100525 + Interview Questions in GENERAL QA IN GENERAL AWARENESS Page 252 InterviewSolution

12551.	When chlorinating water there is a point when the chlorine requirement of the water is met. Such a point is called-1. Break Point Chlorination2. Super Chlorination3. Contact Period4. Chlorine Requirement
Answer» Correct Answer - Option 1 : Break Point Chlorination Concept:- Breakpoint chlorination:- Breakpoint chlorination is a term that gives us an idea of the extent of chlorine added to water. In fact, it represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine. In general practice, chlorine is added beyond breakpoint to ensure a residual of 0.2 - 0.3 mg/l as free chlorine. This residual chlorine takes care of future recontamination. When excess chlorine ( 5 to 15 mg/l ) is added during an epidemic such that it gives a residual of 1 to 2 mg/l beyond breakpoint is called super chlorination.

12551.

When chlorinating water there is a point when the chlorine requirement of the water is met. Such a point is called-1. Break Point Chlorination2. Super Chlorination3. Contact Period4. Chlorine Requirement

Answer» Correct Answer - Option 1 : Break Point Chlorination

Concept:-

Breakpoint chlorination:-

Breakpoint chlorination is a term that gives us an idea of the extent of chlorine added to water.
In fact, it represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine.
In general practice, chlorine is added beyond breakpoint to ensure a residual of 0.2 - 0.3 mg/l as free chlorine. This residual chlorine takes care of future recontamination.

When excess chlorine ( 5 to 15 mg/l ) is added during an epidemic such that it gives a residual of 1 to 2 mg/l beyond breakpoint is called super chlorination.

Discussion

12552.	The pH value of Milk of Magnesia is approximately1. zero2. 73. 104. 14
Answer» Correct Answer - Option 3 : 10 Explanation: Milk of Magnesia is the magnesium compound which acts as an antacid. The term milk of magnesia was first used by English pharmacist Charles Henry Phillips in 1872. Milk of Magnesia is basic in nature. The pH value of the Milk of Magnesia is 10.5. The scale used to express the acidic or alkaline nature of a substance based on the concentration of hydrogen ions in its solution is called a pH scale. pH scale was discovered by Soren Sorensen. The pH value of the acids are less than 7 (0 to 7) Acid substances usually produce a sour taste. The pH value of the Bases are greater than 7 (7 to 14) Base substances usually produce a bitter taste. The pH value of the neutral substance is equal to 7. The pH value of the pure water is 7. The pH value of the blood is close to 7.4.

12552.

The pH value of Milk of Magnesia is approximately1. zero2. 73. 104. 14

Answer» Correct Answer - Option 3 : 10

Explanation:

Milk of Magnesia is the magnesium compound which acts as an antacid.

The term milk of magnesia was first used by English pharmacist Charles Henry Phillips in 1872.
Milk of Magnesia is basic in nature.
The pH value of the Milk of Magnesia is 10.5.

The scale used to express the acidic or alkaline nature of a substance based on the concentration of hydrogen ions in its solution is called a pH scale.

pH scale was discovered by Soren Sorensen.
- The pH value of the acids are less than 7 (0 to 7)
Acid substances usually produce a sour taste.
- The pH value of the Bases are greater than 7 (7 to 14)
Base substances usually produce a bitter taste.
The pH value of the neutral substance is equal to 7.
The pH value of the pure water is 7.
The pH value of the blood is close to 7.4.

Discussion

12553.	Name some process variables, which are appropriate for our plant with examples.
Answer» Process variables with examples, which are appropriate to our plant, are . a. Flow – flow of D₂O in PHT system. b. Temperature – temperature of coolant in PHT system. c. Level – moderator level. d. Speed – speed of turbine. e. Voltage – voltage generated by main generator. f. Neutron flux – number of neutrons produced in reactor during operation. g. pH – pH of moderator.

12553.

Name some process variables, which are appropriate for our plant with examples.

