12583 + Mcqs in Physics Page 178 McqOptions

8851.	An alternating current of frequency \['f\,'\] is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is [CPMT 1978; MP PMT 1993; MP PET 1999; AIIMS 2000; Pb. PET 2004; RPET 2001, 03]
A.	R + 2pfL
B.	\[\sqrt{{{R}^{2}}+4{{\pi }^{2}}{{f}^{2}}{{L}^{2}}}\]
C.	\[\sqrt{{{R}^{2}}+{{L}^{2}}}\]
D.	\[\sqrt{{{R}^{2}}+2\pi fL}\]
Answer» C. \[\sqrt{{{R}^{2}}+{{L}^{2}}}\]

Discussion

8852.	For the magnetic field to be maximum due to a small element of current carrying conductor at a point, the angle between the element and the line joining the element to the given point must be [J & K CET 2005]
A.	0°
B.	90°
C.	180°
D.	45°
Answer» C. 180°

Discussion

8853.	Assertion : A circular loop carrying current lies in XY plane with its center at origin having a magnetic flux in negative Z-axis. Reason : Magnetic flux direction is independent of the direction of current in the conductor.
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

8854.	What is the shape when a non-wetting liquid is placed in a capillary tube [AFMC 2004]
A.	Concave upward
B.	Convex upward
C.	Concave downward
D.	Convex downward
Answer» C. Concave downward

Discussion

8855.	Assertion : \[\vec{A}.\vec{B}=\vec{B}.\vec{A}\] Reason : Dot product of two vectors is commutative.
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

8856.	Mass of moon is \[7.34\times {{10}^{22}}\]kg. If the acceleration due to gravity on the moon is \[1.4\,m/{{s}^{2}}\], the radius of the moon is \[(G=6.667\times {{10}^{-11}}\,N{{m}^{2}}/k{{g}^{2}})\] [AFMC 1998]
A.	\[0.56\times {{10}^{4}}\,m\]
B.	\[1.87\times {{10}^{6}}\,m\]
C.	\[1.92\times {{10}^{6}}\,m\]
D.	\[1.01\times {{10}^{8}}\,m\]
Answer» C. \[1.92\times {{10}^{6}}\,m\]

Discussion

8857.	Assertion : The time period of revolution of a satellite close to surface of earth is smaller than that revolving away from surface of earth. Reason : The square of time period of revolution of a satellite is directly proportional to cube of its orbital radius.
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

8858.	A free body of mass 8 kg is travelling at 2 meter per second in a straight line. At a certain instant, the body splits into two equal parts due to internal explosion which releases 16 joules of energy. Neither part leaves the original line of motion finally [NCERT 1979]
A.	Both parts continue to move in the same direction as that of the original body
B.	One part comes to rest and the other moves in the same direction as that of the original body
C.	One part comes to rest and the other moves in the direction opposite to that of the original body
D.	One part moves in the same direction and the other in the direction opposite to that of the original body
Answer» C. One part comes to rest and the other moves in the direction opposite to that of the original body

Discussion

8859.	Two charges each of \[1\ coulomb\]are at a distance \[1\,km\] apart, the force between them is [CPMT 1977; DPMT 1999]
A.	\[9\times {{10}^{3}}\ Newton\]
B.	\[9\times {{10}^{-3}}\ Newton\]
C.	\[1.1\times {{10}^{-4}}\ Newton\]
D.	\[{{10}^{4}}\ Newton\]
Answer» B. \[9\times {{10}^{-3}}\ Newton\]

Discussion

8860.	The capacity of a parallel plate condenser is \[10\,\mu \,F\], when the distance between its plates is 8 cm. If the distance between the plates is reduced to 4 cm, then the capacity of this parallel plate condenser will be [CBSE PMT 2001]
A.	\[5\,\mu \,F\]
B.	\[10\,\mu \,F\]
C.	\[20\,\mu \,F\]
D.	\[40\,\mu \,F\]
Answer» D. \[40\,\mu \,F\]

Discussion

8861.	Assertion : The coefficient of volume expansion has dimension K?1. Reason : The coefficient of volume expansion is defined as the change in volume per unit volume per unit change in 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8862.	The current in the windings on a toroid is 2.0A. There are 400 turns and the mean circumferential length is 40cm. If the inside magnetic field is 1.0T, the relative permeability is near to [AMU (Med.) 2002]
A.	100
B.	200
C.	300
D.	400
Answer» E.

