50278 + Interview Questions in Physics

1.	Figure 3.33 shows apotentiometer with a cell of 2.0 V and internal resistance 0.40Ω maintaininga potential drop across the resistor wire AB. A standard cell whichmaintains a constant emf of 1.02 V (for very moderate currents up toa few mA) gives a balance point at 67.3 cm length of the wire. Toensure very low currents drawn from the standard cell, a very highresistance of 600 kΩ isput in series with it, which is shorted close to the balance point.The standard cell is then replaced by a cell of unknown emf ε andthe balance point found similarly, turns out to be at 82.3 cm lengthof the wire.(a) What is thevalue ε ?(b) Whatpurpose does the high resistance of 600 kΩ have?(c) Is thebalance point affected by this high resistance?(d) Is thebalance point affected by the internal resistance of the driver cell?(e) Would the method work in the above situation if thedriver cell of the potentiometer had an emf of 1.0 V instead of 2.0V?(f ) Would the circuit work well for determining an extremelysmall emf, say of the order of a few mV (such as the typical emf of athermo-couple)? If not, how will you modify the circuit?
Answer» Figure 3.33 shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Ω maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents up to a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 kΩ is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf ε and the balance point found similarly, turns out to be at 82.3 cm length of the wire. (a) What is the value ε ? (b) What purpose does the high resistance of 600 kΩ have? (c) Is the balance point affected by this high resistance? (d) Is the balance point affected by the internal resistance of the driver cell? (e) Would the method work in the above situation if the driver cell of the potentiometer had an emf of 1.0 V instead of 2.0 V? (f ) Would the circuit work well for determining an extremely small emf, say of the order of a few mV (such as the typical emf of a thermo-couple)? If not, how will you modify the circuit?

1.

Figure 3.33 shows apotentiometer with a cell of 2.0 V and internal resistance 0.40Ω maintaininga potential drop across the resistor wire AB. A standard cell whichmaintains a constant emf of 1.02 V (for very moderate currents up toa few mA) gives a balance point at 67.3 cm length of the wire. Toensure very low currents drawn from the standard cell, a very highresistance of 600 kΩ isput in series with it, which is shorted close to the balance point.The standard cell is then replaced by a cell of unknown emf ε andthe balance point found similarly, turns out to be at 82.3 cm lengthof the wire.(a) What is thevalue ε ?(b) Whatpurpose does the high resistance of 600 kΩ have?(c) Is thebalance point affected by this high resistance?(d) Is thebalance point affected by the internal resistance of the driver cell?(e) Would the method work in the above situation if thedriver cell of the potentiometer had an emf of 1.0 V instead of 2.0V?(f ) Would the circuit work well for determining an extremelysmall emf, say of the order of a few mV (such as the typical emf of athermo-couple)? If not, how will you modify the circuit?

Answer»

Figure 3.33 shows a
potentiometer with a cell of 2.0 V and internal resistance 0.40
Ω maintaining
a potential drop across the resistor wire AB. A standard cell which
maintains a constant emf of 1.02 V (for very moderate currents up to
a few mA) gives a balance point at 67.3 cm length of the wire. To
ensure very low currents drawn from the standard cell, a very high
resistance of 600 kΩ is
put in series with it, which is shorted close to the balance point.
The standard cell is then replaced by a cell of unknown emf ε and
the balance point found similarly, turns out to be at 82.3 cm length
of the wire.

(a) What is the
value ε ?

(b) What
purpose does the high resistance of 600 kΩ have?

(c) Is the
balance point affected by this high resistance?

(d) Is the
balance point affected by the internal resistance of the driver cell?

(e) Would the method work in the above situation if the
driver cell of the potentiometer had an emf of 1.0 V instead of 2.0
V?

(f ) Would the circuit work well for determining an extremely
small emf, say of the order of a few mV (such as the typical emf of a
thermo-couple)? If not, how will you modify the circuit?

