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7251.

How do we get differentforms of energy ?

Answer»

Solution : (i) Energy EXISTS indifferent formsand can be converted from one formto ANOTHER.
(ii) Conventionalenergy resources or non-renewable energy resources energy resources (COAL , diesel etc.) and non -CONVENTIONAL energy resources (solar energy , wind energyetc.) are used to get the different FORMES of energy.
Discussion
7252.

What is the function of a galvanometer in a circuit ?

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SOLUTION : To DETECT the FLOW of CURRENT, if any, in a CIRCUIT.
Discussion
7253.

What iscohesion ?

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Solution :
(b) The FORCE of attraction between MOLECULES of water is called COHESION.
Discussion
7254.

The magneticforce actingon a current -carryingwire placed in a magneticfieldis directlyproportional to .

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the ELECTRICCURRENT
the magneticfield
the lengthfo the WIRE in themagnetic FIELD
all the GIVEN

Solution :all the given
Discussion
7255.

The mass of Earth is ________.

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SOLUTION :`5.972xx10^(24) KG `
Discussion
7256.

What are the advantages of hydroelectric power generation? Also mention its disadvantage ifit exists.

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Solution :(1) Hydroelectric energy dies not cause pollution.
(2)Generation of hydroelectric energy does not involave BURNING of fossil fuel.
(3) If sufficient water storege is availabke then electricity generation can be done as per REQUIREMENT.
(4) RAINWATER can REPLENISH the water storage and POWER generation can be thus be done uninterrupted.
Discussion
7257.

What is the SI unit of electrical conductivity?

Answer»

ohm - METRE
`"ohm"^(-1)"metre"^(-1)`
`"volt AMPERE"^(-1)`
ohm

Answer :B
Discussion
7258.

The device which converts solar energy into electrical energy is/are

Answer»

SOLAR cooker
Solar energy
solar CELL
All of these

Answer :A::B::C::D
Discussion
7259.

A solar water heater cannot be used to get hot water on :

Answer»

a sunny day
a CLOUDY day
a HOT day
a windy day

Answer :B
Discussion
7260.

Name the major constituent of biogas. List three characteristics to prove it as an excellent fuel.

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Solution :Methane is the major constituent of BIOGAS.
Three characteristics to prove it as an EXCELLENT FUEL are :
(i) Smokeless
(ii) LEAVES no residue
(III) Higher heat of combustion.
Discussion
7261.

Tabacco, Laughter club, Alcoholism, Drug abuse.

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SOLUTION :LAUGHTER CLUB.( All OTHERS are ADDICTIONS .)
Discussion
7262.

(Capability, Rehabilitation, Commodities, Human, objectives, normalcy, amusements) The …………………….of disaster management comprise of the following aspects. ……………………… life is saved from the disasters. People are helped to move away from the place of disasters. They are given essential ......................... by the government so that the gravity of disaster is reduced. The disaster conditions are brought back to .......................... . ........................ of the affected and displaced victims is done. Moreover, protective measures for future are also planned to develop ................... among the people to face any possible disasters in future.

Answer»

Solution :The objectives of disaster management comprise of the following aspects. HUMAN life is saved from the disasters. People are helped to MOVE away from the place of disasters. They are given essential commodities by the government so that the gravity of disaster is reduced. The disaster conditions are brought back to normalcy. Rehabilitation of the AFFECTED and displaced victims is done. Moreover, protective measures for future are ALSO planned to develop capability AMONG the people to face any possible disasters in future.
Discussion
7263.

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

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Solution :(i) ALLOY has very large resistance.
(II) It has a high MELTING point.
(iii) It does not bum even at high temperature
Discussion
7264.

Explain how concave lenses are used in the following devices. Medical devices

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SOLUTION :Medical devices:
Certain medical equipments, scanners and CD players use laser LIGHT for their WORKING. The concave lenses are used for the proper working of these devices.
Discussion
7265.

The energy of incident and scattered beam of light are not same, that scattering is called ____.

Answer»

elatic
raman
inelastic
mie

Answer :C
Discussion
7266.

Mention the required material and chemicalsfor the experiment of "scattering of light". Write the experiment procedure.

