12583 + Mcqs in Physics Page 177 McqOptions

8801.	In a capillary tube experiment, a vertical 30 cm long capillary tube is dipped in water. The water rises up to a height of 10cm due to capillary action. If this experiment is conducted in a freely falling elevator, the length of the water column becomes [Orissa JEE 2003; AIEEE 2005]
A.	10 cm
B.	20 cm
C.	30 cm
D.	Zero
Answer» D. Zero

Discussion

8802.	In a beryllium atom, if a0 be the radius of the first orbit, then the radius of the second orbit will be in general [CBSE PMT 1992; Roorkee 1993; BHU 1998]
A.	\[n{{a}_{0}}\]
B.	\[{{a}_{0}}\]
C.	\[{{n}^{2}}{{a}_{0}}\]
D.	\[\frac{{{a}_{0}}}{{{n}^{2}}}\]
Answer» D. \[\frac{{{a}_{0}}}{{{n}^{2}}}\]

Discussion

8803.	In Millikan?s oil drop experiment, an oil drop of mass \[16\times {{10}^{-6}}kg\] is balanced by an electric field of \[{{10}^{6}}V/m.\] The charge in coulomb on the drop, assuming \[g=10\,m/{{s}^{2}}\] is [UP SEAT 2005]
A.	\[6.2\times {{10}^{-11}}\]
B.	\[16\times {{10}^{-9}}\]
C.	\[16\times {{10}^{-11}}\]
D.	\[16\times {{10}^{-13}}\]
Answer» D. \[16\times {{10}^{-13}}\]

Discussion

8804.	If \[\gamma =2.5\] and volume is equal to \[\frac{1}{8}\] times to the initial volume then pressure P' is equal to (Initial pressure = P) [RPET 2003]
A.	\[P'=P\]
B.	\[P'=2P\]
C.	\[P'=P\times {{(2)}^{15/2}}\]
D.	\[P'=7P\]
Answer» D. \[P'=7P\]

Discussion

8805.	The force between two charges \[0.06\,m\] apart is \[5\,N\]. If each charge is moved towards the other by \[0.01\,m\], then the force between them will become [SCRA 1994]
A.	\[7.20\,N\]
B.	\[11.25\,N\]
C.	\[22.50\,N\]
D.	\[45.00\,N\]
Answer» C. \[22.50\,N\]

Discussion

8806.	Assertion : A bulb connected in series with a solenoid is connected to ac source. If a soft iron core is introduced in the solenoid, the bulb will glow brighter. Reason : On introducing soft iron core in the solenoid, the inductance increases.
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

8807.	With the rise in temperature, the dielectric constant \[K\]of a liquid
A.	Increases
B.	Decreases
C.	Remains unchanged
D.	Charges erratically
Answer» C. Remains unchanged

Discussion

8808.	The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is [Roorkee 1995; BHU 2002]
A.	? 1
B.	2
C.	1 : 2
D.	None of these
Answer» B. 2

Discussion

8809.	The following diagram indicates the energy levels of a certain atom when the system moves from 2E level to E, a photon of wavelength \[\lambda \] is emitted. The wavelength of photon produced during its transition from \[\frac{4E}{3}\] level to E is [CPMT 1989]
A.	\[\lambda /3\]
B.	\[3\lambda /4\]
C.	\[4\lambda /3\]
D.	\[3\lambda \]
Answer» E.

