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1901.

One solar panel produces a potential difference of 18 V and current 2 A. Describe how you can obtain a potential difference of 72 volts and current of 9A with a solar array using solar panel. You can use sigh of a battery for a solar panel.

Answer»

Solution :A solar panel producing patential difference of 18 V and current of 3 A is represented below.

ii. FOUR solar PANELS producing 18 V and 3A should be connected in series to from a solar string producing potential difference of 72 V and current of 3 A.

iii. The solar string producing 72 V and 3 A is connected in parallel with two more solar strings producing 72 V and 3 A to form a solar ARRAY producing a potenial difference of 72 V and current of 9 A.
Discussion
1902.

A hot plate of an electric oven connected to a 220V line has two resistance coils A and B, each of 24 Omega resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?

Answer»

Solution :Here, the potential difference V = 220 V
The resistance of each coil `R_A = R_s =24 Omega`
( 1 ) When each of the COILS A or B is connected SEPARATELY, the current through each coil is
`I = V/R_A or V/R_B`
`=220/24 = 9.166 A`
( 2 ) When the coils A and B are connected in series, the EQUIVALENT resistance of the circuit `R_s = R_A + R_B = 24 +24 =48 Omega`
So, the current through the series combination
`I_s =V/R_s`
`=220/48`
`=4.58 A ~~ 4.6 A`
( 3 ) When the coils A and B are connected in PARALLEL, the equivalent resistance`R_p` of the circuit is given by
`1/R_p = 1/R_A + 1/R_B = 1/24 + 1/24 = 2/24`
`:. R_p = 12 Omega`
So, the current through the parallel combination
`I_p = V/R_p = 220/12 =18.33 A`
Discussion
1903.

Define Angular Magnification.

Answer»

Solution :It is DEFINED as the ratio of angle subtended by the FINAL image at the eye (`beta`) to the angle subtended by the object at the naked eye `(ALPHA)`
ANGULAR Magnification `M=(alpha)/(beta)`
Discussion
1904.

Assertion (A) : Electromagnets are made of soft iron. Reason (R): The strenght of anelectromagnet is increased by increasing the currentflowingthrough thesolenoid coil.

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 :B
Discussion
1905.

Mitochodria:

Answer»

Solution :MITOCHONDRIA participates in CELLULAR respiration. It HELPS to COMPLETE electron transfer chain reaction.
Discussion
1906.

Statehow the strength of the magnetic field producedat the centre of a coil by a current through the circularcoil can be increased.

Answer»

Solution :The strenghtof THEMAGNETICFIELD (B) produced at the centre of a COIL by a current through a circular coil can be increased by-
(1) Increaseingthe numberof turns N of the coil `(B prop N)`.
(2) INCREASINGTHE currentI through thecoil `(B prop I)`.
(3) Decreasing the radiusr of the coil `(B prop. (1)/(r))` .
Discussion
1907.

Amphioxus , Herdmania , Doliolum , Oikopleura

Answer»

SOLUTION :Amphioxius . (AMPHIOXUS is Cepholochordate all the REMAINING are UROCHORDATES.)
Discussion
1908.

Calculate the amount of heat generated when 7200 coulombs of charge is transferred in one hour through a potential difference of 50 V.

Answer»

Solution :Q = 7200 C t = 1 h `= 60xx60 = 3600s ` V= 50 V
`I = (Q)/(t) = (7200)/(3600) = 2A`
`R=(V)/(I) = (50V)/(2A)= 25 Omega`
`H = I^(2) Rt `
`= 2xx2xx25xx60xx60`
`=36xx10^(4)J ` or 360 kJ.
Discussion
1909.

Image formed by plane mirror is :

Answer»

ERECT and virtual
erect and inverted
inverted and real
inverted and virtual

Answer :A
Discussion
1910.

_________ deals with the bodieswhich are atrest underthe action of forces .

Answer»

STATICS
Dynamics
Kinematics
Kinetics

Solution :Statics
Discussion
1911.

The resolving power depends on ____________ .

Answer»

DIAMETER of the LENS
WAVELENGTH
REFRACTIVE index
a & b

Answer :D
Discussion
1912.

If the mass of the fissile material is less than the critical mass is termed as ________.

Answer»

SOLUTION :SUBCRITICAL
Discussion
1913.

