12583 + Mcqs in Physics Page 179 McqOptions

8901.	Assertion : The cloud in sky generally appear to be whitish. Reason : Diffraction due to clouds is efficient in equal measure at all wavelengths. [AIIMS 2005]
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

8902.	Assertion : The shape of an automobile is so designed that its front resembles the stream line pattern of the fluid through which it moves. Reason : The resistance offered by the fluid is maximum.
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

8903.	The chemical equivalent of copper and zinc are 32 and 108 respectively. When copper and silver voltameter are connected in series and electric current is passed through for sometimes, 1.6 g of copper is deposited. Then, the mass of silver deposited will be [J & K CET 2005]
A.	3.5 g
B.	2.8 g
C.	5.4 g
D.	None of these
Answer» D. None of these

Discussion

8904.	Assertion : The images formed by total internal reflections are much brighter than those formed by mirrors or lenses. Reason : There is no loss of intensity in total internal reflection.
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

8905.	Assertion : The viscosity of liquid increases rapidly with rise of temperature. Reason : Viscosity of a liquid is the property of the liquid by virtue of which it opposes the relative motion amongst its different layers.
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

8906.	An alternating voltage \[E=200\sqrt{2}\sin (100\,t)\] is connected to a 1 microfarad capacitor through an ac ammeter. The reading of the ammeter shall be [NCERT 1984; MNR 1995; MP PET 1999; RPET 1999; UPSEAT 2000]
A.	10 mA
B.	20 mA
C.	40 mA
D.	80 mA
Answer» C. 40 mA

Discussion

8907.	Which one statement is correct? A parallel plate air condenser is connected with a battery. Its charge, potential, electric field and energy are\[{{Q}_{o}},\ {{V}_{o}},\ {{E}_{o}}\] and \[{{U}_{o}}\]respectively. In order to fill the complete space between the plates a dielectric slab is inserted, the battery is still connected. Now the corresponding values\[Q,\ V,\ E\] and\[U\]are in relation with the initially stated as [IIT 1985]
A.	\[Q>{{Q}_{o}}\]
B.	\[V>{{V}_{o}}\]
C.	\[E>{{E}_{o}}\]
D.	\[U>{{U}_{o}}\]
Answer» B. \[V>{{V}_{o}}\]

Discussion

8908.	Choke coil is used to control [CPMT 1984]
A.	ac
B.	dc
C.	Both ac and dc
D.	Neither ac nor dc
Answer» B. dc

Discussion

8909.	2gm of steam condenses when passed through 40gm of water initially at 25°C. The condensation of steam raises the temperature of water to 54.3°C. What is the latent heat of steam [J & K CET 2005]
A.	540 cal/g
B.	536 cal/g
C.	270 cal/g
D.	480 cal/g
Answer» B. 536 cal/g

Discussion

8910.	Assertion : The air bubble shines in water. Reason : Air bubble in water shines due to refraction of light [AIIMS 2002]
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

8911.	Assertion : Power of machine gun is determined by both, the number of bullet fired per second and kinetic energy of bullets. Reason : Power of any machine is defined as work done (by it) per unit time.
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

8912.	The parts of motor cars are polished by chromium because the angle of contact between water and chromium is
A.	\[{{0}^{o}}\]
B.	\[{{90}^{o}}\]
C.	Less than \[{{90}^{o}}\]
D.	Greater than \[{{90}^{o}}\]
Answer» E.

Discussion

8913.	Assertion : The S.I. unit of thermal conductivity is watt m?1 K-1. Reason : Thermal conductivity is a measure of ability of the material to allow the passage of heat through it.
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

8914.	If velocity of sound in a gas is 360 m/s and the distance between a compression and the nearest rarefaction is 1m, then the frequency of sound is [KCET 1999]
A.	90 Hz
B.	180 Hz
C.	360 Hz
D.	720 Hz
Answer» C. 360 Hz

Discussion

8915.	Assertion : In the case of a stationary wave, a person hear a loud sound at the nodes as compared to the antinodes. Reason : In a stationary wave all the particles of the medium vibrate in phase.
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