Discussion

8810.	The core of a transformer is laminated to reduce energy losses due to [CBSE PMT 1990; Karnataka CET (Med.) 2001]
A.	Eddy currents
B.	Hysteresis
C.	Resistance in winding
D.	None of these
Answer» B. Hysteresis

Discussion

8811.	The diameters of two planets are in the ratio 4 : 1 and their mean densities in the ratio 1 : 2. The acceleration due to gravity on the planets will be in ratio [ISM Dhanbad 1994]
A.	1 : 2
B.	2 : 3
C.	2 : 1
D.	4 : 1
Answer» D. 4 : 1

Discussion

8812.	Assertion : The crystalline solids have a sharp melting point. Reason : All the bonds between the atoms or molecules of a crystalline solids are equally strong, that they 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8813.	Separation between the plates of a parallel plate capacitor is \[d\]and the area of each plate is \[A\]. When a slab of material of dielectric constant\[k\]and thickness \[t(t
A.	\[\frac{{{\varepsilon }_{0}}A}{d+t\left( 1-\frac{1}{k} \right)}\]
B.	\[\frac{{{\varepsilon }_{0}}A}{d+t\left( 1+\frac{1}{k} \right)}\]
C.	\[\frac{{{\varepsilon }_{0}}A}{d-t\left( 1-\frac{1}{k} \right)}\]
D.	\[\frac{{{\varepsilon }_{0}}A}{d-t\left( 1+\frac{1}{k} \right)}\]
Answer» D. \[\frac{{{\varepsilon }_{0}}A}{d-t\left( 1+\frac{1}{k} \right)}\]

Discussion

8814.	Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening. Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours. [AIIMS 2003]
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

8815.	Assertion : A body can have acceleration even if its velocity is zero at a given instant of time. Reason : A body is momentarily at rest when it reverses its direction of 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8816.	When 100 volt dc is applied across a coil, a current of 1 amp flows through it. When 100 volt ac at 50 cycle\[{{s}^{-1}}\] is applied to the same coil, only 0.5 ampere current flows. The impedance of the coil is [Bihar MEE 1995]
A.	\[100\,\Omega \]
B.	\[200\,\Omega \]
C.	\[300\,\Omega \]
D.	\[400\,\Omega \]
Answer» C. \[300\,\Omega \]

Discussion

8817.	Assertion : A transistor amplifier in common emitter configuration has a low input impedence. Reason : The base to emitter region is forward biased. [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

8818.	Assertion : The number of electrons in a P-type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature. Reason : It is due to law of mass action. [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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8819.	Assertion : In a common emitter transistor amplifier the input current is much less than the output current. Reason : The common emitter transistor amplifier has very high input impedance. [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

8820.	The energy of a hydrogen atom in its ground state is \[-13.6\ eV\]. The energy of the level corresponding to the quantum number n = 2 (first excited state) in the hydrogen atom is [CBSE PMT 1996; CBSE PMT 1997, 2001; MP PET 2000; AFMC 2000, 01, 02; BCECE 2003]
A.	? 2.72 eV
B.	? 0.85 eV
C.	? 0.54 eV
D.	? 3.4 eV
Answer» E.

Discussion

8821.	In the following atoms and moleculates for the transition from n= 2 to n = 1, the spectral line of minimum wavelength will be produced by [IIT 1983]
A.	Hydrogen atom
B.	Deuterium atom
C.	Uni-ionized helium
D.	di-ionized lithium
Answer» E.

Discussion

8822.	Two rectangular blocks A and B of different metals have same length and same area of cross-section. They are kept in such a way that their cross-sectional area touch each other. The temperature at one end of A is 100°C and that of B at the other end is 0°C. If the ratio of their thermal conductivity is 1 : 3, then under steady state, the temperature of the junction in contact will be [MP PMT 1985]
A.	25°C
B.	50°C
C.	75°C
D.	100°C
Answer» B. 50°C

Discussion

8823.	(Radius of the earth R = 6400 kilometers) Choose the correct statement from the following : Weightlessness of an astronaut moving in a satellite is a situation of [MP PMT 1995]
A.	Zero g
B.	No gravity
C.	Zero mass
D.	Free fall
Answer» E.

Discussion

8824.	The ratio of the magnetic field at the centre of a current carrying coil of the radius a and at a distance ?a? from centre of the coil and perpendicular to the axis of coil is [MP PET 2002]
A.	\[\frac{1}{\sqrt{2}}\]
B.	\[\sqrt{2}\]
C.	\[\frac{1}{2\sqrt{2}}\]
D.	\[2\sqrt{2}\]
Answer» E.

