50278 + Interview Questions in Physics

1.	Two charges +3.2×10−19 and −3.2×10−19 C placed 2.4˙A apart form an electric dipole. It is placed in a uniform electric field of intensity 4×105 volt/m. The electric dipole moment is
Answer» Two charges $+ 3.2 \times 10^{- 19}$ and $- 3.2 \times 10^{- 19}$ C placed $2.4 ˙ A$ apart form an electric dipole. It is placed in a uniform electric field of intensity $4 \times 10^{5}$ volt/m. The electric dipole moment is

Discussion

2.	A cubical block of ice of mass m and edge L is placed in a large tray of mass M. If the ice melts, how far does the centre of mass of the system "ice plus tray” come down with reference to the point O as shown in figure
Answer» A cubical block of ice of mass m and edge L is placed in a large tray of mass M. If the ice melts, how far does the centre of mass of the system "ice plus tray” come down with reference to the point O as shown in figure

2.

A cubical block of ice of mass m and edge L is placed in a large tray of mass M. If the ice melts, how far does the centre of mass of the system "ice plus tray” come down with reference to the point O as shown in figure

Answer»

A cubical block of ice of mass m and edge L is placed in a large tray of mass M. If the ice melts, how far does the centre of mass of the system "ice plus tray” come down with reference to the point O as shown in figure

Discussion

3.	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 bright. Why?
Answer» 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 bright. Why?

Discussion

4.	A small object is placed 50 cm to the left of a thin convex lens of focal length 30 cm. A convex spherical mirror of radius of curvature 100 cm is placed to the right of the lens at a distance of 50 cm. The mirror is tilted such that the axis of the mirror is a an angle θ=30∘ to the axis of the lens, as shown in the figure. If the origin of the coordinate system is taken to be at the centre of the lens, the coordinates (in cm) of the point (x,y) at which the image is formed are
Answer» A small object is placed $50 c m$ to the left of a thin convex lens of focal length $30 c m$ . A convex spherical mirror of radius of curvature $100 c m$ is placed to the right of the lens at a distance of $50 c m$ . The mirror is tilted such that the axis of the mirror is a an angle $θ = 30^{\circ}$ to the axis of the lens, as shown in the figure. If the origin of the coordinate system is taken to be at the centre of the lens, the coordinates (in cm) of the point $(x, y)$ at which the image is formed are

Discussion

5.	Capillary tube is a very thin tube. If it is dipped in water, water rises upto height h=2Trρg, where r is the radius of tube, ρ is density, and g is acceleration due to gravity. Find dimensional formula of [T]
Answer» Capillary tube is a very thin tube. If it is dipped in water, water rises upto height $h = \frac{2 T}{r ρ g},$ where r is the radius of tube, $ρ$ is density, and g is acceleration due to gravity. Find dimensional formula of [T]

5.

Capillary tube is a very thin tube. If it is dipped in water, water rises upto height h=2Trρg, where r is the radius of tube, ρ is density, and g is acceleration due to gravity. Find dimensional formula of [T]

Answer»

Capillary tube is a very thin tube. If it is dipped in water, water rises upto height $h = \frac{2 T}{r ρ g},$ where r is the radius of tube, $ρ$ is density, and g is acceleration due to gravity. Find dimensional formula of [T]

Discussion

6.	A tap is attached to a water tank as shown in figure. Water level above the tap is maintained at h=0.2 m. The cross-sectional area of the tap is √2×10−4 m2. Assuming constant pressure throughout the stream of water, find the velocity & cross-sectional area of the stream 0.2 m below the opening of the tap :- [Assume g=10 m/s2]
Answer» A tap is attached to a water tank as shown in figure. Water level above the tap is maintained at $h = 0.2 m$ . The cross-sectional area of the tap is $\sqrt{2} \times 10^{- 4} m^{2}$ . Assuming constant pressure throughout the stream of water, find the velocity & cross-sectional area of the stream $0.2 m$ below the opening of the tap :- $[Assume g = 10 {m/s}^{2}]$

