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42651.

A point P is situated at 6.5 cm and 6.65 cm from two coherent source. If the wavelength of light used is 5000 AU, then the point P :

Answer»

is DARK
is BRIGHT
neither bright nor dark
may be dark or bright

Answer :B
Discussion
42652.

The position vector of a particle vecR as a function of time is given by: vecR=4sin(2pit)hati+4cos(2pii)hatj. Where R is in meters,t is in seconds and hati and hatj denote unit vectors along x-and y-directions, respectively. Which one of the following statements is wrong for the motion of particle?

Answer»

Path of the particle is a circle of RADIUS 4 meter
Acceleration vectors is along `-VECR`
Magnitude of acceleration vector is `(v^(2))/(R)` where v is the velocity of particle
Magnitude of the velocity of particle is 8 meter/ second.

Answer :D
Discussion
42653.

If the frequency of incident radiation on a photocell is doubled for the same intensity, then what change will you observe in photoelectric current ?

Answer»

SOLUTION :Photoelectric CURRENT will remain UNCHANGED because photoelectric current is independent of FREQUENCY of incident LIGHT.
Discussion
42654.

The ratio of the magnetic dipole moment to the angular momentum of the electron in the hydrogen atom is :

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`m/e`
`e/(2M)`
`e/m`
`(2m)/(e)`

Solution :We have L=mvr
and `M=IA =(ev)/(2PI r) XX pir^(2)=1/2evr`
`M/L=e/(2m)`
Discussion
42655.

A body moving along a circular path with uniform speed covers a distance of 10m. If the centripetal force acting on it is 5 N. Calculate the work done by the force ?

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1 J
0 J
2 J
3 J

Answer :B
Discussion
42656.

A body starting from rest , moves with uniform acceleration . The distance covered by the body in time is proportional to

Answer»

`SQRT t `
`t^(2/3)`
`t^2`
`t^3`

ANSWER :D
Discussion
42657.

In a step up transformer, the ratio of turns of primary to secondary is 1:10 and primary voltage is 230 V. If the load current is 2A, then current in the primary is

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20A
10A
2A
1A

Answer :A
Discussion
42658.

(a) A giant refracting telescope at an observatory has an objective lens of focal length 15m. If an eyepiece of focal length 1.0cm is used, what is the angular magnification of the telescope? (b) If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens? The diameter of the moon is 3.48 xx 10^(6)m, and the radius of lunar orbit is 3.8xx10^(8)m.

Answer»

Solution :(a) Angular magnification = 1500
(b) DIAMETER of the image = 13.7 CM.
Discussion
42659.

Which of the following statement is not true for detergants ?

Answer»

Sodium lauryl-sulphate is anionic detergent
Cetyl-trimethyl ammonium BROMIDE is CATIONIC detergent
Poly ethylene GLYCOL stearate is nenionic detergent
None of these

Solution :All statement are true.
Discussion
42660.

A parallel plate capacitor connected to a cell gets fully charged. After disconnecting the cell, a thin sheet of a mica is placed between the plates of the capacitor. What happens to capacitance?

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SOLUTION :CAPACITANCE INCREASES
Discussion
42661.

Bottom of a cylindrical container is made of a thin equiconvex lens having bottom side silvered as shown in the figure. The container is completely filled by water. Consider an object in water at a point on the vertical axis of the lens at a height h=4m from the bottom. when we from top in water two images of the point O coicides with each other. (given mu_("lens")=1.5,mu_("water")=(4)/(3)) The radius of curvature (in m) of the lens is.

Answer»


Solution :Focal length of the silvered lends `=-(4)/(2)=-2M`
`(f_(l))omega4(f_(l))a=4R`
`-(1)/(F)=(2)/((f_(l))Omega)-(1)/(f_(m))`
`(2)/(4R)-(!)/(-(R)/(2))=(5)/(2R)`
`IMPLIESR=-(5F)/(2)=5m`
Discussion
42662.

A parallel plate capacitor connected to a cell gets fully charged. After disconnecting the cell, a thin sheet of a mica is placed between the plates of the capacitor. What happens to charge?