Discussion

8825.	What displacement must be added to the displacement \[25\hat{i}-6\hat{j}\,\,m\] to give a displacement of 7.0 m pointing in the x- direction
A.	\[18\hat{i}-6\hat{j}\]
B.	\[32\hat{i}-13\hat{j}\]
C.	\[-18\hat{i}+6\hat{j}\]
D.	\[-25\hat{i}+13\hat{j}\]
Answer» D. \[-25\hat{i}+13\hat{j}\]

Discussion

8826.	A body is vibrating in simple harmonic motion with an amplitude of 0.06 m and frequency of 15 Hz. The velocity and acceleration of body is [AFMC 1999]
A.	\[5.65\,m/s\] and \[5.32\times {{10}^{2}}m/{{s}^{2}}\]
B.	\[6.82\,m/s\] and \[7.62\times {{10}^{2}}m/{{s}^{2}}\]
C.	\[8.91\,m/s\] and \[8.21\times {{10}^{2}}m/{{s}^{2}}\]
D.	\[9.82\,m/s\] and \[9.03\times {{10}^{2}}m/{{s}^{2}}\]
Answer» B. \[6.82\,m/s\] and \[7.62\times {{10}^{2}}m/{{s}^{2}}\]

Discussion

8827.	The kinetic energy of an electron revolving around a nucleus will be [BCECE 2004]
A.	Four times of P.E.
B.	Double of P.E.
C.	Equal to P.E.
D.	Half of its P.E.
Answer» E.

Discussion

8828.	A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance. The magnetic field at P is [MNR 1986; DPMT 2004]
A.	Greater than at Q
B.	Same as at Q
C.	Less than at Q
D.	Greater or less than at Q depending upon the strength of the current
Answer» C. Less than at Q

Discussion

8829.	Assertion : Acceleration is proportional to the displacement. This condition is not sufficient for motion in simple harmonic. Reason : In simple harmonic motion direction of displacement is also considered.
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

8830.	Assertion : Sine and cosine functions are periodic functions. Reason : Sinusoidal functions repeats it values after a definite interval of 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

8831.	Assertion : Simple harmonic motion is a uniform motion. Reason : Simple harmonic motion is the projection of uniform circular 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» F.

Discussion

8832.	According to classical theory, the circular path of an electron in Rutherford atom is [BHU 2001]
A.	Spiral
B.	Circular
C.	Parabolic
D.	Straight line
Answer» B. Circular

Discussion

8833.	Assertion : An aircraft flies along the meridian, the potential at the ends of its wings will be the same. Reason : Whenever there is change in the magnetic flux e.m.f. induces.
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

8834.	Which pair of the following forces will never give resultant force of 2 N [HP PMT 1999]
A.	2 N and 2 N
B.	1 N and 1 N
C.	1 N and 3 N
D.	1 N and 4 N
Answer» E.

Discussion

8835.	Assertion : If the distance between parallel plates of a capacitor is halved and dielectric constant is made three times, then the capacitor becomes 6 times. Reason : Capacity of the capacitor does not depend upon the nature of the material. [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

8836.	An alternating current source of frequency 100 Hz is joined to a combination of a resistance, a capacitance and a coil in series. The potential difference across the coil, the resistance and the capacitor is 46, 8 and 40 volt respectively. The electromotive force of alternating current source in volt is [MP PET 1995]
A.	94
B.	14
C.	10
D.	76
Answer» D. 76

Discussion

8837.	Weight of 1 kg becomes 1/6 on moon. If radius of moon is \[1.768\times {{10}^{6}}\,m\], then the mass of moon will be [RPET 1997]
A.	\[1.99\times {{10}^{30}}\,kg\]
B.	\[7.56\times {{10}^{22}}\,kg\]
C.	\[5.98\times {{10}^{24}}\,kg\]
D.	\[7.65\times {{10}^{22}}\,kg\]
Answer» E.