Discussion

7.	A train is approaching a platform with a speed of 20 km/hr. A bird is sitting on a pole at the platform. When train is 2 km away from the pole, brakes are applied so that the train decelerates uniformly, simultaneously the bird also flies towards the train with a velocity 60 km/hr. It touches the nearest point on the train and flies back and back again and so on. The total distance travelled by the bird before train stops is
Answer» A train is approaching a platform with a speed of $20 km/hr$ . A bird is sitting on a pole at the platform. When train is $2 km$ away from the pole, brakes are applied so that the train decelerates uniformly, simultaneously the bird also flies towards the train with a velocity $60 km/hr$ . It touches the nearest point on the train and flies back and back again and so on. The total distance travelled by the bird before train stops is

Discussion

8.	A force acts on a 1 kg particle such that position of particle as a function of time is given by x=2t2−4, where ′x′ in m and t is in seconds. The work done during initial 4 seconds is
Answer» A force acts on a $1 kg$ particle such that position of particle as a function of time is given by $x = 2 t^{2} - 4$ , where $^{'} x^{'}$ in $m$ and $t$ is in $seconds$ . The work done during initial $4$ seconds is

Discussion

9.	Two Carnot engines A and B are operated in series. The first one A receives heat from a source at temperature 800 K and rejects heat to a reservoir at temperature T K. The second engine B receives the heat rejected by the first engine and in turn rejects to a heat reservoir at temperature 300 K Find the value of temperature T if the efficiencies of two engines are equal. (Take √6=2.45 for calculation)
Answer» Two Carnot engines $A$ and $B$ are operated in series. The first one $A$ receives heat from a source at temperature $800 K$ and rejects heat to a reservoir at temperature $T K$ . The second engine $B$ receives the heat rejected by the first engine and in turn rejects to a heat reservoir at temperature $300 K$ Find the value of temperature $T$ if the efficiencies of two engines are equal. (Take $\sqrt{6} = 2.45$ for calculation)

Discussion

10.	Which of the following predictions of the classical wave model of light (Maxwell's EM theory) were contradicted by the observations during the photoelectric effect experiment?
Answer» Which of the following predictions of the classical wave model of light (Maxwell's EM theory) were contradicted by the observations during the photoelectric effect experiment?

Discussion

11.	The position of the particle moving on X-axis is given by, X=At3+Bt2+Ct+D. The numerical values of A,B,C,D are 1,4,−2 and 5 respectively and SI units are used. Find the average velocity during the interval t=0 to t=4 s.
Answer» The position of the particle moving on $X$ -axis is given by, $X = A t^{3} + B t^{2} + C t + D .$ The numerical values of $A, B, C, D$ are $1, 4, - 2$ and $5$ respectively and SI units are used. Find the average velocity during the interval $t = 0$ to $t = 4 s$ .

Discussion

12.	Calculate the heat of fusion of ice from the following data for ice at 0∘C added to water. Mass of calorimeter = 60gm, mass of calorimeter + water = 460 gm, mass of calorimeter + water + ice = 618 gm, initial temperature of water = 38∘C, final temperature of the mixture = 5∘C. The specific heat of calorimeter = 0.10 cal/g/∘C. Assume that the calorimeter was also at 0∘C initially.
Answer» Calculate the heat of fusion of ice from the following data for ice at $0^{\circ} C$ added to water. Mass of calorimeter = 60gm, mass of calorimeter + water = 460 gm, mass of calorimeter + water + ice = 618 gm, initial temperature of water = $38^{\circ} C$ , final temperature of the mixture = $5^{\circ} C$ . The specific heat of calorimeter = $0.10 c a l / g /^{\circ} C$ . Assume that the calorimeter was also at $0^{\circ} C$ initially.

Discussion

13.	How did we get the three displacements as 30i^ ;10i^+10√3 j^ ; -45 i^
Answer» How did we get the three displacements as 30i^ ;10i^+10√3 j^ ; -45 i^

Discussion

14.	The bob of a pendulum at rest is given a hit to impart a horizontal velocity √gl m/s at the bottommost position of the bob, where l is the length of the string in metres. Find the tangential acceleration at the point where the velocity of the bob is zero. Take g=10 m/s2
Answer» The bob of a pendulum at rest is given a hit to impart a horizontal velocity $\sqrt{g l} m/s$ at the bottommost position of the bob, where $l$ is the length of the string in $metres$ . Find the tangential acceleration at the point where the velocity of the bob is zero. Take $g = 10 {m/s}^{2}$

Discussion

15.	If the momentum of the body is 0 then it's kinetic energy is also 0?
Answer» If the momentum of the body is 0 then it's kinetic energy is also 0?