Answer»

SOLUTION :CHARGE REMAINS CONSTANT
Discussion
42663.

The neutron separation energy is defined as the energy required to remove a neutron from the nucleus. Obtain the neutron separation energies of the nuclei ""_(20)^(41)Ca and ""_(13)^(27)Al from the following data: m(""_(20)^(40)Ca) = 39.962591 u m(""_(20)^(41)Ca) = 40.962278 u m(""_(13)^(26)Al) = 25.986895 u m (""_(13)^(27)Al) = 26.981541 u.

Answer»

Solution :NEUTRON SEPARATION energy `S_(n)` of a nucleus `""_(Z)^(A)X` is
`S(n)=[m_(N)(""_(Z)^(A-1)X)+m(n)-m_(N)(""_(Z)^(A)X)]c^(2)`
From given data, `S(n)(""_(20)^(51)Ca)=8.36MeV, S(n)(""_(13)^(27)Al)=13.06MeV`
Discussion
42664.

What vector represents the rate of flow of energy in electromagnetic waves ?

Answer»

SOLUTION :POYNTING
Discussion
42665.

(A): Atomic energy level spacings are of the order of ev, while the difference in nuclear energy levels is of the order of Mev (R) : Any nucular reaction obeys all conservation laws.

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Both .A. and .R. are TRUE and .R. is the CORRECT explanation of .A.
Both .A. and .R. are true and .R. is not the correct explanation of .A.
A. is true and .R. is false
A. is false and .R. is false

ANSWER :B
Discussion
42666.

In the graph shown the displacement of the body in 5 seconds will be

Answer»

60 m
40 m
80 m
100 m

Answer :C
Discussion
42667.

figure shows, in cross section, two Gaussian spheres and two Gaussian cubes that are centered on a positively charged particle on a positively charged particle . Rank greatest first, and indicate whether the magnitudes are uniform or variable along each surface.

Answer»

NET flux through all the FOUR Gaussion surface will be EQUAL
the magniude of the electric . Fields on the surface (i) and (ii) will be constant
the magnitude of the electric fields on the sufaces (ii) and (iv) will be variable
The magnitude of the electric fields on all the surfaces will be constant

Answer :a,b,c
Discussion
42668.

(a) The refractive index of glass is 1.5. What is the speed of light in glass? ("Speed of light in vacuum is "3.0 xx 10^(8) m s^(-1)) (b) Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?

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Solution :(a) `2.0xx10^(8)ms^(-1)`
(b) No. The refractive index, and hence the speed of light in a medium, DEPENDS on WAVELENGTH. [When no particular wavelength or colour of light is specified, we may take the given refractive index to refer to yellow colour.] Now we know violet colour deviates more than red in a glass PRISM, i.e. nv > nr . Therefore, the violet COMPONENT of WHITE light travels slower than the red component.
Discussion
42669.

n identical condensers are joined in parallel and are charged to potential V so that energy stored in each condenser is E. If they are seperated and joined in series, then the total energy and total potential difference of the combination will be

Answer»

`NEAND (V )/( n) `
`n^2 EandnV `
`(E )/(n^2) and (V )/( n^2)`
`nEand NV`

Answer :D
Discussion
42670.

In an L-C-R circuit , R=sqrt7Omega, X_L=11Omega and X_C=8Omega , then the value of impedance =______

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`4 Omega`
`3OMEGA`
`9Omega`
`3sqrt7Omega`

SOLUTION :`|Z|=sqrt(R^2+(X_L-X_C)^2)`
`=sqrt((sqrt7)^2+(11-8)^2)`
`=sqrt(7+9)`
`=sqrt16` = 4
Discussion
42671.

The figure shows hysteresis curves for soft iron and stell. Which one among the two materials is preferred for use in transformers and galvanometers?

Answer»

SOLUTION :SOFT IRON
Discussion
42672.

