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6701.

What happens to the other bulbs in series circuit, if one bulb blows off?

Answer»

SOLUTION :As all bulbs are connected in series, any bulb that FUSES breaks the FLOW of ELECTRICITY for the REST of bulbs in the circuit.
Discussion
6702.

A given length of a wire is doubled on itself. By what factors does the resistance of the wire change?

Answer»

Solution :When a given LENGTH of wire is doubled on itself, its new length `L.=L/2` and new cross section area A.=2A Hence its new resistance `R.=(RHO L.)/(A.)= (rho(L/2))/((2A))=1/4 (rho L)/A=R/4`
Discussion
6703.

What would be the path of refracting ray and emergence ray, if two glass slabs kept attached to each other are used?

Answer»

Solution :i. For refraction of LIGHT passing through TWO GLASS slabs, the incident ray and the emergent ray are parallel to each other.
ii. The emergent ray is displaced more· with RESPECT to the incident ray in the case of two attached glass slabs as COMPARED to refraction of light through a single glass slab.
Discussion
6704.

""_(92)U^(238) emits 8 alpha particles and 6 beta particles. What is the neutron / proton ratio in the product nucleus.?

Answer»

Solution :`""_(92)U^(238) overset(-8 alpha) to ""_(76)X^(206)+ 8""_(2)He^(4) (8alpha "decay")`
The RESULT of `alpha` decay
`""_(76)X^(206) overset(-6 BETA) to ""_(820)Y^(206)+ 6""_(-6)E^(0)(6 beta "decay")`
Number of PROTON = 82
Number of neutron 124
The ratio in the product nucleus= `(124)/(82)`
`("neutron")/("proton")= (62)/(41)`
Discussion
6705.

A student obtained a sharp image of the grill of a window in the laboratory on a screen, using a convex lens. For getting better results, her teacher suggested focussing of a distant tree instead of the grill. In which direction should the lens be moved for this purpose to get a sharp image on the screen ?

Answer»

TOWARDS the screen
AWAY from the screen
behind the screen
very FAR away from the screen

Solution :NA
Discussion
6706.

What are the advantages of nuclear energy ?

Answer»

Solution :(i) It produces huge amount of energy from very small amount of a unclear fuel.
(ii) It does not produce gases LIKE carbon DIOXIDE which contribute to greenhouse effect or sulphur dioxide which causes ACID rain.
(iii) Once the nuclear fuel is loaded into the reactor, the nuclear power plant can go on producing ELECTRICITY for two to three years at a stretch. Hence, there is no NEED for putting in the nuclear fuel again and again.
Discussion
6707.

What is electric power and electric energy ?

Answer»

SOLUTION :
Discussion
6708.

In alpha - decay ...........

Answer»

ATOMIC number DECREASES by 2 and MASS number decreases by 4
atomic number INCREASES by 2 and mass number decreases by 4
there is no CHANGE in atomic and mass number
neutron number decreases by one

Solution :atomic number decreases by 2 and mass number decreases by 4
Discussion
6709.

Bifocal lenses are used to correct which defect of vision ?

Answer»

SOLUTION :The are USED for a person suffering from both MYOPIA and HYPERMETROPIA.
Discussion
6710.

Find the power of a concave lens of focal length 2m.

Answer»

SOLUTION :`f=-2m`
`P=1/f-1/(-2)=-0.5D`
Discussion
6711.

Regular exercising, massaging, visiting the spa too hwlp to relive the ……..

Answer»


ANSWER :STRESS
Discussion
6712.

Regeneration

Answer»

SOLUTION :Regeneration is the asexual reproduction in PLANARIA in which the BODY is broken up into two parts and RESULTING each part regenerates REMAINING part of the body.
Discussion
6713.

What is a fixed pulley ? State its one use.

Answer»


ANSWER :1, No
Discussion
6714.

The abbreviation of SONAR IS ...............

Answer»

SOLUTION :SOUND NAVIGATION And RANGING
Discussion
6715.

In a certain gas, a source produces 40,000 compression and 40,000 rarefaction pulses in 1 sec. When the second compression pulse is produced , the firsr is 1 cm away from the source. Calculate the wave speed?

Answer»

Solution :We know frequency is equal to number of COMPRESSION or rarefaction pulses TRAVELLED per SECOND, hence frequencey `(upsilon) = 40,000` Hz.
Discussion
6716.

The image from a convex mirror will ________

Answer»

ALWAYS be real
Always be projected
Always be virtual
Never be virtual

Answer :C
Discussion
6717.

Opening a fake Fecebook account and displaying false information to tease or exploit any one financially cannot be considered as cyber crime.