8916.	The colour of the positive column in a gas discharge tube depends on [Kerala (Engg.) 2002]
A.	The type of glass used to construct the tube
B.	The gas in the tube
C.	The applied voltage
D.	The material of the cathode
Answer» C. The applied voltage

Discussion

8917.	Faraday?s 2nd law states that mass deposited on the electrode is directly proportional to [DCE 1999]
A.	Atomic mass
B.	Atomic mass × Velocity
C.	Atomic mass/Valency
D.	Valency
Answer» D. Valency

Discussion

8918.	In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be [AMU 1996]
A.	50 cycles/sec
B.	100 cycles/sec
C.	500 cycles/sec
D.	50,000 cycles/sec
Answer» E.

Discussion

8919.	A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is 1 : 25. The current in the primary is [CBSE PMT 1998]
A.	15 A
B.	50 A
C.	25 A
D.	12.5 A
Answer» C. 25 A

Discussion

8920.	The adiabatic elasticity of hydrogen gas \[(\gamma =1.4)\] at NTP is [MP PMT 1990]
A.	\[1\times {{10}^{5}}\ N/{{m}^{2}}\]
B.	\[1\times {{10}^{-8}}\ N/m2\]
C.	\[1.4\ N/{{m}^{2}}\]
D.	\[1.4\times {{10}^{5}}N/{{m}^{2}}\]
Answer» E.

Discussion

8921.	If the radius of the earth shrinks by 1.5% (mass remaining same), then the value of acceleration due to gravity changes by [BHU 1997]
A.	1%
B.	0.02
C.	3%
D.	0.04
Answer» D. 0.04

Discussion

8922.	Ratio of the wavelengths of first line of Lyman series and first line of Balmer series is [EAMCET (Engg.) 1995; MP PMT 1997]
A.	1: 3
B.	27 : 5
C.	5 : 27
D.	4 : 9
Answer» D. 4 : 9

Discussion

8923.	If a hole is bored along the diameter of the earth and a stone is dropped into hole [CPMT 1984]
A.	The stone reaches the centre of the earth and stops there
B.	The stone reaches the other side of the earth and stops there
C.	The stone executes simple harmonic motion about the centre of the earth
D.	The stone reaches the other side of the earth and escapes into space
Answer» D. The stone reaches the other side of the earth and escapes into space

Discussion

8924.	On passing the current in water voltameter, the hydrogen
A.	Liberated at anode
B.	Liberated at cathode
C.	Does not liberate
D.	Remains in the solution
Answer» C. Does not liberate

Discussion

8925.	Assertion : If \[\vec{A}.\vec{B}=\vec{B}.\vec{C},\]then \[\vec{A}\] may not always be equal to \[\vec{C}\] Reason : The dot product of two vectors involves cosine of the angle between the two vectors.
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» 1 , 3. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8926.	Assertion : Though light of a single frequency (monochromatic) is incident on a metal, the energies of emitted photoelectrons are different. Reason : The energy of electrons emitted from inside the metal surface is lost in collision with the other atoms in the metal.
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

8927.	When a proton is accelerated with 1 volt potential difference, then its kinetic energy is [CPMT 1997; CBSE PMT 1999; RPET 2003]
A.	\[\frac{1}{1840}eV\]
B.	1840 eV
C.	1 eV
D.	1840 c2 eV
Answer» D. 1840 c2 eV

Discussion

8928.	Assertion : Bernoulli's theorem holds for incompressible, non-viscous fluids. Reason : The factor \[\frac{{{v}^{2}}}{2g}\] is called velocity head.
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

8929.	A capillary tube of radius R is immersed in water and water rises in it to a height H. Mass of water in the capillary tube is M. If the radius of the tube is doubled, mass of water that will rise in the capillary tube will now be [RPMT 1997; RPET 1999; CPMT 2002]
A.	M
B.	2M
C.	M/2
D.	4M
Answer» C. M/2

Discussion

8930.	In an ac circuit with voltage V and current I, the power dissipated is [CBSE PMT 1997]
A.	VI
B.	\[\frac{1}{2}VI\]
C.	\[\frac{1}{\sqrt{2}}VI\]
D.	Depends on the phase between V and I
Answer» E.

