52.	The voltage gain of a triode depends upon [CPMT 1992]
A.	Filament voltage
B.	Plate voltage
C.	Plate resistance
D.	Plate current
Answer» D. Plate current

Discussion

53.	A hammer of mass 1 kg having speed of 50 m/s, hit a iron nail of mass 200 gm. If specific heat of iron is \[0.105 cal/gm\,{}^\circ C\]and half the energy is converted into heat. the raise in temperature of nail is
A.	\[7.1{}^\circ C\]
B.	\[9.2{}^\circ C\]
C.	\[10.5{}^\circ C\]
D.	\[12.1{}^\circ C\]
Answer» B. \[9.2{}^\circ C\]

Discussion

54.	DIRECTION: Read the passage given below and answer the questions that follows: In a thermally insulated tube of cross sectional area \[\frac{GMm}{2R}\] a liquid of thermal expansion coefficient \[{{10}^{-3}}\,{{K}^{-1}}\] is flowing. Its velocity at the entrance is \[0.1\text{ }m/s\]. At the middle of the tube a heater of a power of 10kW is heating the liquid. The specific heat capacity of the liquid is 1.5 kJ/(kg K), and its density is \[1500\text{ }kg/{{m}^{3}}\] at the entrance. What is the density of liquid at the exit?
A.	1450 kg/m3
B.	1400 kg/m3
C.	1350 kg/m3
D.	None of these
Answer» D. None of these

Discussion

55.	Assertion : When the lift moves with uniform velocity the man in the lift will feel weightlessness. Reason : In downward accelerated motion of lift, apparent weight of a body decreases.
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» F.

Discussion

56.	A body cools in a surrounding which is at a constant temperature of \[{{\theta }_{0}}\]. Assume that it obeys Newton's law of cooling. Its temperature\[\theta \]is plotted against time t. Tangents are drawn to the curve at the points\[P\left( \theta ={{\theta }_{2}} \right)\]and\[Q\left( \theta ={{\theta }_{1}} \right)\]. These tangents meet the time axis at angle of\[{{\phi }_{2}}\] and \[{{\phi }_{1}}\], as shown, then
A.	\[\frac{\tan {{\phi }_{2}}}{\tan {{\phi }_{1}}}=\frac{{{\theta }_{1}}-{{\theta }_{0}}}{{{\theta }_{2}}-{{\theta }_{0}}}\]
B.	\[\frac{\tan {{\phi }_{2}}}{\tan {{\phi }_{1}}}=\frac{{{\theta }_{2}}-{{\theta }_{0}}}{{{\theta }_{1}}-{{\theta }_{0}}}\]
C.	\[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{1}}}{{{\theta }_{2}}}\]
D.	\[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{2}}}{{{\theta }_{1}}}\]
Answer» C. \[\frac{\tan {{\phi }_{1}}}{\tan {{\phi }_{2}}}=\frac{{{\theta }_{1}}}{{{\theta }_{2}}}\]

Discussion

57.	What will be the input of A and B for the Boolean expression \[(\overline{A+B}.()\overline{A.B\,\,\,})=1\]
A.	\[0,\,\,0\]
B.	\[0,\,\,1\]
C.	\[1,\,\,0\]
D.	\[1,\,\,1\]
Answer» B. \[0,\,\,1\]

Discussion

58.	The YDSE apparatus is as shown in Fig. The condition for point P to be a dark fringe is
A.	\[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=n\lambda \]
B.	\[({{l}_{1}}-{{l}_{2}})+({{l}_{3}}-{{l}_{4}})=\frac{(2n-1)}{2}\lambda \]
C.	\[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=\frac{(2n-1)\lambda }{2}\]
D.	\[({{l}_{1}}-{{l}_{2}})+({{l}_{4}}-{{l}_{3}})=\frac{(2n-1)\lambda }{2}\]
Answer» C. \[({{l}_{1}}-{{l}_{3}})+({{l}_{2}}-{{l}_{4}})=\frac{(2n-1)\lambda }{2}\]

Discussion

59.	X-rays when incident on a metal [BCECE 2003; RPMT 2003]
A.	Exert a force on it
B.	Transfer energy to it
C.	Transfer pressure to it
D.	All of the above
Answer» E.

