50278 + Interview Questions in Physics

1.	As shown in figure, a ring is performing combined translational and rotational motion with angular velocity 2 rad/s and the velocity of its COM is 4 m/s. Find the magnitude of velocity of point C on the ring.
Answer» As shown in figure, a ring is performing combined translational and rotational motion with angular velocity $2 rad/s$ and the velocity of its $COM$ is $4 m/s$ . Find the magnitude of velocity of point $C$ on the ring.

Discussion

2.	A body covers one-third of the distance with a velocity v1, the second one-third of the distance with a velocity v2 and the remaining distance with a velocity v3. The average velocity is
Answer» A body covers one-third of the distance with a velocity $v_{1}$ , the second one-third of the distance with a velocity $v_{2}$ and the remaining distance with a velocity $v_{3}$ . The average velocity is

Discussion

3.	Displacement of an object of mass 2 kg varies as s=3t2+5. Find out the value of workdone on the mass from t=0 to t=5 seconds.
Answer» Displacement of an object of mass $2 k g$ varies as $s = 3 t^{2} + 5$ . Find out the value of workdone on the mass from $t = 0$ to $t = 5$ seconds.

Discussion

4.	1 litre of an ideal gas (γ=1.5) at 300 K is suddenly cpmpressed to half its original volume. (a) Fibd the ratio of the final pressure to the initial pressure. (b) If the original pressure is 100 kPa, find the work done by the gas in the process. (c) What is the change in internal energy ? (d) What is the final temperature ? (e) The gas is now cooled to 300 K keeping its pressure constant. Calculate the work done durting the process. (f) The gas is now expanded isothermally to achieve its original volume of 1 litre Calculate the work done by the gas (g) Calculate the total work done in the cycle.
Answer» 1 litre of an ideal gas $(γ = 1.5)$ at 300 K is suddenly cpmpressed to half its original volume. (a) Fibd the ratio of the final pressure to the initial pressure. (b) If the original pressure is 100 kPa, find the work done by the gas in the process. (c) What is the change in internal energy ? (d) What is the final temperature ? (e) The gas is now cooled to 300 K keeping its pressure constant. Calculate the work done durting the process. (f) The gas is now expanded isothermally to achieve its original volume of 1 litre Calculate the work done by the gas (g) Calculate the total work done in the cycle.

4.

1 litre of an ideal gas (γ=1.5) at 300 K is suddenly cpmpressed to half its original volume. (a) Fibd the ratio of the final pressure to the initial pressure. (b) If the original pressure is 100 kPa, find the work done by the gas in the process. (c) What is the change in internal energy ? (d) What is the final temperature ? (e) The gas is now cooled to 300 K keeping its pressure constant. Calculate the work done durting the process. (f) The gas is now expanded isothermally to achieve its original volume of 1 litre Calculate the work done by the gas (g) Calculate the total work done in the cycle.

Answer»

1 litre of an ideal gas $(γ = 1.5)$ at 300 K is suddenly cpmpressed to half its original volume.

(a) Fibd the ratio of the final pressure to the initial pressure.

(b) If the original pressure is 100 kPa, find the work done by the gas in the process.

(c) What is the change in internal energy ?

(d) What is the final temperature ?

(e) The gas is now cooled to 300 K keeping its pressure constant. Calculate the work done durting the process.

(f) The gas is now expanded isothermally to achieve its original volume of 1 litre Calculate the work done by the gas

(g) Calculate the total work done in the cycle.

Discussion

5.	The idea of secondary wavelets for the propagation of a wave was first given by
Answer» The idea of secondary wavelets for the propagation of a wave was first given by

Discussion

6.	Body A of mass 4m moving with speed u collides with another body B of mass 2m at rest. The collision is head on and elastic in nature. After the collision, the fraction of kinetic energy lost by the colliding body A is
Answer» Body $A$ of mass $4 m$ moving with speed $u$ collides with another body $B$ of mass $2 m$ at rest. The collision is head on and elastic in nature. After the collision, the fraction of kinetic energy lost by the colliding body $A$ is

