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5651.

What is current sensitivity of galvanometer ? How it can be increase ?

Answer»

Solution :1. For galvanometer,
`kphi=NIAB`
`thereforephi/I=(NAB)/k`
Current sensitivity of galvanometer `(phi/I)`, is deflection PER UNIT current.
2. To INCREASE the sensitivity is to increase the number of turns N.
Discussion
5652.

Lenz's law of electromagnetic induction corresponds to the

Answer»

law of CONSERVATION of charge
law of conservation of momentum
law of conservation of momentum
law of conservation of ANGULAR momentum

ANSWER :B
Discussion
5653.

Usethe Rydbergformula to calculatethe wavelenghtof the H_(alpha)line.Giventhat Rydberg'sconstant R = 1.1 xx 10^(7) J m^(-1)

Answer»

SOLUTION :See SHORT Answer QuestionNu,ber 17.
Discussion
5654.

A capacitor made of two parallel plates each of plate area A and separation d is being charged by an external ac source. Show that the displacement current inside the capacitor is the same as the current charging the capacitor.

Answer»

SOLUTION :The CAPACITANCE of the parallel plate capacitor
`C=(in_0A)/d`
EFFECTIVE emf in a purely capacitative circuit driven by an ac voltage V is
`V'=V-q/C`
`therefore` The circuit EQUATION is
`V-q/C=0` or , q=CV
`therefore` Charging current , `I=(dq)/(dt)=C(dV)/(dt)=(in_0A)/d (dV)/(dt)`
Displacement current ,
`I_d=in_0(dphi_E)/(dt)=in_0(d)/(dt)(EA)=in_0(d)/(dt)(V/dA)=(in_0A)/(d)(dV)/(dt)`
`therefore I_d=I`
Discussion
5655.

Heat energy reaches on the earth from the sun in the form of

Answer»

conduction
convection
radiation
scattering

Answer :C
Discussion
5656.

A carrier wave of 500 W is subjected to 100 % amplitude modulation. Ditermine Power in modulated wave.

Answer»

<P>

SOLUTION :Power in A.M WAVE,
`P_(Total)=P_(carrier)+P_("SIDE band")=500+250`
Discussion
5657.

Chain reaction can be initiated by

Answer»

PROMPT neutrons
DELAYED neutrons
SLOWED prompt neutrons
2 or 3

ANSWER :D
Discussion
5658.

Calculate the radius of the earth if the density of the earth is equal to the density of the nucleus. [mass of earth 5.97xx10^(24)kg].

Answer»

Solution :The density of the nucleus of an atom
`rho_(N) = 2.3 xx 10^(17) kg m^(-3)`
`rho_(N) = rho_(E) = 2.3 xx 10^(17) kg m^(-3)`
Mass of the earth `M_(E) = 5.97 xx 10^(24)`kg
Density of the earth,
`rho_(E) = (m_(E))/(V)`
` = (m_(E))/(4/3 pi r^(3))`
`r^(3) = (m_(E))/((4)/(3) pi rho_(E) ) = (5.97 xx 10^(24))/(1.33 xx 3.14 xx2.3 xx 10^(17))`
` = (5.97 xx 10^(24))/(9.60526 xx 10^(17))`
`r^(3) = 0.6215 xx 10^(7) m^(3)`
` r = 183.85 m`
`r APPROX 180 m`.
Discussion
5659.

In young's double slit experiment distance between the slits is 0.5 mm. When the screen is kept at a distance of 100 cm from the slits, the distance of ninth bright fring from the centre of the fringe system is 8.835 mm. Find the wavelength of light used.

Answer»

Solution :GIVEN :
`x_(N) = 8.85xx10^(-3)` d = 0.5 MM= `0.5xx10^(-3)` m, D=1m , n =9
Distance of `n^(th)` bright fringe is given by
`x_(n) =(nlambdaD)/(d)`
`lambda=(x_(n)d)/(nD)=(8.835xx10^(-3)xx0.5xx10^(-3))/(9xx1) = (4.4175)/(9) xx10^(-6)m = 4908 Å`
Discussion
5660.

An iron sphere starts falling just from the top surface of water in a lake having enough depth for the sphere to attain its terminal velocity in the water of the lake after a fall under gravity. Which of the graphs given below will correctly represent the change in kinetic energy with the depth of the lake as the sphere goes straight into water?

Answer»




Solution :Here the kinetic energy INCREASES uniformally till the sphere attains TERMINAL velocity which gives CONSTANT VALUE of K.E. for the rest of its JOURNEY through water assuming that the temperature of water does not change.
Discussion
5661.