Discussion

60.	What happens to the fringe pattern when the Young?s double slit experiment is performed in water instead or air then fringe width [AFMC 2005]
A.	Shrinks
B.	Disappear
C.	Unchanged
D.	Enlarged
Answer» B. Disappear

Discussion

61.	If Fresnel?s biprism experiment as held in water inspite of air, then what will be the effect on fringe width [RPMT 1997, 98]
A.	Decrease
B.	Increase
C.	No effect
D.	None of these
Answer» B. Increase

Discussion

62.	What is the effect on Fresnel?s biprism experiment when the use of white light is made [RPMT 1998]
A.	Fringe are affected
B.	Diffraction pattern is spread more
C.	Central fringe is white and all are coloured
D.	None of these
Answer» D. None of these

Discussion

63.	The electrical circuit used to get smooth \[dc\] output from a rectifier circuit is called [KCET 2003]
A.	Oscillator
B.	Filter
C.	Amplifier
D.	Logic gates
Answer» C. Amplifier

Discussion

64.	A beaker contains 200 gm of water. The heat capacity of the beaker is equal to that of 20 gm of water. The initial temperature of water in the beaker is\[20{}^\circ C\]. If 40 gm of hot water at \[92{}^\circ C\] is poured in it, the final temperature (neglecting radiation loss) will be nearest to
A.	\[58{}^\circ C\]
B.	\[68{}^\circ C\]
C.	\[73{}^\circ C\]
D.	\[78{}^\circ C\]
Answer» C. \[73{}^\circ C\]

Discussion

65.	Starting from the origin a body oscillates simple harmonically with a period of 2 s. After what time will its kinetic energy be 75% of the total energy?
A.	\[\frac{1}{6}s\]
B.	\[\frac{1}{4}s\]
C.	\[\frac{1}{3}s\]
D.	\[\frac{1}{12}s\]
Answer» B. \[\frac{1}{4}s\]

Discussion

66.	Consider the three waves \[{{z}_{1}},{{z}_{2}}\] and \[{{z}_{3}}\] as \[{{z}_{1}}=A\sin (kx-\omega \,t)\], \[{{z}_{2}}=A\sin (kx+\omega \,t)\] and \[{{z}_{3}}=A\sin (ky-\omega \,t)\]. Which of the following represents a standing wave [DCE 2004]
A.	\[{{z}_{1}}+{{z}_{2}}\]
B.	\[{{z}_{2}}+{{z}_{3}}\]
C.	\[{{z}_{3}}+{{z}_{1}}\]
D.	\[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}\]
Answer» B. \[{{z}_{2}}+{{z}_{3}}\]

Discussion

67.	Two travelling waves \[{{y}_{1}}=A\sin [k(x-c\,t)]\] and \[{{y}_{2}}=A\sin [k(x+c\,t)]\] are superimposed on string. The distance between adjacent nodes is [IIT 1992]
A.	\[c\,t/\pi \]
B.	\[c\,t/2\pi \]
C.	\[\pi /2k\]
D.	\[\pi /k\]
Answer» E.

Discussion

68.	4 eV is the energy of the incident photon and the work function in \[2eV.\] What is the stopping potential
A.	2V
B.	4V
C.	6V
D.	\[2\sqrt{2}V\]
Answer» B. 4V

Discussion

69.	Stopping potential for photoelectrons
A.	Does not depend on the frequency of the incident light
B.	Does not depend upon the nature of the cathode material
C.	Depends on both the frequency of the incident light and nature of the cathode material
D.	Depends upon the intensity of the incident light
Answer» D. Depends upon the intensity of the incident light

Discussion

70.	A thin sheet of mica (\[\mu \] m thick) is placed in the path of one of the interfering beams in a biprism arrangement. It is found that the central bright band shifts a distance equal to the width of a bright fringe. The refractive index of mica \[(Given\,\,\lambda =6\times {{10}^{-7}}\,m)\] is
A.	1.0
B.	1.5
C.	1.75
D.	1.25
Answer» C. 1.75

Discussion

71.	A body goes 10 km north and 20 km east. What will be the displacement from initial point?
A.	22.36 km
B.	2 km
C.	5 km
D.	30 km
Answer» B. 2 km

Discussion

72.	If R is the radius of the earth and g the acceleration due to gravity on the earth's surface, the mean density of the earth is [CPMT 1990; BHU 1998; Kerala PMT 2002; MH CET (Med.) 1999; CBSE PMT 1995]
A.	\[4\pi G/3gR\]
B.	\[3\pi R/4gG\]
C.	\[3g/4\pi RG\]
D.	\[\pi RG/12G\]
Answer» D. \[\pi RG/12G\]

Discussion

73.	The equation of a wave on a string of linear mass density \[0.04kg\,{{m}^{-1}}\] is given by \[y=0.02(m)\sin \left[ 2\pi \left( \frac{1}{0.04(s)}-\frac{x}{0.50(m)} \right) \right]\] The tension in the string is
A.	4.0 N
B.	12.5 N
C.	0.5 N
D.	6.25 N
Answer» E.