Discussion

16.	What is the unit for angular velocity and angular acceleration
Answer» What is the unit for angular velocity and angular acceleration

Discussion

17.	A particle moves along a straight line such that its displacement at any time t is given by s=(t3−6t2+3t+4) m. The velocity when the acceleration is zero is
Answer» A particle moves along a straight line such that its displacement at any time $t$ is given by $s = (t^{3} - 6 t^{2} + 3 t + 4) m$ . The velocity when the acceleration is zero is

Discussion

18.	Is this a assumption that one wavelenght is called 2 pi ??? if not then how it is said that one wavelenght is 2 pi only and why not some other value
Answer» Is this a assumption that one wavelenght is called 2 pi ??? if not then how it is said that one wavelenght is 2 pi only and why not some other value

Discussion

19.	A boat moves relative to water with a velocity 'v' which is n times less than the river flow velocity u. At what angle to the north direction must the boat move to minimize drifting if the river flows from west to east?
Answer» A boat moves relative to water with a velocity 'v' which is n times less than the river flow velocity u. At what angle to the north direction must the boat move to minimize drifting if the river flows from west to east?

Discussion

20.	How can we know,which molecule is polar and which is non polar molecule?
Answer» How can we know,which molecule is polar and which is non polar molecule?

Discussion

21.	If the wavelength is equal to the distance travelled by the electron in one second then, A) wavelength =h/p . B) wavelength=h/m . C) wavelength=(h/p)1/2 D) wavelength = (h/m)1/2
Answer» If the wavelength is equal to the distance travelled by the electron in one second then, A) wavelength =h/p . B) wavelength=h/m . C) wavelength=(h/p)^1/2 D) wavelength = (h/m)^1/2

21.

If the wavelength is equal to the distance travelled by the electron in one second then, A) wavelength =h/p . B) wavelength=h/m . C) wavelength=(h/p)1/2 D) wavelength = (h/m)1/2

Answer»

If the wavelength is equal to the distance travelled by the electron in one second then,

A) wavelength =h/p . B) wavelength=h/m . C) wavelength=(h/p)^1/2 D) wavelength = (h/m)^1/2

Discussion

22.	The self gravitional potential energy of a spherical shell of mass M and radius R is
Answer» The self gravitional potential energy of a spherical shell of mass M and radius R is

Discussion

23.	a stone is allowed to fall from the top of a tower 100 M high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m per second .calculate when and where the two stones will meet
Answer» a stone is allowed to fall from the top of a tower 100 M high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m per second .calculate when and where the two stones will meet

Discussion

24.	Why poisson ratio of imcompressible substance is 0.5?
Answer» Why poisson ratio of imcompressible substance is 0.5?

Discussion

25.	A body A is projected upwards with a velocity of 98 m/s. The second body B is projected upwards with the same initial velocity but after 4 sec. Both the bodies will meet after
Answer» A body A is projected upwards with a velocity of 98 m/s. The second body B is projected upwards with the same initial velocity but after 4 sec. Both the bodies will meet after

Discussion

26.	A unit vector parallel to the resultant of the vectors →A=^i+4^j−2^k and →B=3^i−5^j+^k is
Answer» A unit vector parallel to the resultant of the vectors $\to A =^i + 4^j - 2^k$ and $\to B = 3^i - 5^j +^k$ is

Discussion

27.	Two fixed points are A(a, 0) and B(-a, 0). If ∠A−∠B=θ, then the locus of point C of triangle ABC will be
Answer» Two fixed points are A(a, 0) and B(-a, 0). If $∠ A - ∠ B = θ$ , then the locus of point C of triangle ABC will be

27.

Two fixed points are A(a, 0) and B(-a, 0). If ∠A−∠B=θ, then the locus of point C of triangle ABC will be

Answer»

Two fixed points are A(a, 0) and B(-a, 0). If $∠ A - ∠ B = θ$ , then the locus of point C of triangle ABC will be

Discussion

28.	A particle moves on the X-axis according to the equation x=A+Bsinω t. The motion is simple harmonic with amplitude.
Answer» A particle moves on the X-axis according to the equation $x = A + B s i n ω t$ . The motion is simple harmonic with amplitude.