A simple pendulum consists of a small sphere of mass m suspended by a thread of length l. The sphere carries apositive charge q. Thependulum is placed in a uniform electric field of strength E directed vertically downwards. Finds the period of oscillation of the pendulum due to the electrostatic force acting on the sphere, neglecting the effect of the gravitational force.

Answer»

Solution :Let the pendulum be be displaced from its equilibrium position A to position B through a small angle ` THETA ` and then released. Forces acting on pendulum are (i)force F= qEin vertical DOWNWARD direction DUE to the electrical field, and (ii ) the tension `T_0` and hence unbalanced restoring forceis qE `SIN theta`
if ` theta ` is small then ` sin theta =theta =(arc AB)/(1) `
` therefore `Restoring force `=-qE theta =(-qE)/(l) (areAB)`
obviously the MOTION of pendulum is SHM ,whose time period is given as:
`T=2pi sqrt(("inertia factor ")/("spring factor ") )=2pi sqrt((m)/(qE//l))=2pi sqrt((ml)/(qE))`
` (##U_LIK_SP_PHY_XII_C01_E09_020_S01.png" width="80%">
Discussion
42673.

The refractive index of the material ofa double convex lens is 1.5 and its focal length is 5 cm. If the radii of curvature are equal, the value of the radius of curvature (in cm) is

Answer»

5
6.5
8
9.5

Answer :A
Discussion
42674.

Calculate the amount of work done to dissociate a system of three charges of 1muC, 1muC and -4 muC placed on the vertices of an equilateral triangle of side 10 cm.

Answer»

Solution :As shown in Fig.,` q_1 = 1muC = 1XX 10^(-6) C, q_2 = 1muC =1 XX 10^(-6) C`,
`q_3= -4 muC = 4 xx 10^(-6) C and AB = AC = BC = r= 10 cm = 0.1 m`
`:.` Work done to dissociate the system of charges
`W = - u = -1/(4piepsi_0)[(q_1q_2)/r_12 + (q_1q_3)/r_13 + (q_2 q_3)/r_23]`
`=-(9 xx 10^9)[((1XX10^(-6))xx(1xx10^(-6)))/0.1+((1xx10^(-6))xx(-4 xx10^(-6)))/0.1 + ((1 xx 10^(-6))xx(-4 xx 10^(-6)))/0.1]`
`=-(9 xx 10^9) [1 xx 10^(-11) - 4 xx 10^(-11) - 4 xx 10^(-11) ] = 0.63 J`
Discussion
42675.

For some integer m, every even integer is of the form

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m
m + 1
2m
2m + 1

Answer :C
Discussion
42676.

In a p-n junction, a potential barrier of 250 meV exists across the junction. A hole with a kinetic energy of 300 meV approaches the junction. Find the kinetic energy of the hole when it crosses the junction if the hole approached the junction from the p - side and

Answer»

100 MEV
50 meV
50 meV
100 meV

ANSWER :B
Discussion
42677.

Assertion: A point charge produces a uniform electric field. Reason:Due to a point charge electric lines of forces are parallel and equidistant

Answer»

Both Assertion and REASON are true and Reason is the correct EXPLANATION of Assertion
Both Assertion and Reasonare true and Reason is not the correct explanation of Assertion
Assertion is true and Reason is false 
Assertion is false and REASONIS false 

Answer :D
Discussion
42678.

Two polariods are crossedto each other .One of them is rotated through 60^(@) what % of incident unpolarised light will pass through the system ?

Answer»

`37.5` %
0.4
0.2
0.5

Answer :A
Discussion
42679.

Draw the diagram of Wheatstone bridge. Why does no current flow through the galvanometer when the bridge is balanced ?

Answer»

Solution :The circuit arrangement of a Wheatstone BRIDGE has been shown inadjoining FIG.

When the bridge is BALANCED, no current flows through the galvanometer because potential of point B is EXACTLY same as the potential of point D.
Discussion
42680.

Young.s double slit experiment is performed in a liquid. The 10th bright fringe in liquid lies where 6th dark fringe lies in vaccum. The refractive index of the liquid is apporoximately:

Answer»

SOLUTION :`(10 lambdaD)/(d mu)=((2xx6xx -1)/(2))(lambda D)/(d)`
`IMPLIES (10 lambda)/(mu)(D/d)= (5.5)(lambda D)/(d)" or "mu= 1.8`.
Discussion
42681.