Answer»

Process variables with examples, which are appropriate to our plant, are .

a. Flow – flow of D₂O in PHT system.

b. Temperature – temperature of coolant in PHT system.

c. Level – moderator level.

d. Speed – speed of turbine.

e. Voltage – voltage generated by main generator.

f. Neutron flux – number of neutrons produced in reactor during operation.

g. pH – pH of moderator.

Discussion

12554.	What is primary element and what should be its response?
Answer» Primary element is one, which senses the condition of process, and converts it to some other form, which can be measured accurately. Example in a bourden gauge the pressure if changed to the uncoiling (displacement), which can be measured. The response of primary element is that it should convert the condition in to some other form, which can be interpreted and measured easily.

12554.

What is primary element and what should be its response?

Answer»

Primary element is one, which senses the condition of process, and converts it to some other form, which can be measured accurately. Example in a bourden gauge the pressure if changed to the uncoiling (displacement), which can be measured.

The response of primary element is that it should convert the condition in to some other form, which can be interpreted and measured easily.

Discussion

12555.	What is the purpose of instruments?
Answer» The purpose of instruments is to measure, safeguard the process for efficient plant operation. Instruments are very accurate and fast acting. This accuracy and speed is not possible by human. Also in some places there may be too much heat for man to work or some where there may high radiation field. In such cases instruments provide remote operation.

12555.

What is the purpose of instruments?

Answer»

The purpose of instruments is to measure, safeguard the process for efficient plant operation.

Instruments are very accurate and fast acting. This accuracy and speed is not possible by human. Also in some places there may be too much heat for man to work or some where there may high radiation field. In such cases instruments provide remote operation.

Discussion

12556.	If `a=(3t^2+2t+1)` `m/s^2` is the expression according to which the acceleration of a particle varies. Then- `a=(3t^2+2t+1)` `(m)/(s^2)` Q. The expression for instantaneous velocity at any time `t` will be (if the particle was initially at rest)-A. `t^(3)+2t+1`B. `t^(3)+t+1`C. `t^(3)+t^(2)+1`D. `t^(3)+t^(2)+t+C`
Answer» Correct Answer - C `a=3t^(2)+2t+1` `underset(0)overset(1)intdv=underset(0)overset(1)int3t^(2)+2t+1dt , v=t^(3)+t^(2)+t`

Discussion

12557.	If `a=(3t^2+2t+1)` `m/s^2` is the expression according to which the acceleration of a particle varies. Then- `a=(3t^2+2t+1)` `(m)/(s^2)` Q. The change in velocity after 3 seconds of its start is:A. `30m//s`B. `39m//s`C. `3m//s`D. `20m//s`
Answer» Correct Answer - B `V(t=0)=0` `V_(t=3)=(3)^(3)+(3)^(2)+3` `=27+9+3` `=39` `DeltaV=39-0=39m//s.`

Discussion

12558.	In the given figure, a function `y=15e^(-x)` is shown. What is the numerical value of expression `A//(B+C)`?
Answer» Correct Answer - 5 From graph `A=15, B=1, C=2`. Therefore `[A//(B+C)=15//3=5]`

Discussion

12559.	Find first derivation of y w.r.t. x. (i) `y=x^(2) sin x` , (ii) `y=4(e^(x))cos x`
Answer» (i) `(dy)/(dx)=x^(2)(cos x)+(2x)(sin x)=x^(2) cos x+ 2xsin x` (ii) `(dy)/(dx)=4[(e^(x))(cos x)+(e^(x))(-sin x)]=4e^(x)[cos x-sin x]`

Discussion

12560.	Find `1+1/2+1/4+1/8+`…. Upto `oo`.
Answer» Here, `a=1, r=1/2" "` So, `" " S_(oo)=a/(1-r)=1/(1-1/2)=2`

Discussion

12561.	If `vec(A)=4hat(i)+nhat(j)-2hat(k)` and `vec(B)=2hat(i)+3hat(j)+hat(k)`, then find the value of n so that `vec(A) bot vec(B)`
Answer» Dot product of two mutually perpendicular vectors is zero `vec(A).vec(B)=0` `:. (4hat(i)+nhat(j)-2hat(k)).(2hat(i)+3hat(j)+hat(k))=0rArr(4xx2)+(nxx3)+(-2xx1)=0rArr3n=-6 rArr n=-2`