A road runs between two parallel rows of buildings. A motorist moving with speed of 36 km/h sounds the horn. He hears the echo one second after he sounds the horn. He hears the echo one second after he sounded the horn. If speed of sound is 330 m/s then distance between two rows of buildings is :

Answer»

330 m
` 2 SQRT( (165)^(2) - (5)^(2) )` m
165 m
`sqrt((165)^(2) - (5)^(2))` m

Answer :B
Discussion
5662.

A rigid container with thermally insulated walls contains a coil of resistance 100 Omega, carrying current 1 A. Change in internal energy after 5 minute will be:

Answer»

0 KJ
20 kJ
10 kJ
30 kJ

Solution :CHANGE in internal ENERGY = heat PRODUCED due to current
`dU=I^(2)Rt=1^(2)xx100xx300=30 kJ`
`therefore` CORRECT choice is (d).
Discussion
5663.

A block of weight 100N is lying on a rough horizontal surface. If coefficient of friction 1//sqrt3. The least possible force that can move the block is

Answer»

`(100)/(SQRT3)`
`100 sqrt3`
`50 sqrt3`
`50` N

Answer :D
Discussion
5664.

A hollow copper cylinder is of inner radius 4cm and outer radius 5cm. Now hollow portion is completely filled with suitable copper wires. Find percentage change in its electric resistance.

Answer»

Solution :`R_(1)=(rhol)/(pi(5^(2)-4^(2)))=(rhol)/(9pi)=(k)/(9)`
FINAL Resistance `R_(2)=(rhol)/(pi(5^(2)))=(rhol)/(25pi)=(k)/(25)`
Percentage of change `=(R_(2)-_(1))/(R_(1))XX100`
Discussion
5665.

Assertlon (A). When an electric motor is started the Initial current In It Is considerably more than the final current Reasoning : The current falls due to the fall In the back emf

Answer»

Assertion is TRUE, Reason is FALSE
Assertion is false, Reason is true
Both Assertion and Reason are true and Reason is the correct explanation of Assertion·
Both Assertion and Reason are true but Reason is not the correct explanation of Assertion

ANSWER :C
Discussion
5666.

Sound waves are similar to the waves

Answer»

of LASER light PASSING through air
generated in a stretched wire by hitting or plucking the wire
generated in a PIPE filled with air by MOVING the piston attached to the pipe up and down
generated by the mobile phone towers

Answer :C
Discussion
5667.

Magnetic field at 10 cm from extremely long current carrying straight wire is 10^(-5)Wb//m^(2). Then current passing through this wire is ______ .

Answer»

5A
10A
500A
1000A

Solution :`mu_(0)=4pixx10^(-7)Tm//A`
`B=10^(-5)Wb//m`
`y=10xx10^(-2)m`
`B=(mu_(0)I)/(2piy)rArrI=(Bxx2piy)/mu_(0)`
`thereforeI=(10^(-5)xx2pixx10xx10^(-2))/(4pixx10^(-7))=5A`
Discussion
5668.

The electronstatic potential energy between two identical nuclei produced in the fission on of ._(92)^(235)U at the moment of their separation is x then find x//180. Given R_(0)=1.3xx10^(-5)m and epsilon_(0)=8.85xx10^(-2)Fn^(-1).

Answer»


SOLUTION :N//A
Discussion
5669.

In Fizeau'sexperiment the distancec between the source and the reflector is 8 km and there are 720 teeth in the toothed wheel. At what speed would the first, second and third eclipses occur? (Velocity of light =3xx10^(9)ms^(-1))

Answer»


ANSWER :`13rev.//sec,39rev.//sec` and so on
Discussion
5670.

किस नदी को दक्षिण की गंगा के नाम से जाना जाता है?

Answer»

कावेरी
गोदावरी
नर्मदा
कृष्णा

Answer :B
Discussion
5671.

A gas container of 20 l capacity contains a mixture of 10 g of hydrogen and 48 g of oxygen. After the mixture is ignited by a spark the gas formed is heated to 300^@C. Find the pressure of the gas.

Answer»


Solution :In the course of the chemical reaction in which water is produced, 48 g of oxygen react with 6 g of hydrogen. Consequently the CONTAINER contains 54 g of water vapour and 4 g of hydrogen. To FIND the pressure apply Dalton.s LAW.
Discussion
5672.

The position vectors of the head and tail of radius vector are 2 hati+3 hatj+hatk and 2 hati-3 hatj+hatk. The linear mementium is 2 hati+3 hatj+hatk.The angular momentum is :

Answer»

`4 hati-8 HATK`
`2 hati-3 hatj+hatk`
`2 hati+3 hatj+hatk`
`2 hati-hatj+hatk`

ANSWER :A
Discussion
5673.