Discussion

74.	To determine the Young's modulus of a wire, the formula is \[Y=\frac{F}{A}:\frac{L}{\Delta L};\] where \[L\] = length, \[A=\]area of cross-section of the wire, \[\Delta L=\]change in length of the wire when stretched with a force \[F\]. The conversion factor to change it from CGS to MKS system is [MP PET 1983]
A.	1
B.	10
C.	0.1
D.	0.01
Answer» D. 0.01

Discussion

75.	When NPN transistor is used as an amplifier
A.	electrons move from base to emitter
B.	holes move from emitter to base
C.	electrons move from collector to base
D.	holes move from base to emitter
Answer» E.

Discussion

76.	A block rests on a horizontal table which is executing SHM in the horizontal plane with an amplitude 'a'. If the coefficient of friction is \['\mu '\], then the block just starts to slip when the frequency of oscillation is
A.	\[\frac{1}{2\pi }\sqrt{\frac{\mu g}{a}}\]
B.	\[\sqrt{\frac{\mu g}{a}}\]
C.	\[2\pi \sqrt{\frac{a}{\mu g}}\]
D.	\[\sqrt{\frac{a}{\mu g}}\]
Answer» B. \[\sqrt{\frac{\mu g}{a}}\]

Discussion

77.	When a body is taken from the equator to the poles, its weight [EAMCET 1978]
A.	Remains constant
B.	Increases
C.	Decreases
D.	Increases at N-pole and decreases at S-pole
Answer» C. Decreases

Discussion

78.	The instantaneous displacement of a simple pendulum oscillator is given by \[x=A\cos \left( \omega t+\frac{\pi }{4} \right)\]. Its speed will be maximum at time [CPMT 2000]
A.	\[\frac{\pi }{4\omega }\]
B.	\[\frac{\pi }{2\omega }\]
C.	\[\frac{\pi }{\omega }\]
D.	\[\frac{2\pi }{\omega }\]
Answer» B. \[\frac{\pi }{2\omega }\]

Discussion

79.	In extrinsic semiconductors [EAMCET (Engg.) 1999]
A.	The conduction band and valence band overlap
B.	The gap between conduction band and valence band is more than 16 eV
C.	The gap between conduction band and valence band is near about 1 eV
D.	The gap between conduction band and valence band will be 100 eV and more
Answer» D. The gap between conduction band and valence band will be 100 eV and more

Discussion

80.	A particle executing simple harmonic motion has an amplitude of 6 cm. Its acceleration at a distance of 2 cm from the mean position is \[8\,cm/{{s}^{2}}\]. The maximum speed of the particle is [EAMCET (Engg.) 2000]
A.	8 cm/s
B.	12 cm/s
C.	16 cm/s
D.	24 cm/s
Answer» B. 12 cm/s

Discussion

81.	A mass m is suspended separately by two different springs of spring constant K1 and K2 gives the time-period \[{{t}_{1}}\] and \[{{t}_{2}}\]respectively. If same mass m is connected by both springs as shown in figure then time-period t is given by the relation [CBSE PMT 2002]
A.	\[t={{t}_{1}}+{{t}_{2}}\]
B.	\[t=\frac{{{t}_{1}}.{{t}_{2}}}{{{t}_{1}}+{{t}_{2}}}\]
C.	\[{{t}^{2}}={{t}_{1}}^{2}+{{t}_{2}}^{2}\]
D.	\[{{t}^{-2}}={{t}_{1}}^{-2}+{{t}_{2}}^{-2}\]
Answer» E.