If x=(epsilon_(0)lV)/(t) where epsilon_(0) is permittivity of free space, l is the length, V is the potential difference and t is the time, then dimensions of x are the same as that of :

Answer»

resistance
Charge
voltage
current

Solution :Here`x=in_(0)L(DELTAV)/(Deltat)=(qxxL)/(4piExxr^(2))XX(DeltaV)/(Deltat)`
`=(q)/(Deltat)xxLxx(DeltaV)/(DeltaV)xx(Deltax)/(L^(2))=(q)/(Deltat)=` current.
HENCE correct CHOICE is `(d).
Discussion
42682.

The magnetic field in a plane electromagnetic wave is given by B_(y)=(2xx10^(-7)) T sin (0.5xx10^(3)x+1.5xx10^(11)t). Write an expression for the electric field.

Answer»

Solution :`E_(o) =B_(o)c =2xx10^(-7) Txx 3XX10^(8) m//s =6XX10^(1) V//m`
The electric FIELD component is perpendicular to the direction of propagation and the direction of magnetic field. Therefore, the electric field component along the z-axis is obtained as
`E_(z) =60 SIN (0.5 xx10^(3) x +1.5 xx10^(11) t) V//m`
Discussion
42683.

A potential barrier of 0.50 V exists across a p-n junction. An electron with a speed of 5.0 xx 10^5m/s approaches the p-n junction from the n-side. With what speed will it enter the p-side ?

Answer»

Solution :
Suppose the electron has a speed `v_1 `, when it ENTERS the DEPLETION layer and `v_2`, when it comes out of it. As the potential energy increases by `e xx 0.50 `V, from the principle of CONSERVATION of energy.
` 1/2 m upsilon_(1)^(2)= e xx 0.50+ 1/2m upsilon_(2)^(2)`
`1/2( 9.1 xx 10^(-31)) ( 5 xx 10^5 )^2 `
`= 1.6 xx 10^(-19) xx 0.5+1/2xx 9.1xx 10^(-31) xx upsilon_(2)^(2)`
Solving this, ` upsilon _2 = 2.7 xx 10^5 m//s`
Discussion
42684.

The variation of potential with distance R from a fixed point is as shown below. A charge - q is put at R = 3 m and released. The charge will

Answer»

MOVE away from ORIGIN
Move towards the origin
Not move
Trace a cicular path

ANSWER :C
Discussion
42685.

Two highways are perpendicular to each other imagine them to be along the x-axis and the y-axis, respectively. At the instant t = 0, a police car P is at a distance d = 400 m from the intersection and moving at speed of 8 km//h towards it at a speed of 60 km//h along they y-axis. The minimum distance between the cars is

Answer»

`300 m`
`240 m`
`180 m`
`120 m`

Solution :If s be their separation at TIME t then,
`s^(2) = (0.4-80t)^(2) + (0.6-60t)^(2)`
where t is in hour, s in KM. Minimise s using CALCULUS.
Discussion
42686.

An electric dipoleof dipole moment p is kept at a distance r from an infinite long charged wire of linear charge density lambda as shown. Find the force acting on the dipole.

Answer»

SOLUTION :Field intensity at a distance r from the line of charge is `E=(lambda)/(2pi in_(0)r)`
The FORCE on the dipole is `F=rho(DE)/(dr)`
`=p[(-lambda)/(2pi in_(0)r^(2))]= -(p lambda)/(2pi in_(0)r^(2))`
Here the net force on dipole due to the wire will be ATTRACTIVE.
Discussion
42687.

A prism of glass (mu = 1.5) is dipped in to water as shown in the figure. If the refractive index ofwater is 4/3, then the incident ray will be totally reflected if

Answer»

`SIN THETA GT 8/9`
`sin theta LT 8/9`
`sin theta = 9/8`
`sin theta = 8/9`

ANSWER :A
Discussion
42688.