Answer»

Solution :False.
Opening a fake facebook account and displaying false information to tease or exploit ANDY ONE financially is cyber CRIME.
Discussion
6718.

The diagram below shows two parallel rays A and B of red and violet light respectively incident from air on air-glass boundary. Complete the diagram showing the refracted rays for them in the glass. (i) How do the speeds of the rays differ in glass ? (ii) are the two refracted rays in glass parallel ? Give a reason for your answer. (iii) How does the refractive index of glass differ for the two rays ?

Answer»

Solution :The COMPLETED ray diagram is shown below in figure.

(i) In glass, the speed of violet LIGHT is less than that of the red light.
(ii) The two refracted rays INSIDE glass are not parallel. The reason is that the speed of red light in glass is more, while it is less for the violet light, so the red ray BENDS less, while the violet ray bends more (i.e., the ANGLE of refraction `r_(1)` for red ray is more than the angle of refraction `r_(2)` for the violet ray).
(iii) Since `mu=c//V`, so the refractive index of glass is more for the violet light than for the red light (i.e., `mu_(V) gt mu_(R)`).
Discussion
6719.

A large coal-fired power station produces 2000 MW of electrical energy. A wind turbine with 33 m blades can produce 300 kW. How many turbines would be needed to replace the power station ?

Answer»


ANSWER :6667 TURBINES
Discussion
6720.

What is the role of parathorone?

Answer»

Solution :The parathormone regulate CALCIUM and phosphorus metabolism in the body . They act on BONE, KIDNEY and INTESTINE to maintain blood calcium levels.
Discussion
6721.

State two effects produced by the scattering of light by the atmosphere.

Answer»


SOLUTION :NA
Discussion
6722.

When rays of light are incident on a glass slab, then the incident ray and emergent ray are ……….. To each other.

Answer»

PERPENDICULAR
PARALLEL
opposite
concurrent

Answer :A::B::C::D
Discussion
6723.

The energy which cannot be taken as an indirect source of solar energy is

Answer»

Wind energy
energy from FLOWING water
NUCLEAR energy
None of these

Answer :A::C
Discussion
6724.

At what depth is the value of 'g' same as at a height of 40 km from the surface of earth.

Answer»

SOLUTION :`g_(d)=g_(h)`
`g(1-(d)/(R ))=g(1-(2H)/(R ))`
`d= 2h=2xx40=80 km`.
Discussion
6725.

What is the total resistance of n resistors each of resistance 'R' connected in : (a) Series, (b) Parallel.

Answer»

<P>

Solution :`R_(S)=(R+R+ ......... R) = NR`
`(1)/(R_(p))= N((1)/(R)+(1)/(R) + ........... +(1)/(R))`
`:. R_(p) = (R)/(n)`
Discussion
6726.

A beam of light is incident through the holes on side A and emerges out of the hole on the other face of the box as shown in the figure. Which of the following could be inside the box?

Answer»

CONVEX
concave
rectangular glass
prism

Solution : it is clear that parallel rays converge at a POINT and emerges from FACE B. So convex lens would be possible inside the BOX.
Discussion
6727.

A teacher gives a convex lens and a concave mirror of focal length of about 20 cm each to his student and asks him to find their focal lengths by obtaining the image of a distant object.The student uses a distant tree as the object and obtains its sharp image, one by one, on a screen. The distances d_(1) and d_(2) between the lens/mirror and the screen in the two cases and the nature of their respective sharp images are likely to be :

Answer»

(20 cm, 40 cm) and (erect, erect)
(20 cm, 40 cm) and (INVERTED, erect)
(20 cm, 20 cm) and (inverted, inverted)
(20 cm, 20 cm) and (erect, inverted)

Solution :NA
Discussion
6728.

A machine raises a laod a 750 N through a height of 16 m in 5 s.Calculate: (i)the energy spent by the machine , (ii)the power of the machine if it is 100 % efficient.

Answer»

SOLUTION :(i)12000 J (ii)2400 W
Discussion
6729.

Define angle of deviation?

Answer»

Solution :Because of multiple reflections or refraction bending of light occurs. The angle at which emergent ray BENDS with RESPECT to incident ray is called angle of devation. As show in figure it is demoted by a SYMBOL `delta`(delta)

The angle of devation is not the same for all the wave LENGTH of light .Usuallyfor a prism the angle of devation canbe COMPUTER as`delta=(mu-1)` A . Where A is angle of prism and `mu` is refracted inboxof prism material.
Discussion
6730.

Give reasons why different electrical appliances in a domestic circuit are connected in parallel.

