12583 + Mcqs in Physics Page 187 McqOptions

9301.	64 drops each having the capacity \[C\] and potential \[V\]are combined to form a big drop. If the charge on the small drop is\[q\], then the charge on the big drop will be [MP PET 1985; MP PET/PMT 1988; CPMT 1971]
A.	\[2q\]
B.	\[4q\]
C.	\[16q\]
D.	\[64q\]
Answer» E.

Discussion

9302.	The distance between the circular plates of a parallel plate condenser \[40mm\] in diameter, in order to have same capacity as a sphere of radius \[1\ metre\]is [MP PET 1992]
A.	\[0.01mm\]
B.	0.1 \[mm\]
C.	1.0 \[mm\]
D.	10 \[mm\]
Answer» C. 1.0 \[mm\]

Discussion

9303.	Two sound waves of slightly different frequencies propagating in the same direction produce beats due to [MP PET 2000]
A.	Interference
B.	Diffraction
C.	Polarization
D.	Refraction
Answer» B. Diffraction

Discussion

9304.	Maximum number of beats frequency heard by a human being is [RPMT 2000]
A.	10
B.	4
C.	20
D.	6
Answer» B. 4

Discussion

9305.	\[{{F}_{g}}\] and \[{{F}_{e}}\] represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm. The ratio of \[{{F}_{g}}/{{F}_{e}}\] is of the order of [NCERT 1978; CPMT 1978]
A.	\[{{10}^{42}}\]
B.	10
C.	1
D.	\[{{10}^{-43}}\]
Answer» E.

Discussion

9306.	In supplying 400 calories of heat to a system, the work done will be [MP PMT 1989]
A.	400 joules
B.	1672 joules
C.	1672 watts
D.	1672 ergs
Answer» C. 1672 watts

Discussion

9307.	The wavelength of Lyman series is [BHU 1997]
A.	\[\frac{4}{3\times 10967}cm\]
B.	\[\frac{3}{4\times 10967}cm\]
C.	\[\frac{4\times 10967}{3}cm\]
D.	\[\frac{3}{4}\times 10967\ cm\]
Answer» B. \[\frac{3}{4\times 10967}cm\]

Discussion

9308.	Assertion : The sum of two vectors can be zero. Reason : The vector cancel each other, when they are equal and opposite.
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.

Discussion

9309.	An ideal gas at a pressures of 1 atmosphere and temperature of \[{{27}^{o}}C\] is compressed adiabatically until its pressure becomes 8 times the initial pressure, then the final temperature is (g = 3/2) [EAMCET (Engg.)2000]
A.	\[{{627}^{o}}C\]
B.	\[{{527}^{o}}C\]
C.	\[{{427}^{o}}C\]
D.	\[{{327}^{o}}C\]
Answer» E.

Discussion

9310.	The nature of sound waves in gases is [RPMT 1999; RPET 2000; J & K CET 2004]
A.	Transverse
B.	Longitudinal
C.	Stationary
D.	Electromagnetic
Answer» C. Stationary

Discussion

9311.	Sound waves in air are [RPET 2000; AFMC 2001]
A.	Transverse
B.	Longitudinal
C.	De-Broglie waves
D.	All the above
Answer» C. De-Broglie waves

Discussion

9312.	When the wave of hydrogen atom comes from infinity into the first orbit then the value of wave number is [RPET 2003]
A.	109700 cm?1
B.	1097cm?1
C.	109 cm?1
D.	None of these
Answer» B. 1097cm?1

Discussion

9313.	For television broadcasting, the frequency employed is normally [AMU 2002]
A.	30-300 MHz
B.	30-300 GHz
C.	30-300 KHz
D.	30-300 Hz
Answer» B. 30-300 GHz

Discussion

9314.	The device that does not work on the principle of mutual induction is [KCET 1994]
A.	Induction coil
B.	Motor
C.	Tesla coil
D.	Transformer
Answer» D. Transformer

