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301.

A wind mills converts …………energy of wind into mechanical work.

Answer»

SOLUTION :KINETIC.
Discussion
302.

Explain an activity to show that a current carrying conductor experiences a force when placed in a magnetic field.

Answer»

Solution :A small aluminium rod is SUSPENDED horizontally from a stand using two connecting wires. Place a strong horse shoe MAGNET in such a way that the rod lies between the two poles with the MAGNETIC field directed upwards. For this put the northpole of the magnet vertically below and SOUTH pole vertically above the aluminium rod. Connect the aluminium rod in series with a battery, a key and a rheostat. Pass a current through the aluminium rod from one end to other. The rod is displaced towards left. When the DIRECTION of current flowing through the rod is reversed, the displacement of rod will be towards right.
Discussion
303.

12 V battery is connected in a circuit and to this 4W, 12W, resistors are connected in circuit from this information and the current in the circuit.

Answer»

Solution :
The RESULTANT RESISTANCE of 4W. 12W connected in parallel is
`(1)/(R)=(1)/(R_(1))+(1)/(R_(2))`
`(1)/(R)=(1)/(4)+(1)/(12)rArr(1)/(R)=(3+1)/(12)`
`therefore(1)/(R)=(4)/(12)rArrR=(12)/(4)`
`thereforeR=3Omega`
The total resistance in the CIRCUIT is
`R=R_(1)+R_(2)=3+3=6`
`thereforeR=6Omega`
The current in the circuit
`I=(V)/(R)rArrI(12)/(6).`
`thereforeI=2A`
Discussion
304.

_____________ divisions of the National Disaster Response Force are working in India.

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5
12
10
3

Answer :B
Discussion
305.

The Right hand thumb rule is called ............ rule.

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SOLUTION :MAXWELL's cork-screw
Discussion
306.

How will the magenticfieldlines due to a current - carrying conductor be affected on inreasingthe current in theconductor ?

Answer»

SOLUTION :The strenght of magnetic fieldincreaseson INCREASINGTHE CURRENT flowing .
Discussion
307.

A pair of scissors has its blades 15 cm long, while its handles are 7*5cm long. What is its mechanical advantage ?

Answer»


ANSWER :`0*5`
Discussion
308.

Complete the chart : Complete the chart as per the objectives of the first aid :

Answer»

SOLUTION :
Discussion
309.

State second law of thermodynamics . Describe the working of carnot engine . Obtain an expression for the efficiency .

Answer»

Solution :Second Law of Thermodynamics : First law of thermodyamics is based on Law of conservation of ENERGY . While second law of thermodynamics gives information about the transformation of heat energy . So , there are TWO conventional statements of second law depending on common experience .
1) Kelvin - Plank statement : It is impossible for an engine working in a cyclic process to extract heat from a hot body and to convert it completely into work .
2) Clausius Statement : It is impossible for a self ACTING machine , unaided by any external agency to transfer heat from a cold body to a hot reservoir . In other words heat cannot by itself flow from a colder body to a hotter body .
Carnot's Engine : Carnot's engine works on the principle of reversible process with -in the TEMPERATURES`T_(1)andT_(2)`
It consists of four continuous processes .
The total process is known as Carnot Cycle .
Step 1 : In Carnot cycle the 1st step consists of isothermal expansion of gases. So temperature T is constant , P , V changes areshown as `P_(1)V_(1)T_(1)rarr^("to")P_(2)V_(2)T_(1)`
work done in isothermal process
`W_(1rarr2)=Q_(1)=muRT_(1)log_(e)(V_(2)/(V_(1)))"" .....(1)`
Step : 2 In this stage gases will expand adiabatically . So energy to the system Q is constant .
So , P,V relation is `P_(2)V_(2)T_(1)overset("to")rarrP_(3)V_(3)T_(2)`
Work done in adiabaticallyprocess
`W_(2rarr3)=(muR(T_(1)-T_(2)))/(gamma-1)"" ...(2)`