Discussion

7.	Semiconductor is opaque for light of wavelength less than 800 nm and it is not opaque for light of wavelength greater than 800 nm. Energy gap of semiconductor in electron volt is [Take hc=1240 eV−nm](Answer up to two decimal places)
Answer» Semiconductor is opaque for light of wavelength less than 800 nm and it is not opaque for light of wavelength greater than 800 nm. Energy gap of semiconductor in electron volt is [Take $h c = 1240 e V - n m$ ](Answer up to two decimal places)

Discussion

8.	N cells each of emf E and identical resistance r are grouped into sets of K cells connected in series. The sets are connected in parallel to a load of resistance R, then
Answer» N cells each of emf E and identical resistance r are grouped into sets of K cells connected in series. The sets are connected in parallel to a load of resistance R, then

Discussion

9.	An elevator which is moving with an upward acceleration of "a m/s2”. A person drops a coin to measure the acceleration 'a m/s2'. Find 'a' if the coin took 0.5s to hit the ground and the coin was dropped from a height of 3 m.
Answer» An elevator which is moving with an upward acceleration of "a $m / s^{2}$ ”. A person drops a coin to measure the acceleration 'a $m / s^{2}$ '. Find 'a' if the coin took 0.5s to hit the ground and the coin was dropped from a height of 3 m.

Discussion

10.	In the circuit, shown in fig. ‘K’ is open. The charge on capacitor C in steady state is q1. Now key is closed and at steady state, the charge on C is q2. The ratio of charges (q1q2) is
Answer» In the circuit, shown in fig. ‘K’ is open. The charge on capacitor C in steady state is $q_{1}$ . Now key is closed and at steady state, the charge on C is $q_{2}$ . The ratio of charges $(\frac{q_{1}}{q_{2}})$ is

Discussion

11.	Two blocks of masses m1=3m and m2=m are attached to the ends of a string which passes over a frictionless fixed pulley (which is a uniform disc of mass M=2m and radius R) as shown in Fig. The masses are then released. The acceleration of the system is
Answer» Two blocks of masses $m_{1} = 3 m$ and $m_{2} = m$ are attached to the ends of a string which passes over a frictionless fixed pulley (which is a uniform disc of mass $M = 2 m$ and radius R) as shown in Fig. The masses are then released. The acceleration of the system is

11.

Two blocks of masses m1=3m and m2=m are attached to the ends of a string which passes over a frictionless fixed pulley (which is a uniform disc of mass M=2m and radius R) as shown in Fig. The masses are then released. The acceleration of the system is

Answer»

Two blocks of masses $m_{1} = 3 m$ and $m_{2} = m$ are attached to the ends of a string which passes over a frictionless fixed pulley (which is a uniform disc of mass $M = 2 m$ and radius R) as shown in Fig. The masses are then released. The acceleration of the system is

Discussion

12.	Statement 1: A charged particle when placed at rest in any EFL always moves along the electric field lines. Statement 2: A point charge q when placed at rest in the EFL of another point charge Q, moves radially away from charge Q along EFL.
Answer» Statement 1: A charged particle when placed at rest in any EFL always moves along the electric field lines. Statement 2: A point charge q when placed at rest in the EFL of another point charge Q, moves radially away from charge Q along EFL.

12.

Statement 1: A charged particle when placed at rest in any EFL always moves along the electric field lines. Statement 2: A point charge q when placed at rest in the EFL of another point charge Q, moves radially away from charge Q along EFL.

Answer»

Statement 1: A charged particle when placed at rest in any EFL always moves along the electric field lines.

Statement 2: A point charge q when placed at rest in the EFL of another point charge Q, moves radially away from charge Q along EFL.

Discussion

13.	Light of wavelength 5.0×10−7m falls on a pair of narrow slits separated by a distance 2d. The interference pattern on a screen placed 2.0 m away shows that there is first dark fringe at the positions exactly opposite to each slit. The separation between the slits is:
Answer» Light of wavelength $5.0 \times 10^{- 7} m$ falls on a pair of narrow slits separated by a distance 2d. The interference pattern on a screen placed 2.0 m away shows that there is first dark fringe at the positions exactly opposite to each slit. The separation between the slits is:

Discussion

14.	In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be
Answer» In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be