Discussion

29.	Two cars leave with a time gap of 1 minute from the same point. They move with an acceleration of 0.2 m/s2. How long after the departure of the second car, does the distance between them become equal to three times its value, when the second car just starts?
Answer» Two cars leave with a time gap of 1 minute from the same point. They move with an acceleration of 0.2 m/s². How long after the departure of the second car, does the distance between them become equal to three times its value, when the second car just starts?

Discussion

30.	There are m points on a straight line AB and n points on another line AC, none of them being the point A. Triangles are formed from these points as vertices when (i) A is excluded (ii) A is included. Then the ratio of the number of triangles in the two cases is
Answer» There are m points on a straight line AB and n points on another line AC, none of them being the point A. Triangles are formed from these points as vertices when (i) A is excluded (ii) A is included. Then the ratio of the number of triangles in the two cases is

Discussion

31.	Which of the following statements on critical constants of gases are correct? I : Larger the TcPc value of a gas, larger would be the excluded volume. II : Critical temperature (Tc) of a gas is greater than its Boyle's temperature (TB). III : At the critical point in the Van der Walls gas isotherm. ⟮dPdVm⟯Tc=0
Answer» Which of the following statements on critical constants of gases are correct? I : Larger the $\frac{T_{c}}{P_{c}}$ value of a gas, larger would be the excluded volume. II : Critical temperature ( $T_{c}$ ) of a gas is greater than its Boyle's temperature ( $T_{B}$ ). III : At the critical point in the Van der Walls gas isotherm. $⟮ \frac{d P}{d V_{m}} ⟯ T_{c} = 0$

31.

Which of the following statements on critical constants of gases are correct? I : Larger the TcPc value of a gas, larger would be the excluded volume. II : Critical temperature (Tc) of a gas is greater than its Boyle's temperature (TB). III : At the critical point in the Van der Walls gas isotherm. ⟮dPdVm⟯Tc=0

Answer»

Which of the following statements on critical constants of gases are correct?

I : Larger the $\frac{T_{c}}{P_{c}}$ value of a gas, larger would be the excluded volume.

II : Critical temperature ( $T_{c}$ ) of a gas is greater than its Boyle's temperature ( $T_{B}$ ).

III : At the critical point in the Van der Walls gas isotherm.

$⟮ \frac{d P}{d V_{m}} ⟯ T_{c} = 0$

Discussion

32.	A potentiometer wire of length 10 m and a resistance 30Ω is connected in series with a battery of emf 2.5 V and internal resistance 5Ω and an external resistance R. If the fall of potential along the potentiometer wire is 50 μV/mm, the value of R is (in Ω)
Answer» A potentiometer wire of length 10 m and a resistance $30 Ω$ is connected in series with a battery of emf 2.5 V and internal resistance $5 Ω$ and an external resistance R. If the fall of potential along the potentiometer wire is $50 μ V / m m$ , the value of R is (in $Ω$ )

Discussion

33.	A plate current of 10 mA is obtained when 60 volts are applied across a diode tube. Assuming the Langmuir - child equation ip∝V32p to hold, find the dynamic resistance rp in this operating condition.
Answer» A plate current of 10 mA is obtained when 60 volts are applied across a diode tube. Assuming the Langmuir - child equation $i_{p} \propto V_{p}^{\frac{3}{2}}$ to hold, find the dynamic resistance $r_{p}$ in this operating condition.

Discussion

34.	In a double slit experiment, green light of 5303 ∘A falls on a double slit having a separation of 19.44 μm and a width of 4.05 μm. The number of bright fringes between the first and the second diffraction minima is :
Answer» In a double slit experiment, green light of $5303 \circ A$ falls on a double slit having a separation of $19.44 μ m$ and a width of $4.05 μ m$ . The number of bright fringes between the first and the second diffraction minima is :

Discussion

35.	A particle rests on the top of a smooth hemisphere of radius r. It is imparted a horizontal velocity of √gr. Find the normal reaction when it makes an angle θ=60∘ with vertical.
Answer» A particle rests on the top of a smooth hemisphere of radius $r$ . It is imparted a horizontal velocity of $\sqrt{g r}$ . Find the normal reaction when it makes an angle $θ = 60^{\circ}$ with vertical.