2.	The acceleration of the particle moving in straight line is given by a = 4t -30where a is in m/s, and t is in s. The velocity and displacement as function of time is(the initial displacement at t = 0 s is s = -5m/s and the initial velocity is v = 3 m/s)
Answer» The acceleration of the particle moving in straight line is given by a = 4t -30where a is in m/s, and t is in s. The velocity and displacement as function of time is(the initial displacement at t = 0 s is s = -5m/s and the initial velocity is v = 3 m/s)

3.	For the given uniformly charged ring, what will be the maximum value of electric field?
Answer» For the given uniformly charged ring, what will be the maximum value of electric field?

4.	The charge flown through a circuit in the time interval between t and t+dt is given by dq=e−t/τdt, where τ is a constant. Find the toatal charge flown through the circuit t = 0 to t = τ
Answer» The charge flown through a circuit in the time interval between t and t+dt is given by $d q = e^{- t / τ} d t$ , where $τ$ is a constant. Find the toatal charge flown through the circuit t = 0 to t = $τ$

5.	A rod of mass M and length 2L is suspendedat its middle by a wire. It exhibits torsionaloscillations. If two masses each of m areattached at distance L/2 from its centre onboth sides, it reduces the oscillation frequencyby 20%. The value of ratio m/M is close to
Answer» A rod of mass M and length 2L is suspendedat its middle by a wire. It exhibits torsionaloscillations. If two masses each of m areattached at distance L/2 from its centre onboth sides, it reduces the oscillation frequencyby 20%. The value of ratio m/M is close to

6.	A Zener diode is specified to have break-down voltage of 9.1 V with a maximum power dissipation of 364 mW. What is the maximum current that the diode can handle ?
Answer» A Zener diode is specified to have break-down voltage of $9.1 V$ with a maximum power dissipation of $364 mW .$ What is the maximum current that the diode can handle ?

7.	A car is travelling on a track which has radius of curvature 50 m. What is the maximum safe speed with which the car can travel on this track? Take g=10 m/s2. Assume coefficient of friction to be 0.8.
Answer» A car is travelling on a track which has radius of curvature $50 m$ . What is the maximum safe speed with which the car can travel on this track? Take $g = 10 {m/s}^{2}$ . Assume coefficient of friction to be 0.8.

8.	A ray of light, travelling in a medium of refractive index μ, is incident at an angle i on a composite transparent plate consisting of three plates of refractive indices μ1,μ2 and μ3. The ray emerges from the composite plate into a medium of refractive index μ,, at angle x, Then
Answer» A ray of light, travelling in a medium of refractive index $μ$ , is incident at an angle i on a composite transparent plate consisting of three plates of refractive indices $μ_{1}, μ_{2} a n d μ_{3}$ . The ray emerges from the composite plate into a medium of refractive index $μ^{,}$ , at angle x, Then

9.	An LVDT has an output of 10 mV across its terminals when the core moves through a distance of 4 mm. The output of this LVDT is connected to a 10 V voltmeter through an amplifier of gain 1000. If the milli-voltmerer scale has 100 divisions and scale can read upto 1/5 of a divsion. Then the resolution of the overall setup is ____ μm.8
Answer» An $L V D T$ has an output of $10 m V$ across its terminals when the core moves through a distance of $4 m m .$ The output of this LVDT is connected to a $10 V$ voltmeter through an amplifier of gain $1000.$ If the milli-voltmerer scale has $100$ divisions and scale can read upto $1 / 5$ of a divsion. Then the resolution of the overall setup is ____ $μ m$ . 8

10.	The variation of pressure P with volume V for an ideal monoatomic gas during an adiabatic process is shown in figure. At point A, find the magnitude of the rate of change of pressure with volume.
Answer» The variation of pressure $P$ with volume $V$ for an ideal monoatomic gas during an adiabatic process is shown in figure. At point $A$ , find the magnitude of the rate of change of pressure with volume.