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Solution :Aim: To show the scattering of light.
Material REQUIRED : BREAKER, Sodium thiosulphate , Sulphuric acid.
Procedure: 1) Take a solution of sodium-thio-sulphate (hypo) and sulphuric acid in glass beaker.
2) place the beaker in an openplace where abundant sun light is available .
3) Watch the formation of grains of sulphur and observe thechanges in the beaker.
4) We will NOTICE that sulphur participates as the reaction is in progress. At the beginning , the grains of sulphur are smaller in SIZE and as the reaction progress, their size increases due to precipitation.
5) Sulphur grains appear blue in colour at the beginning and SLOWLY their colour becomes white as their size increases.
6) The reason for this is scattering of light.
7)At the beginning, the size of grains is small and almost comparable to the wavelength of blue light. Hence they appearblue in colour.
8) As the size of grains increases, their size becomes comparables to wavelength of other colours.
9) As a result, they acts as scattering centres of all colours.
Discussion
7267.

A lens produces a magnification of - 0.5. Is this a converging or diverging lens ? If the focal length of the lens is 6 cm, draw a ray diagram showing the image formation in this case.

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Solution :MAGNIFICATION of - 0.5 means that image FORMED is real, inverted and diminished one. It is possible only if the lens is a converging (convex) lens.
Here `f=+6` cm and `m=(upsilon)/(U)=-0.5`
`rArr upsilon =-0.5 u=(-u)/(2)`
Hence as per lens formula `(1)/(upsilon)-(1)/(u)=(1)/(f)`, we have
`(1)/(((-u)/(2)))-(1)/(u)=(1)/(6)`
`rArr (-2)/(u)-(1)/(u)=(1)/(6)`or`(-3)/(u)=(1)/(6)`or `u=-18` cm and hence `upsilon = +9` cm.
The RAY DIAGRAM showing image formations is drawn here.
Discussion
7268.

Identify the basic salt from the following salts :

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`Na_(2)CO_(3)`
`NH_(4)Cl`
`NaNO_(3)`
KCl

Answer :A
Discussion
7269.

Identify the position of sun in the following diagram if the linear speed of the planet is greater at C than at D.

Answer»

Solution :SUN should be at B as speed of PLANET is GREATER when it is closer to sun.
Discussion
7270.

………… are used to sterilize the surgical devices as they can kill the germs and microbes

Answer»

SOLUTION : RADIATIONS
Discussion
7271.

In the process of respiration, state the function of alveoli.

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Solution :In lungs, the BRONCHIOLES terminate in balloon-like STRUCTURES called alveoli. The alveoli provide extensive surface where the exchange of gases can take place. The thin, moist, permeable WALLS of alveoli facilitate quick diffusion and exchange of gases. Moreover it is richly supplied with blood capillaries. [The ALVEOLAR area, if spread out, it covers about 80 m2 which is more than our body surface area]
Discussion
7272.

Find the focal length of a lens of power -2.0 D. What type of lens is this ?

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Solution :Given that power of LENS P = -2.0 D
As power `P = (1)/(F)`, hence focal LENGTH of lens `f = (1)/(P) = (1)/(-2.0 D) = - 0.5 m`
The -ve sign of focal length MEANS that the lens is a concave lens.
Discussion
7273.

Draw a loop ACDBA as -V_(2)+I_(2)R_(1)-I_(1)R_(1)+V_(1)=0.

Answer»

SOLUTION :
Discussion
7274.

A stone of mass 500g is thrown vertically upwards with a velocity of 15 m s^(1). Calculate :(a)The potential energy at the greatest height,(b)The kintic energy on reaching the ground ,and (c )the total energy at its half way point.

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SOLUTION :(a) 56.25 J (B)56.25 J (C )56.25J
Discussion
7275.

Define the terms Polymerization

Answer»

Solution :The REACTION by which MONOMER MOLECULES are CONVERTED into a polymer is called POLYMERIZATION .
Discussion
7276.

Assertion (A) : Following is a balanced chemical equatin for the action of steam on iron: 3Fe + 4H_(2)O rarr Fe_(3)O_(4) + 4H_(2) Reason (R ) : The law of conservation of mass holds good for a chemical equation.

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 correct explanation of the assertion.
(A) is true but (R ) is FALSE.
(A) is false but (R ) is true.

Solution :Both (A) and (R ) are true and (R ) is correct explanation of the assertion.
Discussion
7277.

Study the following electric circuit and calculate the energy drawn from the battery in 10 s.

Answer»

Solution :From ohm.s law V =IR
`(1)/(R) = (1)/(R_(1))+(1)/(R_(2))=(1)/(30)+(1)/(20)=(20+30)/(600) implies (50)/(600)= (1)/(12) OMEGA`
`:. R = 12 Omega`
As `V= IR implies 3 = Ixx12`
`I=(3)/(12)=(1)/(4) A`
Electrical energy W = VT
`3xx(1)/(4) xx10`
`= (30)/(4) = (15)/(2) = 7.5 J`
Discussion
7278.