Discussion

36.	A particle is released from rest from a height of 4h, on a smooth track as shown in figure. When the particle reaches point C, then the normal reaction on it by the track is: (C is the highest point on the circular part of the track)
Answer» A particle is released from rest from a height of $4 h$ , on a smooth track as shown in figure. When the particle reaches point $C$ , then the normal reaction on it by the track is: ( $C$ is the highest point on the circular part of the track)

Discussion

37.	A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in Li++ will be (Ionisation energy of hydrogen atom is 13.6 eV)
Answer» A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in $L i^{+ +}$ will be (Ionisation energy of hydrogen atom is 13.6 eV)

Discussion

38.	Ultra pure form of germanium is used to make:
Answer» Ultra pure form of germanium is used to make:

Discussion

39.	An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is (h=6.62×10−34Js; c=3×108m/s)
Answer» An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is $(h = 6.62 \times 10^{- 34} J s$ ; $c = 3 \times 10^{8} m / s)$

Discussion

40.	A square frame λ of mass m and side a carries a current i. It is placed in a B-field in the x-y plane making an angle 45∘with x–axis. Find the initial angular acceleration of the frame if I0=4ma23kgm2.
Answer» A square frame $λ$ of mass m and side a carries a current i. It is placed in a B-field in the x-y plane making an angle $45^{\circ}$ with x–axis. Find the initial angular acceleration of the frame if $I_{0} = \frac{4 m a^{2}}{3} k g m^{2}$ .

Discussion

41.	Two small balls, each of mass m are connected by a light rigid rod of length L. The system is suspended from its centre by a thin wire of torsional constant k. The rod is rotated about the wire through an angle θ0 and released. Find the force exerted by the rod on one of the balls as the system passes through the mean position.
Answer» Two small balls, each of mass m are connected by a light rigid rod of length L. The system is suspended from its centre by a thin wire of torsional constant k. The rod is rotated about the wire through an angle $θ_{0}$ and released. Find the force exerted by the rod on one of the balls as the system passes through the mean position.

41.

Two small balls, each of mass m are connected by a light rigid rod of length L. The system is suspended from its centre by a thin wire of torsional constant k. The rod is rotated about the wire through an angle θ0 and released. Find the force exerted by the rod on one of the balls as the system passes through the mean position.

Answer»

Two small balls, each of mass m are connected by a light rigid rod of length L. The system is suspended from its centre by a thin wire of torsional constant k. The rod is rotated about the wire through an angle $θ_{0}$ and released. Find the force exerted by the rod on one of the balls as the system passes through the mean position.

Discussion

42.	An astronomical telescope consists of an objective of focal length 60 cm and an eye - piece of focal length 5 cm. It is focused on a distant object such that the rays emerging from the eye - lens are parallel. The object subtends an angle of 2∘ at the objective. The angular width of the image is
Answer» An astronomical telescope consists of an objective of focal length 60 cm and an eye - piece of focal length 5 cm. It is focused on a distant object such that the rays emerging from the eye - lens are parallel. The object subtends an angle of $2^{\circ}$ at the objective. The angular width of the image is

Discussion

43.	The product of perpendiculars from any point P (θ) on the hyperbola x24−y29 = 1to its asymptotes is equal to:
Answer» The product of perpendiculars from any point P $(θ)$ on the hyperbola $\frac{x^{2}}{4} - \frac{y^{2}}{9}$ = 1to its asymptotes is equal to:

Discussion

44.	A ball is dropped from a height h0 on a horizontal floor and keeps rebounding after hitting the floor. Find: (i) speed after n rebounds (ii) Total distance travelled by the ball before stopping (iii) Height it rises after nth rebound (iv) Total time before stopping (coefficient of restitution is e)
Answer» A ball is dropped from a height $h_{0}$ on a horizontal floor and keeps rebounding after hitting the floor. Find: (i) speed after $n$ rebounds (ii) Total distance travelled by the ball before stopping (iii) Height it rises after nth rebound (iv) Total time before stopping (coefficient of restitution is $e$ )

44.