Discussion

12562.	Find the sum of first `n`natural numbers.
Answer» Let sum be `S_(n)` then `S_(n)=1+2+3+…. +n, S_(n)=n/2[1+n]=[(n(n+1))/2]`

Discussion

12563.	Consider three vectors `vec(A)=2 hat(i)+3 hat(j)-2 hat(k)" " vec(B)=5hat(i)+nhat(j)+hat(k)" " vec(C)=-hat(i)+2hat(j)+3 hat(k)` If these three vectors are coplanar, then value of n will be
Answer» Correct Answer - D For coplanar vectors `vec(A).(vec(B)xxvec(C))=\|(A_(x),A_(y),A_(z)),(B_(x),B_(y),B_(z)),(C_(x),C_(y),C_(z))\|=0` `implies \|(2,3,-2),(5,n,1),(-1,2,3)\|=2(3n-2)-3(15+1)-2 (10+n)=0 implies4n-72=0implies n=18`

Discussion

12564.	Figure shows an irregular wedge of mass `m` placed on a smooth horizontal surface. Part `BC` is rough. If the coefficient of friction between the block and wedge is `mu`, and the block comes to rest with respect to wedge at a point `E` on the rough surface then `BE` will beA. `(H)/(mu)`B. `(H-h)/(mu)`C. `(h)/(mu)`D. none of these
Answer» Correct Answer - B By work `-` energy theorem on the system `:` `-(mu mg )(BE)-mgh=-(1)/(4) m u^(2)` `=-(1)/(4)m(4gH)rArr BE=(H-h)/(mu)`

Discussion

12565.	Figure shows an irregular wedge of mass `m` placed on a smooth horizontal surface. Part `BC` is rough. The magnitude of velocity of wedge when the block comes to rest `(w.r.t.` wedge `)` on part `BC` is `:`A. `sqrt(gH)`B. `sqrt(g(H-h))`C. `2sqrt(gH)`D. none of these
Answer» Correct Answer - A When the block comes to rest, the wedge continues to move at `V=(u)/(2)=sqrt(gH)` on the smooth surface. (since, momentum of wedge`-` block system remains conserved) .

Discussion

12566.	In a `p-n` junction diode, change in temperature due to heatingA. does not affect resistance of p-n junctionB. affects only forward resistanceC. affects only reverse resistanceD. affects the overall V-I characteristics of p-n junction.
Answer» Correct Answer - D Due to increase in temperature because of heating, thermal collision between the electron and holes increases. Thus, net electron-hole pair increases. This leads to increase in the current in diode and overall resistance of the diode changes. This in turn changes both the forward biasing and the reverse biasing. Thus, the overall I-V characteristics of p-n junction diode gets affected.

Discussion

12567.	An `EM` wave is propagating in a medium whith a velocity `vecv=vhati`. The instantaneous oscillating electric field of this of em wave is along `+y` axis. Then the direction of oscillating magnetic field of the `EM` wave will be alongA. `-y-direction`B. `+z-direction`C. `-z-`directionD. `-x-`direction
Answer» Correct Answer - B Here, velocity of EM wave, `v=vhat(i)` Instaneous oscillating electric field, `E=Ehat(j)` As we already know that, during the propogation of = EM waves through a medium oscillating electric and magnetic field vectors are mutually perpendicular to each other end to the direction of each other and to the direction of propogation of the wave `(ExxB)`. i.e. `ExxB=v rArr (Ehat(j) xx B = vhat(i)` ............(i) As we know that from vector algebra, `hat(j) xx hat(k)= hat(i)`..........(ii) ltbr. Comparing Eqs. (i) and (ii), we get `B= Bhat(k)`, Where B (say) be the magnitude of magnetic field. Thus, we can say that the direction of oscillating magnetic field of the em wave will be along +z direction.

