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1351.

Continue heating even after ice starts melting.

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SOLUTION : The graph of temperature VERSUS TIME is SHOWN below.
Discussion
1352.

Human disasters increased after the World War -II.

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Solution :The reasons for increase in HUMAN disasters after the World War -II are as follows:
i. Condition of NATURAL imbalance has occurred due to greed of economic progress of human being.
ii. The increasing population led to increasing demands which further led to the emergence of some problems which reached its peak.
iii. Economic inequality, racial and religious differences, etc., have led to the condition of instability in the COUNTRY.
iv. Incidences like terrorism, abduction, social differences, etc., have become common.
v. Although production of certain harmful chemicals has been banned in developed NATIONS, they are still being PRODUCED in developing and poor countries. This can also lead to disasters.
vi. Increase in atomic energy plants in many countries pose a threat to life, in case of radiation leakage due to carelessness.
Discussion
1353.

Liquor is produced from…………obtained through fermentation of substances.

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ANSWER :ALCOHOL
Discussion
1354.

Identify my class/phylum and give one example of it : (a) We form the highest number of animals on the planet . We have bilateral symmetry and our exoskeleton is in the form of chitin.

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SOLUTION :Phylum : Arthropoda, EXAMPLE : PRAWN , CRAB.
Discussion
1355.

The rehabilitation work starts in ............. phase.

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ANSWER :TRANSITIONAL
Discussion
1356.

Two electric bulbs A and B are disigned for the same voltage. Their power ratings are P _(A) and P _(B) respectively with P _(A) lt P _(B). If they are joined in series across a V-volt supply

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A will DRAW more POWER than B
B will draw more power than A
A and B will draw the same power
NOTHING can be decided

Answer :A
Discussion
1357.

A truck and a car are moving with the same K.E. on a straight road. Their engines are simultaneously switched off. Which one will stop at a lesser distance ?

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Solution :By Work -ENERGY Theorem Loss in K.E. =W.D. against the force `XX` distance of friction
or K.E. `=mu mg S`
For cosntant K.E. `=S prop 1/m`
`:.` TRUCK will stop in a LESSER distance.
Discussion
1358.

Draw a ray diagram showing the path of rays of light when it enters with oblique incidence (i) from air into water , (ii) from water into air.

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SOLUTION :
Discussion
1359.

Opposition to the construction of large dams is due to

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social reasons
ECONOMIC reasons
environmental reasons
All of these

Solution :Opposition to the CONSTRUCTION of large dams by LOCAL people is DUE to social, economic and environmental problems.
Discussion
1360.

What is electric power ? State its SI unit.

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SOLUTION :RATE at which ene.rgy is CONSUMED is called electric power. Its unit is watt.
Discussion
1361.

Can we find the focal length of a concave lens using the distant object method ? Give reasons.

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Solution :No. We cannot find the focal length of the concave lens by the distant OBJECT METHOD as no image is formed on the screen. (Concave lens FORMS virtual images, which cannot be caught on the screen).
Discussion
1362.

Frequency (v) and time period (J) are related as

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`1//30`s
30 s
`1//24` s
none of these

ANSWER :A
Discussion
1363.

Choose the odd one out :Newton, ohm,Kepler, Galileo

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SOLUTION :OHM. OTHERS are CONCERNED with LAWS of gravity.
Discussion
1364.

The step of disaster management that forms an important link between measures after disaster and national development.

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ANSWER :RESTORATION
Discussion
1365.

A given length of a wire is doubled on itself and this process is repeated once again. By what factor does the resistance of the wire change?

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Solution :Resistance of a wire is DIRECTLY proportional to the length of the wire. As its length increases it.s resistance increases.
Let x be the resistance of a wire of length L
If length of wires is doubled to 2L its resistance is doubled to 2x
If it is doubled again, the length of the wire becomes 4L and its resistance becomes 4x.
THUS if a given length of a wire is doubled on itself and this PROCESS is repeated once again it.s resistance increases by a FACTOR of 4
Discussion
1366.