Discussion

15.	A small block of a mass m = 1 kg is placed over a wedge of mass M = 4 kg as shown in the figure. Mass ‘m’ is released from rest. All surfaces are smooth. Origin ‘O’ is as shown in the figure. Normal reaction between the two blocks at an instant when absolute acceleration of ‘m’ is 5√3m/s2 (at an angle 60∘ with the horizontal) is ___N. Consider that the normal reaction at the instant is making 30∘ with the horizontal.
Answer» A small block of a mass m = 1 kg is placed over a wedge of mass M = 4 kg as shown in the figure. Mass ‘m’ is released from rest. All surfaces are smooth. Origin ‘O’ is as shown in the figure. Normal reaction between the two blocks at an instant when absolute acceleration of ‘m’ is $5 \sqrt{3} m / s^{2}$ (at an angle $60^{\circ}$ with the horizontal) is ___N. Consider that the normal reaction at the instant is making $30^{\circ}$ with the horizontal.

Discussion

16.	The two nearest harmonics of a tube closed at one end and open at the other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?
Answer» The two nearest harmonics of a tube closed at one end and open at the other end are $220 Hz$ and $260 Hz$ . What is the fundamental frequency of the system?

Discussion

17.	In which case nuclear force is stronger ? In case of nucleons having parallel spin or opposite spin ? Please explain the reasons.
Answer» In which case nuclear force is stronger ? In case of nucleons having parallel spin or opposite spin ? Please explain the reasons.

Discussion

18.	The moment of inertia of a thin rod of mass M and length L about an axis passing through the point at a distance L4 from one of its end and perpendicular to the rod is
Answer» The moment of inertia of a thin rod of mass $M$ and length $L$ about an axis passing through the point at a distance $\frac{L}{4}$ from one of its end and perpendicular to the rod is

Discussion

19.	A steam cylindrical pipe of inner radius 5 cm and outer radius 7 cm, having conductivity 0.07 W/mK, carries steam at 100∘C. If the temperature at the outer wall of the pipe jacket is 20∘C, then find the heat lost through the jacket per metre length in an hour.
Answer» A steam cylindrical pipe of inner radius $5 cm$ and outer radius $7 cm$ , having conductivity $0.07 W/mK$ , carries steam at $100^{\circ} C$ . If the temperature at the outer wall of the pipe jacket is $20^{\circ} C$ , then find the heat lost through the jacket per metre length in an hour.

Discussion

20.	The initial velocity of the particle is 10 m/sec and its retardation is 2 m/sec2. The distance moved by the particle in 5th second of its motion is
Answer» The initial velocity of the particle is $10 m/sec$ and its retardation is $2 {m/sec}^{2}$ . The distance moved by the particle in $5^{th}$ second of its motion is

Discussion

21.	A 660 Hz tuning fork sets up vibration in a string clamped at both ends. The wave speed for a transverse wave on this string is 220 ms−1 and the string vibrates in three loops. (a) Find the length of the string. (b) If the maximum amplitude of a particle is 0.5 cm, write a suitable equation describing the motion.
Answer» A 660 Hz tuning fork sets up vibration in a string clamped at both ends. The wave speed for a transverse wave on this string is $220 m s^{- 1}$ and the string vibrates in three loops. (a) Find the length of the string. (b) If the maximum amplitude of a particle is 0.5 cm, write a suitable equation describing the motion.

Discussion

22.	Metal spheres each of radius 2 cm are packed into a rectangular box of dimensions 16cm×8cm×8cm. When 16 spheres are packed the box is filled with preservative liquid. Find the volume of this liquid.(π=3.14)
Answer» Metal spheres each of radius 2 cm are packed into a rectangular box of dimensions $16 c m \times 8 c m \times 8 c m$ . When 16 spheres are packed the box is filled with preservative liquid. Find the volume of this liquid. $(π = 3.14)$

Discussion

23.	Which of the following statements is incorrect?
Answer» Which of the following statements is incorrect?

Discussion

24.	Two blocks A and B of masses m and 2m respectively are held at rest such that the spring is in natural length. Find out the accelerations of both the blocks just after release:
Answer» Two blocks $A$ and $B$ of masses $m$ and $2 m$ respectively are held at rest such that the spring is in natural length. Find out the accelerations of both the blocks just after release:

Discussion

25.	A homogenous rod of length ℓ = ηx and mass, M is lying on a smooth horizontal floor. A bullet of mass 'm' hits the rod at a distance 'x' from the middle of the rod at a velocity v0 perpendicular to the rod and comes to rest after collision. If the velocity of the farther end of the rod just after the impact is in the opposite direction of v0, then:
Answer» A homogenous rod of length ℓ = ηx and mass, M is lying on a smooth horizontal floor. A bullet of mass 'm' hits the rod at a distance 'x' from the middle of the rod at a velocity $v_{0}$ perpendicular to the rod and comes to rest after collision. If the velocity of the farther end of the rod just after the impact is in the opposite direction of $v_{0}$ , then:

Discussion

26.	Two rods (one semi-circular and other straight) of the same material and the same cross-sectional area are joined as shown in the figure. The points A and B are maintained at different temperature. The ratio of the heat transferred through a cross-section of a semicircular rod to the heat transferred through a cross section of the straight rod in a given time is
Answer» Two rods (one semi-circular and other straight) of the same material and the same cross-sectional area are joined as shown in the figure. The points $A$ and $B$ are maintained at different temperature. The ratio of the heat transferred through a cross-section of a semicircular rod to the heat transferred through a cross section of the straight rod in a given time is

Discussion

27.	An inclined plane is located at an angle of α=53∘ to the horizontal. There is a hole at point B in inclined plane as shown in the figure. A particle is projected along the plane with speed v0 at an angle β=37∘ to the horizontal in such a way so that it gets into the hole. Find the speed v0 (in m/s), if h=1 m, l=8 m and √5≅2.25. (Neglect any type of friction)
Answer» An inclined plane is located at an angle of $α = 53^{\circ}$ to the horizontal. There is a hole at point $B$ in inclined plane as shown in the figure. A particle is projected along the plane with speed $v_{0}$ at an angle $β = 37^{\circ}$ to the horizontal in such a way so that it gets into the hole. Find the speed $v_{0}$ (in $m / s$ ), if $h = 1 m$ , $l = 8 m$ and $\sqrt{5} ≅ 2.25$ . (Neglect any type of friction)

Discussion

28.	Figure shows a system of three concentric metal shells A, B and C with radii a, 2a and 3a respectively. Shell B is earthed and shell C is given a charge Q. Now if shell C is connected to shell A, then the final charge on the shell B is−Qx11, where the value of x is
Answer» Figure shows a system of three concentric metal shells $A, B$ and $C$ with radii $a, 2 a$ and $3 a$ respectively. Shell $B$ is earthed and shell $C$ is given a charge $Q$ . Now if shell $C$ is connected to shell $A$ , then the final charge on the shell $B is \frac{- Q x}{11}$ , where the value of $x$ is

Discussion

29.	All the graphs below are intended to represent the same motion. One of them does it incorrectly. Pick the incorrect option.
Answer» All the graphs below are intended to represent the same motion. One of them does it incorrectly. Pick the incorrect option.

Discussion

30.	List one gives certain physical quantity and List - II gives there magnitude. List - IList - II(I) Acceleration of 2 kg(P) 0(II) Acceleration of 4 kg(Q) 3(III) Acceleration of 6 kg(R) 6(IV) Friction between 2 kg & 4 kg(S)83(T)163(U)185 If external force of 40 N is applied horizontly on 4 kg block, Correct match for acceleration and friction is
Answer» List one gives certain physical quantity and List - II gives there magnitude. $\begin{matrix} List - I & List - II (I) Acceleration of 2 kg & (P) 0 (II) Acceleration of 4 kg & (Q) 3 (III) Acceleration of 6 kg & (R) 6 (IV) Friction between 2 kg & 4 kg & (S) \frac{8}{3} (T) \frac{16}{3} (U) \frac{18}{5} \end{matrix}$ If external force of 40 N is applied horizontly on 4 kg block, Correct match for acceleration and friction is

Discussion

31.	Two travelling waves y1=Asin[K(x+ct)] and y2=Asin[K(x–ct)] are superposed on a string. The distance between the adjacent nodes will be
Answer» Two travelling waves $y_{1} = A s i n [K (x + c t)]$ and $y_{2} = A s i n [K (x - c t)]$ are superposed on a string. The distance between the adjacent nodes will be