Discussion

12568.	________ represent the features of both emergence and submergence.1. Compound coasts2. Neutral coasts3. Simple coasts4. Retrograded coasts
Answer» Correct Answer - Option 1 : Compound coasts The correct answer is Compound coasts. The boundary between the coast and the shore is known as the coastline; it marks the seaward limit of the coast. The outline of the coast may be modified by sea waves. Submergence of the shoreline may take place because of a rise in sea level or a downward adjustment of the land surface; from a geometrical point of view, the two are indistinguishable. According to D.W. Johnson, coastlines can be divided into the following classes: Coastline of Emergence Coastline of Submergence Neutral coastline Compound coastline Fault coastline This classification has two bases: The change of levels, i.e., if sea level falls, the shores emerge, The nature of shorelines, because it is necessary to know the nature of seashore before emergence and submergence, whether the shore was upland or downland, for instance. Compound Coastlines: Such coastlines show the forms of two of the previous classes combined, for example, submergence followed by emergence or vice versa. The coastlines of Norway and Sweden are examples of compound coastlines. Hence, Option 1 is correct.

12568.

________ represent the features of both emergence and submergence.1. Compound coasts2. Neutral coasts3. Simple coasts4. Retrograded coasts

Answer» Correct Answer - Option 1 : Compound coasts

The correct answer is Compound coasts.

The boundary between the coast and the shore is known as the coastline; it marks the seaward limit of the coast.
The outline of the coast may be modified by sea waves.
Submergence of the shoreline may take place because of a rise in sea level or a downward adjustment of the land surface; from a geometrical point of view, the two are indistinguishable.
According to D.W. Johnson, coastlines can be divided into the following classes:
- Coastline of Emergence
- Coastline of Submergence
- Neutral coastline
- Compound coastline
- Fault coastline
This classification has two bases:
- The change of levels, i.e., if sea level falls, the shores emerge,
- The nature of shorelines, because it is necessary to know the nature of seashore before emergence and submergence, whether the shore was upland or downland, for instance.
Compound Coastlines:
- Such coastlines show the forms of two of the previous classes combined, for example, submergence followed by emergence or vice versa. The coastlines of Norway and Sweden are examples of compound coastlines. Hence, Option 1 is correct.

Discussion

12569.	∆U = q - p∆V. If the process is carried out at constant volume, then ∆V=0. Answer the following questions. 1. Give the equation for ∆U. 2. 1000J was supplied to a system at constant volume. It resulted in the increase of temperature of the system from 45 °C to 50 °C. Calculate the change in internal energy.
Answer» 1. ∆U = q_v 2. Since the volume kept constant, ∆V=0 ∴ ∆U = q_v = 1000J

12569.

∆U = q - p∆V. If the process is carried out at constant volume, then ∆V=0. Answer the following questions. 1. Give the equation for ∆U. 2. 1000J was supplied to a system at constant volume. It resulted in the increase of temperature of the system from 45 °C to 50 °C. Calculate the change in internal energy.

Answer»

1. ∆U = q_v

2. Since the volume kept constant, ∆V=0

∴ ∆U = q_v = 1000J

Discussion

12570.	An ideal gas with adiabatic exponent (`gamma=1.5`) undergoes a process in which work done by the gas is same as increase in internal energy of the gas. Here R is gas constant. The molar heat capacity C of gas for the process is:A. C=4RB. C=0C. C=2RD. C=R
Answer» Correct Answer - A `intPdV=intnC_(v)dt` `rArr dQ=2 dU rArr nCdT=2 nC_(v)=dT rArr C=2C_(v)rArr C=(2R)/(1.5-1) =4R`

Discussion

12571.