Discussion

82.	A particle of mass m oscillates with a potential energy\[U={{U}_{0}}+\alpha \,\,{{x}^{2}}\], where \[{{U}_{0}}\] and a are constants and x is the displacement of particle from equilibrium position. The time period of oscillation is
A.	\[2\pi \sqrt{\frac{m}{\alpha }}\]
B.	\[2\pi \sqrt{\frac{m}{2\alpha }}\]
C.	\[\pi \sqrt{\frac{2m}{\alpha }}\]
D.	\[2\pi \sqrt{\frac{m}{{{\alpha }^{2}}}}\]
Answer» C. \[\pi \sqrt{\frac{2m}{\alpha }}\]

Discussion

83.	Universal time is based on [SCRA 1989]
A.	Rotation of the earth on its axis
B.	Earth's orbital motion around the earth
C.	Vibrations of cesium atom
D.	Oscillations of quartz crystal
Answer» D. Oscillations of quartz crystal

Discussion

84.	Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is\[\pi /2\] at point A and n at point B. Then the difference between the resultant intensities at\[\pi \] and B is
A.	\[2I\]
B.	\[4I\]
C.	\[5I\]
D.	\[7I\]
Answer» C. \[5I\]

Discussion

85.	A constant volume gas thermometer shows pressure reading of 50cm and 90cm of mercury at 0°C and 100°C respectively. When the pressure reading is 60 cm of mercury, the temperature is [MNR 1991; UPSEAT 2000; Pb. CET 2004]
A.	25°C
B.	40°C
C.	15°C
D.	12.5°C
Answer» B. 40°C

Discussion

86.	For moving ball of cricket, the correct statement about de-Broglie wavelength is
A.	It is not applicable for such big particle
B.	\[\frac{h}{\sqrt{2mE}}\]
C.	\[\sqrt{\frac{h}{2mE}}\]
D.	\[\frac{h}{2mE}\]
Answer» C. \[\sqrt{\frac{h}{2mE}}\]

Discussion

87.	Two particles are executing simple harmonic motion of the same amplitude A and frequency \[\omega \] along the x-axis. Their mean position is separated by distance\[{{X}_{0}}({{X}_{0}}>A)\]. If the maximum separation between them is \[({{X}_{0}}+A)\], the phase difference between their motion is
A.	\[\frac{\pi }{3}\]
B.	\[\frac{\pi }{4}\]
C.	\[\frac{\pi }{6}\]
D.	\[\frac{\pi }{2}\]
Answer» B. \[\frac{\pi }{4}\]

Discussion

88.	Equation of a progressive wave is given by \[y=4\sin \left[ \pi \left( \frac{1}{5}-\frac{x}{9} \right)+\frac{\pi }{6} \right]\] Then which of the following is correct?
A.	v = 5cm
B.	\[\lambda =18cm\]
C.	a = 0.04 cm
D.	f=50Hz
Answer» C. a = 0.04 cm

Discussion

89.	On increasing the reverse bias to a large value in a PN-junction diode, current [MP PMT 1994; BHU 2002]
A.	Increases slowly
B.	Remains fixed
C.	Suddenly increases
D.	Decreases slowly
Answer» D. Decreases slowly

Discussion

90.	A pendulum clock keeps correct time at \[0{}^\circ C\]. Its mean coefficient of linear expansions is a\[{{\alpha }^{o}}{{C}^{-1}}\]. The loss in seconds per day by the clock if the temperature rises by \[t{}^\circ C\] is
A.	\[\frac{\frac{1}{2}\alpha t\times 864000}{1-\frac{\alpha \,t}{2}}\]
B.	\[\frac{1}{2}\alpha \,t\times 86400\]
C.	\[\frac{\frac{1}{2}\alpha \,t\times 86400}{{{\left( 1+\frac{\alpha \,t}{2} \right)}^{2}}}\]
D.	\[\frac{\frac{1}{2}\alpha \,t\times 86400}{1+\frac{\alpha \,t}{2}}\]
Answer» C. \[\frac{\frac{1}{2}\alpha \,t\times 86400}{{{\left( 1+\frac{\alpha \,t}{2} \right)}^{2}}}\]

Discussion

91.	What is the current in the circuit shown below [AFMC 2000; RPMT 2001]
A.	0 amp
B.	\[{{10}^{-2}}\]amp
C.	1 amp
D.	0.10 amp
Answer» B. \[{{10}^{-2}}\]amp

Discussion

92.	In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is [UPSEAT 2004]
A.	5/27
B.	1/93
C.	4/9
D.	3/2
Answer» B. 1/93

Discussion

93.	Consider the following I. Waves created on the surfaces of a water pond by a vibrating sources. II. Wave created by an oscillating electric field in air. III. Sound waves travelling under water. Which of these can be polarized [AMU 2001]
A.	I and II
B.	II only
C.	II and III
D.	I, II and III
Answer» C. II and III

Discussion

94.	A medium can carry a longitudinal wave because it has the property of [KCET 1994]
A.	Mass
B.	Density
C.	Compressibility
D.	Elasticity
Answer» E.