Glycolysis takes place in………..

Answer»

CYTOPLASM
mitochondria
OXYSOMES
RIBOSOMES

SOLUTION :cytoplasm
Discussion
7279.

What type of mirror is used in solar funance? Give an illustration?

Answer»

Solution :Concave mirrors are USED in solar FURNACES, b·ecause concave mirrors are. the only TYPE of mirror that reflects light in toward a SINGLE focal point. A convex mirror does have a focal point, but it is an imaginary point that EXISTS behind the mirrored surface. The light will reflect up and away from the focal point.
Discussion
7280.

Name the nuclear reactors in India.

Answer»

SOLUTION :ONE in Maharashtra, Rajasthan , GUJARAT , U.Pand two in TAMIL NADU, Kalpakkamand Kudankulam.
Discussion
7281.

What is the thne difference between actual sunset and apparentsunset?

Answer»

2S
20S
2MINUTES
20minutes

Answer :C
Discussion
7282.

How can the magnitude of the induced current be increased?

Answer»

Solution :The magnitude of the induced current can be increased by:
(i) TAKING the conductor in the FORM of a coil of many turns of INSULATED WIRE.
(ii) Increasing the strength of the magnetic field used.
(iii) Increasing the RATE of change of magnetic flux associated with the coil.
Discussion
7283.

Complete the following chart

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SOLUTION :
Discussion
7284.

What is electrical resistivity of a material ? State its SI unit and define it.

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Solution :It is found that the resistance R of a uniform metallic conductor depends on its length 1, on its area of cross-section A, the nature of its material and TEMPERATURE
Precise measurements have shown that at a given temperature,
`R PROP l and R prop 1/A`
Combining above two relations,
`R prop l/A`
`:. R =rho l/A` .......(12.6)
Where `rho` (rho) is a constant of proportionality and is called the electrical resistivity of the material of the conductor.
From equation (12.6)
`rho = (RA)/l ` .... ...(12.7)
`:.` The SI unit of `rho`
`= ("The SI unit of resistance "xx" The SI unit of area of cross - section")/("The SI unit of length")`
`=(Omegam^2)/m`
`=Omegam` (ohm-metre)
In equation (12.7), if A = 1 unit and l = 1 unit, `rho = R`.
The electrical resistivity of a material is the resistance of a conductor (of that material) having unit length and unit area of cross-section.
[Notes : (1) Resistivity depends on temperature.
(2) Resistivity is also called SPECIFIC resistance.]
Discussion
7285.

What will you do if the domestic gas cylinder bursts?

Answer»

Sprinkle water
Throw SAND or soil
cover the CYLINDER with wet bedsheet
Run away

Answer :C
Discussion
7286.

An ammeter is always connected in series acrose a ciruit element what happens when it is connected in parallel with a circuit element.

Answer»

Solution :An ammeter is law RESISTANCE device when it is connected in parallel the resistance of the circuit reduces consider BLU THEREFORE a large CURRENT flows through the ciruit by virtue of circuit element may damage.
Discussion
7287.

Two rings of radii R and nR made from the same wire have the ratio of moments of inertia about an axis passing through their centres equal to 1:8. The value of n is

Answer»

2
`2sqrt(2)`
4
`1/2`

SOLUTION :As radius of round ring is N times, length and hence mass of wire is also n times.
`I_(1)/I_(2) =(MR^(2))/(nM(nR)^(2)) =1/n^(3) =1/8 rArr n=2`
Discussion
7288.

The molecular formula of acetic acid (ethanoic acid) is ……………..

Answer»

HCOOH
`CH_(3)COOH`
`C_(2)H_(5)COOH`
`C_(3)H_(7)COOH`

ANSWER :B
Discussion
7289.

Energy can neither be created nor destroyed. Then why is there so much noise about energy crisis ?

Answer»

Solution :Yes, it is true that ENERGY can neicher be created nor be destroyed and one form of energy can be converted into another fom. But the fact is that energy in the usable form is dissipated to the surroundings in the less-usable form. For example, when a CANDLE burms, it ghves HEAC, ight, and othe substances but the generated heat, light, and other substances cannot be put together to GIVE wax to be USED again.
Discussion
7290.

Wavelength of radiation incident on a surface is 850 nm. Will the surface become visible when exposed to this radiation ? Explain.