According to IE rules for service connection for low and medium voltage line, the height of service line conductors erected across a street must NOT be less than:1. 5.490 m2. 5.975 m3. 6.10 m4. 5.18 m

Answer» Correct Answer - Option 2 : 5.975 m

Clearance above ground at the lowest Conductor:

Voltage Level	Description	Distance
Low & Medium Voltage	Across a street	5.975 m
High Voltage	Across a street	6.1 m
Low & Medium Voltage	Along a street	5.5 m
High Voltage	Along a street	5.8 m
Low & Medium Voltage	Elsewhere than along or across any street	4 m
High Voltage	Elsewhere than along or across any street	5.2 m
33 kV & EHV	Clearance above ground (+0.3 m for every 33 kV)	Min 5.2 m

Discussion

12572.	Heat of sun reach the earth by : A. Radiation B. Convection C. absorption D. Conduction
Answer» A. Radiation

Discussion

12573.	Land breeze blows during :A. à day B. à night C. à winter D. à summer
Answer» Land breeze blows during à night.

Discussion

12574.	A hot plate 1 m × 1.5 m is maintained at 300°C. Air at 25°C blows over the plate. If the convective heat transfer coefficient is 20 W/m2°C, calculate the rate of heat transfer.
Answer» Area of the plate exposed to heat transfer, A = 1 × 1.5 = 1.5 m² Plate surface temperature, t_s = 300°C Temperature of air (fluid), t_f = 20°C Convective heat-transfer coeffficient, h = 20 W/m²°C Rate of heat transfer, Q : From Netwon’s law of cooling, Q = hA (t_s – t_f ) = 20 × 1.5(300 – 20) = 8400 W or 8.4 kW.

12574.

A hot plate 1 m × 1.5 m is maintained at 300°C. Air at 25°C blows over the plate. If the convective heat transfer coefficient is 20 W/m2°C, calculate the rate of heat transfer.

Answer»

Area of the plate exposed to heat transfer, A = 1 × 1.5 = 1.5 m²

Plate surface temperature, t_s = 300°C

Temperature of air (fluid), t_f = 20°C

Convective heat-transfer coeffficient, h = 20 W/m²°C

Rate of heat transfer, Q :

From Netwon’s law of cooling,

Q = hA (t_s – t_f )

= 20 × 1.5(300 – 20) = 8400 W or 8.4 kW.

Discussion

12575.	The transfer of heat by radiation : A. does not require any medium. B. require any medium. C. does not require any space. D. require any space.
Answer» Does not require any medium. The transfer of heat by radiation does not require any medium

12575.

The transfer of heat by radiation : A. does not require any medium. B. require any medium. C. does not require any space. D. require any space.

Answer»

Does not require any medium.

The transfer of heat by radiation does not require any medium

Discussion

12576.	The quantity of heat radiation is dependent on (a) area of the body only (b) shape of the body only (c) temperature of the body only (d) on all (a), (b) and (c).
Answer» (c) temperature of the body only

Discussion

12577.	Thermal radiation travels through vacuum on ………………..lineA. straight B. zigzag C. vertical D. diagonal
Answer» Straight. Thermal radiation travels through vacuum on straight line and with the velocity of light.

12577.

Thermal radiation travels through vacuum on ………………..lineA. straight B. zigzag C. vertical D. diagonal

Answer»

Straight.

Thermal radiation travels through vacuum on straight line and with the velocity of light.

Discussion

12578.	When the wavelength of radiation falling on a metal is changed from 500 nm to 200 nm, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to (1) 0.52 eV (2) 1.02 eV(3) 0.61 eV (4) 0.81 eV
Answer» (3) 0.61 eV K₁ = hc/λ₁- Φ₀ K₂ = hc/λ₂- Φ₀ \(\therefore\) K₂= 3K₁ ⇒ 3[hc/500 - Φ₀] = hc/200 - Φ₀ ⇒ Φ_{0 = 0.61}eV

12578.