Discussion

8863.	The charges on two sphere are\[+7\,\mu C\] and \[-5\,\mu C\] respectively. They experience a force F. If each of them is given and additional charge of \[-2\,\mu C\], the new force of attraction will be [RPET 2002]
A.	F
B.	F / 2
C.	\[F/\sqrt{3}\]
D.	2F
Answer» B. F / 2

Discussion

8864.	Three charges are placed at the vertices of an equilateral triangle of side ?a? as shown in the following figure. The force experienced by the charge placed at the vertex A in a direction normal to BC is [AIIMS 2003]
A.	\[{{Q}^{2}}/(4\pi {{\varepsilon }_{0}}{{a}^{2}})\]
B.	\[-{{Q}^{2}}/(4\pi {{\varepsilon }_{0}}{{a}^{2}})\]
C.	Zero
D.	\[{{Q}^{2}}/(2\pi {{\varepsilon }_{0}}{{a}^{2}})\]
Answer» D. \[{{Q}^{2}}/(2\pi {{\varepsilon }_{0}}{{a}^{2}})\]

Discussion

8865.	A machine which is 75 percent efficient, uses 12 joules of energy in lifting up a 1 kg mass through a certain distance. The mass is then allowed to fall through that distance. The velocity at the end of its fall is (in \[m{{s}^{-1}})\][Kerala PMT 2002]
A.	\[\sqrt{24}\]
B.	\[\sqrt{32}\]
C.	\[\sqrt{18}\]
D.	\[\sqrt{9}\]
Answer» D. \[\sqrt{9}\]

Discussion

8866.	The capacity of a parallel plate condenser is \[15\mu \,F\], when the distance between its plates is 6 cm. If the distance between the plates is reduced to 2 cm, then the capacity of this parallel plate condenser will be [AFMC 2000]
A.	\[15\mu \,F\]
B.	\[30\mu \,F\]
C.	\[45\mu \,F\]
D.	\[60\mu \,F\]
Answer» D. \[60\mu \,F\]

Discussion

8867.	The mass of the electron varies with
A.	The size of the cathode ray tube
B.	The variation of ?g?
C.	Velocity
D.	Size of the electron
Answer» D. Size of the electron

Discussion

8868.	Assertion : Newton?s third law of motion is applicable only when bodies are in motion. Reason : Newton?s third law applies to all types of forces, e.g. gravitational, electric or magnetic forces etc.
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

8869.	At what temperature velocity of sound is double than that of at 0°C [RPMT 1999]
A.	819 K
B.	819°C
C.	600°C
D.	600 K
Answer» C. 600°C

Discussion

8870.	The root mean square value of the alternating current is equal to [MP PMT 1993]
A.	Twice the peak value
B.	Half the peak value
C.	\[\frac{1}{\sqrt{2}}\] times the peak value
D.	Equal to the peak value
Answer» D. Equal to the peak value

Discussion

8871.	Assertion : When distance between two bodies is doubled and also mass of each body is also doubled, gravitational force between them remains the same. Reason : According to Newton?s law of gravitation, force is directly proportional to mass of bodies and inversely proportional to 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

8872.	The radius of the first (lowest) orbit of the hydrogen atom is \[{{a}_{0}}.\] The radius of the second (next higher) orbit will be [MP PET 2002; MP PMT 2004]
A.	\[4{{a}_{0}}\]
B.	\[6{{a}_{0}}\]
C.	\[8{{a}_{0}}\]
D.	\[10{{a}_{0}}\]
Answer» B. \[6{{a}_{0}}\]

Discussion

8873.	In charging a battery of motor-car, the following effect of electric current is used [MP PET 1993; AFMC 2003]
A.	Magnetic
B.	Heating
C.	Chemical
D.	Induction
Answer» D. Induction

Discussion

8874.	In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is [AIEEE 2002]
A.	4 A
B.	2 A
C.	6 A
D.	10 A
Answer» C. 6 A

Discussion

8875.	An antenna behaves as resonant circuit only when its length is [MNR 2002]
A.	\[\frac{\lambda }{2}\]
B.	\[\frac{\lambda }{4}\]
C.	l
D.	\[\frac{\lambda }{2}\] or integral multiple of \[\frac{\lambda }{2}\]
Answer» E.