In this stage gases will be compressed isothermallt . So`P_(1)V` changes are `P_(3)V_(3)T_(2)overset"to"rarrP_(4)V_(4)T_(2)`
work done in isothermal compression
`W_(3rarr4)=Q_(2)=muRTlog_(e)((V_(3))/(V_(4)))""...(3)`
Step 3 : In this stage gases will be compressed isothermally , So`P_(1)V` changes are `P_(3)V_(3)T_(2)overset("to")rarrP_(4)V_(4)T_(2)`
Work done in isothermal compression
`W_(3rarr4)=Q_(1)-muRTlog_(e)((V_(3))/(V_(4)))""....(3)`
Step 4 : In the fourth stage the gas suffers adiabatic compression and returns to original stage .
So , P,V changes are`P_(4)V_(4)T_(2)overset("to")rarrP_(1)V_(1)T_(1)`
`W_(4rarr1)=(muR(T_(2)-T_(1)))/(gamma-1)""...(4)`
Total work done in Carnot Cycle
`W=W_(1,2)+W_(2,3)+W_(3,4)+W_(4,1)`
Total work done `W=muRT_(1)log((V_(2))/(V_(1)))`
`+(muR)/(gamma-1)(T_(1)-T_(2))-muRT_(2)log(V_(3)/(V_(4)))-(muR)/(gamma-1)(T_(1)-T_(2))`
`therefore W=muRT_(1)log((V_(2))/(V_(1)))-muRT_(2)log(V_(3)/(V_(4)))`
The total work done `W=Q_(1)-Q_(2)` i.e., the difference to heat energy absorbed from source and heat energy given to sink Efficiency of Carnot engine
`eta=("work done by Carnot engine")/("heat energy supplied")`
`thereforeeta=(Q_(1)-Q_(2))/(Q_(1))" or " eta=1-(Q_(2))/(Q_(1))=1-(T_(2))/(T_(1))`
Discussion
310.

Through which of the following two wires, does the electric current flow more easily? (a) A thick wire (b) a thin wire of the same material and of the same length when connected to the same source. State the reason.

Answer»

Solution :The THICK WIRE because its RESISTANCE WOULD be less compared to that of the THIN wire.
Discussion
311.

Distinguish between ideal gas and real gas.

Answer»

SOLUTION :
Discussion
312.

Two conducting wires have equal lengths equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be:

Answer»

`1:2`
`2:1`
`1:4`
`4:1`

Solution :As Two conducting wires have equal lengths equal diameters (i.e., equal CROSS section wire and are of the same MATERIAL, their resistances are same. Thus, `R_1=R_2=R` (say). In SERIES arrangement,
`R_s=R_1+R_2=2R` and in parallel arrangement `1/R_p=1/R_1+1/R_2=1/R+1/R=2/R or R_p=R/2`
When joined across a voltage source in series heat PRODUCED in time t `H_s=V^2/R_p.t =(V^2t)/((2R))=(V^2t)/(2R)`
and heat produced in parallel arrangement `H_p=V^2/R_p.t=(V^2t)/(R/2)=(2V^2t)/R`
`therefore H_s/H_p= ((V^2t)/(2R))/((2V^2t)/R)=1/4 or H_s:H_p=1:4]`
Discussion
313.

Assertion (A): No current can flow so long as an electric circuit is open. Reason (R ): Resistance of an open circuit is infinite.

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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 :RESISTANCE of an OPEN circuit is infinite (or exceedingly large) due to the presence of an air gap between the terminals of a key (SWITCH) and so no CURRENT can flow.
Discussion
314.

In torches, search lights and headlights of vehicles, the bulb is placed

Answer»

between the POLE and the focus of the reflector
very near to the focus of the reflector
between the focus and CENTRE of CURVATURE of the reflector
at the centre of curvature of the reflector

Answer :B
Discussion
315.

A cylindrical conductor of length l and uniform area of cross section A has resistance R. Another conductor of length 2.5l and resistance 0.5R of the same material has an area of cross section

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5A
2.5A
0.5A
`1/5A`

SOLUTION :Here `R=(RHO L)/A and 0.5R=(rho(2.5l))/A. IMPLIES A.=5A`
Discussion
316.