Thenumberofproductsformedin asynthesis reactionis_____

Answer»

ONE
TWO
three
four

Answer :A
Discussion
1914.

Burns from steam are worse those from boiling water at the same temperature. Is it true? If so, why?

Answer»

Solution :(1) A given quantity of steam contains more heat than the same quantity of boiling water at the same TEMPERATURE . (2) When steam comes in CONTACT with one's body, it releases extra heat of 540 calories PER gram and causes a more serious BURN than that caused by boiling water.
Discussion
1915.

Specific latent heat of fusion :

Answer»

Solution :The amount of heat energy ABSORBED at CONSTANT temperature by unit mass of a SOLID to CONVERT into liquid phase is called the SPECIFIC latent heat of fusion.
Discussion
1916.

Two circularcoils A and B having n and 2n number of turns have diameters 2d and d. If they carry the same current.A] Which coil producesthe maximum magnetic field at the centre ?B] Which coil produces the minimum magnetic field at the centre ?

Answer»

Solution :Magnetic field `B prop (n l)/(d)`. Hence, for COIL A, B `prop (2 n)/(d)` and for COILB, `B prop (2n)/(d)` .
THUS, answer are :A] Coil a B and B ] Coil A .
Discussion
1917.

In a myopic eye, the image of the object is formed .....

Answer»

BEHIND the RETINA
on the retina
in FRONT of the retina
 on the BLIND spot

Answer :C
Discussion
1918.

Explain the use of concave lenses in the following: Spectales

Answer»

Solution :( c) SPECTACLES - Concave LENSES are used in spectcles to CORRECT nearsightedness.
Discussion
1919.

Define refractive index of a transparent medium. What is its unit ? Which has a higher refractive index, glass or water ?

Answer»

Solution :The RATIO of the speed of light in the free SPACE (c ) to the speed of light in given MEDIUM (V) is called its refractive index.
n = c/v
It has no unit, GLASS has more refractive index than water.
Discussion
1920.

Name the instrument used to measure (i) electric current in a circuit, (ii) potential difference between two points in a circuit.

Answer»

SOLUTION :(i) AMMETER (II) VOLTMETER
Discussion
1921.

Three resistors of 5 Omega, 10 Omega and 15 Omega are connected in series and the combination is connected to the battery of 30 V. Ammeter and voltmeter are connected in the circuit. Draw a circuit diagram to connect all the devices in proper correctorder. What is the current flowing and potential difference across 10 Omega resistance ?

Answer»

Solution :
`R= R_(1)+R_(2)+R_(3)=30 Omega`
`I= V//R= 30//30 =1 A`
V across `10 Omega== IR_(2)=1xx10=10 V`
Discussion
1922.

At what distance should an object be placed from alens of focal length 25 cm to obtain an image on a screen placed at a distance of 50 cm from the lens ? What will be the magnification produced in this case?

Answer»


Solution :Given: Focal length (f)=25 cm
image distance (v)=50 cm
To find: Object distance (U)
FORMULA: `(1)/(f)=(1)/(v)-(1)/(u)`
CALCULATION: From formula,
`(1)/(25)=(1)/(250)-(1)/(u)`
`therefore" "(1)/(u)=(1)/(50)-(1)/(25)=-(1)/(50)`
`therefore" "u=-50 cm`
The NEGATIVE SIGN indicates that object is placed on left of the lens.
Discussion
1923.

Describe about the role among conservator, organizer, guide, plant friend , etc., you wish to perform and your plans for that role.

Answer»

Solution :In ORDER to perform the role of the conservator of environment, we must conserve whatever resources are leftwith usand prevent the depletion of natural resources.
This can BEDONE by GETTING into healthy disussions with my friends, neighbours, PARENTS and by conducting street plays or seminars.
Discussion
1924.

A concave lens of refractive index mu_(1) is kept in a medium of refractive index (mu_(2)) . A parallel beam of light is incident on the lens . Draw the path of the rays of light emerging from a lens . If mu_(1) gt mu_(2)

Answer»

SOLUTION :
Discussion
1925.