Discussion

8876.	Assertion : A current I flows along the length of an infinitely long straight and thin walled pipe. Then the magnetic field at any point inside the pipe is zero. Reason : \[\oint{\overset{\to }{\mathop{B}}\,.d\overset{\to }{\mathop{l}}\,}={{\mu }_{o}}I\]
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

8877.	The ratio of momenta of an electron and an \[\alpha -\]particle which are accelerated from rest by a potential difference of 100 V is [MNR 1994; RPET 1997]
A.	1
B.	\[\sqrt{\frac{2{{m}_{e}}}{{{m}_{\alpha }}}}\]
C.	\[\sqrt{\frac{{{m}_{e}}}{{{m}_{\alpha }}}}\]
D.	\[\sqrt{\frac{{{m}_{e}}}{2{{m}_{\alpha }}}}\]
Answer» E.

Discussion

8878.	Assertion : If an electron is not deflected while passing through a certain region of space, then only possibility is that there is no magnetic region. Reason : Force is directly proportional to the magnetic field applied.
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

8879.	Consider telecommunication through optical fibres. Which of the following statements is not true [AIEEE 2003]
A.	Optical fibres may have homogeneous core with a suitable cladding
B.	Optical fibres can be of graded refractive index
C.	Optical fibres are subject to electromagnetic interference from outside
D.	Optical fibres have extremely low transmission loss
Answer» D. Optical fibres have extremely low transmission loss

Discussion

8880.	Which one of the following statements is true for the speed v and the acceleration a of a particle executing simple harmonic motion [CBSE PMT 2004]
A.	When v is maximum, a is maximum
B.	Value of a is zero, whatever may be the value of v
C.	When v is zero, a is zero
D.	When v is maximum, a is zero
Answer» E.

Discussion

8881.	Assertion : X-ray travel with the speed of light. Reason : X-rays are electromagnetic rays. [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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8882.	Snow is more heat insulating than ice, because
A.	Air is filled in porous of snow
B.	Ice is more bad conductor than snow
C.	Air is filled in porous of ice
D.	Density of ice is more
Answer» B. Ice is more bad conductor than snow

Discussion

8883.	The radii of two metallic spheres \[P\] and \[Q\] are \[{{r}_{1}}\] and\[{{r}_{2}}\] respectively. They are given the same charge. If \[{{r}_{1}}>{{r}_{2}}\]. then on connecting them with a thin wire, the charge will flow [MP PMT 1985]
A.	From P to Q
B.	From Q to P
C.	Neither the charge will flow from P to Q nor from Q to P
D.	The information is incomplete
Answer» E.

Discussion

8884.	The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true [IIT JEE (Screening) 2000]
A.	Its kinetic energy increases and its potential and total energies decrease
B.	Its kinetic energy decreases, potential energy increases and its total energy remains the same
C.	Its kinetic and total energies decrease and its potential energy increases
D.	Its kinetic, potential and total energies decreases
Answer» B. Its kinetic energy decreases, potential energy increases and its total energy remains the same

Discussion

8885.	In a circuit \[L,\,C\text{ and }R\]are connected in series with an alternating voltage source of frequency \[f\]. The current leads the voltage by 45°. The value of \[C\] is [CBSE PMT 2005]
A.	\[\frac{1}{2\pi f(2\pi fL+R)}\]
B.	\[\frac{1}{\pi f(2\pi fL+R)}\]
C.	\[\frac{1}{2\pi f(2\pi fL-R)}\]
D.	\[\frac{1}{\pi f(2\pi fL-R)}\]
Answer» B. \[\frac{1}{\pi f(2\pi fL+R)}\]

Discussion

8886.	The specific heat at constant pressure and at constant volume for an ideal gas are \[{{C}_{p}}\] and \[{{C}_{v}}\] and its adiabatic and isothermal elasticities are \[{{E}_{\varphi }}\] and \[{{E}_{\theta }}\] respectively. The ratio of \[{{E}_{\varphi }}\] to \[{{E}_{\theta }}\] is [MP PMT 1989; MP PET 1992]
A.	\[{{C}_{v}}/{{C}_{p}}\]
B.	\[{{C}_{p}}/{{C}_{v}}\]
C.	\[{{C}_{p}}{{C}_{v}}\]
D.	\[1/{{C}_{p}}{{C}_{v}}\]
Answer» C. \[{{C}_{p}}{{C}_{v}}\]