Discussion

95.	A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance [AFMC 1996; AIIMS 2000; Pb. PET 2000]
A.	First increases then decreases to zero
B.	Decreases
C.	Increases
D.	Remains same
Answer» B. Decreases

Discussion

96.	An unknown frequency x produces 8 beats per seconds with a frequency of 250 Hz and 12 beats with 270 Hz source, then x is [CPMT 1997; KCET 2000]
A.	258 Hz
B.	242 Hz
C.	262 Hz
D.	282 Hz
Answer» B. 242 Hz

Discussion

97.	A wire of diameter 1mm breaks under a tension of 1000 N. Another wire, of same material as that of the first one, but of diameter 2 mm breaks under a tension of [Orissa JEE 2003]
A.	500 N
B.	1000 N
C.	10000 N
D.	4000 N
Answer» E.

Discussion

98.	Assertion : When radius of circular loop carrying current is doubled, its magnetic moment becomes four times. Reason : Magnetic moment depends on area of the loop.
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

99.	One nanometre is equal to [SCRA 1986; MNR 1986]
A.	\[{{10}^{9}}mm\].
B.	\[{{10}^{-6}}\,cm\]
C.	\[{{10}^{-7}}cm\]
D.	\[{{10}^{-9}}cm\]
Answer» D. \[{{10}^{-9}}cm\]

Discussion

100.	The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the [AIEEE 2003]
A.	Variation of scattering mechanism with temperature
B.	Crystal structure
C.	Variation of the number of charge carriers with temperature
D.	Type of bon
Answer» D. Type of bon

Discussion

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

Two identical piano wires kept under the same tension T have a fundamental frequency of 600 Hz. The fractional increase in the tension of one of the wires which will lead to occurrence of 6 beats/s when both the wires oscillate together would be

The voltage gain of a triode depends upon [CPMT 1992]

A hammer of mass 1 kg having speed of 50 m/s, hit a iron nail of mass 200 gm. If specific heat of iron is \[0.105 cal/gm\,{}^\circ C\]and half the energy is converted into heat. the raise in temperature of nail is

Assertion : When the lift moves with uniform velocity the man in the lift will feel weightlessness. Reason : In downward accelerated motion of lift, apparent weight of a body decreases.

What will be the input of A and B for the Boolean expression \[(\overline{A+B}.()\overline{A.B\,\,\,})=1\]

The YDSE apparatus is as shown in Fig. The condition for point P to be a dark fringe is

X-rays when incident on a metal [BCECE 2003; RPMT 2003]

What happens to the fringe pattern when the Young?s double slit experiment is performed in water instead or air then fringe width [AFMC 2005]

If Fresnel?s biprism experiment as held in water inspite of air, then what will be the effect on fringe width [RPMT 1997, 98]

What is the effect on Fresnel?s biprism experiment when the use of white light is made [RPMT 1998]

The electrical circuit used to get smooth \[dc\] output from a rectifier circuit is called [KCET 2003]

A beaker contains 200 gm of water. The heat capacity of the beaker is equal to that of 20 gm of water. The initial temperature of water in the beaker is\[20{}^\circ C\]. If 40 gm of hot water at \[92{}^\circ C\] is poured in it, the final temperature (neglecting radiation loss) will be nearest to

Starting from the origin a body oscillates simple harmonically with a period of 2 s. After what time will its kinetic energy be 75% of the total energy?

Consider the three waves \[{{z}_{1}},{{z}_{2}}\] and \[{{z}_{3}}\] as \[{{z}_{1}}=A\sin (kx-\omega \,t)\], \[{{z}_{2}}=A\sin (kx+\omega \,t)\] and \[{{z}_{3}}=A\sin (ky-\omega \,t)\]. Which of the following represents a standing wave [DCE 2004]

Two travelling waves \[{{y}_{1}}=A\sin [k(x-c\,t)]\] and \[{{y}_{2}}=A\sin [k(x+c\,t)]\] are superimposed on string. The distance between adjacent nodes is [IIT 1992]

4 eV is the energy of the incident photon and the work function in \[2eV.\] What is the stopping potential

Stopping potential for photoelectrons

A thin sheet of mica (\[\mu \] m thick) is placed in the path of one of the interfering beams in a biprism arrangement. It is found that the central bright band shifts a distance equal to the width of a bright fringe. The refractive index of mica \[(Given\,\,\lambda =6\times {{10}^{-7}}\,m)\] is

A body goes 10 km north and 20 km east. What will be the displacement from initial point?

