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9051.

If 50 g steam of temperature90^(@)C is released on an ice slab of temperature0^(@)C, how much ice will melt? How much energy will be transferred to the ice when the steam will be transformed to water? (Given: Latent heat of melting the ice = L_("melt") = 80 " cal/g " Latent heat of vaporisation of water = L_(vap) = 540 " cal/g ")

Answer»

SOLUTION :393.75g,31.5 KCAL
Discussion
9052.

An isotope of _________ is used in the airlines to detect the explosives in the luggage.

Answer»

SOLUTION :CALIFORNIUM `(CF^(252))`
Discussion
9053.

How would be these advantages differ from the advantage of using a long - tern perspective in managing our resources ?

Answer»

SOLUTION :Exploiting resources with short - term aim isbeneficial for the presentgeneration to meet currett BASIC human needs while using with a LONG - term perspective aims to FULFIL the need of future generation . A long term perpective in managing our resources is a sustainable practice that enables the present generation to use natural resources is a sustainable practice that enables the presentgeneration to use natural resources judiciously so that their availability is ensured for the future GENERATIONS too .
Discussion
9054.

An incense stick when rotated, forms complete circles. Explain this statement using the concept of "Persistence of Vision."

Answer»

Solution :1. This happen due to persistence of VISION.
2. The impressionof IMAGE remains on retina for `1^(th)/16` of a second even after the object is REMOVED.
3. During this time, the second image id formed, which merges with the first image. This gives the imperssion of complete circle when ROTATED.
Discussion
9055.

A child is sitting on a swing. Its minimum and maximum heights from the ground 0.75 m and 2 m respectively, its maximum sped will be

Answer»

`10ms^(-1)`
`5 ms^(-1)`
`8 m//s`
`15 ms^(-1)`

Solution :MAXIMUM K.E = Drop in P.E.
`1/2 m V_("max")^(2)=mg(h_(2)-h_(1))impliesV_("max")=5MS^(-1)`
Discussion
9056.

On what basis would you classify energy sources as : (i) renewable and non-renewable ? (ii) exhaustible and inexhaustible ? Are the options given in (a) and (b) the same ?

Answer»

Solution :(i) Energy sources can be classified as renewable and non-renewable on the following basis:
(a) Quantity available in nature
(b) Mode of replenishment
(c) Rate of CONSUMPTION
(ii) Energy source can be classified as EXHAUSTIBLE and INEXHAUSTIBLE sources of energy on the basis of the rate of consumption and replenishment:
(a) If the rate of consumption is higher than the rate of replenishment, then the source of exhaustible.
(b) If the rate of consumption is LOWER than the rate of replenishment, then the source of energy is inexhaustible.
Thus the options given in (a) and (b) are essentially the same.
Discussion
9057.

velocity of sound in the atmosphere of a planet is 500ms^-(1). The minimum distance between the sources of sound and the obstacle to hear the echo, should be

Answer»

17 m
20 m
25 m
50 m

Solution :The minimum distance of source of sound and hear the ECHO,
`d=(vt)/(2)`
`t=0.1s,d=(500xx0.1)/(2)impliesd=25m`
Discussion
9058.

Which of the following has highest heat capacity?

Answer»

Water
Air
Soil
none of the above

Answer :A
Discussion
9059.

Which is an important characteristic of the social health?

Answer»

Solution :Ability to change one's own BEHAVIOUR ACCORDING to the CHANGING social conditions is an important characteristic of the social health.
Discussion
9060.

Calculate the velocityof a moving body of mass 7 kg whose liner momentumis 5 kg ms^(-1)

Answer»

Solution :GIVEN,p=5kg `ms^(-1)`
m=7kg
`p=mxxv`
`V=(p)/(m)=(5)/(7)`
`:. V=0.71 ms^(-1)`
Discussion
9061.

Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface.

Answer»

SOLUTION :A pencil ABC partly IMMERSED in WATER appears to be bent at the water SURFACE as shown in the Fig. 11.14. It is on account of bending of light ray away from the normal when refraction of light takes place from water (optically denser medium) to air (optically RARER medium).
Discussion
9062.

Hydrogen compounds are abundantly available on earth, and it has high calorific value. But this is not used as a common fuel. Give any two reasons. What are the processes that are being developed to use hydrogen as a common fuel ?

Answer»

Solution :Hydrogen is not used as a COMMON fuel because :
(i) When hydrogen is lighted, it burns with an explosion.
(ii) It is very DIFFICULT to STORE and transport hydrogen.
Hydrogen as a fuel :
Fuel cells are being developed that can store energy produced by BURNING hydrogen. Development of some MATERIALS that can absorb hydrogen and then release it at a steady rate.
Discussion
9063.

Which rule is useful to determinate the direction of field lines around a bar magnet?