Answer»

Solution :( 1 ) In a parallel circuit, the TOTAL current is divided through different electrical gadgets and total resistance is also decreased. So this is helpful particularly when each gadget has different resistance and reqUires different current to operate properly (due to their different power ratings).
( 2 ) In a parallel circuit, each electrical appliance GETS the same voltage (p.d.) equal to 220 V as that of the power supply LINE. Due to this, all the appliances work properly.
( 3 ) In a parallel circuit, if one electrical appliance stops working due to some defect, other appliances are not AFFECTED. They continue to work without any problem.
( 4 )In a parallel circuit, each appliance has its own switch due to which it can be TURNED .ON. or turned .OFF. independently, without affecting other appliances.
Discussion
6731.

Draw a labelled diagram of the human eye. What is the significance of the blind spot ?

Answer»

Solution :
The blind spot is a small REGION in the RETINA where the optical nerves enter the retina. The region contains no light-sensitive cells and hence, the IMAGE FORMED here is not sensed by the eye. Hence, it is called blind spot.
Discussion
6732.

How is a largeinducedelectriccurrent obtained in a loop ?

Answer»

Solution :A large induced electriccurrentis obtained ina loop by usingthe followingthree methods :
(1)INCREASINGTHE speed of the magnet movingtowards or away from the loop, increases the rate of change of magneticfieldlines linked with the loop. This increases the currentinduced in the loop.
(2) By increasing the NUMBER of TURNS in theloop , a large induced ELECTRICCURRENT is obtained .
(3) By movingtheconductor(or loop) speedilyin the magneticfield ,in a direction perpendicularto the magnetic FIELD ,a large induced electriccurrentis obtained .
Discussion
6733.

Kineticsdeals with the motion of bodiesconsideringthe __________.

Answer»

SOLUTION :CAUSE of MOTION
Discussion
6734.

State theprinciple on whichthe workingof an electricgeneratoris based .

Answer»

SOLUTION :Whena COILIS ROTATED properlyin a magneic field ,electromotivefrocein the CIRCUIT CONTAINING the coil .
OR
Whena coil is rotated in a magnetic field , electric currentins inducedin the ciruitcontainingthe coil .
Discussion
6735.

whena turningforkvibrates, wavesproducedin thestemare

Answer»

LONGITUDINAL
TRANSVERSE
sometimeslongitudinaland sometimestransverse
nietherlongitudial nortransverse

SOLUTION : longitudinal
Discussion
6736.

The temperatures T_(1) and T(2) of two heat reservoirs in an ideal carnot engine are 1500^(@)C and 500^(@)C. Which of these (a) increasing T_(1) by 100^(@)C or (b) decreasing T_(2) by 100^(@)C would result in greater improvement of the efficiency of the engine?

Answer»

SOLUTION :`eta=1-T_2/T_1 `
(i) `T_1` is INCREASED from `1500^@C" to " 1600^@C`
`T_1 =1873k`
`T_2` REMAIN constant `T_2 = 773k`
`eta_1=(1873-773)/(1873)=58.73%`
(ii) `T_1` remain constant `=1500^@C`
`T_1 = 1500+273=1773k`
`T_2` is decreased by 100 i.e., `400^@C`
`T_2=400+273=673k`
`eta_2=(1773-673)/1773=(1100)/1773=62.04%`
`eta_2 gt eta_1`
Discussion
6737.

A wire with…….insulation is used for earthing,.

Answer»

RED
BLACK
GREEN
white

Answer :C
Discussion
6738.

The moment of a force about a given axis depends:

Answer»

(a) only on the magnitude of FORCE
(b) only on the PERPENDICULAR DISTANCE of force from the axis
(C) NEITHER on the force nor or the perpendicular distance of force from the axis
(d) both, on the force and its perpendicular distance from the axis.

Solution :(d) both, on the force and its perpendicular distance from the axis
Discussion
6739.

Four identical cells of emf 1.5 V each were connected in four different ways as shown below : The potential difference between the points X and Y would be equal to 6.0 V in case/cases :

Answer»

A and B
A and C
A and D
A only

Solution :NA
Discussion
6740.

A uniform ring of mass M and radius R is placed directly above a uniform sphere of mass 8M and of same radius R. The centre of the ring is at a distance of d = sqrt(3)R from the centre of the sphere. The gravitational attractionbetween the sphere and the ring is

Answer»

`(GM^2)/(R^2)`
`(3GM^2)/(R^3)`
`(2GM^2)/(SQRT(2)R^2)`
`(sqrt(3)GM^2)/(R^2)`

ANSWER :D
Discussion
6741.

Three types of expansions in solids are _________, __________ and _______.