Discussion

8931.	Assertion : The bridges declared unsafe after a long use. Reason : Elastic strength of bridges losses with time.
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

8932.	The fact that photons carry energy was established by [ISM Dhanbad 1994]
A.	Doppler's effect
B.	Compton's effect
C.	Bohr's theory
D.	Diffraction of light
Answer» D. Diffraction of light

Discussion

8933.	Two charges placed in air repel each other by a force of \[{{10}^{-4}}N\]. When oil is introduced between the charges, the force becomes \[2.5\times {{10}^{-5}}N\]. The dielectric constant of oil is [MP PET 2003]
A.	2.5
B.	0.25
C.	2.0
D.	4.0
Answer» E.

Discussion

8934.	1000 small water drops each of radius r and charge \[q\]coalesce together to form one spherical drop. The potential of the big drop is larger than that of the smaller drop by a factor of [CPMT 1991, 97; NCERT 1984; MP PMT 1996; MP PET 2002]
A.	1000
B.	100
C.	10
D.	1
Answer» C. 10

Discussion

8935.	Assertion : Acceleration of a magnet falling through a long solenoid decreases. Reason : The induced current produced in a circuit always flow in such direction that it opposes the change or the cause the produced it.
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

8936.	The order of the size of nucleus and Bohr radius of an atom respectively are [MP PET 2001; MP PMT 2001]
A.	\[{{10}^{-14}}m,\ {{10}^{-10}}m\]
B.	\[{{10}^{-10}}\,m,\,{{10}^{-8}}\,m\]
C.	\[{{10}^{-20}}m,\ {{10}^{-16}}m\]
D.	\[{{10}^{-8}}\,m,\,{{10}^{-6}}\,m\]
Answer» B. \[{{10}^{-10}}\,m,\,{{10}^{-8}}\,m\]

Discussion

8937.	Assertion : It is not possible for a system, unaided by an external agency to transfer heat from a body at lower temperature to another body at higher temperature. Reason : According to Clausius statement, ? No process is possible whose sole result is the transfer of heat from a cooled object to a hotter object.
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

8938.	A coil has L = 0.04 H and \[R=12\,\Omega \]. When it is connected to 220V, 50Hz supply the current flowing through the coil, in amperes is [Kerala PMT 2004]
A.	10.7
B.	11.7
C.	14.7
D.	12.7
Answer» E.

Discussion

8939.	Assertion : Newton?s rings are formed in the reflected system. When the space between the lens and the glass plate is filled with a liquid of refractive index greater than that of glass, the central spot of the pattern is dark. Reason : The reflection is Newton?s ring cases will be from a denser to a rarer medium and the two interfering rays are reflected under similar conditions. [AIIMS 1998]
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

8940.	Assertion : If three identical bulbs are connected in series as shown in figure then on closing the switches. Bulb C short circuited and hence illumination of bulbs A and B decreases. Reason : Voltage on A and B 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» E. If assertion is false but reason is true.

Discussion

8941.	If fa and ff represent the carrier wave frequencies for amplitude and frequency modulations respectively, then
A.	\[{{f}_{a}}>{{f}_{f}}\]
B.	\[{{f}_{a}}<{{f}_{f}}\]
C.	\[{{f}_{a}}\approx {{f}_{f}}\]
D.	\[{{f}_{a}}\ge {{f}_{f}}\]
Answer» C. \[{{f}_{a}}\approx {{f}_{f}}\]

Discussion

8942.	A 10 ohm resistance, 5 mH coil and 10 mF capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is halved, the resonance frequency [MP PET 1995]
A.	Is halved
B.	Is doubled
C.	Remains unchanged
D.	In quadrupled
Answer» D. In quadrupled

Discussion

8943.	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 [AIEEE 2005]
A.	Zero
B.	\[\frac{M{{L}^{2}}}{K}\]
C.	\[\sqrt{MK}\,L\]
D.	\[\frac{K{{L}^{2}}}{2M}\]
Answer» D. \[\frac{K{{L}^{2}}}{2M}\]