Discussion

9315.	The magnetic induction at the centre O in the figure shown is [IIT 1988; KCET 2002]
A.	\[\frac{{{\mu }_{0}}i}{4}\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\]
B.	\[\frac{{{\mu }_{0}}i}{4}\left( \frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}} \right)\]
C.	\[\frac{{{\mu }_{0}}i}{4}({{R}_{1}}-{{R}_{2}})\]
D.	\[\frac{{{\mu }_{0}}i}{4}({{R}_{1}}+{{R}_{2}})\]
Answer» B. \[\frac{{{\mu }_{0}}i}{4}\left( \frac{1}{{{R}_{1}}}+\frac{1}{{{R}_{2}}} \right)\]

Discussion

9316.	If n drops, each of capacitance C, coalesce to form a single big drop, then the ratio of the energy stored in the big drop to that in each small drop will be [UPSEAT 2002]
A.	\[n:\text{ 1}\]
B.	\[{{n}^{\text{1}/\text{3}}}:\text{ 1}\]
C.	\[{{n}^{\text{5}/\text{3}}}:\text{ 1}\]
D.	\[{{n}^{\text{2}}}:\text{ 1}\]
Answer» D. \[{{n}^{\text{2}}}:\text{ 1}\]

Discussion

9317.	Assertion : The displacement-time graph of a body moving with uniform acceleration is a straight line. Reason : The displacement is proportional to time for uniformly accelerated motion.
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

9318.	The charge on electron was discovered by [BHU 1995; RPMT 1999; DCE 2004]
A.	J.J. Thomson
B.	Neil Bohr
C.	Millikan
D.	Chadwick
Answer» D. Chadwick

Discussion

9319.	In an ac circuit, the current lags behind the voltage by \[\pi /3\]. The components in the circuit are [MP PMT 2000]
A.	R and L
B.	R and C
C.	L and C
D.	Only R
Answer» B. R and C

Discussion

9320.	Assertion : X-rays are used for studying the structure of crystals. Reason : The distance between the atoms of crystals is of the order of wavelength of X-rays.
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.

Discussion

9321.	Assertion : \[^{90}Sr\] from the radioactive fall out from a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells. Reason : The energetics b-particles emitted in the decay of \[^{90}Sr\] damage the bone marrow. [AIIMS 2004]
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.

Discussion

9322.	Assertion : The work done in bringing a body down from the top to the base along a frictionless incline plane is the same as the work done in bringing it down the vertical side. Reason : The gravitational force on the body along the inclined plane is the same as that along the vertical side.
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

9323.	A loss free transformer has 500 turns on its primary winding and 2500 in secondary. The meters of the secondary indicate 200 volts at 8 amperes under these conditions. The voltage and current in the primary is [MP PMT 1996]
A.	100 V, 16 A
B.	40 V, 40 A
C.	160 V, 10 A
D.	80 V, 20 A
Answer» C. 160 V, 10 A

Discussion

9324.	In a water-fall the water falls from a height of 100 m. If the entire K.E. of water is converted into heat, the rise in temperature of water will be [MP PMT 2001]
A.	0.23°C
B.	0.46°C
C.	2.3°C
D.	0.023°C
Answer» B. 0.46°C

Discussion

9325.	Assertion : Photosensitivity of a metal is high if its work function is small. Reason : Work function \[=h{{f}_{0}}\] where \[{{f}_{0}}\] is the threshold frequency. [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» C. If assertion is true but reason is false.

Discussion

9326.	Assertion : When an object is placed between two plane parallel mirrors, then all the images found are of equal intensity. Reason : In case of plane parallel mirrors, only two images are possible.
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

9327.	Assertion : The polar caps of earth are cold in comparison to equatorial plane. Reason : The radiation absorbed by polar caps is less than the radiation absorbed by equatorial plane.
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

9328.	Assertion : The illumination of earth's surface from sun is more at noon than in the morning. Reason : Luminance of a surface refers to brightness of the surface.
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

9329.	Assertion : An electron and proton enters a magnetic field with equal velocities, then, the force experienced by the proton will be more than electron. Reason : The mass of proton is 1837 times more than electron.
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

9330.	Assertion : All the radioactive elements are ultimately converted in lead. Reason : All the elements above lead are unstable.
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

9331.	Assertion : The energy of charged particle moving in a uniform magnetic field does not change. Reason : Work done by magnetic field on the charge is zero.
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.

