50278 + Interview Questions in Physics

1.	You are given an isolated capacitor of capacitance C (without dielectric) C charged to a potential difference V. Find how many times will each of the following becomes if a dielectric slab of dielectric constant 4 is inserted between its plates, completely filling the gap between the plates: a. capacitance b. potential difference c. field between the plates d. energy stored by the plates
Answer» You are given an isolated capacitor of capacitance C (without dielectric) C charged to a potential difference V. Find how many times will each of the following becomes if a dielectric slab of dielectric constant 4 is inserted between its plates, completely filling the gap between the plates: a. capacitance b. potential difference c. field between the plates d. energy stored by the plates

1.

You are given an isolated capacitor of capacitance C (without dielectric) C charged to a potential difference V. Find how many times will each of the following becomes if a dielectric slab of dielectric constant 4 is inserted between its plates, completely filling the gap between the plates: a. capacitance b. potential difference c. field between the plates d. energy stored by the plates

Answer»

You are given an isolated capacitor of capacitance C (without dielectric) C charged to a potential difference V. Find how many times will each of the following becomes if a dielectric slab of dielectric constant 4 is inserted between its plates, completely filling the gap between the plates:

a. capacitance

b. potential difference

c. field between the plates

d. energy stored by the plates

2.	How dynamics differ from mechanics?
Answer» How dynamics differ from mechanics?

3.	If at 298 K the bond energies of C - H, C - C, C - C and H - H bonds are respectively 414, 347, 615 and 435 kJ mol−1, the value of enthalpy change for the reaction H2C = CH2(g) → H3C − CH3(g) at 298K will be
Answer» If at $298 K$ the bond energies of C - H, C - C, C - C and H - H bonds are respectively 414, 347, 615 and 435 $k J m o l^{- 1}$ , the value of enthalpy change for the reaction $H_{2} C = C H_{2} (g) \to H_{3} C - C H_{3} (g)$ at 298K will be

4.	What is the momentum of photon of energy 3 MeV in kgms−1?
Answer» What is the momentum of photon of energy 3 MeV in $k g m s^{- 1}$ ?

5.	A tuning fork of frequency 250 Hz produces 4 beats per second with a wire of length 25 cm vibrating in its fundamental mode. The beat frequency decreases when the length is slightly shortened. What could be the minimum length by which the wire be shortened so that it produces no beats with the tuning fork?
Answer» A tuning fork of frequency $250 H z$ produces $4$ beats per second with a wire of length $25 c m$ vibrating in its fundamental mode. The beat frequency decreases when the length is slightly shortened. What could be the minimum length by which the wire be shortened so that it produces no beats with the tuning fork?

6.	A cracker rocket is ejecting gases at a rate of 0.05kg/s with a velocity 400 m/s. What will be the accelerating force on the rocket?
Answer» A cracker rocket is ejecting gases at a rate of 0.05kg/s with a velocity 400 m/s. What will be the accelerating force on the rocket?

7.	IA,IB and IC are the moments of inertia of a ring, semicircular ring and an arc of the same mass about the axes as shown below. Which of the following options is correct?
Answer» $I_{A}, I_{B}$ and $I_{C}$ are the moments of inertia of a ring, semicircular ring and an arc of the same mass about the axes as shown below. Which of the following options is correct?

9.	A ball moving with a momentum of 5 kg m/s strikes against a wall at an angle of 45° and is reflected at the same angle. Calculate the change in momentum (in magnitude).
Answer» A ball moving with a momentum of $5 kg m/s$ strikes against a wall at an angle of 45° and is reflected at the same angle. Calculate the change in momentum (in magnitude).