Discussion

8944.	If a cylinder containing a gas at high pressure explodes, the gas undergoes [MP PET/PMT 1988]
A.	Reversible adiabatic change and fall of temperature
B.	Reversible adiabatic change and rise of temperature
C.	Irreversible adiabatic change and fall of temperature
D.	Irreversible adiabatic change and rise of temperature
Answer» D. Irreversible adiabatic change and rise of temperature

Discussion

8945.	A length L of wire carries a steady current I. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is [NCERT 1980; AIIMS 1980; MP PMT 1995, 99]
A.	A quarter of its first value
B.	Unaltered
C.	Four times of its first value
D.	A half of its first value
Answer» D. A half of its first value

Discussion

8946.	A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be [MP PET 2002]
A.	100
B.	200
C.	400
D.	300
Answer» D. 300

Discussion

8947.	Assertion : A transistor is a voltage-operating device. Reason : Base current is greater than the collector 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

8948.	Assertion : Glassy solids have sharp melting point. Reason : The bonds between the atoms of glassy solids get broken at the same temperature.
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

8949.	Assertion : Two bulbs of same wattage, one having a carbon filament and the other having a metallic filament are connected in series. Metallic bulbs will glow more brightly than carbon filament bulb. Reason : Carbon is a semiconductor.
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

8950.	Two cylinders P and Q have the same length and diameter and are made of different materials having thermal conductivities in the ratio 2 : 3. These two cylinders are combined to make a cylinder. One end of P is kept at 100°C and another end of Q at 0°C. The temperature at the interface of P and Q is [MP PMT 1994; EAMCET 2000]
A.	\[{{30}^{o}}C\]
B.	\[{{40}^{o}}C\]
C.	\[{{50}^{o}}C\]
D.	\[{{60}^{o}}C\]
Answer» C. \[{{50}^{o}}C\]

Discussion

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

Assertion : The cloud in sky generally appear to be whitish. Reason : Diffraction due to clouds is efficient in equal measure at all wavelengths. [AIIMS 2005]

Assertion : The shape of an automobile is so designed that its front resembles the stream line pattern of the fluid through which it moves. Reason : The resistance offered by the fluid is maximum.

The chemical equivalent of copper and zinc are 32 and 108 respectively. When copper and silver voltameter are connected in series and electric current is passed through for sometimes, 1.6 g of copper is deposited. Then, the mass of silver deposited will be [J & K CET 2005]

Assertion : The images formed by total internal reflections are much brighter than those formed by mirrors or lenses. Reason : There is no loss of intensity in total internal reflection.

Assertion : The viscosity of liquid increases rapidly with rise of temperature. Reason : Viscosity of a liquid is the property of the liquid by virtue of which it opposes the relative motion amongst its different layers.

An alternating voltage \[E=200\sqrt{2}\sin (100\,t)\] is connected to a 1 microfarad capacitor through an ac ammeter. The reading of the ammeter shall be [NCERT 1984; MNR 1995; MP PET 1999; RPET 1999; UPSEAT 2000]

Choke coil is used to control [CPMT 1984]

2gm of steam condenses when passed through 40gm of water initially at 25°C. The condensation of steam raises the temperature of water to 54.3°C. What is the latent heat of steam [J & K CET 2005]

Assertion : The air bubble shines in water. Reason : Air bubble in water shines due to refraction of light [AIIMS 2002]

Assertion : Power of machine gun is determined by both, the number of bullet fired per second and kinetic energy of bullets. Reason : Power of any machine is defined as work done (by it) per unit time.

The parts of motor cars are polished by chromium because the angle of contact between water and chromium is

Assertion : The S.I. unit of thermal conductivity is watt m?1 K-1. Reason : Thermal conductivity is a measure of ability of the material to allow the passage of heat through it.

If velocity of sound in a gas is 360 m/s and the distance between a compression and the nearest rarefaction is 1m, then the frequency of sound is [KCET 1999]

Assertion : In the case of a stationary wave, a person hear a loud sound at the nodes as compared to the antinodes. Reason : In a stationary wave all the particles of the medium vibrate in phase.