Answer»

SOLUTION :LINEAR EXPANSION, SUPERFICIAL and CUBICAL expansion
Discussion
6742.

Melting Point of ice

Answer»

SOLUTION :The constant TEMPERATURE at which the ice converts into WATER is called the melting POINT of ice.
Discussion
6743.

According to Charle's law, at constant pressure the temperature is inversely temperature.

Answer»

Solution :VOLUME is DIRECTLY proportional to TEMPERATURE at constant PRESSURE.
Discussion
6744.

Describe rocket propulsion.

Answer»

Solution :(i) Propulsion of rockets is based on the law of conservation of linear momentum as well as Newton.s III law of MOTION.
(ii) Rockets are filled with a fuel (either liquid or solid) in the propellant TANK. When the rocket is fired, this fuel is burnt and a HOT gas is ejected with a high speed from the nozzle of the rocket, producing a huge momentum.
(iii) To balance this momentum, an EQUAL and opposite reaction force is produced in the combustion chamber, which makes the rocket project forward.
(iv) While in motion, the mass of the rocket gradually decreases, until the fuel is completely burnt out.
(v) Since, there is no net external force acting on it, the linear momentum of the system is CONSERVED.
(vi) The mass of the rocket decreases with altitude, which results in the gradual increase in velocity of the rocket.
(vii) At one stage, it reaches a velocity, which is sufficient to just escape from the gravitational pull of the Earth. This velocity is called escape velocity.
Discussion
6745.

(Nocardia, Geobacter. Ideonella sakaiensis, Pseudomonas, Alcanouorax borkumensis, hydrocarbonoclastic, Acidophillium, streptomyces) Bacteria like ……………………. Spp. And ………………… have the ability to destroy the pyridines and other chemicals. Hence, these bacteria are used to clear the oil spills. These are called ......................... bacteria. It has been observed that species like Vibrio, ............................. can decompose the PET. Similarly, species of fungi like ....................... have ability of decomposing rubber from garbage. Sulphuric acid is source of energy for some species of bacteria like .......................... . Hence, these bacteria can control the soil pollution occurring due to acid rain. .......................... convert the salts of uranium into insoluble salts.

Answer»

Solution :Bacteria like Pseudomonas spp. and Alcanovorax borkumensis have the ability to destroy the PYRIDINES and other chemicals. Hence, these bacteria are used to clear the oil spills. These are CALLED hydrocarbonoclastic bacteria. It has been observed that species like Vibrio, Ideonella sakaiensis can decompose the PET. Similarly, species of FUNGI like Nocardia have ability of decomposing rubber from garbage. SULPHURIC acid is source of energy for some species of bacteria like Acidophillium. Hence, these bacteria can control the soil pollution occurring DUE to acid rain. Geobacter convert the salts of uranium into insoluble salts.
Discussion
6746.

"Derive R"=(rhol)/(A).

Answer»

Solution :1. Resistance of a conductor `(R)` is directly proportional to its LENGTH (l) for a constant potential difference.
`Ralphal""-(1)`
2. Resistance of a conductor is inversely proportional to its cross section area.
`Ralpha(1)/(A)""-(1)`
3. From (1) and (2), we get `Ralpha(1)/(A)` (at constant temperature)
`rArrR=(rho1)/(A)`
Where, `RHO` is a proportionalty constant and it is CALLED specific resitance or RESISTIVITY.
4. The S.I. unit of resistivity is `Omega-m.`
Discussion
6747.

What are thepotentialsof the liveandneutral wires used in our country? Whatis the potentical differencebetween these wires ?

Answer»

Solution :In ourcountry,the potential of the live WIRE (red INSULATED ) is a potentical of 220V (HIGH potential) whereas that of theneutral wire (blackinsulated) is 0 V (groundpotential).
The potential DIFFERNCE betweenthesewiree is 220-0=220V .
Discussion
6748.

Which birds are always present in any weather and at any place in Maharashtra ?

Answer»

HORNBILLS
Crows
SUN birds
Sparrows

ANSWER :B
Discussion
6749.

Draw a neat labelled diagram of Hope's apparatus.

Answer»

SOLUTION :
Discussion
6750.

We feel exhausted afterexercising.

Answer»

Solution :(1) When we undertake constant exercises, there MAY be SHORTAGE of OXYGEN for the cells. (2) Therefore, our muscles andother tissues perform anaerobicrespiration in such condition. (3) In this process, lacticacid is formed. Molecules of ATP produced in oxidation of food are also much less. (4) Thus, there isless energy in the BODY and accumulation oflactic acid too. All this brings about a feeling of EXHAUSTION.
Discussion