11.	Flux emerging from curved surface of hemisphere due to charge Q may be
Answer» Flux emerging from curved surface of hemisphere due to charge Q may be

12.	What does the author mean by 'buck up'?
Answer» What does the author mean by 'buck up'?

13.	Match the column I with column II Column IColumn IIA. When non−conservative forces are actingP. Work done by force may be negative.B. In the case of a pendulum, work done by tensionQ. Net Workdone is zeroC. When there is frictionR. The only force acting is gravityD. In Projectile motionS. Work done by force in a roundtrip is not equal to zero.
Answer» Match the column I with column II $\begin{matrix} C o l u m n I & C o l u m n I I A . W h e n n o n - c o n s e r v a t i v e f o r c e s a r e a c t i n g & P . W o r k d o n e b y f o r c e m a y b e n e g a t i v e . B . I n t h e c a s e o f a p e n d u l u m, w o r k d o n e b y t e n s i o n & Q . N e t W o r k d o n e i s z e r o C . W h e n t h e r e i s f r i c t i o n & R . T h e o n l y f o r c e a c t i n g i s g r a v i t y D . I n P r o j e c t i l e m o t i o n & S . W o r k d o n e b y f o r c e i n a r o u n d t r i p i s n o t e q u a l t o z e r o . \end{matrix}$

14.	A point charge q moves with velocity v along a straight line. Displacement current density at a point located at a distance r from charge and in the line of motion of the charge will be
Answer» A point charge q moves with velocity v along a straight line. Displacement current density at a point located at a distance r from charge and in the line of motion of the charge will be

15.	If each resistance in the figure is of 9Ω then reading of ammeter is
Answer» If each resistance in the figure is of $9 Ω$ then reading of ammeter is

16.	An open lift is coming down from the top of a building at a constant speed v=10 m/s. A boy standing on the lift throw a stone vertically upwards at a speed of 30 m/s w.r.t. himself. The time after which he will catch the stone is:
Answer» An open lift is coming down from the top of a building at a constant speed v=10 m/s. A boy standing on the lift throw a stone vertically upwards at a speed of 30 m/s w.r.t. himself. The time after which he will catch the stone is:

17.	A triangular wire frame, each side of 2 m is placed in a region of time variant magnetic field having dBdt=√3 T/s . The magnetic field is perpendicular to the plane of the triangle. The base of the triangle AB has a resistance 1 Ω while the other two sides have resistance 2 Ω each. The magnitude of the potential difference between the points A and B will be (Note: Magnetic field is absent inside the triangular loop)
Answer» A triangular wire frame, each side of $2 m$ is placed in a region of time variant magnetic field having $\frac{d B}{d t} = \sqrt{3} T / s$ . The magnetic field is perpendicular to the plane of the triangle. The base of the triangle $A B$ has a resistance $1 Ω$ while the other two sides have resistance $2 Ω$ each. The magnitude of the potential difference between the points $A$ and $B$ will be (Note: Magnetic field is absent inside the triangular loop)

18.	(a) State Biot—Savart law and express this law in the vector form. (b) Two identical circular coils, P and Q each of radius R, carrying currents 1 A and √3 A respectively, are placed concentrically and perpendicular to each other lying in the XY and YZ planes. Find the magnitude and direction of the net magnetic field at the centre of the coils.
Answer» (a) State Biot—Savart law and express this law in the vector form. (b) Two identical circular coils, P and Q each of radius R, carrying currents 1 A and $\sqrt{3}$ A respectively, are placed concentrically and perpendicular to each other lying in the XY and YZ planes. Find the magnitude and direction of the net magnetic field at the centre of the coils.

19.	For a body, absorptive power is 0.6, then emissivity of the body must be
Answer» For a body, absorptive power is 0.6, then emissivity of the body must be

20.	Need some questions based on stoichiometry
Answer» Need some questions based on stoichiometry

21.	A whistle producing sound waves of frequency 9500Hz is approaching a stationary person with speed v m per second .the velocity of sound is 300m per s .if the person can hear frequencies upto a max of 10000 Hz the max value of v upto which he can hear is ans 15m per second
Answer» A whistle producing sound waves of frequency 9500Hz is approaching a stationary person with speed v m per second .the velocity of sound is 300m per s .if the person can hear frequencies upto a max of 10000 Hz the max value of v upto which he can hear is ans 15m per second

23.	A block of mass 2 kg placed on a long frictionless horizontal table is pulled horizontally by a constant force F. It is found to move 10 m in the first two seconds. Find the magnitude of F.
Answer» A block of mass 2 kg placed on a long frictionless horizontal table is pulled horizontally by a constant force F. It is found to move 10 m in the first two seconds. Find the magnitude of F.