A ball is dropped from a height h0 on a horizontal floor and keeps rebounding after hitting the floor. Find: (i) speed after n rebounds (ii) Total distance travelled by the ball before stopping (iii) Height it rises after nth rebound (iv) Total time before stopping (coefficient of restitution is e)

Answer»

A ball is dropped from a height $h_{0}$ on a horizontal floor and keeps rebounding after hitting the floor. Find: (i) speed after $n$ rebounds

(ii) Total distance travelled by the ball before stopping

(iii) Height it rises after nth rebound

(iv) Total time before stopping

(coefficient of restitution is $e$ )

Discussion

45.	We have 3 conducting spheres A,B and C of radius 2R, R and R2 respectively. Out of the 3, A is charged to some charge. Charged sphere A touches B and then both are separated by distance d. Force between A and B is F. Again this sphere B touches C and is separated by distance d from C then force between B and C is
Answer» We have 3 conducting spheres A,B and C of radius 2R, R and $\frac{R}{2}$ respectively. Out of the 3, A is charged to some charge. Charged sphere A touches B and then both are separated by distance d. Force between A and B is F. Again this sphere B touches C and is separated by distance d from C then force between B and C is

Discussion

46.	If a car covers 25th of the total distance with v1 speed and 35th distance with v2 then average speed is
Answer» If a car covers $\frac{2}{5^{t h}}$ of the total distance with $v_{1}$ speed and $\frac{3}{5^{t h}}$ distance with $v_{2}$ then average speed is

Discussion

47.	Explain briefly the various non-conventional sources of energy.
Answer» Explain briefly the various non-conventional sources of energy.

Discussion

48.	The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is [NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]
Answer» The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is [NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]

48.

The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is [NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]

Answer»

The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is

[NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]

Discussion

49.	The temperature inside a refrigerator is t 2°C and the room temperature is t 1°C. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be
Answer» The temperature inside a refrigerator is $t_{2} ° C$ and the room temperature is $t_{1} ° C$ . The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

Discussion

50.	In the given circuit, inductor of L=1 mH and resistance R=1 Ω are connected in series to the ends of two parallel conducting rods as shown. Now a rod of length 10 cm is moved with constant velocity of 1 cm/s in magnetic field B=1 T. If rod starts moving at t=0, then the current in circuit after 1 millisecond is x×103 A. Then the value of x is (given e−1=0.37)
Answer» In the given circuit, inductor of $L = 1 m H$ and resistance $R = 1 Ω$ are connected in series to the ends of two parallel conducting rods as shown. Now a rod of length $10 c m$ is moved with constant velocity of $1 c m / s$ in magnetic field $B = 1 T$ . If rod starts moving at $t = 0$ , then the current in circuit after 1 millisecond is $x \times 10^{3} A$ . Then the value of $x$ is (given $e^{- 1} = 0.37$ )

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Two charges +3.2×10−19 and −3.2×10−19 C placed 2.4˙A apart form an electric dipole. It is placed in a uniform electric field of intensity 4×105 volt/m. The electric dipole moment is

A cubical block of ice of mass m and edge L is placed in a large tray of mass M. If the ice melts, how far does the centre of mass of the system "ice plus tray” come down with reference to the point O as shown in figure

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 bright. Why?

Capillary tube is a very thin tube. If it is dipped in water, water rises upto height h=2Trρg, where r is the radius of tube, ρ is density, and g is acceleration due to gravity. Find dimensional formula of [T]

A force acts on a 1 kg particle such that position of particle as a function of time is given by x=2t2−4, where ′x′ in m and t is in seconds. The work done during initial 4 seconds is

Which of the following predictions of the classical wave model of light (Maxwell's EM theory) were contradicted by the observations during the photoelectric effect experiment?

The position of the particle moving on X-axis is given by, X=At3+Bt2+Ct+D. The numerical values of A,B,C,D are 1,4,−2 and 5 respectively and SI units are used. Find the average velocity during the interval t=0 to t=4 s.

How did we get the three displacements as 30i^ ;10i^+10√3 j^ ; -45 i^

The bob of a pendulum at rest is given a hit to impart a horizontal velocity √gl m/s at the bottommost position of the bob, where l is the length of the string in metres. Find the tangential acceleration at the point where the velocity of the bob is zero. Take g=10 m/s2

If the momentum of the body is 0 then it's kinetic energy is also 0?