Ifyouwantto makea RefractingTelescope , whatcomponentswillyouchoose ?

Answer»

Oneconvexlensandoneconcavelens
Twoconvex LENSES
Oneconcavemirror ,oneplanemirrorandoneconvexlens
Oneconcavemirror , oneconvex MIRROR and oneconvexlens .

ANSWER :B
Discussion
317.

Give some uses and advantages of solar energy.

Answer»

Solution :Uses:
(i) For cooking food in a solar cooker.
(ii) For heating water in solar geysers.
(iii) For generating electricity in space satellites , calculators, WATCHES , etc. by solar cells.
(iv) For generating electricity on a large scale by a solar power plant.
(v) To MELT metals in solar FURNACES.
Advantages :
(i) It does not cause any pollution.
(ii) It is a renewable source of ENERGY .
(iii) It is FREE of cost.
Discussion
318.

The strongest attractive forces are

Answer»

ELECTROSTATIC
GRAVITATIONAL
NUCLEAR
nothing can be decided

Solution :nuclear
Discussion
319.

What will you do? Why? Child of your neighbour is addicted to tobacco chewing.

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Solution :I would FIRST explain the child the ill effects of tobacco CHEWING and counsel the child on how to STOP the ADDICTION. I will ALOS inform the child's parents and discuss the matter with them.
Discussion
320.

What are the disadvantage of fossil fuels?

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Solution :The disadvantages of FOSSIL fuels are: (II) Burning of coal and petroleum produces a lot of pollutants causing air pollution.
(ii) Fossil fuels release oxides of carbon, NITROGEN, sulphur, etc., that CAUSE acid RAIN, which affects the soil fertlity and potable water
(iii) Burning of fossil fuels produces gases such as carbon dioxide that cause greenhouse effect and global warming
Discussion
321.

What is a nuclear fusion reaction ? List any two advantages of nuclear fusion reactions.

Answer»

Solution :A reaction in which two nuclei of lighter elements COMBINE to form a heavy nucleus with a liberation of tremendoms AMOUNT of energy is nuclear fusion reaction….
Two advantages are :
(i) Large amount of energy is produced from a very SMALL amount of FUEL.
(ii) Produces nonpolluting waste/does not produce gases which pollute the environment/cause green HOUSE effect.
Discussion
322.

Draw a schematic circuit diagram for a circuit in which three resistors R_(1), R_(2)and R_(3)a plug key under dosed condition, an ammeter are joined In series with a 5V battery. Also a voltmeter is connected to measure the potential difference across the resistor R_(1)

Answer»

SOLUTION :Circuit DIAGRAM to show `R_(1), R_(2)`and `R_(3)` connected in series with a battery, ammeter and a KEY. Voltmeter Vis connected parallel to `R_(1)` .Direction of current.
Discussion
323.

Which of the following distance-time graphs is not possible?

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Solution :DISTANCE TRAVELLED by a body can never be negative. So, graph (a) is not POSSIBLE.
Discussion
324.

Name and define the smallest commercial unit of electricity.

Answer»

Solution :The smallest commercial UNIT of electricity is the watt-hour (WH).
It is DEFINED as the amount of electric energyconsumed by an ELECTRICAL DEVICE of power rating 1 W in one hour.
Discussion
325.

Mention the two main components of the transport system in plants. State one specific function of each one of these components.

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Solution :These two components are : (i) PHLOEM (II) XYLEM.
Phloem transports food PREPARED by the leaves to other parts of the plant.
Xylem transports water and soluble mineral ions from roots to theleaves in the UPWARD direction.
Discussion
326.

The reaction CuSO_(4(ag)) + Zn_((s)) to ZnSO_(4(aq)) + Cu_((s)) is a …………. Reaction.

Answer»

DISPLACEMENT
DOUBLE displacement
DECOMPOSITION
COMBINATION

ANSWER :A
Discussion
327.