24.	A cube of mass M starts at rest from point 1 at a height 4R, where R is the radius of the circular track. The cube slides down the frictionless track and around the loop. The force which the track exerts on the cube at point 2 is:
Answer» A cube of mass M starts at rest from point 1 at a height 4R, where R is the radius of the circular track. The cube slides down the frictionless track and around the loop. The force which the track exerts on the cube at point 2 is:

25.	An electric dipole has fixed dipole moment →p, which makes angle θ with respect to x-axis. When subjected to an electric field −→E1=E ^i, it experiences a torque →T1=τ ^k. When subjected to another electric field −→E2=√3E1^j, it experiences a torque →T2=−→T1. The angle θ is
Answer» An electric dipole has fixed dipole moment $\to p$ , which makes angle $θ$ with respect to x-axis. When subjected to an electric field $_{1} = E^i$ , it experiences a torque $_{1} = τ^k$ . When subjected to another electric field $_{2} = \sqrt{3} E_{1}^j$ , it experiences a torque $_{2} = -_{1}$ . The angle $θ$ is

26.	Two positively charged spheres of masses m1 and m2 , are suspended from a common point at the ceiling by identical insulating massless strings of length l. Charges on the two spheres are q1 and q2 , respectively. At equilibrium both strings make the same angle θ with the vertical. Then
Answer» Two positively charged spheres of masses $m_{1}$ and $m_{2}$ , are suspended from a common point at the ceiling by identical insulating massless strings of length l. Charges on the two spheres are $q_{1}$ and $q_{2}$ , respectively. At equilibrium both strings make the same angle $θ$ with the vertical. Then

27.	A mass rests on a rough horizontal surface having coefficient of friction between the surfaces as μ. A force F at 30∘ with horizontal pulls the mass. Limiting friction between surface and mass is
Answer» A mass rests on a rough horizontal surface having coefficient of friction between the surfaces as $μ$ . A force F at $30^{\circ}$ with horizontal pulls the mass. Limiting friction between surface and mass is

28.	∫sec4x.tanx dx=
Answer» $\int {sec}^{4} x . tan x d x =$

Explore topic-wise InterviewSolutions in Current Affairs.

How dynamics differ from mechanics?

If at 298 K the bond energies of C - H, C - C, C - C and H - H bonds are respectively 414, 347, 615 and 435 kJ mol−1, the value of enthalpy change for the reaction H2C = CH2(g) → H3C − CH3(g) at 298K will be

What is the momentum of photon of energy 3 MeV in kgms−1?

A cracker rocket is ejecting gases at a rate of 0.05kg/s with a velocity 400 m/s. What will be the accelerating force on the rocket?

IA,IB and IC are the moments of inertia of a ring, semicircular ring and an arc of the same mass about the axes as shown below. Which of the following options is correct?

What is escape velocity

A ball moving with a momentum of 5 kg m/s strikes against a wall at an angle of 45° and is reflected at the same angle. Calculate the change in momentum (in magnitude).

A uniform rod of length 2.0 m specific gravity 0.5 and mass 2 kg is hinged at one end to the bottom of a tank of water (specific gravity = 0.5) filled upto a height of 1.0 m as shown in figure. Taking the case θ≠0∘ the force exerted by the hinge on the rod is (g=10m/s2)

Flux emerging from curved surface of hemisphere due to charge Q may be

What does the author mean by 'buck up'?