What is the unit for angular velocity and angular acceleration

A particle moves along a straight line such that its displacement at any time t is given by s=(t3−6t2+3t+4) m. The velocity when the acceleration is zero is

Is this a assumption that one wavelenght is called 2 pi ??? if not then how it is said that one wavelenght is 2 pi only and why not some other value

A boat moves relative to water with a velocity 'v' which is n times less than the river flow velocity u. At what angle to the north direction must the boat move to minimize drifting if the river flows from west to east?

How can we know,which molecule is polar and which is non polar molecule?

If the wavelength is equal to the distance travelled by the electron in one second then, A) wavelength =h/p . B) wavelength=h/m . C) wavelength=(h/p)1/2 D) wavelength = (h/m)1/2

The self gravitional potential energy of a spherical shell of mass M and radius R is

a stone is allowed to fall from the top of a tower 100 M high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m per second .calculate when and where the two stones will meet

Why poisson ratio of imcompressible substance is 0.5?

A body A is projected upwards with a velocity of 98 m/s. The second body B is projected upwards with the same initial velocity but after 4 sec. Both the bodies will meet after

A unit vector parallel to the resultant of the vectors →A=^i+4^j−2^k and →B=3^i−5^j+^k is

Two fixed points are A(a, 0) and B(-a, 0). If ∠A−∠B=θ, then the locus of point C of triangle ABC will be

A particle moves on the X-axis according to the equation x=A+Bsinω t. The motion is simple harmonic with amplitude.

Two cars leave with a time gap of 1 minute from the same point. They move with an acceleration of 0.2 m/s2. How long after the departure of the second car, does the distance between them become equal to three times its value, when the second car just starts?

There are m points on a straight line AB and n points on another line AC, none of them being the point A. Triangles are formed from these points as vertices when (i) A is excluded (ii) A is included. Then the ratio of the number of triangles in the two cases is

A potentiometer wire of length 10 m and a resistance 30Ω is connected in series with a battery of emf 2.5 V and internal resistance 5Ω and an external resistance R. If the fall of potential along the potentiometer wire is 50 μV/mm, the value of R is (in Ω)

A plate current of 10 mA is obtained when 60 volts are applied across a diode tube. Assuming the Langmuir - child equation ip∝V32p to hold, find the dynamic resistance rp in this operating condition.

In a double slit experiment, green light of 5303 ∘A falls on a double slit having a separation of 19.44 μm and a width of 4.05 μm. The number of bright fringes between the first and the second diffraction minima is :

A particle rests on the top of a smooth hemisphere of radius r. It is imparted a horizontal velocity of √gr. Find the normal reaction when it makes an angle θ=60∘ with vertical.

A particle is released from rest from a height of 4h, on a smooth track as shown in figure. When the particle reaches point C, then the normal reaction on it by the track is: (C is the highest point on the circular part of the track)

A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in Li++ will be (Ionisation energy of hydrogen atom is 13.6 eV)

Ultra pure form of germanium is used to make:

An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is (h=6.62×10−34Js; c=3×108m/s)

A square frame λ of mass m and side a carries a current i. It is placed in a B-field in the x-y plane making an angle 45∘with x–axis. Find the initial angular acceleration of the frame if I0=4ma23kgm2.

An astronomical telescope consists of an objective of focal length 60 cm and an eye - piece of focal length 5 cm. It is focused on a distant object such that the rays emerging from the eye - lens are parallel. The object subtends an angle of 2∘ at the objective. The angular width of the image is

The product of perpendiculars from any point P (θ) on the hyperbola x24−y29 = 1to its asymptotes is equal to:

A ball is dropped from a height h0 on a horizontal floor and keeps rebounding after hitting the floor. Find: (i) speed after n rebounds (ii) Total distance travelled by the ball before stopping (iii) Height it rises after nth rebound (iv) Total time before stopping (coefficient of restitution is e)

If a car covers 25th of the total distance with v1 speed and 35th distance with v2 then average speed is

Explain briefly the various non-conventional sources of energy.

The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 Å. The wavelength of this light when it passes through glass is [NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]

The temperature inside a refrigerator is t 2°C and the room temperature is t 1°C. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

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 bright. Why?