11.	is perceived gravity is a centrifugal force
Answer» is perceived gravity is a centrifugal force

13.	A reinforced square footing of size 2m and uniform effective depth 200mm is provided for a 350mm×350mm column. The line of action of ultimate vertical compression load of 360kN passes through the centroid of the footing as well as the column. The nominal transverse one way shear stress (in MPa, round off to two decimal places) in the footing is ______.0.27
Answer» A reinforced square footing of size $2 m$ and uniform effective depth $200 m m$ is provided for a $350 m m \times 350 m m$ column. The line of action of ultimate vertical compression load of $360 k N$ passes through the centroid of the footing as well as the column. The nominal transverse one way shear stress (in MPa, round off to two decimal places) in the footing is ______. 0.27

14.	There are two charged particles with same radius are touched with each other then returned to initial position then what is the new force. Initially Q1=8C And Q2=-4C
Answer» There are two charged particles with same radius are touched with each other then returned to initial position then what is the new force. Initially Q1=8C And Q2=-4C

15.	The velocity υ (in cm/s) of a particle is given in terms of time (t) by the equation: υ=at+bt+c. Dimensions of a, b and c are
Answer» The velocity $υ$ (in cm/s) of a particle is given in terms of time (t) by the equation: $υ = a t + \frac{b}{t + c} .$ Dimensions of a, b and c are

16.	Four point charges, each of +q are rigidly fixed at the four corners of a square planar soap film of side 'a'. The surface tension of the soap film is γ. The system of charges and planar film are in equilibrium, and a=c[q2γ]1/N, where 'c' is a constant. Then N is
Answer» Four point charges, each of $+ q$ are rigidly fixed at the four corners of a square planar soap film of side ' $a$ '. The surface tension of the soap film is $γ$ . The system of charges and planar film are in equilibrium, and $a = c {[\frac{q^{2}}{γ}]}^{1 / N}$ , where ' $c$ ' is a constant. Then $N$ is

12.	An accelerometer has a seismic mass of 0.05 kg and a spring constant of 2×103 N/m. If the maximum mass displacement is +0.05 m before the mass hits the stop. Then the maximum measurable acceleration is _____ m/s2.2000
Answer» An accelerometer has a seismic mass of $0.05 k g$ and a spring constant of $2 \times 10^{3} N / m$ . If the maximum mass displacement is $+ 0.05 m$ before the mass hits the stop. Then the maximum measurable acceleration is _____ $m / s^{2} .$ 2000

17.	wheel is making revolutions about its axis with uniform angular acceleration. Starting from rest, it reaches 100 rev/sec in 4 seconds. Find the angular acceleration.
Answer» wheel is making revolutions about its axis with uniform angular acceleration. Starting from rest, it reaches 100 rev/sec in 4 seconds. Find the angular acceleration.

18.	If angle between the asymptotes of the hyperbola x2a2−y2b2=1 is 450, then value of eccentricity e is
Answer» If angle between the asymptotes of the hyperbola $\frac{x^{2}}{a^{2}} - \frac{y^{2}}{b^{2}} = 1 i s 45^{0}$ , then value of eccentricity e is

19.	In a voltage series feedback network the open loop gain A = - 100, Ri=10 kΩ and R0=20 kΩ. If feedback factor β is -0.1, then Zif and Z0f respectively are
Answer» In a voltage series feedback network the open loop gain A = - 100, $R_{i} = 10 k Ω a n d R_{0} = 20 k Ω$ . If feedback factor $β$ is -0.1, then $Z_{i f} a n d Z_{0 f}$ respectively are

20.	relation between firs†an d secnd law ofmotio
Answer» relation between firs†an d secnd law ofmotio

21.	A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 50 oscillations per minute at a place whose dip angle is 45∘ and 150 oscillations per minute at a place whose dip angle is 30∘. The ratio of earth's total magnetic field at the two places is
Answer» A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes $50$ oscillations per minute at a place whose dip angle is $45^{\circ}$ and $150$ oscillations per minute at a place whose dip angle is $30^{\circ}$ . The ratio of earth's total magnetic field at the two places is

22.	A point charge +q is moved inside a spherical shell of radius R and carrying charge Q from a point A to another point B which is diametrically opposite. Find the work in moving the charge from A to B. Give reasons
Answer» A point charge +q is moved inside a spherical shell of radius R and carrying charge Q from a point A to another point B which is diametrically opposite. Find the work in moving the charge from A to B. Give reasons