A body is moving along the +ve X-axis with uniform acceleration of 4ms^(2) Its velocity at x = 0 is 10 ms^(-1). The time taken by the body to reach a point at x = 12m is

Answer»

(25, 3S) 
(38, 4s)
(48,8s) 
(1s, 28)

ANSWER :A
Discussion
42689.

The working of a dynamo is based on the principle of

Answer»

HEATING EFFECT of current
chemical effect of current
magnetic effect of current
electromagnetic induction

Answer :D
Discussion
42690.

When the medium moves and the source and observer are stationary:

Answer»

`LAMDA` CHANGES
`lamda` REMAINS constant
FREQUENCY changes
none of these

Answer :A
Discussion
42691.

Based on what principle does a transformer work? Explain.

Answer»

Solution :A transformer is a device used for varying the AC voltages. It WORKS on the principle of MUTUAL induction. (It is an indispensable device in electrical POWER transmission and distribution).
Discussion
42692.

The function sin^(2)(omegat) represents :

Answer»

a periodic, but not simple harmonicmotion with a PERIOD`2pi//omega`
a periodic, butnot simple HARMONIC motion witha period `pi//omega`
a simple harmonic motion with a period `2pi//omega`
a simple harmonic motion with a period `pi//omega`

SOLUTION :`sin^(2) WT=(1-cos2" wt")/(2)=(1)/(2)-(1)/(2)cos2` wt
`implies` Motion is periodic but not SHM.
So the correct CHOICE is (b).
Discussion
42693.

According to maxwell,s hypothesis a changing electric field gives reises to:

Answer»

and emf
electric current
magnetic field
pressure gradiant

Answer :C
Discussion
42694.

Lorentz force acting on a charged particle is zero. If electric field is 5V/m, then |(vecBxxvecV)|= ______ .

Answer»

zero
infinite
5
none of these

Solution :LORENTZ FORCE `vecF=q[VECE+(vecvxxvecB)]`
`0=q[vecE+(vecvxxvecB)]`
`therefore0=[vecE+(vecvxxvecB)]`
`THEREFORE-(vecvxxvecB)=vecE`
`therefore(vecBxxvecv)=vecE""[becausevecvxxvecB=-(vecBxxvecv)]`
`therefore(vecBxxvecv)=5`
Discussion
42695.

Coefficient of thermal conductivity K is given by :

Answer»

`(Q.t)/(A(T_(1)-T_(2))d)`
`(Q.d)/(A(T_(1)-T_(2))t)`
`(A(T_(1)-T_(2))d)/(Q.t)`
`(A(T_(1)-T_(2))t)/(Q.d)`

Solution :`Q("k A(T_(1)-T_(2))t)/(d)rArrk=(QD)/(A(T_(1)-T_(2))t)`
Thus CORRECT CHOICE is (B).
Discussion
42696.

The output across the load resistance R is (##AAK_P7_NEET_PHY_SP7_C29_E04_031_Q01.png" width="80%">

Answer»

HALF WAVE rectified
Full wave rectified
Quarter rectified
ac

Answer :B
Discussion
42697.

Jim asked Ms. Greene to keep the old newspapers for the school-going children who ...... them.

Answer»

burnt
bought
read
collected

Answer :D
Discussion
42698.

Name the semiconductor device that can be used to regulate an irregulation dc power supply. With the help of I-V characteristics of this device, explain its working.

Answer»

SOLUTION :ZENER DIODE.
Discussion
42699.

Six identical capacitors of each capacitance .C.are arranged as shown in fig .The equivalentcapacitance between A and B is (KC)/8 . The value of .K. is ..........

Answer»


ANSWER :4
Discussion
42700.

What is the advantage in choosing the wavelength of a light radiation as a standard of length?

Answer»

Solution :Advantage are (1) wavelength of light radiation can be EASILY and accurately reproduced (2) It is not affected by ENVIRONMENTAL conditions such as temperature, pressure etc.(3) It is independent of other PHYSICAL QUANTITIES.
Discussion