Answer»

SOLUTION :As we know, the range of WAVELENGTH of visible radiation is from 400 nm to 700 nm. The radiation having wavelength greater greater than 700 nm is termed as infra - red radiations which only produces warmth , so the wavelength of radiation 850 nm cannot be visible.
Discussion
7291.

a) What do you mean by a precipitation reaction? Explain by giving example. (b) Explain the following in terms of gain or loss of oxygen with examples.

Answer»

Solution :(a) Any rcaction in with an insoluble solid is produced is called a precipitate reaction. For cxample:
`underset ("Choride Sulphate")underset("BARIUM Sodium")(BaCl_(2aq)+Na_(2)SO_(4aq))overset("Heat")rarr underset("Sulphate") underset("Barium")(BaSO_(4("S")))darrunderset("Choride")underset("Sodium")(2NaCl_((aq)))`
(b) Oxidation : It is defined as process which involves gain of oxygen
For exumple :
`underset("Magnesium")2Mg_(("s")) underset("Oxygen")(+O_(2)("g"))rarr underset("Magnesiumoxide")(2MgO_(("s")))`
Reduction : t is defined al process which involver loss of oxygen.
For example :
`underset("oxide")underset("COPPER")(CuO_(("s")))+ underset("hydrogen")(H_(2("g")))overset("Heat")rarrunderset("copper")(Cu_(("s"))+)underset("water")(H_(2)O_(("g")))`
Discussion
7292.

COROLLA

Answer»

SOLUTION :ATTRACTING insects for POLLINATION. PROTECTING inner WHORLS.
Discussion
7293.

What can you say about the resistance of an ammeter?

Answer»

Solution :The resistance of an AMMETER should be very LOW, ideally ZERO.
Discussion
7294.

Plot a graph between internal energy U and Temperature (T) of an ideal gas.

Answer»

SOLUTION :
Discussion
7295.

Complete the following chart:

Answer»

SOLUTION :
Discussion
7296.

Namethe devices whoseworkingis based on the magneticeffect of eletric current .

Answer»

SOLUTION :Workingof an ELECTROMAGNET and electricmotor is basedon the magetic EFFECT of eleectriccurrent .
Discussion
7297.

Three blocks of masses m_1= 10 kg, m_2= 20kg are connected by strings on smooth horizontal surface and pulled by a force of 60 N. Find the acceleration of the system and frictions in the string.

Answer»

Solution :All the blocks more with common acceleration a under the force F = 60 N.
`F= (m_1 + m_2 + m_3)a`
`a=(F)/((m_(1)+m_(2)+m_(3))=1m//s^(2)`
To determine, `T_1 to` Free body DIAGRAM of mass `m_1.`

`T_1= m_1a = 10xx 1= 10 N`
To determine, `T_2 -` Free body diagram of `m_3.`

`F-T_(2)=m_3a`
SOLVING, we get `T_(2)=30N`
Discussion
7298.

Name any two phenomena which arise due to scattering of light in the earth's atmosphere.

Answer»

SOLUTION :The blue COLOUR of the SKY and the ocean, the REDDENING of the sky during SUNSET or sunrise.
Discussion
7299.

What will be required to make a DC generator?

Answer»

Solution :(C) Electric GENERATOR (DC)
A generator which converts mechanical energy into electrical energy in the form of direct current is called as D.C. generator.
Construction: The main components of D.C. generator are:
i. Rectangular coil (ABCD): It consists of a large number of turns of insulated copper wire wound on an iron core in rectangular shape.
ii. Strong magnets: The coil is placed between the two pole pieces (N and S) of a strong magnet that PRODUCES a strong magnetic field.
(iii.) Split ring: It consists of two halves of a metallic ring to which the ends of the coil are connected.
iv. Brushes: Carbon brushes `(B_(1) and B_(2))` are used to press the rings.
v. Axle: The function of axle is to rotate with the coil.

Working:
i. When the axle is rotated with the help of a machine from outside, the coil ABCD starts rotating.
ii. On rotating the axle, the branch AB MOVE upwards and branch CD move downwards and coil ABCD rotates clockwise.
iii. According to Fleming's right hand rule, electric current flows in the direction `ArarrBrarrCrarrD`.
Therefore, current flows in the external circuit through galvanometer.
iv. After HALF rotation, the branch AB and CD exchange their position and the induced current flows as `Drarr CrarrBrarrA`.
v. Since, the branch which is moving upwards is always in contact with brush B1 and the branch which is moving downwards is always in contact with brush `B_(2)`, current flows in the same direction in the external circuit, thereby PRODUCING direct current.
Discussion
7300.

………… was the first scientist to use a glass prism to obtain the spectrum of sunlight.

Answer»

SOLUTION :SIR ISAAC NEWTON
Discussion