23.	The current in a LR circuit builds up to 3/4th of its steady state value in 4 sec. The time cons†an t of this circuit is 1) 1/\ln2 2) 2/\ln2 3) 3/\ln2 4) 4/\ln
Answer» The current in a LR circuit builds up to 3/4th of its steady state value in 4 sec. The time cons†an t of this circuit is 1) 1/\ln2 2) 2/\ln2 3) 3/\ln2 4) 4/\ln

24.	A mass m is attached to a string of length l0, Young's modulus Y and area of cross section A. It is pushed with a velocity v as shown. Find the time in which the block comes to an instantaneous rest.
Answer» A mass m is attached to a string of length $l_{0}$ , Young's modulus Y and area of cross section A. It is pushed with a velocity v as shown. Find the time in which the block comes to an instantaneous rest.

25.	A spherical metal Shell A of radius RA and a solid metal sphere B of radius Re(<RA) are kept far apart and each is given charge ′+Q′. Now they are connceted by a thin metal wire. Then
Answer» A spherical metal Shell $A$ of radius $R_{A}$ and a solid metal sphere $B$ of radius $R_{e} (< R_{A})$ are kept far apart and each is given charge $^{'} + Q^{'}$ . Now they are connceted by a thin metal wire. Then

Explore topic-wise InterviewSolutions in Current Affairs.

The acceleration of the particle moving in straight line is given by a = 4t -30where a is in m/s, and t is in s. The velocity and displacement as function of time is(the initial displacement at t = 0 s is s = -5m/s and the initial velocity is v = 3 m/s)

For the given uniformly charged ring, what will be the maximum value of electric field?

The charge flown through a circuit in the time interval between t and t+dt is given by dq=e−t/τdt, where τ is a constant. Find the toatal charge flown through the circuit t = 0 to t = τ

A rod of mass M and length 2L is suspendedat its middle by a wire. It exhibits torsionaloscillations. If two masses each of m areattached at distance L/2 from its centre onboth sides, it reduces the oscillation frequencyby 20%. The value of ratio m/M is close to

A Zener diode is specified to have break-down voltage of 9.1 V with a maximum power dissipation of 364 mW. What is the maximum current that the diode can handle ?

A car is travelling on a track which has radius of curvature 50 m. What is the maximum safe speed with which the car can travel on this track? Take g=10 m/s2. Assume coefficient of friction to be 0.8.

A ray of light, travelling in a medium of refractive index μ, is incident at an angle i on a composite transparent plate consisting of three plates of refractive indices μ1,μ2 and μ3. The ray emerges from the composite plate into a medium of refractive index μ,, at angle x, Then

The variation of pressure P with volume V for an ideal monoatomic gas during an adiabatic process is shown in figure. At point A, find the magnitude of the rate of change of pressure with volume.

is perceived gravity is a centrifugal force

An accelerometer has a seismic mass of 0.05 kg and a spring constant of 2×103 N/m. If the maximum mass displacement is +0.05 m before the mass hits the stop. Then the maximum measurable acceleration is _____ m/s2.2000

There are two charged particles with same radius are touched with each other then returned to initial position then what is the new force. Initially Q1=8C And Q2=-4C

The velocity υ (in cm/s) of a particle is given in terms of time (t) by the equation: υ=at+bt+c. Dimensions of a, b and c are

Four point charges, each of +q are rigidly fixed at the four corners of a square planar soap film of side 'a'. The surface tension of the soap film is γ. The system of charges and planar film are in equilibrium, and a=c[q2γ]1/N, where 'c' is a constant. Then N is

wheel is making revolutions about its axis with uniform angular acceleration. Starting from rest, it reaches 100 rev/sec in 4 seconds. Find the angular acceleration.