The colour of the positive column in a gas discharge tube depends on [Kerala (Engg.) 2002]

Faraday?s 2nd law states that mass deposited on the electrode is directly proportional to [DCE 1999]

In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be [AMU 1996]

A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is 1 : 25. The current in the primary is [CBSE PMT 1998]

The adiabatic elasticity of hydrogen gas \[(\gamma =1.4)\] at NTP is [MP PMT 1990]

If the radius of the earth shrinks by 1.5% (mass remaining same), then the value of acceleration due to gravity changes by [BHU 1997]

Ratio of the wavelengths of first line of Lyman series and first line of Balmer series is [EAMCET (Engg.) 1995; MP PMT 1997]

If a hole is bored along the diameter of the earth and a stone is dropped into hole [CPMT 1984]

On passing the current in water voltameter, the hydrogen

Assertion : If \[\vec{A}.\vec{B}=\vec{B}.\vec{C},\]then \[\vec{A}\] may not always be equal to \[\vec{C}\] Reason : The dot product of two vectors involves cosine of the angle between the two vectors.

Assertion : Though light of a single frequency (monochromatic) is incident on a metal, the energies of emitted photoelectrons are different. Reason : The energy of electrons emitted from inside the metal surface is lost in collision with the other atoms in the metal.

When a proton is accelerated with 1 volt potential difference, then its kinetic energy is [CPMT 1997; CBSE PMT 1999; RPET 2003]

Assertion : Bernoulli's theorem holds for incompressible, non-viscous fluids. Reason : The factor \[\frac{{{v}^{2}}}{2g}\] is called velocity head.

A capillary tube of radius R is immersed in water and water rises in it to a height H. Mass of water in the capillary tube is M. If the radius of the tube is doubled, mass of water that will rise in the capillary tube will now be [RPMT 1997; RPET 1999; CPMT 2002]

In an ac circuit with voltage V and current I, the power dissipated is [CBSE PMT 1997]

Assertion : The bridges declared unsafe after a long use. Reason : Elastic strength of bridges losses with time.

The fact that photons carry energy was established by [ISM Dhanbad 1994]

Two charges placed in air repel each other by a force of \[{{10}^{-4}}N\]. When oil is introduced between the charges, the force becomes \[2.5\times {{10}^{-5}}N\]. The dielectric constant of oil is [MP PET 2003]

1000 small water drops each of radius r and charge \[q\]coalesce together to form one spherical drop. The potential of the big drop is larger than that of the smaller drop by a factor of [CPMT 1991, 97; NCERT 1984; MP PMT 1996; MP PET 2002]

Assertion : Acceleration of a magnet falling through a long solenoid decreases. Reason : The induced current produced in a circuit always flow in such direction that it opposes the change or the cause the produced it.

The order of the size of nucleus and Bohr radius of an atom respectively are [MP PET 2001; MP PMT 2001]

A coil has L = 0.04 H and \[R=12\,\Omega \]. When it is connected to 220V, 50Hz supply the current flowing through the coil, in amperes is [Kerala PMT 2004]

Assertion : If three identical bulbs are connected in series as shown in figure then on closing the switches. Bulb C short circuited and hence illumination of bulbs A and B decreases. Reason : Voltage on A and B decreases

If fa and ff represent the carrier wave frequencies for amplitude and frequency modulations respectively, then

A 10 ohm resistance, 5 mH coil and 10 mF capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is halved, the resonance frequency [MP PET 1995]

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 [AIEEE 2005]

If a cylinder containing a gas at high pressure explodes, the gas undergoes [MP PET/PMT 1988]

A length L of wire carries a steady current I. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is [NCERT 1980; AIIMS 1980; MP PMT 1995, 99]

A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be [MP PET 2002]

Assertion : A transistor is a voltage-operating device. Reason : Base current is greater than the collector current.

Assertion : Glassy solids have sharp melting point. Reason : The bonds between the atoms of glassy solids get broken at the same temperature.

Assertion : Two bulbs of same wattage, one having a carbon filament and the other having a metallic filament are connected in series. Metallic bulbs will glow more brightly than carbon filament bulb. Reason : Carbon is a semiconductor.