The current I passed in any instruement in alternating current circuit is I = 2 sin omegat amp and potential difference applied is given by V = 5 cos omegat volt then power loss in instruement is

Answer»

2.5 watt
5 watt
10 watt
zero

Solution :`I = 2 sinomega t`
`V = 5 cos omega t = 5 sin ((pi)/(2) - OMEGAT)`Since, there is a phase difference of `(pi)/(2)` between the current and VOLTAGE
`therefore` AVERAGE POWER over a COMPLETE cycle is zero.
Discussion
5674.

Essential difference between electrosatic shielding by a conducting shel and magnetiostatic shielding id due to

Answer»

electrostatic FIELD lines can end on charge and conductors have free charges
linesof b CANALSO end but conductors cannot end them
lines of b cannot end on any material and perfectshielding is not possible
shells of high permeability materials can be used to divert lines of b from the interior REGION

Answer :A::C::D
Discussion
5675.

A coffee maker makes coffee by passing steam through a mixture of coffee powder, milk and water. If the steam is mixed at the rate of 50 g per minute in a mug containing 500 g of mixture, then it takes about t_(0) seconds to make coffee at 70^(@)C when the initial temperature of the mixture is 25^(@)C. The value of t_(0) is close to (ratio of latent heat of evaporation to specific heat of water is 540^(@)C) and specific heat of the mixture can taken to be the same as that of water)

Answer»

30
45
60
90

Answer :B
Discussion
5676.

A particles moving with KE 5Mev. Its mass is 1.6 x 10^-27 Kg What is the energy of particle in joule?

Answer»

SOLUTION :`KE=5Mev = 5*10^6*1.6*10^-19 J`
Discussion
5677.

Match the items of column I with those of Column II and choose the correct option from the codes given below.

Answer»


ANSWER :A
Discussion
5678.

In a cyclic process the change in internal energy of a system is :

Answer»

MINIMUM but not ZERO
zero
maximum but not infinite
infinite

Answer :B
Discussion
5679.

Why did the boy run to school?

Answer»

There was traffic on road
He was being chased
He was GETTING LATE for school
For the SHEER joy of it

Answer :D
Discussion
5680.

If the velocity of the particle reduced to one third, then the percentage increase in its deBroglie wavelength is

Answer»

1
2
3
4

Answer :B
Discussion
5681.

Name two optical sources used in optical communication.

Answer»

SOLUTION :`(i)` LASER `(II)` LED.
Discussion
5682.

What is the de-Broglie wavelength of a nitrogen molecule in air at 300 K?Assume that the molecule is moving with the root-mean square speed of molecules at this this temperature.(Atomic mass of nitrogen-14.0076 u)

Answer»

Solution :Mass of nitrogen atom,
`m=2xx14xx1.66xx10^(-27)=46.48xx10^(-27)kg`
T=300 K
`K_(B)`=Boltzmaan.s constant
`=1.38xx10^(-23)Jmol^(-1)K^(-1)`
`h=6.63xx10^(-34)Js`
`implies` AVERAGE kinetic energy
`lt(1)/(2)MV^(2)gt=(3)/(2)k_(B)T`
`therefore v=sqrt((3K_(B)T)/(m))`
`therefore` Momentum p=mv=`sqrt(3mk_(g)T)`
`therefore` de-Broglie wavelength,
`lambda=(h)/(p)`
`therefore lambda=(h)/(sqrt(3mk_(B)T))`
`=(6.63xx10^(-34))/(sqrt(3xx46.49xx10^(-27)xx1.38xx10^(-23)xx300))`
`=(6.63xx10^(-34))/(sqrt(57728.16xx10^(-50)))`
`=(6.63xx10^(-34))/(240.266xx10^(-25))`
`=0.02759xx10^(-9)m`
`~~0.028nm`
Discussion
5683.

Two forks A and B when sounded together produce 4 beat/s. The fork A is in unison with 30 cm length of a sonometer wire and B is in unison with 25 cm length of the same wire at the same tension Calculate the frequency of the forks.

Answer»

Solution :LET FREQUENCY of fork Abe .n.. Then frequency of B would be `(n+-4)`
`:. Nprop (1)/(30) and n+4 PROP (1)/(25)`
on SOLVING we get `n_(A)=20 z and n_(B)=24Hz`
Discussion
5684.

The rate of recombinationor generation are governed by the law(s) of

Answer»

MASS conservation
Electrical neutrality
Thermodynamics
Chromodynamics

Answer :C
Discussion
5685.

A light ray strikes a horizontal plane mirror and gets deviated by pi//3 what angle should the mirror be tilted so that the reflected ray becomes vertical?

Answer»

`pi/6`
`pi/2`
`pi/3`
`pi/4`

ANSWER :A
Discussion
5686.

In a Young's double slit experiment, slits are separated by 0.5 mm and the screen is placed 150 cm away. A beam of light consisting of two wavelengths 650 nm and 520 nm is used tc obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is.....