If angle between the asymptotes of the hyperbola x2a2−y2b2=1 is 450, then value of eccentricity e is

In a voltage series feedback network the open loop gain A = - 100, Ri=10 kΩ and R0=20 kΩ. If feedback factor β is -0.1, then Zif and Z0f respectively are

relation between firs†an d secnd law ofmotio

A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 50 oscillations per minute at a place whose dip angle is 45∘ and 150 oscillations per minute at a place whose dip angle is 30∘. The ratio of earth's total magnetic field at the two places is

A point charge +q is moved inside a spherical shell of radius R and carrying charge Q from a point A to another point B which is diametrically opposite. Find the work in moving the charge from A to B. Give reasons

The current in a LR circuit builds up to 3/4th of its steady state value in 4 sec. The time cons†an t of this circuit is 1) 1/\ln2 2) 2/\ln2 3) 3/\ln2 4) 4/\ln

A mass m is attached to a string of length l0, Young's modulus Y and area of cross section A. It is pushed with a velocity v as shown. Find the time in which the block comes to an instantaneous rest.

A spherical metal Shell A of radius RA and a solid metal sphere B of radius Re(&lt;RA) are kept far apart and each is given charge ′+Q′. Now they are connceted by a thin metal wire. Then

(4)86 Calculate the entropy change for the conversion of 1 g ice to water at 273 K, AH, for ice = 6.025 kJ mot-1None of these(1)1.226 J/K(2) 22.07 J/K6025 J/K(E)(4) 602.5 J/K87. Calculate the entropy change for the conversinn of

The acceleration- time graph of a particle moving along a straight line is as shown in figure. At what time the particle acquires its initial speed?

Three identical blocks of masses m = 2kg each are drawn by a force F = 10.2 N with an acceleration of 0.6 m/s2 on a frictionless surface, then the tension in the string between the blocks B and C is

39. If a body loses three-fourth of its initial velocity on penetrating 15cm in a wooden block, then much it penetrate more before coming to rest?? (assume retardation of body is uniform)

A uniform force of (3^i+^j) N acts on a particle of mass 2 kg. Hence the particle is displaced from position (2^i+^k) m to position (4^i+3^j−^k) m. The work done by the force on the particle is -

The electric potential inside a charged sphere depends on the distance from its center as V=ar2+b where a and b are constants. The space charge distribution ρ(r) inside the sphere is given by

why does mass change while moving and what is rest mass?

Find the number of 80V 30microfarad capacitors needed to form a composite capacitor of 400V 30 microFarad A. 25 B. 40 C. 60 D. 30

The central fringe of the interference pattern produced by light of wavelength 6000 oA is found to shift to the position of 4th bright fringe after a glass plate of refractive index 1.5 is introduced in path of one of beams. The thickness of the glass plate would be

Derivation of equations of motion on graph

A long string with charge per unit length λ on it passes through a cube of side a. The minimum and maximum flux through the cube will be

Photoelectric emission is observed from a metallic surface for frequencies v1 and v2 of the incident light rays (v1&gt;v2). If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is

What happens In a capacitor ,if the entire space is filled with a conductor instead of a dielectric,does the capacitance become infinity?

A part of the circuit is shown in the figure. All the capacitors have capacitance of 2μF.

Which of the following relationships between the acceleration a and the displacement x of a particle involve simple harmonic motion? (a) a = 0.7x (b) a = –200x⁵ (c) a = –10x (d) a = 100x³

48.A sample of gas goes form state A to state B in 4 different manner. let the W be the work done by the gas and Δ U be the change in internal energy. correctly match the graphs with the statements provided.