A point charge q moves with velocity v along a straight line. Displacement current density at a point located at a distance r from charge and in the line of motion of the charge will be

If each resistance in the figure is of 9Ω then reading of ammeter is

An open lift is coming down from the top of a building at a constant speed v=10 m/s. A boy standing on the lift throw a stone vertically upwards at a speed of 30 m/s w.r.t. himself. The time after which he will catch the stone is:

For a body, absorptive power is 0.6, then emissivity of the body must be

Need some questions based on stoichiometry

A whistle producing sound waves of frequency 9500Hz is approaching a stationary person with speed v m per second .the velocity of sound is 300m per s .if the person can hear frequencies upto a max of 10000 Hz the max value of v upto which he can hear is ans 15m per second

A block of mass 2 kg placed on a long frictionless horizontal table is pulled horizontally by a constant force F. It is found to move 10 m in the first two seconds. Find the magnitude of F.

A cube of mass M starts at rest from point 1 at a height 4R, where R is the radius of the circular track. The cube slides down the frictionless track and around the loop. The force which the track exerts on the cube at point 2 is:

An electric dipole has fixed dipole moment →p, which makes angle θ with respect to x-axis. When subjected to an electric field −→E1=E ^i, it experiences a torque →T1=τ ^k. When subjected to another electric field −→E2=√3E1^j, it experiences a torque →T2=−→T1. The angle θ is

Two positively charged spheres of masses m1 and m2 , are suspended from a common point at the ceiling by identical insulating massless strings of length l. Charges on the two spheres are q1 and q2 , respectively. At equilibrium both strings make the same angle θ with the vertical. Then

A mass rests on a rough horizontal surface having coefficient of friction between the surfaces as μ. A force F at 30∘ with horizontal pulls the mass. Limiting friction between surface and mass is

∫sec4x.tanx dx=

A point charge q is placed at the apex of a cone as shown in figure. find the flux linked through the base of the cone.

A wire whose cross sectional area is increasing linearly from its one end to the other, is connected across a battery of V volts.which of the following quantities remain constant in the wire?(a)drift velocity(b)current density (c) electric current (d) electric field.justify your answer.

Light from a bathroom bulb gets dimmer for a moment when the geyser is switched on. Why?

A wire of uniform cross-section is bent in the shape shown in the figure. The coordinates of the centre of mass of each side are shown in the figure. Origin is taken at O. Find the coordinates of the center of mass of the given system.

Find the derivative of y=esinθ with respect to θ

Two bodies of mass 0.4 kg and 0.8 kg move towards each other with initial velocities 5 m/s and 2 m/s respectively. After the collision, they stick together. Then, find the distance travelled by the combined mass, 12 sec after the collision.

The angular speed of a flywheel making 60 revolutions/minute is

The energy required to take the electron from second orbit to third orbit of hydrogen atom is approximately

Find the absolue maximum value and the absolute minimum value of the following function in the given intervals: f(x)=(x−1)2+3,xϵ[−3,1]

For a projectile thrown with a speed v, the horizontal range is √3v22g. The vertical range is v28g. The angle which the projectile makes with the horizontal initially is

At what temperature does the rms speed of oxygen molecules equal the escape velocity of - (i) Earth, (ii) the Moon? The gravitational acceleration of the Moon is 0.6g.

Find the heat current, i.

The effect of electric field strength due to a dielectric slab in uniform electric field.

A liquid flows in the tube, left to right as shown in figure. d1 and d2 are the diameter of tube as shown in figure. Find the ratio of speed V1V2.

A 2kg block is dropped from a height of 0.4 m on a spring of force constant K = 1960 Nm−1. The maximum compression of the spring is 0.1 m0.2 m0.3 m0.4 m

A stone dropped is from the top of a building and One second later another stone is thrown down with velocity 20m/s.how far below the top will the second over take the first?

If effective nuclear charge of F(Z=9) is X and effective nuclear charge of Li (Z=3) is Y then find the value of |X-Y|

Both the strings, shown in figure, are made of same material and have same cross-section. The pulleys are light. The wave speed of a transverse wave in the string AB is V1 and in CD it is V2. Then V1V2 is

When a load of 20 kg is hung from a wire is cross-sectional area 1 sq mm, it's elongated length is 600.5 cm. If the load is withdrawn the wire shrinks by 0.5 cm in length. Calculate the youngs modulus of the wire?