Discussion

9332.	The relation between phase difference (Df) and path difference (Dx) is [MNR 1995; UPSEAT 1999, 2000]
A.	\[\Delta \varphi =\frac{2\pi }{\lambda }\Delta x\]
B.	\[\Delta \varphi =2\pi \lambda \Delta x\]
C.	\[\Delta \varphi =\frac{2\pi \lambda }{\Delta x}\]
D.	\[\Delta \varphi =\frac{2\Delta x}{\lambda }\]
Answer» B. \[\Delta \varphi =2\pi \lambda \Delta x\]

Discussion

9333.	Velocity of sound waves in air is 330 m/sec. For a particular sound in air, a path difference of 40 cm is equivalent to a phase difference of 1.6p. The frequency of this wave is [CBSE PMT 1990]
A.	165 Hz
B.	150 Hz
C.	660 Hz
D.	330 Hz
Answer» D. 330 Hz

Discussion

9334.	The wavelength of ultrasonic waves in air is of the order of [EAMCET 1989]
A.	\[5\times {{10}^{-5}}\,cm\]
B.	\[5\times {{10}^{-8}}\,cm\]
C.	\[5\times {{10}^{5}}\,cm\]
D.	\[5\times {{10}^{8}}\,cm\]
Answer» B. \[5\times {{10}^{-8}}\,cm\]

Discussion

9335.	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

9336.	Choke coil works on the principle of [MP PET/PMT 1988]
A.	Transient current
B.	Self induction
C.	Mutual induction
D.	Wattless current
Answer» C. Mutual induction

Discussion

9337.	In a hydrogen atom, the distance between the electron and proton is \[2.5\times {{10}^{-11}}\,m\]. The electrical force of attraction between them will be [Pb. PMT 2000]
A.	\[2.8\times {{10}^{-7}}\,N\]
B.	\[3.7\times {{10}^{-7}}N\]
C.	\[6.2\times {{10}^{-7}}N\]
D.	\[9.1\times {{10}^{-7}}N\]
Answer» C. \[6.2\times {{10}^{-7}}N\]

Discussion

9338.	Assertion : A P-N photodiode is made from a semiconductor for which Eg = 2.8 eV. This photo diode will not detect the wavelength of 6000 nm. Reason : A PN photodiode detect wavelength l if \[\frac{hc}{\lambda }>{{E}_{g}}\].
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.

Discussion

9339.	Assertion : In vacuum tubes (valves), vacuum is necessary for the movement of electrons between electrodes otherwise electrons collide with air particle and loses their energy. Reason : In semiconductors devices, external heating or vacuum is not required.
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

9340.	Assertion : The following circuit represents 'OR' gate Reason : For the above circuit \[Y=\bar{X}=\overline{\overline{A+B}}=A+B\]
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.

Discussion

9341.	Assertion : Two P-N junction diodes placed back to back, will work as a NPN transistor. Reason : The P-region of two PN junction diodes back to back will form the base of NPN transistor.
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

9342.	Assertion : We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals. Reason : The current through the PN junction is not same in forward and reversed bias.
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

9343.	Assertion : Semiconductors do not Obey's Ohm's law. Reason : Current is determined by the rate of flow of charge carriers.
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

9344.	A charge q coulomb moves in a circle at n revolutions per second and the radius of the circle is r metre. Then magnetic field at the centre of the circle is
A.	\[\frac{2\pi q}{nr}\times {{10}^{-7}}\] N/amp/metre
B.	\[\frac{2\pi q}{r}\times {{10}^{-7}}\] N/amp/metre
C.	\[\frac{2\pi nq}{r}\times {{10}^{-7}}\]N/amp/metre
D.	\[\frac{2\pi q}{r}\] N/amp/metre
Answer» D. \[\frac{2\pi q}{r}\] N/amp/metre

Discussion

9345.	The angular speed of earth, so that the object on equator may appear weightless, is \[(g=10\,m/{{s}^{2}}\], radius of earth 6400 km) [Pb. PMT 2001]
A.	\[1.25\times {{10}^{-3}}rad/sec\]
B.	\[1.56\times {{10}^{-3}}rad/sec\]
C.	\[1.25\times {{10}^{-1}}rad/sec\]
D.	1.56 rad/sec
Answer» B. \[1.56\times {{10}^{-3}}rad/sec\]