Discussion

32.	A calorimeter of mass m contains an equal mass of water in it. The temperature of the water and calorimeter is t2>0∘C. A block of ice of mass m and temperature t3<0∘C is gently dropped into the calorimeter. Let C1,C2 andC3 be the specific heats of material of calorimeter, water and ice respectively and L be the Latent heat of ice. The whole mixture in the calorimeter becomes water, if
Answer» A calorimeter of mass m contains an equal mass of water in it. The temperature of the water and calorimeter is $t_{2} > 0^{\circ} C$ . A block of ice of mass m and temperature $t_{3} < 0^{\circ} C$ is gently dropped into the calorimeter. Let $C_{1}, C_{2}$ and $C_{3}$ be the specific heats of material of calorimeter, water and ice respectively and L be the Latent heat of ice. The whole mixture in the calorimeter becomes water, if

Discussion

33.	The figure shows a compressed light spring and block system kept on a horizontal frictionless plane. Which of the following graph shows the correct relation between acceleration (a) of block and distance (x) moved by it when released till spring come to its natural state?
Answer» The figure shows a compressed light spring and block system kept on a horizontal frictionless plane. Which of the following graph shows the correct relation between acceleration $(a)$ of block and distance $(x)$ moved by it when released till spring come to its natural state?

Discussion

34.	A block of mass m suspended from a spring executes vertical SHM of time period T as shown in the figure. The amplitude of the SHM is A and the spring is never in compressed state during the oscillation. The magnitude of minimum force exerted by the spring on the block is
Answer» A block of mass $m$ suspended from a spring executes vertical SHM of time period $T$ as shown in the figure. The amplitude of the SHM is $A$ and the spring is never in compressed state during the oscillation. The magnitude of minimum force exerted by the spring on the block is

Discussion

35.	Find the value of x for which x(^i+^j+^k) is a unit vector.
Answer» Find the value of x for which $x (^i +^j +^k)$ is a unit vector.

Discussion

36.	The power factor of the circuit is 1√2 . The capacitance of the circuit is equal to
Answer» The power factor of the circuit is $\frac{1}{\sqrt{2}}$ . The capacitance of the circuit is equal to

Discussion

37.	Find the angle in radians through which a pendulum swings if its length is 75 cm and the tip describes an arc of length: (i) 10 cm (ii) 15 cm (iii) 21 cm
Answer» Find the angle in radians through which a pendulum swings if its length is 75 cm and the tip describes an arc of length: (i) 10 cm (ii) 15 cm (iii) 21 cm

37.

Find the angle in radians through which a pendulum swings if its length is 75 cm and the tip describes an arc of length: (i) 10 cm (ii) 15 cm (iii) 21 cm

Answer»

Find the angle in radians through which a pendulum swings if its length is 75 cm and the tip describes an arc of length:

(i) 10 cm (ii) 15 cm (iii) 21 cm

Discussion

38.	An ant moves from A to B and then comes back to point A. Find the distance (d) and displacement (s) of the ant in this entire journey.
Answer» An ant moves from A to B and then comes back to point A. Find the distance (d) and displacement (s) of the ant in this entire journey.

38.

An ant moves from A to B and then comes back to point A. Find the distance (d) and displacement (s) of the ant in this entire journey.

Answer»

An ant moves from A to B and then comes back to point A. Find the distance (d) and displacement (s) of the ant in this entire journey.

Discussion

39.	Two stars of masses m & 3m are released. The initial distance between them is r. Find the speed of approach when distance between them decreases to r2.
Answer» Two stars of masses m & 3m are released. The initial distance between them is r. Find the speed of approach when distance between them decreases to $\frac{r}{2}$ .

Discussion

40.	When work is done on a body by an external force, its
Answer» When work is done on a body by an external force, its

Discussion

41.	Two ends of a conducting rod of varying cross-section are maintained at 200∘C and 0∘C respectively. In staedy state
Answer» Two ends of a conducting rod of varying cross-section are maintained at $200^{\circ} C$ and $0^{\circ} C$ respectively. In staedy state

Discussion

42.	A source of constant voltage V is connected to a resistance R and two ideal inductors L1 and L2 through a switch S as shown. There is no mutual inductance between the two inductors. The switch S is initially open. At t=0, the switch is closed and current begins to flow. Which of the following options is/are correct?
Answer» A source of constant voltage $V$ is connected to a resistance $R$ and two ideal inductors $L_{1}$ and $L_{2}$ through a switch $S$ as shown. There is no mutual inductance between the two inductors. The switch $S$ is initially open. At $t = 0$ , the switch is closed and current begins to flow. Which of the following options is/are correct?