When the wavelength of radiation falling on a metal is changed from 500 nm to 200 nm, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to (1) 0.52 eV (2) 1.02 eV(3) 0.61 eV (4) 0.81 eV

Answer»

(3) 0.61 eV

K₁ = hc/λ₁- Φ₀

K₂ = hc/λ₂- Φ₀

\(\therefore\) K₂= 3K₁

⇒ 3[hc/500 - Φ₀]

= hc/200 - Φ₀

⇒ Φ_{0 = 0.61}eV

Discussion

12579.	If intensity (I) versus wavelength (λ) for three identical black bodies at temperature T1, T2 and T3 are shown in figure, then
Answer» We know that emissive power is E \(\propto\) T⁴ According wein's displacement law \(\lambda_{max}T = constant\) T \(\propto\) \(\frac1{\lambda_{max}}\) So, We can say T₁ > T₂ > T₃

12579.

If intensity (I) versus wavelength (λ) for three identical black bodies at temperature T1, T2 and T3 are shown in figure, then

Answer»

We know that emissive power is

E \(\propto\) T⁴

According wein's displacement law

\(\lambda_{max}T = constant\)

T \(\propto\) \(\frac1{\lambda_{max}}\)

So, We can say

T₁ > T₂ > T₃

Discussion

12580.	A long straight cylindrical shell has inner radius Ri and outer radius Ro. It carries current i, uniformly distributed over its cross section. A wire is parallel to the cylinder axis, in the hollow region (rRo). We conclude that the wire: A. is on the cylinder axis and carries current i in the same direction as the current in the shell B. may be anywhere in the hollow region but must be carrying current i in the direction opposite to that of the current in the shell C. may be anywhere in the hollow region but must be carrying current i in the same direction as the current in the shell D. is on the cylinder axis and carries current i in the direction opposite to that of the current in the shell E. does not carry any current
Answer» D. is on the cylinder axis and carries current i in the direction opposite to that of the current in the shell

Discussion

12581.	Polarisation is the distortion of the shape of the shape of an anion by the cation. Which of the following statements is correct ?A. Maximum polarisation is done by a cation of high chargeB. A large cation is likely to bring large degree of polarisationC. A smaller anion is likwly to undergo a high degree of polarisationD. Minimum polarisation is done by a cation of small size
Answer» Correct Answer - 1 Cation having high charge density produces high degree of polarisation.

Discussion

12582.	A uniformly charged spherical shell of radius R and charge Q is rotating about its diameter with constant angular speed ω. The magnetic moment of shell is
Answer» The magnetic moment \(\frac ML=\frac{q}{2m}\) M = \(\frac{q}{2m}L\) \(\because\) L = I\(\omega\) Moment of inertia of spherical shell about diameter I = \(\frac23mR^2\) Then M = \(\frac{q}{2m}I\omega\) = \(\frac{q}{2m}(\frac23MR^2\omega)\) = \(\frac{qm\omega R^2}{3m}\) M = \(\frac{q\omega R^2}3\)

12582.

A uniformly charged spherical shell of radius R and charge Q is rotating about its diameter with constant angular speed ω. The magnetic moment of shell is

Answer»

The magnetic moment

\(\frac ML=\frac{q}{2m}\)

M = \(\frac{q}{2m}L\)

\(\because\) L = I\(\omega\)

Moment of inertia of spherical shell about diameter I = \(\frac23mR^2\)

Then M = \(\frac{q}{2m}I\omega\)

= \(\frac{q}{2m}(\frac23MR^2\omega)\)

= \(\frac{qm\omega R^2}{3m}\)

M = \(\frac{q\omega R^2}3\)

Discussion

12583.	The seismic mass of an accelerometer oscillates sinusoidally at 100 Hz with a maximum displacement of 10 mm from its mean position.The peak acceleration of the seismic mass is1. 3947.84 m/s22. 3141.50 m/s23. 314.15 m/s24. 100.00 m/s2
Answer» Correct Answer - Option 1 : 3947.84 m/s² Given that, displacement (x_m) = 10 mm Peak acceleration \(= {\omega ^2}{x_m}\) = (2πf)²x_m = (2π × 100)² × 10 × 10^-3 = 3947.84 m/sec²

12583.