Discussion

9346.	For which of the two pairs, the angle of contact is same [J & K CET 2004]
A.	Water and glass; glass and mercury
B.	Pure water and glass; glass and alcohol
C.	Silver and water; mercury and glass
D.	Silver and chromium; water and chromium
Answer» C. Silver and water; mercury and glass

Discussion

9347.	Two bodies of masses m and 4 m are moving with equal K.E. The ratio of their linear momentums is [Orissa JEE 2003; AIIMS 1999]
A.	4 : 1
B.	1 : 1
C.	1 : 2
D.	1 : 4
Answer» D. 1 : 4

Discussion

9348.	Assertion : We can not move even a finger without disturbing all the stars. Reason : Every body in this universe attracts every other body with a force which is inversely proportional to the square of distance between 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

9349.	Two tuning forks A and B vibrating simultaneously produce 5 beats. Frequency of B is 512. It is seen that if one arm of A is filed, then the number of beats increases. Frequency of A will be [MP PMT 1991]
A.	502
B.	507
C.	517
D.	522
Answer» D. 522

Discussion

9350.	A body weight 500 N on the surface of the earth. How much would it weigh half way below the surface of the earth [Pb. PET 2001; BHU 2004]
A.	125 N
B.	250 N
C.	500 N
D.	1000 N
Answer» C. 500 N

Discussion

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

64 drops each having the capacity \[C\] and potential \[V\]are combined to form a big drop. If the charge on the small drop is\[q\], then the charge on the big drop will be [MP PET 1985; MP PET/PMT 1988; CPMT 1971]

The distance between the circular plates of a parallel plate condenser \[40mm\] in diameter, in order to have same capacity as a sphere of radius \[1\ metre\]is [MP PET 1992]

Two sound waves of slightly different frequencies propagating in the same direction produce beats due to [MP PET 2000]

Maximum number of beats frequency heard by a human being is [RPMT 2000]

\[{{F}_{g}}\] and \[{{F}_{e}}\] represents gravitational and electrostatic force respectively between electrons situated at a distance 10 cm. The ratio of \[{{F}_{g}}/{{F}_{e}}\] is of the order of [NCERT 1978; CPMT 1978]

In supplying 400 calories of heat to a system, the work done will be [MP PMT 1989]

The wavelength of Lyman series is [BHU 1997]

Assertion : The sum of two vectors can be zero. Reason : The vector cancel each other, when they are equal and opposite.

An ideal gas at a pressures of 1 atmosphere and temperature of \[{{27}^{o}}C\] is compressed adiabatically until its pressure becomes 8 times the initial pressure, then the final temperature is (g = 3/2) [EAMCET (Engg.)2000]

The nature of sound waves in gases is [RPMT 1999; RPET 2000; J & K CET 2004]

Sound waves in air are [RPET 2000; AFMC 2001]

When the wave of hydrogen atom comes from infinity into the first orbit then the value of wave number is [RPET 2003]

For television broadcasting, the frequency employed is normally [AMU 2002]

The device that does not work on the principle of mutual induction is [KCET 1994]

The magnetic induction at the centre O in the figure shown is [IIT 1988; KCET 2002]

If n drops, each of capacitance C, coalesce to form a single big drop, then the ratio of the energy stored in the big drop to that in each small drop will be [UPSEAT 2002]

Assertion : The displacement-time graph of a body moving with uniform acceleration is a straight line. Reason : The displacement is proportional to time for uniformly accelerated motion.

The charge on electron was discovered by [BHU 1995; RPMT 1999; DCE 2004]

In an ac circuit, the current lags behind the voltage by \[\pi /3\]. The components in the circuit are [MP PMT 2000]

Assertion : X-rays are used for studying the structure of crystals. Reason : The distance between the atoms of crystals is of the order of wavelength of X-rays.

Assertion : The work done in bringing a body down from the top to the base along a frictionless incline plane is the same as the work done in bringing it down the vertical side. Reason : The gravitational force on the body along the inclined plane is the same as that along the vertical side.