Discussion

8838.	Assertion : The equivalent thermal conductivity of two plates of same thickness in contact (series) is less than the smaller value of thermal conductivity. Reason : For two plates of equal thickness in contact (series) the equivalent thermal conductivity is given by [AIIMS 1997] \[\frac{1}{K}=\frac{1}{{{K}_{1}}}+\frac{1}{{{K}_{2}}}\]
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

8839.	Assertion : Specific heat of a body is always greater than its thermal capacity. Reason : Thermal capacity is the required for raising temperature of unit mass of the body through unit degree.
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

8840.	Assertion : The average speed of a body over a given interval of time is equal to the average velocity of the body in the same interval of time if a body moves in a straight line in one direction. Reason : Because in this case distance travelled by a body is equal to the displacement of the body.
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

8841.	Assertion : Zener diode works on a principle of breakdown voltage. Reason : Current increases suddenly after breakdown voltage.
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

8842.	The earth?s magnetic field at a given point is \[0.5\times {{10}^{-5}}Wb\text{-}{{m}^{-2}}\]. This field is to be annulled by magnetic induction at the center of a circular conducting loop of radius 5.0cm. The current required to be flown in the loop is nearly [AIIMS 2003]
A.	0.2 A
B.	0.4A
C.	4A
D.	40A
Answer» C. 4A

Discussion

8843.	A conducting sphere of radius 10cm is charged \[10\mu \,C\]. Another uncharged sphere of radius 20 cm is allowed to touch it for some time. After that if the sphere are separated, then surface density of charges, on the spheres will be in the ratio of [AIIMS 2002]
A.	1 : 4
B.	1 : 3
C.	2 : 1
D.	1 : 1
Answer» D. 1 : 1

Discussion

8844.	The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correct [MP PET 1993]
A.	Lines of force minimum but induced e.m.f. is zero
B.	Lines of force maximum but induced e.m.f. is zero
C.	Lines of force maximum but induced e.m.f. is not zero
D.	Lines of force maximum but induced e.m.f. is also maximum
Answer» C. Lines of force maximum but induced e.m.f. is not zero

Discussion

8845.	The natural frequency of a L-C circuit is equal to [CPMT 1978, 97]
A.	\[\frac{1}{2\pi }\sqrt{LC}\]
B.	\[\frac{1}{2\pi \sqrt{LC}}\]
C.	\[\frac{1}{2\pi }\sqrt{\frac{L}{C}}\]
D.	\[\frac{1}{2\pi }\sqrt{\frac{C}{L}}\]
Answer» C. \[\frac{1}{2\pi }\sqrt{\frac{L}{C}}\]

Discussion

8846.	The concept of stationary orbits was proposed by [Pb. PMT 2000]
A.	Neil Bohr
B.	J.J. Thomson
C.	Ruther ford
D.	I. Newton
Answer» B. J.J. Thomson

Discussion

8847.	A long solenoid of length L has a mean diameter D. It has n layers of windings of N turns each. If it carries a current ?i? the magnetic field at its centre will be [MP PMT 2000]
A.	Proportional to D
B.	Inversely proportional to D
C.	Independent of D
D.	Proportional to L
Answer» D. Proportional to L

Discussion

8848.	A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is B. It is then bent into a circular loop of n turns. The magnetic field at the centre of the coil will be [AIEEE 2004]
A.	nB
B.	n2B
C.	2nB
D.	2n2B
Answer» C. 2nB

Discussion

8849.	Assertion : In the case of free fall of the lift, the man will feel weightlessness. Reason : In free fall, acceleration of lift is equal 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» B. If both assertion and reason are true but reason is not the correct explanation of the assertion.