Eight identical capacitor of capacitance C each are connected along edge of a pyramid having square base, ABCD as shown. Equivalent capacitance across A and D is:

A particle covers one fourth of it's distance with speed v and remaining with speed 2v, then average speed of particle is 1) 8/5v 2)3/2v 3) v 4) 5/8v

Two identical rings P and Q of radius 0.1 m are mounted coaxially at a distance 0.5 m apart. The charges on the two rings are 2 μC and 4 μC respectively. The work done in transferring a charge of 5 μC from the centre of P to that of Q is

Two particles are projected simultaneously from two towers of different heights, one is horizontally with speed 10 m/s and other at an angle 45^° below the horizontal with speed v as shown in figure. The velocity v for which particles collides in air is

One mole of an ideal gas undergoes a process in which T=T0+aV3, where T0 and ‘a’ are positive constants and V is the volume. The volume for which pressure will be minimum is

One end of a taut string of length 3 m along the x-axis is fixed at x=0. The speed of the waves in the string is 100 m/s. The other end of the string is vibrating in the y-direction so that stationary waves are set up in the string. The possible waveform (s) of these stationary wave is (are)

A spherical metal Shell A of radius RA and a solid metal sphere B of radius Re(<RA) are kept far apart and each is given charge ′+Q′. Now they are connceted by a thin metal wire. Then

Photoelectric emission is observed from a metallic surface for frequencies v1 and v2 of the incident light rays (v1>v2). If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is

26.	(4)86 Calculate the entropy change for the conversion of 1 g ice to water at 273 K, AH, for ice = 6.025 kJ mot-1None of these(1)1.226 J/K(2) 22.07 J/K6025 J/K(E)(4) 602.5 J/K87. Calculate the entropy change for the conversinn of
Answer» (4)86 Calculate the entropy change for the conversion of 1 g ice to water at 273 K, AH, for ice = 6.025 kJ mot-1None of these(1)1.226 J/K(2) 22.07 J/K6025 J/K(E)(4) 602.5 J/K87. Calculate the entropy change for the conversinn of

27.	The acceleration- time graph of a particle moving along a straight line is as shown in figure. At what time the particle acquires its initial speed?
Answer» The acceleration- time graph of a particle moving along a straight line is as shown in figure. At what time the particle acquires its initial speed?

29.	39. If a body loses three-fourth of its initial velocity on penetrating 15cm in a wooden block, then much it penetrate more before coming to rest?? (assume retardation of body is uniform)
Answer» 39. If a body loses three-fourth of its initial velocity on penetrating 15cm in a wooden block, then much it penetrate more before coming to rest?? (assume retardation of body is uniform)

30.	A uniform force of (3^i+^j) N acts on a particle of mass 2 kg. Hence the particle is displaced from position (2^i+^k) m to position (4^i+3^j−^k) m. The work done by the force on the particle is -
Answer» A uniform force of $(3^i +^j) N$ acts on a particle of mass $2 kg .$ Hence the particle is displaced from position $(2^i +^k) m$ to position $(4^i + 3^j -^k) m .$ The work done by the force on the particle is -

31.	The electric potential inside a charged sphere depends on the distance from its center as V=ar2+b where a and b are constants. The space charge distribution ρ(r) inside the sphere is given by
Answer» The electric potential inside a charged sphere depends on the distance from its center as $V = a r^{2} + b$ where a and b are constants. The space charge distribution $ρ (r)$ inside the sphere is given by

32.	why does mass change while moving and what is rest mass?
Answer» why does mass change while moving and what is rest mass?

34.	The central fringe of the interference pattern produced by light of wavelength 6000 oA is found to shift to the position of 4th bright fringe after a glass plate of refractive index 1.5 is introduced in path of one of beams. The thickness of the glass plate would be
Answer» The central fringe of the interference pattern produced by light of wavelength $6000 o A$ is found to shift to the position of $4^{t h}$ bright fringe after a glass plate of refractive index $1.5$ is introduced in path of one of beams. The thickness of the glass plate would be

35.	Derivation of equations of motion on graph
Answer» Derivation of equations of motion on graph

36.	A long string with charge per unit length λ on it passes through a cube of side a. The minimum and maximum flux through the cube will be
Answer» A long string with charge per unit length λ on it passes through a cube of side a. The minimum and maximum flux through the cube will be

37.	Photoelectric emission is observed from a metallic surface for frequencies v1 and v2 of the incident light rays (v1>v2). If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is
Answer» Photoelectric emission is observed from a metallic surface for frequencies $v_{1}$ and $v_{2}$ of the incident light rays $(v_{1} > v_{2})$ . If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is