30.	A wire whose cross sectional area is increasing linearly from its one end to the other, is connected across a battery of V volts.which of the following quantities remain constant in the wire?(a)drift velocity(b)current density (c) electric current (d) electric field.justify your answer.
Answer» A wire whose cross sectional area is increasing linearly from its one end to the other, is connected across a battery of V volts.which of the following quantities remain constant in the wire?(a)drift velocity(b)current density (c) electric current (d) electric field.justify your answer.

31.	Light from a bathroom bulb gets dimmer for a moment when the geyser is switched on. Why?
Answer» Light from a bathroom bulb gets dimmer for a moment when the geyser is switched on. Why?

32.	Two different coils have self-inductance L1 = 8mH and L2 = 2mH respectively. The current in both the coils is increased at a same rate. At a certain instant of time, the power being supplied to both the coils is equal. At that instant, the current, the induced voltage, and the energy stored in L1 and L2 are I1 and I2, V1 and V2, and W1 and W2 respectively. Then
Answer» Two different coils have self-inductance $L_{1}$ = 8mH and $L_{2}$ = 2mH respectively. The current in both the coils is increased at a same rate. At a certain instant of time, the power being supplied to both the coils is equal. At that instant, the current, the induced voltage, and the energy stored in $L_{1}$ and $L_{2}$ are $I_{1}$ and $I_{2}$ , $V_{1}$ and $V_{2}$ , and $W_{1}$ and $W_{2}$ respectively. Then

33.	A wire of uniform cross-section is bent in the shape shown in the figure. The coordinates of the centre of mass of each side are shown in the figure. Origin is taken at O. Find the coordinates of the center of mass of the given system.
Answer» A wire of uniform cross-section is bent in the shape shown in the figure. The coordinates of the centre of mass of each side are shown in the figure. Origin is taken at $O$ . Find the coordinates of the center of mass of the given system.

34.	Find the derivative of y=esinθ with respect to θ
Answer» Find the derivative of $y = e^{sin θ}$ with respect to $θ$

35.	Two bodies of mass 0.4 kg and 0.8 kg move towards each other with initial velocities 5 m/s and 2 m/s respectively. After the collision, they stick together. Then, find the distance travelled by the combined mass, 12 sec after the collision.
Answer» Two bodies of mass $0.4 kg$ and $0.8 kg$ move towards each other with initial velocities $5 m/s$ and $2 m/s$ respectively. After the collision, they stick together. Then, find the distance travelled by the combined mass, $12 sec$ after the collision.

36.	The angular speed of a flywheel making 60 revolutions/minute is
Answer» The angular speed of a flywheel making $60 revolutions/minute$ is

37.	The energy required to take the electron from second orbit to third orbit of hydrogen atom is approximately
Answer» The energy required to take the electron from second orbit to third orbit of hydrogen atom is approximately

39.	A large tank is filled with water (density ρ), upto height h. Water is coming out from section (4). Fluid pressure at section (3) at the instant shown is (Given : Area A2=A4=2A3 and A2,A3,A4 are very small as compared to A1; atmospheric pressure =P0. Assume water to be non-viscous and incompressible)
Answer» A large tank is filled with water (density $ρ$ ), upto height $h$ . Water is coming out from section (4). Fluid pressure at section (3) at the instant shown is (Given : Area $A_{2} = A_{4} = 2 A_{3}$ and $A_{2}, A_{3}, A_{4}$ are very small as compared to $A_{1}$ ; atmospheric pressure $= P_{0}$ . Assume water to be non-viscous and incompressible)

40.	For a projectile thrown with a speed v, the horizontal range is √3v22g. The vertical range is v28g. The angle which the projectile makes with the horizontal initially is
Answer» For a projectile thrown with a speed $v$ , the horizontal range is $\frac{\sqrt{3} v^{2}}{2 g}$ . The vertical range is $\frac{v^{2}}{8 g}$ . The angle which the projectile makes with the horizontal initially is