Discussion

43.	The emf of a storage battery is 90 V before charging and 100 V after charging. When charging began the current was 10 A. What is the current at the end of charging if the internal resistance of the storage battery during the whole process of charging may be taken as constant and equal to 2 Ω?
Answer» The emf of a storage battery is $90 V$ before charging and $100 V$ after charging. When charging began the current was $10 A$ . What is the current at the end of charging if the internal resistance of the storage battery during the whole process of charging may be taken as constant and equal to 2 $Ω$ ?

Discussion

44.	A second pendulum is mounted in a space shuttle. Its period of oscillations will decrease when rocket is
Answer» A second pendulum is mounted in a space shuttle. Its period of oscillations will decrease when rocket is

Discussion

45.	What do you mean by super conductor??? which transition metal oxide has appearance and conductivity like copper??
Answer» What do you mean by super conductor??? which transition metal oxide has appearance and conductivity like copper??

Discussion

46.	Why is voltmeter connected parallel and ammeter in series(2)
Answer» Why is voltmeter connected parallel and ammeter in series(2)

Discussion

47.	The distance of the closest approach of an alpha particle fired at a nucleus with kinetic energy K is r0. The distance of the closest approach when the alpha particle is fired at the same nucleus with kinetic energy 2K will be
Answer» The distance of the closest approach of an alpha particle fired at a nucleus with kinetic energy K is $r_{0}$ . The distance of the closest approach when the alpha particle is fired at the same nucleus with kinetic energy 2K will be

Discussion

48.	A traveling wave in a stretched string is described by the equation; y = A sin (kx- ωt). The maximum particle velocity is :
Answer» A traveling wave in a stretched string is described by the equation; y = A sin (kx- $ω$ t). The maximum particle velocity is :

48.

A traveling wave in a stretched string is described by the equation; y = A sin (kx- ωt). The maximum particle velocity is :

Answer»

A traveling wave in a stretched string is described by the equation;

y = A sin (kx- $ω$ t). The maximum particle velocity is :

Discussion

49.	One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance x0 from the block. The spring is then compressed by 2x0 and released. The time taken to strike the wall is
Answer» One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance $x_{0}$ from the block. The spring is then compressed by $2 x_{0}$ and released. The time taken to strike the wall is

49.

One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance x0 from the block. The spring is then compressed by 2x0 and released. The time taken to strike the wall is

Answer»

One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance $x_{0}$ from the block. The spring is then compressed by $2 x_{0}$ and released. The time taken to strike the wall is

Discussion

50.	The root mean square speed of gas molecules
Answer» The root mean square speed of gas molecules

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

As shown in figure, a ring is performing combined translational and rotational motion with angular velocity 2 rad/s and the velocity of its COM is 4 m/s. Find the magnitude of velocity of point C on the ring.

A body covers one-third of the distance with a velocity v1, the second one-third of the distance with a velocity v2 and the remaining distance with a velocity v3. The average velocity is

Displacement of an object of mass 2 kg varies as s=3t2+5. Find out the value of workdone on the mass from t=0 to t=5 seconds.

The idea of secondary wavelets for the propagation of a wave was first given by

Body A of mass 4m moving with speed u collides with another body B of mass 2m at rest. The collision is head on and elastic in nature. After the collision, the fraction of kinetic energy lost by the colliding body A is

Semiconductor is opaque for light of wavelength less than 800 nm and it is not opaque for light of wavelength greater than 800 nm. Energy gap of semiconductor in electron volt is [Take hc=1240 eV−nm](Answer up to two decimal places)

N cells each of emf E and identical resistance r are grouped into sets of K cells connected in series. The sets are connected in parallel to a load of resistance R, then

An elevator which is moving with an upward acceleration of "a m/s2”. A person drops a coin to measure the acceleration 'a m/s2'. Find 'a' if the coin took 0.5s to hit the ground and the coin was dropped from a height of 3 m.