Answer»


ANSWER :RIGHT HAND THUMB RULE
Discussion
9064.

Explan the correction of the eye defect Hypermetropia.

Answer»

Solution :1) A person with hypermetropia can see distant objcts clearly but cannot see objects at near distances. This is also known as 'Far sightedness'.
2) EYE lens can be form a clear image on the retina when any object is placed beyond near point.
3) To CORRECT the defect of hypermetropia , we need to use a lens which FORMS an image of an object beyond near point at H. When the object is between H and L. This is posible only when a double convex lens is used.
4) The image acts like an object for the eye lens. HENCE final image due to eye is formed at retina.
Here object distance (u)=-25 CM
Image distance(v) = distance of near point =-d
f is the focal length of bi-convex lens.
We known, `(1)/(f)=(1)/(v)-(1)/(u)implies(1)/(f) = (1)/(-d)-(1)/(-25)implies(1)/(f)=(1)/(-d)+(1)/(25)implies(1)/(f)=(d-25)/(25d)`
5) If d `gt` 25, then f becomes positive, it indicates that we need to used biconvex lens.
Discussion
9065.

Match the following. {:((a)"Sonalika",-,(i)"Sugarcane"),((b)"IR8",-,(ii)"Groundnut"),((c)"Saccharum",-,(iii)"Semi-dwarf wheat"),((iv)"TMV-2",-,(d)"Semi-dwarf Rice"):}

Answer»

SOLUTION :(a) (II), (B) (IV), (C) (i), (d) (ii)
Discussion
9066.

A piece of wire of resistances R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R' then the ratio R/R' is

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`1/25`
`1/5`
5
25

Solution :When a wire of resistance R is cut in five EQUAL parts, resistance of each PAT `R_1=R/5 OMEGA` Now, all these pieces are joined in parallel, HENCE,
`1/R.=1/R_1+1/R_1+....5 time s=5/R_1or R.=R_1/5 =1/5 times R/5 =R/25 therefore R/R.=R/((R//25))=25.]`
Discussion
9067.

Draw the diagram of an electricgenerator .

Answer»

SOLUTION :
Discussion
9068.

Can the temperature of a body be negative on kelvin scale?

Answer»

SOLUTION :The temperature of a BODY can NEVER be negative on kelvin. Because lowest temperature on kelvin SCALE is 0 kelvin.
Discussion
9069.

If Three resistors of 6Omega,9Omegaand21Omega are connected in series to a 12 V battery, find a] The total resistance of the circuit. b] The current flowing through the circuit. c] The potential difference across the 21Omega resistor.

Answer»

SOLUTION :a] TOTAL resistance = `6+9+21=36Omega`
b] Current = `V//R=12//36=0.33A`
c] P.D. ACROSS `21Omega=0.33xx21=7V`
Discussion
9070.

a. Two lenses have power of (i) +2d (ii) -4D. What is the nature and focal length of each lens? b. An object is kept at a distance of 100 cm from lens of power -4D. Calculate the image distance.

Answer»

Solution :a. (i) CONVEX lens =+50 CM
(ii) CONCAVE lens =25 cm
b. `1/f=1/v-1/u`
`f=1/(-4D)=-25cm`
`u=-100cm`
`1/v=1/f+1/u`
`=-1/25-1/100`
`=(-5)/100=-1/20`
`v=-20cm`
Discussion
9071.

A patientwithblood groupO wasinjuredinan accident and haslost. Whichbloodgroupthedoctorshouldeffectivelyusefortransfusionin thiscondition?

Answer»

A GROUP
B group
O group
AB group

ANSWER :C
Discussion
9072.

A shining metal 'M', on burning gives a dazzling white flame and changes to a white powder 'N'. Represent the above reaction in the form of a balanced chemical equation.

Answer»

SOLUTION :`2MG + O_(2) RARR 2Mg^(O)`
Discussion
9073.

Name the physical quantity responsible for a flow of electrons in a metal wire.

Answer»

Solution :Potential difference (i.e., difference of electric pressure) ACROSS a metal wire is responsible for a flow of electrons in a metal wire.
[This difference of potential may be PRODUCED by a CELL or a battery CONSISTING of two or more CELLS.]
Discussion
9074.

A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere. (a) What does the student mean by saying that the sun can be see after it has set ? (b) Do you think that the students' conclusion is correct ?

Answer»


SOLUTION :NA
Discussion
9075.

1 N is nearly equal to

Answer»

0.1 KG WT
1 kg wt
`(1)/(19.8)` kg wt
9.8 kg wt

Answer :A
Discussion
9076.

Assertion (A) : A straight wire carries current in thevertically upwards .Magnetic fieldlines aroundit areconcentric circles in horizontal planein an anticlockwisedirection. Reason (R) : Direction of magneticfieldis given by righthandthumb rule .