An electric heater consumes 4.4 kW power when connected with a 220V line voltage. Calculate the resistance of the heater.

Answer»

SOLUTION :`11 OMEGA`
Discussion
328.

What is the name of physical quantity which is equal to V/I?

Answer»

SOLUTION :ELECTRICAL RESISTANCE.
Discussion
329.

What is meant by mass defect ?

Answer»

SOLUTION :The mass of DAUGHTER NUCLEUS FORMED during nuclear reaction (fission and fusion) is lesser than the sum of masses of two parent nuclei. This difference in mass is called mass defect.
Discussion
330.

What is the meaning of the symbol kWh? Which quantity does it represent?

Answer»

Solution :The kilowatt-HOUR [symbolized kWh] is a UNIT of energy equivalent to one kilowatt [KW] of power expended for one hour [1 H] of time. It REPRESENTS 3,6000,000 joules `[3.600xx10^(6)J]`.
Discussion
331.

Is cofficient of performance of refrigerator always constant?

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Solution :No. As the INSIDE TEMPERATURE of the REFRIGERATOR DECREASES, its coefficient of PERFORMANCE decreases.
Discussion
332.

The direction of themagnetic fieldlines in a region outside a bar magnet is …..

Answer»

from N-poleto S-poleof the magnet
from S-pole to N-poleof the magnet
comingout from BOTHTHE POLES of the magnet
ENTERING into both the polesof the magnet.

Solution :from N-poleto S-poleof the magnet
Discussion
333.

The magnetic field due to a current-carrying solenoid is independent of

Answer»

its NUMBER of turns
its length
the CURRENT PASSING through it
allof the above

ANSWER :B
Discussion
334.

In Maharashtra…………. is in action through State Reserve Force

Answer»

WHO
NDRF
MCC
NCC

Answer :D
Discussion
335.

v_(esc)= __________________

Answer»


SOLUTION :NA
Discussion
336.

Dynamo converts :

Answer»

MECHANICAL ENERGY to ELECTRIC energy
electric energy to mechanical energy
none of these

Answer :A
Discussion
337.

A man can read the number written on a distant bus clearly but he finds difficulty in reading a book. b. What type of spectacle lens should he use to correct the defect?

Answer»

Solution :HYPERMETROPIA is CORRECTED by using spectacles containing CONVEX lenses of suitable POWER.
Discussion
338.

Compare the above system with the probable systems in hilly / mountainous areas or plains or plateau regions.

Answer»

Solution :Water harvesting system in the hilly areas are quite different from those of plain areas . Partsof Himachal Pradesh had evolved the local system of canal irrigation called kulhs over four hundred years ago . The water flowing in the streams was DIVERTED into MAN MADE CHANNELS which took this water to numerous villages down the hillside . The management of the water flowing in these kulhs was DONE by a common agreement betweenall the villages . interestingly , during the planting season , water was first used by the village farthest away from the source of the kulh , then by villages progressively higher up . These kulsh were managed by two or three people who were paid bythevillagers . In addition to irrigation , water from these kulhs also percolated into the soil and fed springs at various points .
Discussion
339.

A convex lens is immersed in a container of water. Will this cause a change its focal length ?

Answer»

Solution :YES. The refractive index of glass with respect to air is more than the refractive index of glass with respect to WATER. The FOCAL length of the convex LENS will increase.
Discussion
340.

Atul buit a small house . Heused well - insulated copper wires of goodqualityfor wiringand switches, sockets andplugs too . Hehowever , had a room - heater of poor quality . Once on awinter night he was sleepoing with his familyin a closed roomwiththe heaterOn. Duringsleep he wassuffocated . Hencehe wokeup and found flames of heater on fire . Hisson Raghav got up quicklyand switched off the main switch . He madeacall to the fire brigade .The fire crew of fire brigade reached quickly and put off fire . Atul and his family thanked the firement . Whatvalues do you learn from Raghav in this episode ?

Answer»

Solution :We LEARN the values like .
(a) AWARENESS (b)PRESENCE of mind .
Discussion
341.