In the circuit, shown in fig. ‘K’ is open. The charge on capacitor C in steady state is q1. Now key is closed and at steady state, the charge on C is q2. The ratio of charges (q1q2) is

Two blocks of masses m1=3m and m2=m are attached to the ends of a string which passes over a frictionless fixed pulley (which is a uniform disc of mass M=2m and radius R) as shown in Fig. The masses are then released. The acceleration of the system is

Statement 1: A charged particle when placed at rest in any EFL always moves along the electric field lines. Statement 2: A point charge q when placed at rest in the EFL of another point charge Q, moves radially away from charge Q along EFL.

Light of wavelength 5.0×10−7m falls on a pair of narrow slits separated by a distance 2d. The interference pattern on a screen placed 2.0 m away shows that there is first dark fringe at the positions exactly opposite to each slit. The separation between the slits is:

In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be

The two nearest harmonics of a tube closed at one end and open at the other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?

In which case nuclear force is stronger ? In case of nucleons having parallel spin or opposite spin ? Please explain the reasons.

The moment of inertia of a thin rod of mass M and length L about an axis passing through the point at a distance L4 from one of its end and perpendicular to the rod is

A steam cylindrical pipe of inner radius 5 cm and outer radius 7 cm, having conductivity 0.07 W/mK, carries steam at 100∘C. If the temperature at the outer wall of the pipe jacket is 20∘C, then find the heat lost through the jacket per metre length in an hour.

The initial velocity of the particle is 10 m/sec and its retardation is 2 m/sec2. The distance moved by the particle in 5th second of its motion is

Metal spheres each of radius 2 cm are packed into a rectangular box of dimensions 16cm×8cm×8cm. When 16 spheres are packed the box is filled with preservative liquid. Find the volume of this liquid.(π=3.14)

Which of the following statements is incorrect?

Two blocks A and B of masses m and 2m respectively are held at rest such that the spring is in natural length. Find out the accelerations of both the blocks just after release:

Figure shows a system of three concentric metal shells A, B and C with radii a, 2a and 3a respectively. Shell B is earthed and shell C is given a charge Q. Now if shell C is connected to shell A, then the final charge on the shell B is−Qx11, where the value of x is

All the graphs below are intended to represent the same motion. One of them does it incorrectly. Pick the incorrect option.

Two travelling waves y1=Asin[K(x+ct)] and y2=Asin[K(x–ct)] are superposed on a string. The distance between the adjacent nodes will be

The figure shows a compressed light spring and block system kept on a horizontal frictionless plane. Which of the following graph shows the correct relation between acceleration (a) of block and distance (x) moved by it when released till spring come to its natural state?

A block of mass m suspended from a spring executes vertical SHM of time period T as shown in the figure. The amplitude of the SHM is A and the spring is never in compressed state during the oscillation. The magnitude of minimum force exerted by the spring on the block is

Find the value of x for which x(^i+^j+^k) is a unit vector.

The power factor of the circuit is 1√2 . The capacitance of the circuit is equal to

Find the angle in radians through which a pendulum swings if its length is 75 cm and the tip describes an arc of length: (i) 10 cm (ii) 15 cm (iii) 21 cm

An ant moves from A to B and then comes back to point A. Find the distance (d) and displacement (s) of the ant in this entire journey.

Two stars of masses m &amp; 3m are released. The initial distance between them is r. Find the speed of approach when distance between them decreases to r2.

When work is done on a body by an external force, its

Two ends of a conducting rod of varying cross-section are maintained at 200∘C and 0∘C respectively. In staedy state

The emf of a storage battery is 90 V before charging and 100 V after charging. When charging began the current was 10 A. What is the current at the end of charging if the internal resistance of the storage battery during the whole process of charging may be taken as constant and equal to 2 Ω?

A second pendulum is mounted in a space shuttle. Its period of oscillations will decrease when rocket is

What do you mean by super conductor??? which transition metal oxide has appearance and conductivity like copper??

Why is voltmeter connected parallel and ammeter in series(2)

The distance of the closest approach of an alpha particle fired at a nucleus with kinetic energy K is r0. The distance of the closest approach when the alpha particle is fired at the same nucleus with kinetic energy 2K will be

A traveling wave in a stretched string is described by the equation; y = A sin (kx- ωt). The maximum particle velocity is :

One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance x0 from the block. The spring is then compressed by 2x0 and released. The time taken to strike the wall is

The root mean square speed of gas molecules

Two stars of masses m & 3m are released. The initial distance between them is r. Find the speed of approach when distance between them decreases to r2.