Discussion

8850.	A \[10\,pF\] capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor [KCET 1999]
A.	\[1.25\times {{10}^{-8}}\,J\]
B.	\[2.5\times {{10}^{-7}}\,J\]
C.	\[3.5\times {{10}^{-5}}\,J\]
D.	\[4.5\times {{10}^{-2}}\,J\]
Answer» B. \[2.5\times {{10}^{-7}}\,J\]

Discussion

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

In a capillary tube experiment, a vertical 30 cm long capillary tube is dipped in water. The water rises up to a height of 10cm due to capillary action. If this experiment is conducted in a freely falling elevator, the length of the water column becomes [Orissa JEE 2003; AIEEE 2005]

In a beryllium atom, if a0 be the radius of the first orbit, then the radius of the second orbit will be in general [CBSE PMT 1992; Roorkee 1993; BHU 1998]

In Millikan?s oil drop experiment, an oil drop of mass \[16\times {{10}^{-6}}kg\] is balanced by an electric field of \[{{10}^{6}}V/m.\] The charge in coulomb on the drop, assuming \[g=10\,m/{{s}^{2}}\] is [UP SEAT 2005]

If \[\gamma =2.5\] and volume is equal to \[\frac{1}{8}\] times to the initial volume then pressure P' is equal to (Initial pressure = P) [RPET 2003]

The force between two charges \[0.06\,m\] apart is \[5\,N\]. If each charge is moved towards the other by \[0.01\,m\], then the force between them will become [SCRA 1994]

Assertion : A bulb connected in series with a solenoid is connected to ac source. If a soft iron core is introduced in the solenoid, the bulb will glow brighter. Reason : On introducing soft iron core in the solenoid, the inductance increases.

With the rise in temperature, the dielectric constant \[K\]of a liquid

The ratio of the kinetic energy to the total energy of an electron in a Bohr orbit is [Roorkee 1995; BHU 2002]

The following diagram indicates the energy levels of a certain atom when the system moves from 2E level to E, a photon of wavelength \[\lambda \] is emitted. The wavelength of photon produced during its transition from \[\frac{4E}{3}\] level to E is [CPMT 1989]

The core of a transformer is laminated to reduce energy losses due to [CBSE PMT 1990; Karnataka CET (Med.) 2001]

The diameters of two planets are in the ratio 4 : 1 and their mean densities in the ratio 1 : 2. The acceleration due to gravity on the planets will be in ratio [ISM Dhanbad 1994]

Assertion : The crystalline solids have a sharp melting point. Reason : All the bonds between the atoms or molecules of a crystalline solids are equally strong, that they get broken at the same temperature.

Separation between the plates of a parallel plate capacitor is \[d\]and the area of each plate is \[A\]. When a slab of material of dielectric constant\[k\]and thickness \[t(t

Assertion : When a bottle of cold carbonated drink is opened, a slight fog forms around the opening. Reason : Adiabatic expansion of the gas causes lowering of temperature and condensation of water vapours. [AIIMS 2003]

Assertion : A body can have acceleration even if its velocity is zero at a given instant of time. Reason : A body is momentarily at rest when it reverses its direction of motion.

When 100 volt dc is applied across a coil, a current of 1 amp flows through it. When 100 volt ac at 50 cycle\[{{s}^{-1}}\] is applied to the same coil, only 0.5 ampere current flows. The impedance of the coil is [Bihar MEE 1995]

Assertion : A transistor amplifier in common emitter configuration has a low input impedence. Reason : The base to emitter region is forward biased. [AIIMS 2004]

Assertion : The number of electrons in a P-type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature. Reason : It is due to law of mass action. [AIIMS 2005]

Assertion : In a common emitter transistor amplifier the input current is much less than the output current. Reason : The common emitter transistor amplifier has very high input impedance. [AIIMS 2005]

The energy of a hydrogen atom in its ground state is \[-13.6\ eV\]. The energy of the level corresponding to the quantum number n = 2 (first excited state) in the hydrogen atom is [CBSE PMT 1996; CBSE PMT 1997, 2001; MP PET 2000; AFMC 2000, 01, 02; BCECE 2003]