Discussion

8887.	Assertion : The angle of contact of a liquid decrease with increase in temperature. Reason : With increase in temperature, the surface tension of liquid increase.
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

8888.	The capacity of a parallel plate capacitor with no dielectric substance but with a separation of 0.4 cm is \[2\mu \,F\]. The separation is reduced to half and it is filled with a dielectric substance of value 2.8. The final capacity of the capacitor is [CBSE PMT 2000]
A.	\[11.2\mu F\]
B.	\[15.6\mu F\]
C.	\[19.2\mu F\]
D.	\[22.4\mu F\]
Answer» B. \[15.6\mu F\]

Discussion

8889.	Two bodies of different masses \[{{m}_{1}}\] and \[{{m}_{2}}\] have equal momenta. Their kinetic energies \[{{E}_{1}}\] and \[{{E}_{2}}\] are in the ratio [EAMCET 1990]
A.	\[\sqrt{{{m}_{1}}}:\sqrt{{{m}_{2}}}\]
B.	\[{{m}_{1}}:{{m}_{2}}\]
C.	\[{{m}_{2}}:{{m}_{1}}\]
D.	\[m_{1}^{2}:m_{2}^{2}\]
Answer» D. \[m_{1}^{2}:m_{2}^{2}\]

Discussion

8890.	A wire in the form of a square of side ?a? carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space =\[{{\mu }_{o}})\] [EAMCET 2001]
A.	\[\frac{{{\mu }_{0}}i}{2\pi a}\]
B.	\[\frac{{{\mu }_{0}}i\sqrt{2}}{\pi a}\]
C.	\[\frac{2\sqrt{2}{{\mu }_{o}}i}{\pi a}\]
D.	\[\frac{{{\mu }_{0}}i}{\sqrt{2}\pi \,a}\]
Answer» D. \[\frac{{{\mu }_{0}}i}{\sqrt{2}\pi \,a}\]

Discussion

8891.	The capacity of a pure capacitor is 1 farad. In dc circuits, its effective resistance will be [MP PMT 2000]
A.	Zero
B.	Infinite
C.	1 ohm
D.	1/2 ohm
Answer» C. 1 ohm

Discussion

8892.	In Bohr's model, the atomic radius of the first orbit is \[{{r}_{0}}\], then the radius of the third orbit is [AIIMS 1997; CPMT 2001; KCET (Engg./Med.) 1999; Pb. PMT 2004]
A.	\[\frac{{{r}_{0}}}{9}\]
B.	\[{{r}_{0}}\]
C.	\[9{{r}_{0}}\]
D.	\[3{{r}_{0}}\]
Answer» D. \[3{{r}_{0}}\]

Discussion

8893.	There are two charges \[+1\,\mu C\] and \[+5\,\mu C\]. The ratio of the forces acting on them will be [CPMT 1979]
A.	1 : 5
B.	1 : 1
C.	5 : 1
D.	1 : 25
Answer» C. 5 : 1

Discussion

8894.	Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is [CBSE PMT 1999]
A.	\[2\times {{10}^{-1}}\,T\]
B.	\[4.31\times {{10}^{-2}}\,T\]
C.	\[6.28\times {{10}^{-4}}\,T\]
D.	\[9.81\times {{10}^{-4}}\,T\]
Answer» D. \[9.81\times {{10}^{-4}}\,T\]

Discussion

8895.	Assertion : For projection angle \[{{\tan }^{-1}}(4)\], the horizontal range and the maximum height of a projectile are equal. Reason : The maximum range of projectile is directly proportional to square of velocity and inversely proportional to acceleration due to gravity.
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

8896.	Assertion : The back emf in a dc motor is maximum when the motor has just been switched on. Reason : When motor is switched on it has maximum speed.
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

8897.	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

8898.	When three forces of 50 N, 30 N and 15 N act on a body, then the body is
A.	At rest
B.	Moving with a uniform velocity
C.	In equilibrium
D.	Moving with an acceleration
Answer» E.