Compare the power used in the 2Omega resistor in each of the following circuits: a 6 V battery in series with 1 Omega and 2 Omegaresistors

Answer»

SOLUTION :As `1Omega` resistor and `2Omega`resistor are connected in series, the eqUivalent resistance `R_s = 1 + 2 = 3 Omega `
Now, the VOLTAGE of the battery V = 6 V So, the current FLOWING through the circuit,
`I_s = V/R_s= 6/3 =2 A`
In a series combination the same current 2 A flows through each resistor. Hence the current flowing through `2Omega` resistor is also 2 A.
`:.`Power used in `2 Omega` resistor,
`P_1 = I_s^2 R`
`=(2)^2 xx2 =8 W`
Discussion
1926.

Distinguish between Aves and Mammalia :

Answer»

SOLUTION :
Discussion
1927.

A concave lens of refractive index mu_(1) is kept in a medium of refractive index (mu_(2)) . A parallel beam of light is incident on the lens . Draw the path of the rays of light emerging from a lens . If mu_(1) lt mu_(2)

Answer»

SOLUTION :
Discussion
1928.

What are transgenic organisms?

Answer»

Solution :PLANTS or animals expressing a modified endogenous gene or a FOREIGN gene are KNOWN as transgenic ORGANISMS.
Discussion
1929.

A concave lens of refractive index mu_(1) is kept in a medium of refractive index (mu_(2)) . A parallel beam of light is incident on the lens . Draw the path of the rays of light emerging from a lens . If mu_(1) = mu_(2)

Answer»

SOLUTION :
Discussion
1930.

Why can't we see clearly through fog? Name the phenomenon responsible for it.

Answer»

Solution :(i) The minimum distance at which an object is placed from the normal eye so that it can be seenclearly without giving any strain on the eye is called the distance of the distinct vision.
(ii) This distance is 25 cm for a normal human eye.
(iii) If the object is placed at a distance less than 25 cm, ciliary muscles are UNABLE to adjust the lens there is a strain on the eye and it cannot be SEEN clearly.
(iv) Hence an object should be placed at 25 cm or more to have a clear and SHARP image of it on the RETINA.
Discussion
1931.

Consuming liquor is always bad.

Answer»

Solution :(1) When the liquor is produced from alcohol wrong processes can be carried out which makes the liquor highly toxic. It MAY costthe life too.(2) Due to alcohol in the liquor, there is direct EFFECT on the nervous systemand expecially on the brain and other vital organs such as liver and kidneys. (3) The lifespan of person DECREASES due to alcoholism. (4) In students, the brain functioning is affected and the ability to MEMORIZE and think rationally is lost. The learning process becomes slow. (5) Due to all these effects, there are social , mental and familial problems in the society.Therefore, consuming liquor is always BAD.
Discussion
1932.

High ionizing power : alpha ray :: Low ionizing power:__________

Answer»

100 times greater than the `BETA` RAYS
1000 times greater than the `GAMMA` rays
very less IONIZATION
both (a) and (b)

Solution : both (a) and (b)
Discussion
1933.

An object is placed at a distance 10cm from a concave mirror of focal length 15cm. Find the position and nature of the image.

Answer»

Solution :Focal length of convex lens mirror, f=+15cm Object distance,
u=-10cm According to the mirror formula
`1/v-1/u=1/f`
`1/v=1/f-1/u`
`=1/(15)+1/(10)=(25)/(150)`
The positive value of v indicates that the image is FORMED BEHIND the mirror.
Magnification, `m=("Image distance")/("Object distance")=-v/u=(-6)/(10)=+0.6`
The positive vaJue of magnification indicates that the image formed is VIRTUAL and erect
Discussion
1934.

Most of the sources of energy we use represent stored solar energy which of the following is not ultimately derived from the sun's energy

Answer»

GEOTHERMAL ENERGY
Wind energy
NUCLEAR energy
Bio mass

Answer :C
Discussion
1935.

Explain why one should care for the biotic and abiotic factors of ecosystem.

Answer»

Solution :i. Ecosystem consists of biotic and ABIOTIC factors and their interactions with each other .These factors have significant roles in the ecosystem.
ii. In an ecosystem, producers synthesize their own food. Herbivores feed UPON these herbivores.This prevents the overpopulation of the herbivores which is equally important.
iii. Even termites and insects present in during are important for cleaning the environment .Decomposers like fungi present is soil are essential for decomposing organic matter ( from DEAD plants and animals and recycling nutrients back to producers i.e., green plants).
iv. Biotic and abioticfactors are essential to maintain BALANCE in the environment.Changes in any of these factors will disrupt the interactions occurring in the ecosystem.
Therefore, we should care for the biotic and abiotic factors of ecosystem.
Discussion
1936.