Answer»

Both (A) and (R) are true and (R) is CORRECT EXPLANATION of the assertion
Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
(A) is true but (R) is FALSE.
(A) is false but (R) is true.

Answer :A
Discussion
9077.

The SI unit of power is __________.

Answer»

VOLT - ampere
Watt
both (a) and (B)
only (b)

ANSWER :C
Discussion
9078.

(i) Draw a ray diagram to show the formation of image by a concave lens when an object is placed in front of it. (ii) In the above diagram mark the object distance (u) and the image distance (v) with their proper signs (+ve-veas per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the concave lens in this case. (iii) Find the nature and power of a lens which forms a real and inverted image of magnification -1 at a distance of 40 cm from its optical centre.

Answer»

SOLUTION :
(ii) Marking -U and -v
Relation`1/f=1/v-1/u`
(iii) As m=-1 HENCE the lens is CONVEX.
`:.m=v/u`
`:.v=-u`
THUS object is at 2F
`2f=40cm`
`:.f=20cm=0.2m`
`p=1/f=1/0.2=+5D`
Discussion
9079.

A convex lens converges the rays of light falling on it.

Answer»

Solution :(1) A convex lens can be regarded as MADE of a very large number of portions of triangular prisms. The BASES of these prisms are towards the central thicker portion of the lens.
(2) A ray of light passing through a prism BENDS towards its base. Hence, a convex lens converges the RAYS falling on it.
Discussion
9080.

Assertion (A): The metals and alloys are good conductors of electricity.Reason (R) : Bronze is an alloy of copper and tin and it is not a good conductor of electricity.

Answer»

Both (A) and (R) are TRUE and (R) is CORRECT EXPLANATION of the ASSERTION.
Both (A) and (R) are true but (R) is not the correct explanation of the assertion.
(A) is true but (R) is false.
(A) is false but (R) is true.

Solution : is false but (R) is true.
Discussion
9081.

Draw the ray diagram showing the position of the object and image, to get the real inverted image whose size is same as the object using a convex lens.

Answer»

SOLUTION :
Discussion
9082.

Consider the following criticisms that are generally addressed when a new project is launched :I. Displacement of peasants and local tribals without compensation. II. Swallowing up large amount of public money without any benefits. III. Deforestation and loss of biodiversity. The criticisms about large dams in particular are

Answer»

I and II
II and III
I and III
I, II and III

Solution :I and III
Discussion
9083.

Sona was standing outside her house in the afternoon enjoying the light drizzle after the heavy rain. Suddenly she saw a rainbow in the sky. Sona called out her father and asked him what a rainbow is and how it is formed. Sona's father told her that rainbow is an arch of seven colours visible in the sky which is produced by the splitting of white sunlight by tiny raindrops in the atmosphere. He also told Sona that a similar phenomenon can also be observed in a science laboratory by passing white light through a transparent object. (a) What is the name of the phenomenon which produces rainbow ? (b) Name the seven colours of the rainbow. Which of them deviates the most ? (c) When the rainbow is formed, state whether the sun is shining in the sky or not. (d) Name the transparent object which can be used to observe the phenomenon similar to a rainbow in the science laboratory. (e) What values are displayed by Sona's father ?

Answer»

SOLUTION :(a) DISPERSION of light.
(b) Violet, Indigo, Blue, Green, Yellow, Orange and Red. The violet colour DEVIATES the most.
(C) Yes, the sun is shining in the sky.
(d) GLASS prism.
(e) The values displayed by Sona's father are (i) Understanding of scientific facts (such as the dispersion of light), and (ii) Desire to impart knowledge to his daughter.
Discussion
9084.

If the relative humicity is less than 60%,we feel that the air is dry.

Answer»
Discussion
9085.

Scrotum :

Answer»

SOLUTION :PROTECTION and TEMPERATURE CONTROL of TESTIS.
Discussion
9086.

The essential difference between an ACgenerator and a DC generator ?

Answer»

AC GENERATOR has an electromagnetwhile a DCgeneratorhas permanentmagnet
DC generatorgenerates ahigher voltage.
AC generatorgenerates a HIGHER voltage
AC generatorhas SLIP rings whils the DC generatorhas a commutator

Answer :D
Discussion
9087.

Elders always instruct you to get out to the home to interact with relatives and others and play outdoor games but not to spend time continously with television, phone and internet. Why the children of your age are instructed same in each home ?

Answer»

Solution :a. Children of today's age prefer to spend their TIME after studies in watching television or plyaiyng games on on computer and mobile phones.
b. Due to this they TEND to develop a negative ATTITUDE, lose concentration on essential subjects and in EXTREME cases it can also affect their physical and mental health adversely.
c. In order to AVOID this, parents instruct and encourage children to go outside their home, play in the open ground and interact with friends and relatives.
d. This is essential for their social health as well as physical health.
Discussion
9088.