If R is the radius of the earth and g the acceleration due to gravity on the earth's surface, the mean density of the earth is [CPMT 1990; BHU 1998; Kerala PMT 2002; MH CET (Med.) 1999; CBSE PMT 1995]

The equation of a wave on a string of linear mass density \[0.04kg\,{{m}^{-1}}\] is given by \[y=0.02(m)\sin \left[ 2\pi \left( \frac{1}{0.04(s)}-\frac{x}{0.50(m)} \right) \right]\] The tension in the string is

When NPN transistor is used as an amplifier

A block rests on a horizontal table which is executing SHM in the horizontal plane with an amplitude 'a'. If the coefficient of friction is \['\mu '\], then the block just starts to slip when the frequency of oscillation is

When a body is taken from the equator to the poles, its weight [EAMCET 1978]

The instantaneous displacement of a simple pendulum oscillator is given by \[x=A\cos \left( \omega t+\frac{\pi }{4} \right)\]. Its speed will be maximum at time [CPMT 2000]

In extrinsic semiconductors [EAMCET (Engg.) 1999]

A particle executing simple harmonic motion has an amplitude of 6 cm. Its acceleration at a distance of 2 cm from the mean position is \[8\,cm/{{s}^{2}}\]. The maximum speed of the particle is [EAMCET (Engg.) 2000]

A mass m is suspended separately by two different springs of spring constant K1 and K2 gives the time-period \[{{t}_{1}}\] and \[{{t}_{2}}\]respectively. If same mass m is connected by both springs as shown in figure then time-period t is given by the relation [CBSE PMT 2002]

A particle of mass m oscillates with a potential energy\[U={{U}_{0}}+\alpha \,\,{{x}^{2}}\], where \[{{U}_{0}}\] and a are constants and x is the displacement of particle from equilibrium position. The time period of oscillation is

Universal time is based on [SCRA 1989]

Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is\[\pi /2\] at point A and n at point B. Then the difference between the resultant intensities at\[\pi \] and B is

A constant volume gas thermometer shows pressure reading of 50cm and 90cm of mercury at 0°C and 100°C respectively. When the pressure reading is 60 cm of mercury, the temperature is [MNR 1991; UPSEAT 2000; Pb. CET 2004]

For moving ball of cricket, the correct statement about de-Broglie wavelength is

Two particles are executing simple harmonic motion of the same amplitude A and frequency \[\omega \] along the x-axis. Their mean position is separated by distance\[{{X}_{0}}({{X}_{0}}>A)\]. If the maximum separation between them is \[({{X}_{0}}+A)\], the phase difference between their motion is

Equation of a progressive wave is given by \[y=4\sin \left[ \pi \left( \frac{1}{5}-\frac{x}{9} \right)+\frac{\pi }{6} \right]\] Then which of the following is correct?

On increasing the reverse bias to a large value in a PN-junction diode, current [MP PMT 1994; BHU 2002]

A pendulum clock keeps correct time at \[0{}^\circ C\]. Its mean coefficient of linear expansions is a\[{{\alpha }^{o}}{{C}^{-1}}\]. The loss in seconds per day by the clock if the temperature rises by \[t{}^\circ C\] is

What is the current in the circuit shown below [AFMC 2000; RPMT 2001]

In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is [UPSEAT 2004]

Consider the following I. Waves created on the surfaces of a water pond by a vibrating sources. II. Wave created by an oscillating electric field in air. III. Sound waves travelling under water. Which of these can be polarized [AMU 2001]

A medium can carry a longitudinal wave because it has the property of [KCET 1994]

A man is standing at a spring platform. Reading of spring balance is 60 kg wt. If man jumps outside platform, then reading of spring balance [AFMC 1996; AIIMS 2000; Pb. PET 2000]

An unknown frequency x produces 8 beats per seconds with a frequency of 250 Hz and 12 beats with 270 Hz source, then x is [CPMT 1997; KCET 2000]

A wire of diameter 1mm breaks under a tension of 1000 N. Another wire, of same material as that of the first one, but of diameter 2 mm breaks under a tension of [Orissa JEE 2003]

Assertion : When radius of circular loop carrying current is doubled, its magnetic moment becomes four times. Reason : Magnetic moment depends on area of the loop.

One nanometre is equal to [SCRA 1986; MNR 1986]

The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the [AIEEE 2003]