A loss free transformer has 500 turns on its primary winding and 2500 in secondary. The meters of the secondary indicate 200 volts at 8 amperes under these conditions. The voltage and current in the primary is [MP PMT 1996]

In a water-fall the water falls from a height of 100 m. If the entire K.E. of water is converted into heat, the rise in temperature of water will be [MP PMT 2001]

Assertion : Photosensitivity of a metal is high if its work function is small. Reason : Work function \[=h{{f}_{0}}\] where \[{{f}_{0}}\] is the threshold frequency. [AIIMS 1997]

Assertion : When an object is placed between two plane parallel mirrors, then all the images found are of equal intensity. Reason : In case of plane parallel mirrors, only two images are possible.

Assertion : The polar caps of earth are cold in comparison to equatorial plane. Reason : The radiation absorbed by polar caps is less than the radiation absorbed by equatorial plane.

Assertion : The illumination of earth's surface from sun is more at noon than in the morning. Reason : Luminance of a surface refers to brightness of the surface.

Assertion : An electron and proton enters a magnetic field with equal velocities, then, the force experienced by the proton will be more than electron. Reason : The mass of proton is 1837 times more than electron.

Assertion : All the radioactive elements are ultimately converted in lead. Reason : All the elements above lead are unstable.

Assertion : The energy of charged particle moving in a uniform magnetic field does not change. Reason : Work done by magnetic field on the charge is zero.

The relation between phase difference (Df) and path difference (Dx) is [MNR 1995; UPSEAT 1999, 2000]

Velocity of sound waves in air is 330 m/sec. For a particular sound in air, a path difference of 40 cm is equivalent to a phase difference of 1.6p. The frequency of this wave is [CBSE PMT 1990]

The wavelength of ultrasonic waves in air is of the order of [EAMCET 1989]

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]

Choke coil works on the principle of [MP PET/PMT 1988]

In a hydrogen atom, the distance between the electron and proton is \[2.5\times {{10}^{-11}}\,m\]. The electrical force of attraction between them will be [Pb. PMT 2000]

Assertion : A P-N photodiode is made from a semiconductor for which Eg = 2.8 eV. This photo diode will not detect the wavelength of 6000 nm. Reason : A PN photodiode detect wavelength l if \[\frac{hc}{\lambda }>{{E}_{g}}\].

Assertion : In vacuum tubes (valves), vacuum is necessary for the movement of electrons between electrodes otherwise electrons collide with air particle and loses their energy. Reason : In semiconductors devices, external heating or vacuum is not required.

Assertion : The following circuit represents 'OR' gate Reason : For the above circuit \[Y=\bar{X}=\overline{\overline{A+B}}=A+B\]

Assertion : Two P-N junction diodes placed back to back, will work as a NPN transistor. Reason : The P-region of two PN junction diodes back to back will form the base of NPN transistor.

Assertion : We can measure the potential barrier of a PN junction by putting a sensitive voltmeter across its terminals. Reason : The current through the PN junction is not same in forward and reversed bias.

Assertion : Semiconductors do not Obey's Ohm's law. Reason : Current is determined by the rate of flow of charge carriers.

A charge q coulomb moves in a circle at n revolutions per second and the radius of the circle is r metre. Then magnetic field at the centre of the circle is

The angular speed of earth, so that the object on equator may appear weightless, is \[(g=10\,m/{{s}^{2}}\], radius of earth 6400 km) [Pb. PMT 2001]

For which of the two pairs, the angle of contact is same [J & K CET 2004]

Two bodies of masses m and 4 m are moving with equal K.E. The ratio of their linear momentums is [Orissa JEE 2003; AIIMS 1999]

Assertion : We can not move even a finger without disturbing all the stars. Reason : Every body in this universe attracts every other body with a force which is inversely proportional to the square of distance between them.

Two tuning forks A and B vibrating simultaneously produce 5 beats. Frequency of B is 512. It is seen that if one arm of A is filed, then the number of beats increases. Frequency of A will be [MP PMT 1991]

A body weight 500 N on the surface of the earth. How much would it weigh half way below the surface of the earth [Pb. PET 2001; BHU 2004]