Discussion

8899.	Assertion : A double convex lens (m = 1.5) has focal length 10 cm. When the lens is immersed in water (m = 4/3) its focal length becomes 40 cm. Reason : \[\frac{1}{f}=\frac{{{\mu }_{l}}-{{\mu }_{m}}}{{{\mu }_{m}}}\,\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] [AIIMS 1999]
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

8900.	Two vectors \[\overrightarrow{A}\]and \[\overrightarrow{B}\]lie in a plane, another vector \[\overrightarrow{C}\]lies outside this plane, then the resultant of these three vectors i.e.,\[\overrightarrow{A}+\overrightarrow{B}+\overrightarrow{C}\] [CPMT 1983]
A.	Can be zero
B.	Cannot be zero
C.	Lies in the plane containing \[\overrightarrow{A}+\overrightarrow{B}\]
D.	Lies in the plane containing \[\vec{C}\]
Answer» C. Lies in the plane containing \[\overrightarrow{A}+\overrightarrow{B}\]

Discussion

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

An alternating current of frequency \['f\,'\] is flowing in a circuit containing a resistance R and a choke L in series. The impedance of this circuit is [CPMT 1978; MP PMT 1993; MP PET 1999; AIIMS 2000; Pb. PET 2004; RPET 2001, 03]

For the magnetic field to be maximum due to a small element of current carrying conductor at a point, the angle between the element and the line joining the element to the given point must be [J & K CET 2005]

Assertion : A circular loop carrying current lies in XY plane with its center at origin having a magnetic flux in negative Z-axis. Reason : Magnetic flux direction is independent of the direction of current in the conductor.

What is the shape when a non-wetting liquid is placed in a capillary tube [AFMC 2004]

Assertion : \[\vec{A}.\vec{B}=\vec{B}.\vec{A}\] Reason : Dot product of two vectors is commutative.

Mass of moon is \[7.34\times {{10}^{22}}\]kg. If the acceleration due to gravity on the moon is \[1.4\,m/{{s}^{2}}\], the radius of the moon is \[(G=6.667\times {{10}^{-11}}\,N{{m}^{2}}/k{{g}^{2}})\] [AFMC 1998]

Assertion : The time period of revolution of a satellite close to surface of earth is smaller than that revolving away from surface of earth. Reason : The square of time period of revolution of a satellite is directly proportional to cube of its orbital radius.

A free body of mass 8 kg is travelling at 2 meter per second in a straight line. At a certain instant, the body splits into two equal parts due to internal explosion which releases 16 joules of energy. Neither part leaves the original line of motion finally [NCERT 1979]

Two charges each of \[1\ coulomb\]are at a distance \[1\,km\] apart, the force between them is [CPMT 1977; DPMT 1999]

The capacity of a parallel plate condenser is \[10\,\mu \,F\], when the distance between its plates is 8 cm. If the distance between the plates is reduced to 4 cm, then the capacity of this parallel plate condenser will be [CBSE PMT 2001]

Assertion : The coefficient of volume expansion has dimension K?1. Reason : The coefficient of volume expansion is defined as the change in volume per unit volume per unit change in temperature.

The current in the windings on a toroid is 2.0A. There are 400 turns and the mean circumferential length is 40cm. If the inside magnetic field is 1.0T, the relative permeability is near to [AMU (Med.) 2002]

The charges on two sphere are\[+7\,\mu C\] and \[-5\,\mu C\] respectively. They experience a force F. If each of them is given and additional charge of \[-2\,\mu C\], the new force of attraction will be [RPET 2002]

Three charges are placed at the vertices of an equilateral triangle of side ?a? as shown in the following figure. The force experienced by the charge placed at the vertex A in a direction normal to BC is [AIIMS 2003]

A machine which is 75 percent efficient, uses 12 joules of energy in lifting up a 1 kg mass through a certain distance. The mass is then allowed to fall through that distance. The velocity at the end of its fall is (in \[m{{s}^{-1}})\][Kerala PMT 2002]

The capacity of a parallel plate condenser is \[15\mu \,F\], when the distance between its plates is 6 cm. If the distance between the plates is reduced to 2 cm, then the capacity of this parallel plate condenser will be [AFMC 2000]

The mass of the electron varies with

Assertion : Newton?s third law of motion is applicable only when bodies are in motion. Reason : Newton?s third law applies to all types of forces, e.g. gravitational, electric or magnetic forces etc.