Draw graphs showing the variation of acceleration due to gravity withdepth below the earth's surface.

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SOLUTION :
`G propto (R -d)" for " r LT 0` below surface of EARTH i.e., AC.
g is max. for r=0 on surface.
Discussion
342.

Atul buit a small house . Heused well - insulated copper wires of goodqualityfor wiringand switches, sockets andplugs too . Hehowever , had a room - heater of poor quality . Once on awinter night he was sleepoing with his familyin a closed roomwiththe heaterOn. Duringsleep he wassuffocated . Hencehe wokeup and found flames of heater on fire . Hisson Raghav got up quicklyand switched off the main switch . He madeacall to the fire brigade .The fire crew of fire brigade reached quickly and put off fire . Atul and his family thanked the firement . How Atul.s heater was on fire ?

Answer»

SOLUTION :The cause of firwas short -circuiting DUE to DEFECTIVE heater of poor QUALITY .
Discussion
343.

Draw the ray diagrams for the image formation in a convex lens when an object is placed

Answer»

SOLUTION :i) at FOCUS `F_1`
(II) BEYOND `2F_1`
Discussion
344.

Atul buit a small house . Heused well - insulated copper wires of goodqualityfor wiringand switches, sockets andplugs too . Hehowever , had a room - heater of poor quality . Once on awinter night he was sleepoing with his familyin a closed roomwiththe heaterOn. Duringsleep he wassuffocated . Hencehe wokeup and found flames of heater on fire . Hisson Raghav got up quicklyand switched off the main switch . He madeacall to the fire brigade .The fire crew of fire brigade reached quickly and put off fire . Atul and his family thanked the firement . Namethe safety devicemissing in the electricwiringof Atul.shouse.

Answer»

SOLUTION :ELECTRIC fuseis the SAFETY DEVICE which was missingin wiringof Atul.s HOUSE .
Discussion
345.

Is there any relation between the angle of incidence (i) and anglefo emergence (x)and angle of deviation (d) ?

Answer»

SOLUTION :A+d =i+r
Discussion
346.

A positively charged particle (alpha-particle) projected towards west is deflected towards north be a magnetic field. The direction of magnetic field is:

Answer»

towards south
towards east
downward
upward

Solution :Since the POSITIVELY charged particle (alpha-particle) projected towards west, so the DIRECTION of current is towards west. Now the deflection is towards north, so the force is towards north.
Now hold the forefinger, centre finger and thumb of our left-HAND at right angles to one ANOTHER. Let us adjust the hand in such a WAY that our centre finger points towards west and thumb points towards north. If we look at our forefinger, it will be pointing, upward. Thus, the magnetic field is in the upward direction. So, the correct answer is (d).
Discussion
347.

The human eye can focus objects at different distances by adjusting the focal length of the eye-lens. This is due to :

Answer»

PRESBYOPIA
accommodation
Near- SIGHTEDNESS
far- sightedness

SOLUTION :NA
Discussion
348.

Can a body have zero velocity and finite acceleration?

Answer»

SOLUTION :Yes, at the HIGHEST point of vertical UPWARD MOTION under gravity.
Discussion
349.

An object of height 5 cm is placed 20 cm away from a convex mirror. Its image is formed at a distance of 12 cm behind the mirror. Calculate the focal length of the mirror using mirror formula. Also draw a scale diagram to locate the image. From the diagram, find out the length of the image formed.

Answer»

SOLUTION :`h_(0) = 5 cm,u = -20 cm,v = + 12 cm`
As we know, `1/f = 1/v + 1/u rArr 1/f = 1/12 - 1/20 = 30 cm, h_(1) = 3 cm` (on measurement)
Discussion
350.

Draw a diagram of a combination of three movable pulleys and one fixed pulley to lift up a load. In the diagram, show the directions of load, effort and tension in each strand. Find : (i) the mechanical advantage, (ii) the velocity ratio, and (iii) the efficiency of the combination, in the ideal situation.

Answer»


Answer :(i) `2^(3)`, (ii) `2^(3)`, (III) 1
Discussion