ENDOSPERM

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SOLUTION :NOURISHMENT of the GROWING EMBRYO.
Discussion
1367.

Name some source of direct current. Solar cell, dry cell, battery

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SOLUTION :SOLAR CELL, DRY cell, BATTERY.
Discussion
1368.

What are the environmental consequences of the increasing demand for energy ? What steps would you suggest to reduce energy consumption?

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Solution :(i) Burning of fossil fuels to meet the increasing demand for energy causes air pollution.
(ii) Construction of DAMS on rivers to generate hydroelectricity destroys large ecosystems which GET submerged under water in the dams. Further , large amounts of methane (which is a greenhouse gas) is produced when submerged vegetation rots under anaerobic conditions .
In order to reduce energy consumption:
(i) Fossil fuels should be used with care and caution to derive maximum benefit out of them.
(ii) Fuel saving devices such as pressure cookers, etc., should be used.
(iii) Efficiency of energy sources should be maintained by getting them REGULARLY serviced.
(iv) And last of all , we should be ECONOMICAL in our energy consumption as energy saved is energy produced.
Discussion
1369.

Can we say that sound is a form of mechanical energy?

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SOLUTION :YES, sound is a form of mechanical ENERGY.
Discussion
1370.

Whatchange should be madein an AC generator , so that it may become a DCgeneator ?

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SOLUTION :If wereplacerings `R_(1)` and `R_(2)`of an AC generatorby a SPLITRING typecommutator , THENIT will become a DC generator .
Discussion
1371.

Goldstein discovered cathode rays.

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SOLUTION :Goltstein DISCOVERED POSITIVE RAYS.
Discussion
1372.

"Coal is a non-renewable source of energy." Because,

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COAL is REPLENISHED soon in the nature
coal is abundant in nature
the RESERVES of coal are depleting at a fast rate and it is DIFFICULT to replenish
coal leaves residue when burnt.

Answer :C
Discussion
1373.

The body of leech has

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23 SEGMENTS
33 segments
38 segments
40 segments

Solution :33 segments
Discussion
1374.

Explain the series connection of parallel resistors.

Answer»

Solution :(i) If we consider the connectrion of a set of parallel resistors that are connected in SERIES we get a series - parallel circuit
(ii) Let `R_(1)` and `R_(2)` be connected in parallel to give an effective RESISTANCE of `RP_(1)`.
(iii) Similarly, let `R_(3)` and `R_(4)` be connected in parallel to give an effective resistance of `RP_(2)`.
(iv) Then, both of these parallel segment are connected in series.
(v) Using equation `(1)/(R_(p))=(1)/(R_(1))+(1)/(R_(2))+(1)/(R_(3))` we get
`(1)/(R_(p_(1)))=(1)/(R_(1))+(1)/(R_(2))`
`(1)/(R_(p_(2)))=(1)/(R_(3))+(1)/(R_(4))`
Finally, using equation the `R_(S)=R_(1)+R_(2)+R_(3)` NET effective resistance is GIVEN by `R_("total")=R_(P_(1))+R_(P_(2))`
Discussion
1375.

Explain in brief DNA fingerprinting. Give two examples where this technique is used.

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SOLUTION :(1) As the fingerprints are unique for every individual, SIMILARLY the nucleotide sequence in the DNA molecule is also unique.
(2) By knowing this sequence, one can find out the identity of any person. Such technique to establish the identity of a person by taking into CONSIDERATION the · nucleotide sequence is called DNA fingerprinting.
(3) Its main use is in forensic sciences to confirm the identity of the criminal.
(4) Similarly, identity of parents in CASE of DISPUTED parentage for any child can be understood by taking DNA fingerprints of both the parents and a child.
Discussion
1376.

If A is a radioactive element which emits an alpha-particle and produces ""_104Rf^(259). Write the atomic number and mass number of the element A.