At what temperature velocity of sound is double than that of at 0°C [RPMT 1999]

The root mean square value of the alternating current is equal to [MP PMT 1993]

The radius of the first (lowest) orbit of the hydrogen atom is \[{{a}_{0}}.\] The radius of the second (next higher) orbit will be [MP PET 2002; MP PMT 2004]

In charging a battery of motor-car, the following effect of electric current is used [MP PET 1993; AFMC 2003]

In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is [AIEEE 2002]

An antenna behaves as resonant circuit only when its length is [MNR 2002]

Assertion : A current I flows along the length of an infinitely long straight and thin walled pipe. Then the magnetic field at any point inside the pipe is zero. Reason : \[\oint{\overset{\to }{\mathop{B}}\,.d\overset{\to }{\mathop{l}}\,}={{\mu }_{o}}I\]

The ratio of momenta of an electron and an \[\alpha -\]particle which are accelerated from rest by a potential difference of 100 V is [MNR 1994; RPET 1997]

Assertion : If an electron is not deflected while passing through a certain region of space, then only possibility is that there is no magnetic region. Reason : Force is directly proportional to the magnetic field applied.

Consider telecommunication through optical fibres. Which of the following statements is not true [AIEEE 2003]

Which one of the following statements is true for the speed v and the acceleration a of a particle executing simple harmonic motion [CBSE PMT 2004]

Assertion : X-ray travel with the speed of light. Reason : X-rays are electromagnetic rays. [AIIMS 2001]

Snow is more heat insulating than ice, because

The radii of two metallic spheres \[P\] and \[Q\] are \[{{r}_{1}}\] and\[{{r}_{2}}\] respectively. They are given the same charge. If \[{{r}_{1}}>{{r}_{2}}\]. then on connecting them with a thin wire, the charge will flow [MP PMT 1985]

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true [IIT JEE (Screening) 2000]

In a circuit \[L,\,C\text{ and }R\]are connected in series with an alternating voltage source of frequency \[f\]. The current leads the voltage by 45°. The value of \[C\] is [CBSE PMT 2005]

Assertion : The angle of contact of a liquid decrease with increase in temperature. Reason : With increase in temperature, the surface tension of liquid increase.

The capacity of a parallel plate capacitor with no dielectric substance but with a separation of 0.4 cm is \[2\mu \,F\]. The separation is reduced to half and it is filled with a dielectric substance of value 2.8. The final capacity of the capacitor is [CBSE PMT 2000]

Two bodies of different masses \[{{m}_{1}}\] and \[{{m}_{2}}\] have equal momenta. Their kinetic energies \[{{E}_{1}}\] and \[{{E}_{2}}\] are in the ratio [EAMCET 1990]

A wire in the form of a square of side ?a? carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space =\[{{\mu }_{o}})\] [EAMCET 2001]

The capacity of a pure capacitor is 1 farad. In dc circuits, its effective resistance will be [MP PMT 2000]

In Bohr's model, the atomic radius of the first orbit is \[{{r}_{0}}\], then the radius of the third orbit is [AIIMS 1997; CPMT 2001; KCET (Engg./Med.) 1999; Pb. PMT 2004]

There are two charges \[+1\,\mu C\] and \[+5\,\mu C\]. The ratio of the forces acting on them will be [CPMT 1979]

Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is [CBSE PMT 1999]

Assertion : For projection angle \[{{\tan }^{-1}}(4)\], the horizontal range and the maximum height of a projectile are equal. Reason : The maximum range of projectile is directly proportional to square of velocity and inversely proportional to acceleration due to gravity.

Assertion : The back emf in a dc motor is maximum when the motor has just been switched on. Reason : When motor is switched on it has maximum speed.

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.

When three forces of 50 N, 30 N and 15 N act on a body, then the body is

Assertion : A double convex lens (m = 1.5) has focal length 10 cm. When the lens is immersed in water (m = 4/3) its focal length becomes 40 cm. Reason : \[\frac{1}{f}=\frac{{{\mu }_{l}}-{{\mu }_{m}}}{{{\mu }_{m}}}\,\left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\] [AIIMS 1999]

Two vectors \[\overrightarrow{A}\]and \[\overrightarrow{B}\]lie in a plane, another vector \[\overrightarrow{C}\]lies outside this plane, then the resultant of these three vectors i.e.,\[\overrightarrow{A}+\overrightarrow{B}+\overrightarrow{C}\] [CPMT 1983]