A solution is made from 25 ml of ethanol and 75 ml of water. Calculate the volume percentage.

Answer»

Solution :(a) (i) To measure the speed of an automobile
• A source emitting electromagnetic wave is attached to a police car
• The wave is reflected by a moving source.
• From the frequency shift, the over SPEEDING vehicles can be determined.
(ii) Tracking a satellite
• The frequency of radio waves decreases as the satellite passes away from the EARTH.
• By this CHANGE in frequency, the location of the satellites is determined.
(iii) RADAR
• The radio waves are detected by the receivers.
• The frequency change tracks the speed and location of the aircrafts.
(IV) SOLAR
• There is a frequency change between the sent signal and received signal.
• This helps to determine the speed of submariners and marine animals.
(b) Volume of ethanol= 25 ml
Volume of water = 75 ml
`"Volume percentage"=("Volume of the solute")/("Volume of the solution")XX100`
=`(25)/(25+75)xx100=(25)/(100)xx100=25%`
Discussion
1937.

Environment day falls on :

Answer»

28th Feb
23RD March
5th June
14th NOV.

Answer :C
Discussion
1938.

What type of material LED ?

Answer»

SOLUTION :NON OHMIC
Discussion
1939.

Draw a schematic diagram of an electric circuit consisting of a battery of two cells each of 1.5V, 5 Omega ,10 Omega, 15 Omega resistors and a plug key, all connected in series.

Answer»

SOLUTION :SCHEMATIC DIAGRAM is SHOWN here.
Discussion
1940.

Why are birds and mammals called warm blooded ?

Answer»

Solution :Birds and mammals can MAINTAIN their body temperature to a CONSTANT LEVEL , THEREFORE they are called warm blooded .
Discussion
1941.

Solids which break or rupture above the elastic limit are classified as

Answer»

BRITTLE
elastic
ductile
malleable

SOLUTION :brittle
Discussion
1942.

Satellites working in the field of telecommunication, television broadcasting and meteorological services.

Answer»

SOLUTION :INSAT and GSAT
Discussion
1943.

Which of the following is the reason for some road accidents.

Answer»

SELFIE
LIQUOR
Both (a) and (b)
NONE of these

Answer :C
Discussion
1944.

The electric current in an external circuit flows from the ………………….. .

Answer»


ANSWER :POSITIVE, NEGATIVE
Discussion
1945.

The focal length of a plane mirror is

Answer»

0
`OO`
It does not have a FOCAL length
None of the above

Solution :For a PLANE mirror v = -u and so `(1)/(f) = (1)/(v) + (1)/(u) = (1)/((-u)) + (1)/((u)) = 0 RARR f = oo`
Discussion
1946.

Tomato is a natural source of which acid ?

Answer»

ACETIC acid
Citric acid
Tartaric acid
OXALIC acid

SOLUTION :oxalic acid
Discussion
1947.

When a boy weighing 20 kgf sits at one end of a 4m long see saw, if gets depressed at this end. How can it be brought to the horizontal position by a man weighing 40 kgf.

Answer»

SOLUTION :IF the man sits at a distance 1M from the CENTRE on the side opposite to the BOY.
Discussion
1948.

If one of the focus of a bi-covnex lens is plane, it is known as a ___________ .

Answer»

CONVEX lens
plano - convex lens
concave lens
plano - convex lens

Answer :B
Discussion
1949.

____________ are said to be in a stateof weightlessness.

Answer»

SOLUTION :SPACE STATIONS
Discussion
1950.

A magnetic compass shows a deflection when placed near a current-carrying wire. How does the deflection of the compass get affected, if the current in thewire is increased ? Support your answer with a reason.

Answer»

Solution :Ifthe current in the wire is INCREASED, the deflection increases. This is so as the magnetic field is DIRECTLY proportionalto the MAGNITUDE of currentpassing through the straight CONDUCTOR. This causes the COMPASS needleto deflectmore.
Discussion