Answer»

`9.75 mm`
`15.6` mm
`1.56` mm
`7.8` mm

Solution :`n_(1)barX_(1)=n_(2)barX_(2)`
`(n_(1)lambda_(1)D)/(d)=(n_(2)lambda_(2)D)/(d)`
`:. n_(1) lambda_(1)=n_(2)lambda_(2)`
`:.(n_(1))/(n_(2))=(lambda_(2))/(lambda_(1))=(520)/(650)=(4)/(5)`
`:.n_(1)=4 and n_(2)=5`
Now `x=(n_(1)lambda_(1)D)/(d) or x=(n_(2) lambda_(2)D)/(d)`
`=(4xx65xx10^(-6)xx150)/(6.65)`
`=780000xx10^(-6) CM`
`=7.8 mm`
Discussion
5687.

The self - inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of

Answer»

`4MUF`
`8muF`
`1muF`
`2MUF`

ANSWER :C
Discussion
5688.

The frequency from 3Hz to 30MHz is knownas

Answer»

AUDIO band
Medium FREQUENCY band
Very HIGH frequency band
High frequency band

Answer :D
Discussion
5689.

Derive the relation between electric field and electric potential.

Answer»

SOLUTION :
` DV = (DW)/(q_0)`
`E = -(dV)/(DX)`
Discussion
5690.

Which of the following substances has the highest elasticity ?

Answer»

Rubber
Copper
Sponge
STEEL.

Solution :Young.s modulus of steel is maximum. Hence steel has HIGHEST elasticity.
So correct choice is (d).
Discussion
5691.

Which of the following equations can represent the current through a circuit containing resistor and an ac source V =V_0 sin wt

Answer»

`[ i= i_m SIN (OMEGA t + pi/2)]`
`[ i= i_m sin (omega t - pi/2)]`
`[ i= i_m sin omega t]`
`[ i= i_m sin (omega t - pi/4)]`

ANSWER :C
Discussion
5692.

Two plane mirrors A and B are aligned parallel to each other, as shown in the figure. A light ray is incident at an angle of 30^@at a point just nside one end of A. The plane of incidence coincides with the plane of the figure. Themaximum number of times the ray undergoesreflections (including the first one) before itemerges out is)

Answer»

28
30
32
34

Answer :B
Discussion
5693.

The following four wires of length L and radius r are made of the same material .Which of these will have the largest extension,when the same tension is applied?

Answer»

L= 100CM, r=0.2mm
L=200cm, r=0.4mm
L=300cm,r=0.6mm
L=400cm,r=0.8mm.

Solution :`Y=F/A L/(DELTAL)rArrDeltal=(FL)/(YA)`
Since Y and F is same
`thereforeDeltalpropL/A` or `DeltalpropL/(r^(2))`
`L/(r^(2))` is MAXIMUM when L = 100 cm and r = 0·02 mm So CORRECT choice is (a).
Discussion
5694.

A pop-gun consists of a cylindrical barrel 3cm^2 in cross-secion closed at one end by a cork and having a well fitting piston at the other. If the piston is pushed slowly in, the cord is finally ejected, giving a pop, the frequency of which is found to be 512Hz. Assuming that the initial distance between the cork and the piston was 25cm and there is no leakage of air, If the force required to eject the cork is 0.75 x xkg-wt. Find the value of x. Atmospheric pressure = 1kg wt//cm^2, v = 340 m//s.

Answer»


ANSWER :2
Discussion
5695.

In the following circuit, bulb rated as 1.5 V , 0.45 W . If bulbs glows with full intensity then what will be the equivalent resistance between X and Y

Answer»

`0.45 OMEGA`
`1 Omega`
`3 Omega`
`5 Omega`

ANSWER :B
Discussion
5696.

Which one of the following is more monochromatic?

Answer»

MERCURY light
Sodium light
White light
Neon light

Answer :B
Discussion
5697.

In determining the angle of minimum deviation for a given prism, a graph is plotted between the angle of incidence (j) and the angle of deviation (delta). Which of the following graphs will correctly

Answer»




ANSWER :D
Discussion
5698.

The objective of a telescope focussed for infinity is taken out and replaced by a diaphragm of diameter D.A screen placed on the other side of the eye-piece shows a sharp image of diameter d. What was the magnifying power of the telescope?

Answer»


ANSWER :D/d
Discussion
5699.

Is the permeability of a ferromagnetic material independent of magnetic field ? If not , is it more for lower or higher fields ?

Answer»

Solution :PERMEABILITY of ferromagnetic MATERIAL depends upon the MAGNETIC FIELD . It is more for LOWER magnetic field .
Discussion
5700.

How many photon per second, on the average are emitted by the source ?

Answer»

SOLUTION :If N is the number of PHOTONS emitted per second by the source then, power transmitted in the beam `= N xx "energy of each PHOTON"`
P = NE
Discussion