The displacement of a body is proportional to t^(3), where t is time elapsed. What is the nature of acceleration - time graph of the body?

Answer»

Solution :as`s ALPHA t^(3) rArr KT^(3)`
VELOCITY, `V=(ds)/(dt)=3kt^(2)`
acceleration, `a=(dv)/(dt)=6kt`
i.e., `a alpha t`.
`rArr` motion is uniform, ACCELERATED motion, a – t graph is straight-line.
Discussion
9089.

Calculate the drift speed of electrons in copper wire carrying acurrent of 1A and cross sectional area 10^(-6)m^(2).

Answer»

Solution :Current I = 1 A
Cross sectional area `A=10^(-6)m^(2)`
The electron density of COPPER `'n'=8.5xx10^(28)m^(-3)("Experimentally FOUND")`
Magnitude of electric charge `'e'=1.602xx10^(-19)C=q`
`"Drift speed"(v_(d))=(I)/(nqA)=(1)/(8.510^(28)xx1.602xx10^(-19)xx10^(-6))=(1)/(13.617xx10^(3))=0.07mm//sec`
Discussion
9090.

What are that number of primary colours ?

Answer»

1
2
3
4

Answer :C
Discussion
9091.

The far point of a myopia person is 200 cm. Calculate the power of a lens required to enable him to see distant objects clearly.

Answer»

Solution :Required FOCAL LENGTH, f = -200 cm = -2m.
`:. P = (1)/(f) = (1)/(-2m) = -0.5 D`.
Discussion
9092.

State law of equipartition of energy. Using this law, determine the values of C_(p), C_(v) and Y for diatomic gases.

Answer»

<P>

Answer :CORRECT LAW, `C_(p)=(7)/(2)R. C_(v)=(5)/(2)R" "Y=1.4`
Discussion
9093.

From the above table, which one does not pass the electricity ?

Answer»

SOLUTION :GLASS and AIR do not PASS the ELECTRICITY.
Discussion
9094.

If the image formed by a spherical mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it ? Draw a labelled diagram to support your answer.

Answer»

SOLUTION :CONVEX MIRROR
When the object is at infinity

When the object is placed at any position between infinity and pole of the convex mirror.
Discussion
9095.

What is the basic cause of atmospheric refraction ?

Answer»

SOLUTION :The basic CAUSE of atmospheric refraction is VARIATION in OPTICAL density of different layers of earth's ATMOSPHERE.
Discussion
9096.

State whether the following statementare true or false :Thewirewithgreeninsulation is usuallythe livewireof an electrica supply .

Answer»


SOLUTION :The wiregreen insulation isthe EARTH wire , WHEREASE the wirewithred insultation is the livewireof an electric supply .
Discussion
9097.

Name two characteristics of a heater coil.

Answer»

Solution :A heater COIL should have (i) HIGH resistivity and (it) high melting POINT.
Discussion
9098.

If in figure, R_1 = 10 Omega,R_2=40 Omega, R_3 = 30 Omega, R_4 = 20 Omega, R_5 = 60 Omega a 12 V battery is connected to the arrangement. Calculate ( a ) the total resistance in the circuit and ( b ) the total current flowing in the circuit.

Answer»

SOLUTION :( a ) Suppose, we replace the parallel resistors `R_1 and R_2` by an eqUivalent resistor of resistance, R.. Similarly we replace the parallel resistors `R_3,R_4 and R_5`by an eqUivalent single resistor of resistance R". Then using equation of equivalent resistance of parallel combination of resistances,
we have `1/(R.) = 1/10 +1/40 =5/40 , " that is " R. = 8 OMEGA`

Similarly, `1/(R.) = 1/30 + 1/20 + 1/60 + 6/60` , that is,`R.. =1 0Omega`
Thus, the total resistance,R = R. + R.. = `18 Omega`
( b ) To CALCULATE teh current, we use the Ohm.s law, and get
`I = V/R =(12V)/(18Omega) = 0.67 A`.
Discussion
9099.

Name two forms of energy in which solar energy manifests itself in oceans.

Answer»

Solution :(i) TIDAL energy , and (II) OCEAN THERMAL energy.
Discussion
9100.

Energy required to move a body of mass m from an orbit of radius 2R to 3R is

Answer»

Solution :Gravitational P.E. of mass m in orbit of radius `R=U = -(GMm)/(R )`
`U_i= -(GMm)/(2R)`
`U_f= -(GMm)/(3R)`
`triangleU=U_(F) -U_(i)=GMm[(1)/(2)-(1)/(3)]` `=(GMm)/(6R)`.
Discussion