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Solution :`""_(Z)X^(A) overset(alpha "DECAY")to ""_(Z-2)Y^(A-4)+ ""_(2)He^(4)(alpha "decay")`
`""_(106)X^(263) overset(alpha "decay")to ""_(104)RF^(259)+ ""_(2)He^(4)(alpha "decay")`
In a elements having NUMBER is 106 and mass number is 263
Discussion
1377.

A total reflecting equilateral prism can be used to deviate a ray of light through :

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`30^(@)`
`60^(@)`
`75^(@)`
`90^(@)`

ANSWER :B
Discussion
1378.

At what distance from a convex lens of focal length 5 m should a boy stand so that his image is half his height ?

Answer»

Solution :DATA : Convex LENS ,`f=2.5` m,
`M=-1/2, u=?`
`M=-1/2 =V/u therefore v=- u/2`
`1/f=1/v -1/u=1/(-(u)/(2))-1/u`
`- 2/u-1/u=- 3/u`
`therefore u=-3f=-3xx5 m =-15 m`
This is the object distance .
The boy should stand at 15m from the convex lens so that his image is half his height.
Discussion
1379.

{:(1,"Heat",-,(a),"Joule"),(2,"Thermometer",-,(b),"Heating"),(3,"The SI of heat",-,(c),"Temperature"),(4,"Cool a cup of cofee, adding cold milk",-,(d),"Energy"),(5, "gain by heat by a body",-, (e), "thermal equilibrium"):} {:(1,"Boyle's Law",-,(a),K_(B)=(R)/(n)),(2,"Absolute Scale",-,(b),V prop t),(3,"Charle's Law",-,(c),P prop (1)/(V)),(4,"Boltzmann constant",-,(d),Vprop n),(5, "Avagadro's Law",-, (e), "OK (zero kelvin)"):}

Answer»

<P>

Solution :1 (d) ENERGY 2 (c) Temperature 3 (a) Joule 4 (e) thermal equilibrium5 (b) Heating
1 (c) `P prop (1)/(V)` 2 (e) OK (zero kelvin) 3(b) `V prop t` 4 (A) `K_(B)=(R)/(n) 5 (d) V prop n`
Discussion
1380.

Name a substance whose resistance decreases with temperature.

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SOLUTION :GERMANIUM (a semi-conductor)
Discussion
1381.

Connecting too many appliances in a circuit causes

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SHORT CIRCUIT
OPEN circuit
overloading
earthing

Answer :C
Discussion
1382.

How does the strength of the magnetic field at the centre of a circular coil of a wire depend on: (a) radius of the coil (b) number of turns in the coil.

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SOLUTION :(a) More the RADIUS weaker the FIELD.
(b) Field strength is directly proportional to the NUMBER of TURNS in the coil.
Discussion
1383.

Name two devices which can be utilised for the cooking of food so as to save fuel.

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ANSWER :SOLAR COOKER ; PRESSURE cooker
Discussion
1384.

An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect ? Explain.

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SOLUTION :Out of SYLLABUS
Discussion
1385.

An electric bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?

Answer»

<P>

Solution :POWER P = VI
`= 220V xx 0.50 A`
`=110 J/s`
`=110W`
Discussion
1386.

What are the environmental consequences of the increasing demand for energy ? What steps would you suggest to reduce energy consumption ?

Answer»

Solution :(i) Burning of fossil fuels to meet increasing demand of energy results in air pollution.
(II) CONSTRUCTION of dams on rivers to generate hydro ELECTRIC energy which leads to the destruction of ecosystem.
In order to reduce energy consumption:
(i) Use fossil fuels with Care and Caution.
(ii) Use FUEL SAVING devices like, solar cooker.
(iii) Consumers energy economically as energy saved in energy produced.
Discussion
1387.