The seismic mass of an accelerometer oscillates sinusoidally at 100 Hz with a maximum displacement of 10 mm from its mean position.The peak acceleration of the seismic mass is1. 3947.84 m/s22. 3141.50 m/s23. 314.15 m/s24. 100.00 m/s2

Answer» Correct Answer - Option 1 : 3947.84 m/s²

Given that, displacement (x_m) = 10 mm

Peak acceleration \(= {\omega ^2}{x_m}\)

= (2πf)²x_m

= (2π × 100)² × 10 × 10^-3

= 3947.84 m/sec²

Discussion

12584.	A straight rigid rod of mass `M` and length `L` lies on a smooth horizontal table. Taking the co-ordinate axes as shown in the figure and assuming an average force `ltFgt` acting for a small time interval `(/_ )`, at the end `A`, making an angle `30^@` with the `X`-axis, Based on the above passege, answer the following questions. Angular velocity of rod about `O` isA. `(3sqrt(5)ltFgt(/_ ))/(ML)`B. `(2sqrt(5)ltFgt(/_ ))/(ML)`C. `(2sqrt(3)ltFgt(/_ ))/(ML)`D. `(3sqrt(3)ltFgt(/_ ))/(ML)`
Answer» Correct Answer - D Angular impulse `=/_Iomega` `sqrt3/4(:F:)/_xxL=(ML^2)/12xximpliesomega=(3sqrt3( : F : )/_L)/(ML)`

Discussion

12585.	When a particle oscillates in simple harmonic motion, both in potential energy and kinetic energy vary sinusoidally with time. If `v` be the frequency of the motion of the particle, the frequency associated with the kinetic energy is `:`A. `4v`B. `2v`C. `v` is highest when the spring comes back to natural positionD. `(v)/(2)`
Answer» Correct Answer - B `x=A sin wt` `K.E.=(1)/(2)KA^(2)W^(2)cos^(2)wt` `PE=(1)/(2)mA^(2)w^(2)sin^(2)wt` frequency of kinetic energy is `2V` Ans. `(B)`

Discussion

12586.	Two elastic waves move along the same direction in the same medium. The pressure amplitudes of both the waves are equal, but the wavelength of the first wave is three times that of the second. If the average power transmitted through unit area by the first wave is `W_(1)` and that by the second is `W_(2)`, thenA. `W_(1)=W_(2)`B. `W_(1)=3W_(2)`C. `W_(2)=3W_(1)`D. `W_(1)=9W_(2)`
Answer» Correct Answer - A `I=(Power)/(Area)=(P_(0)^(2))/(2rhov)` `I=I_(f)=I_(2)` `w_(1)=w_(2) Ans. (A)`

Discussion

12587.	If error in measurement of radius of a sphere is 1%, what will be the error in measurement of volume?A. `1%`B. `3%`C. `5%`D. `7%`
Answer» Correct Answer - B `V=(4)/(3)pir^3` `%` error is volume`=3xx%` error in radius `=3xx1=3%`

Discussion

12588.	(i). Why does R3P=O exist but R3N=O does not? (ii). Why is NH3 more basic than PH3? (iii). Why sulphur is a polyatomic solid whereas oxygen is a diatomic gas
Answer» (i) Nitrogen does not contains d-orbitals. As a result, it cannot expand its covalency beyond four and cannot form pπ – dπ multiple bonds. In contrast, P contains the d-orbitals, and can expand its covalency beyond 4 and can form pπdπ multiple bonds. Hence R₃P = O exist but R₃N = O does not. (ii) Due to smaller atomic size the density of lone pair electrons on N in NH₃ is larger than that of P in PH₃. So, NH₃ is a stronger Lewis base than that of PH₃. (iii) The intermolecular forces in oxygen are weak van der Waals forces, which causes it to exist as gas. On the other hand, sulphur does not form strong S=S double bonds hence exists as a puckered structure held together by strong covalent bonds and exists as a polyatomic molecule. So, it exists as a solid.