In the following atoms and moleculates for the transition from n= 2 to n = 1, the spectral line of minimum wavelength will be produced by [IIT 1983]

(Radius of the earth R = 6400 kilometers) Choose the correct statement from the following : Weightlessness of an astronaut moving in a satellite is a situation of [MP PMT 1995]

The ratio of the magnetic field at the centre of a current carrying coil of the radius a and at a distance ?a? from centre of the coil and perpendicular to the axis of coil is [MP PET 2002]

What displacement must be added to the displacement \[25\hat{i}-6\hat{j}\,\,m\] to give a displacement of 7.0 m pointing in the x- direction

A body is vibrating in simple harmonic motion with an amplitude of 0.06 m and frequency of 15 Hz. The velocity and acceleration of body is [AFMC 1999]

The kinetic energy of an electron revolving around a nucleus will be [BCECE 2004]

A vertical straight conductor carries a current vertically upwards. A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance. The magnetic field at P is [MNR 1986; DPMT 2004]

Assertion : Acceleration is proportional to the displacement. This condition is not sufficient for motion in simple harmonic. Reason : In simple harmonic motion direction of displacement is also considered.

Assertion : Sine and cosine functions are periodic functions. Reason : Sinusoidal functions repeats it values after a definite interval of time.

Assertion : Simple harmonic motion is a uniform motion. Reason : Simple harmonic motion is the projection of uniform circular motion.

According to classical theory, the circular path of an electron in Rutherford atom is [BHU 2001]

Assertion : An aircraft flies along the meridian, the potential at the ends of its wings will be the same. Reason : Whenever there is change in the magnetic flux e.m.f. induces.

Which pair of the following forces will never give resultant force of 2 N [HP PMT 1999]

Assertion : If the distance between parallel plates of a capacitor is halved and dielectric constant is made three times, then the capacitor becomes 6 times. Reason : Capacity of the capacitor does not depend upon the nature of the material. [AIIMS 1997]

Weight of 1 kg becomes 1/6 on moon. If radius of moon is \[1.768\times {{10}^{6}}\,m\], then the mass of moon will be [RPET 1997]

Assertion : Specific heat of a body is always greater than its thermal capacity. Reason : Thermal capacity is the required for raising temperature of unit mass of the body through unit degree.

Assertion : The average speed of a body over a given interval of time is equal to the average velocity of the body in the same interval of time if a body moves in a straight line in one direction. Reason : Because in this case distance travelled by a body is equal to the displacement of the body.

Assertion : Zener diode works on a principle of breakdown voltage. Reason : Current increases suddenly after breakdown voltage.

The earth?s magnetic field at a given point is \[0.5\times {{10}^{-5}}Wb\text{-}{{m}^{-2}}\]. This field is to be annulled by magnetic induction at the center of a circular conducting loop of radius 5.0cm. The current required to be flown in the loop is nearly [AIIMS 2003]

A conducting sphere of radius 10cm is charged \[10\mu \,C\]. Another uncharged sphere of radius 20 cm is allowed to touch it for some time. After that if the sphere are separated, then surface density of charges, on the spheres will be in the ratio of [AIIMS 2002]

The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correct [MP PET 1993]

The natural frequency of a L-C circuit is equal to [CPMT 1978, 97]

The concept of stationary orbits was proposed by [Pb. PMT 2000]

A long solenoid of length L has a mean diameter D. It has n layers of windings of N turns each. If it carries a current ?i? the magnetic field at its centre will be [MP PMT 2000]

A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is B. It is then bent into a circular loop of n turns. The magnetic field at the centre of the coil will be [AIEEE 2004]

Assertion : In the case of free fall of the lift, the man will feel weightlessness. Reason : In free fall, acceleration of lift is equal to acceleration due to gravity.

A \[10\,pF\] capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor [KCET 1999]