Calculate the resistance of a conductor if the current flowing through it is 0.25 A when the applied potential difference is 1.0 V.

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Solution :V=1.0 V
I =0.25 A
V= IR
`R= (V)/(I)`
`=(1)/(0.25)= 4 OMEGA`
Discussion
1388.

Define the term 'induced current'.

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SOLUTION :It is the electric CURRENT which originates in a CONDUCTOR by use of FLUCTUATING magnetic field around the conductor .
Discussion
1389.

a) What are the advantages of sexual reproduction over asexual reproduction. b) List any four reasons for adopting contraceptive method c) If a woman is using copper T, will it help in protecting her from sexually transmitted diseases. Why?

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SOLUTION :Advantages of sexual reproduction.
* In sexual reproduction more variations are produced thus it ensures survival of SPECIES in a pollination.
* The new formed individual has characteristics of both the parents.
* Variations are more vaible in sexual mode then in asexual ONE. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.
b) Four reasons for adopting CONTRACEPTIVE methods are
* To increase the gap between two children.
* To prevent unwanted pregnancy.
* To prevent transmission of STD.s
* To control populations growth.
c) If a woman is using copper-T it will not help in protecting her from sexually transmitted diseases. Copper-T prevents only implantation in the uterus.
Discussion
1390.

When there is an electric current passing through a wire, the particles moving are

Answer»

Electrons
Protons
Atoms
Ions

Answer :A
Discussion
1391.

Answer the following : If you compare the graviational force on the Earth due to the sun to that due to the moon you would find that the Sun's pull is greater than the Moon's pull. However, the tidal effect to the Moon's pull is greater than the tidal effect of the Sun. Why ?

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Solution :The tidal effect DEPENDS INVERSELY on the CUBE of the distance, while gravitational FORCE depends on the square of the distance.
Discussion
1392.

What is peristence of vision ?

Answer»

Solution :If the time interval between two consecutive light pulses is LESS than 0.1 second, human eye cannot DISTINGUISH them SEPARATELY . It is called persistence of VISION.
Discussion
1393.

Discuss how the brain perceives the image formed on the retina.

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Solution :RETINA contains light sensitive CELLS known as rods and cones. These cells get activated upon illumination and generate ELECTRICAL signals or pulses.
The electrical signals are sent to the brain through optic nerves.
In the brain, the signals are processed, INTERPRETED and the objects in front of the EYE are perceived.
Discussion
1394.

Get informationabout major wind- power stations in India and their capacity. Make a table of their location , state and their power capacity in MW.

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SOLUTION :
Discussion
1395.

An electric motor of power 100 W is used to drive the stirrer in a water bath. If 50% of the energy supplied to the motor is spent in stirring the water,calculate the work done on water in one minute.

Answer»

Solution :Given ,power SUPPLIED =100Q,time t=1 MINUTE =60 s power used in stirring the water
=50% of the power supplied
`(50)/(100)xx100 W=50 W`
Work done on water =power used `XX` time
Discussion
1396.

Hertz is the unit of ............

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SOLUTION :FREQUENCY
Discussion
1397.

Observe the diagram given and answer the question asked. a. Identify the eye defect.

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SOLUTION :The eye defect is MYOPIA. Myopia or nersightedness is the defect of VISION in which a HUMAN eye can see can see nearby objects clearly but is unable to see distant objects clearly.
Discussion
1398.

Find the time period of the wave whose frequency is 500 Hz?

Answer»

SOLUTION :TIME PERIOD `T= (1)/(upsilon) = (1)/(500) = 0.002` s.
Discussion
1399.

A body weight 700N on earth. What will be its weight on a planet having 1//7 of earth's mass and half of earth's radius?

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400 N
300 N
200 N
100N

Solution :400 N
Discussion
1400.

Which of the following have a wider field of view ? (a) Animals having two eyes on the opposite sides of their head. (b) Animals having two eyes at the front of their head.

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SOLUTION :NA
Discussion