12588.

(i). Why does R3P=O exist but R3N=O does not? (ii). Why is NH3 more basic than PH3? (iii). Why sulphur is a polyatomic solid whereas oxygen is a diatomic gas

Answer»

(i) Nitrogen does not contains d-orbitals. As a result, it cannot expand its covalency beyond four and cannot form pπ – dπ multiple bonds. In contrast, P contains the d-orbitals, and can expand its covalency beyond 4 and can form pπdπ multiple bonds. Hence R₃P = O exist but R₃N = O does not.

(ii) Due to smaller atomic size the density of lone pair electrons on N in NH₃ is larger than that of P in PH₃. So, NH₃ is a stronger Lewis base than that of PH₃.

(iii) The intermolecular forces in oxygen are weak van der Waals forces, which causes it to exist as gas. On the other hand, sulphur does not form strong S=S double bonds hence exists as a puckered structure held together by strong covalent bonds and exists as a polyatomic molecule. So, it exists as a solid.

Discussion

12589.	Why does R3P=O exist but R3N=O does not (R = alkyl group)?
Answer» N (unlike P) lacks the d-orbital. This restricts nitrogen to expand its coordination number beyond four. Hence, R₃N=O does not exist.

Discussion

12590.	General electronic configuration of transition metal is– (a) (n-1)d1-10 ns0-2(b) ns0-1(n-1)d1-10(c) ns0-2 (n-1)d0-10 (d) None of these
Answer» General electronic configuration of transition metal is (n-1)d^1-10 ns^0-2

Discussion

12591.	Which one of the following is non crystalline or amorphous ?(a) Diamond (b) Graphite(c) Glass(d) Common salt
Answer» Graphite is non crystalline or amorphous

Discussion

12592.	The chemical formula of lunar caustic is–(a) Ag S2(b) Ag2 SO4(c) AgNO3(d) AgCl
Answer» The chemical formula of lunar caustic is AgNO₃

Discussion

12593.	Which one of the following is non crystalline or amorphous ?(a) Diamond(b) Graphite(c) Glass(d) Common salt
Answer» Graphite is non crystalline or amorphous .

Discussion

12594.	Which of following metals occurs in native state?A. MagnesiumB. PlatinumC. PotassiumD. Sodium
Answer» Correct Answer - B Among the given metals, platinum has the least reactivity thus, it occurs I native state. While all other metals occurs in their oxides, sulphies and chloride forms.

Discussion

12595.	Refractory materials are generally used in furnaces becauseA. do not require replacementB. possess great strengthC. can withstand high temperatureD. are chemically inert
Answer» Correct Answer - C Refraction material of silicon

Discussion

12596.	Which of the following metals are found in native state ?A. Cu, Pt, MgB. Ag , Pt , AuC. Al, Ag, ZnD. Au, Pb, Fe
Answer» Correct Answer - B Less reactive metals

Discussion

12597.	Which of the following statements is false? (a) The repeat unit in natural rubber is isoprene. (b) Both starch and cellulose are polymers of glucose. (c) Artificial silk is derived from cellulose. (d) Nylon-66 is an example of elastomer.
Answer» (d) Nylon-66 is an example of elastomer.

Discussion

12598.	In tensile test, necking starts at (a) lower yield stress (b) Upper yield stress (c) ultimate tensile stress (d) just before fracture
Answer» (c)ultimate tensile stress

Discussion

12599.	In tensile test, the engineering stress corresponding to the maximum load is called (a) yield strength (b) tensile strength (c) Shear strength (d) Upper yield stress
Answer» (b) tensile strength

Discussion

12600.	Cast iron is made by meltingA. pig iron with zincB. pig iron with scrap iron and tinC. pig iron with scrap iron and cokeD. pig iron with lead and zinc
Answer» Correct Answer - C Cast iron contain 4% carbon

Discussion

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