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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 8501. |
State the merits and demerits of a parallel combination of resistors. |
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Answer» Solution :Merits: ( 1 ) If three bulbs are connected in parallel, and one of the bulbs gets fused, then the current continues to flow through the other bulbs and they continue to emit light. That is why, in house, the electrical appliances are connected in parallel with the main line. ( 2 ) The EQUIVALENT resistance in the parallel combination of resistors is less than any of the individual resistances. Hence, more current can be obtained by connecting resistors in parallel. DEMERITS: ( 1 )In a parallel combination, eqUivalent resistance is smaller than the smallest resistance connected, so TOTAL current INCREASES. As a result, current cannot be controlled in the circuit. ( 2 ) If the bulbs working on different voltages (having different voltage rating) are connected in parallel with a given voltage source then each BULB cannot light up with its complete efficiency. e.g., When three bulbs working on 220V, 230V and 240V respectively are connected in parallel and the same voltage 220V is applied to all the three bulbs then only the bulb working on 220V will light up with complete efficiency. |
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| 8502. |
Calculate the amount of heat energy to be supplied to convert 4 kg of ice at 0^@C completely into water at0^@C if latent heat of fusion for ice is 80 cal/g. |
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Answer» heat of fusion for ICE (L) = 80 cal /g . To find ,Heat energy (Q) Formula :Q=mL Calculation: Formula formula, `Q= 4 xx 10^3 xx 80 = 320000 cal ` = 320 kcal . |
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| 8503. |
Describe an activity to show refraction of light through a prism. Draw relevant figure, marking angle of incidence, refraction emergence, and deviation. |
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Answer» Solution :To study refraction of light through a triangular glas prism : (1) Fix a sheet of WHITE paper on a drawing board using drawing pins. (2) Place the glass prism on the board with its triangular base lying at the bottom. Trace the outline of the base using pencil. (3) Fix TWO pins - P and Q - on a line as SHOWN in the figure. (4) Observe the image of P and Q through the face AC. (5) Fix two more pins R and S such that they lie in the straight line containing images of P and Q. (6) Remove the prism and the pins. (7) Label the points where PQ and RS meet the boundary of the prism at E and F respectively. Join PE, EF and FS as shown. (8) Draw perpendicular NN. and MM. to the faces AB and AC of the prism at points E and F respectively. (9) Mark the angle of incidence `angle i`, angle of refraction `angle r` anad angle of emergence `angle e` as shown.  INFERENCE : At face Ab, as the incident ray PE is travelling from rarer medium [air] to denser medium [glass], it is bent towards the normal NN. along EF. At face AC, ray EF gets refracted by travelling from denser to rarer medium. Hence, the emergent ray FS bends away from the normal, towrds the base of the prism. This is different from refraction in a glass slab because, the incidence ray is not parallel to the emergent ray as in the glass slab. |
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| 8504. |
Can the couple acting on a rigid body produce translatory motion ? |
| Answer» SOLUTION :No. It can PRODUCE only ROTATORY MOTION. | |
| 8505. |
A physical quantity P is related to four observables a, b, c and d as P=a^(3)b^(2)//sqrtcd. The percentage errors in the measurements of a, b, c and d are 1%, 3% 4% and 2% respectively. What is the percentage error in the quantity P? If the value of P calculated using this formula turns out to be 3.763, to what value should you round off the result? |
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Answer» Solution :Relative error in P is given by `(DeltaP)/(P)=3(Deltaa)/(a)+2(Deltab)/(B)+(1)/(2)(Deltac)/(c)+(Deltad)/(d)` So, PERCENTAGE error `(DeltaP)/(P)xx100=3((Deltaa)/(a)xx100)+2((Deltab)/(b)xx100)+(1)/(2)((Deltac)/(c)xx100)+(Deltad)/(d)xx100` `=(3xx1%)+(2XX3%)+((1)/(2)xx4%)+(1xx2%)` `=13%` Rounded off value of P = 3.8. |
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| 8506. |
If a force of 10 N acts on surfaces of areas in the ratio 1:2, then the ratio of thrusts is |
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Answer» `1:2` |
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| 8507. |
In whichof the following substances , isethanol not used? |
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Answer» TONICS |
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| 8508. |
What is real gas ? |
| Answer» SOLUTION :If the molecules or ATOMS of a gas INTERACT with each other with a definite amount of intermolecular or inter ATOMIC force of attraction, then , the gas is said to be REAL. | |
| 8509. |
Roshan observed a beautiful rainbow in the western Sky from his school ground. When did Roshan observe the rainbow?[Morning, Noon, Evening, ,Prediction of time is impossible]. |
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Answer» |
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| 8510. |
India has not produced any space mission . |
| Answer» Solution :False : INDIA is RUNNING space MISSION since 1984 . | |
| 8511. |
A bullet loses(1)/(20) of its velocity after penetrating a plank. How many planks are required to stop the bullet? |
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Answer» 9 |
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| 8512. |
How is Plaster of Paris prepared? What reaction takes place when it sets to a hard mass? |
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Answer» Solution :Plaster of PARIS is prepared by HEATING gypsum to a temperature of `100^@C` . The following reaction takes place ` CaSO_4. 2H_2O OVERSET(100^@C)(to) CaSO_(4) 1/2H_2O+ 1(1)/(2) H_2O` : On mixing with water, it REACT to a hard mass to form gypsum again i.e, the reverse reaction takes place. |
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| 8513. |
Twinkling of stars is due to |
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Answer» variation of REFRACTIVE index in the earth's atmosphere |
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| 8514. |
What are essential percautions to be used while using electricity ? |
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Answer» Solution :Precautions to be followed for using electricity are : 1. Switch off all switches including main switch whenever there is sparking or fire. 2. All connections muct be tight. Wires muct be covered with proper insulations of proper thickness. All joints muct be covered with insulating tape of a good quality. Defective switches should be immediately replaced. 3. Fuses should be always connected to be wire. The earth wire must be connected to the body of electric appliance. 4. Fuse must be of proper rating and should always be connected to live wire. 5. Whenever repairs are needed, switch off main switch. If however, repairs need a direct handling of live wire, USE of rubber gloves or rubber shoes or a plier with insulated handle is a must. 6. If INSPITE of all the precautions, a person gets a SHOCK due to accidental touching a live wire, one should try to PROVIDE such a person with support of some non-conducting material like wood, plastic or rubber. Never try to pull AWAY person by your hand. 7. Always put dry rubber shoes while repairing the circuit. |
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| 8515. |
Is optical density of a medium same as its mass density ? Name a transparent medium which has smaller mass density, but is optically denser. |
| Answer» Solution :No, Infact, MASS density is mass per unit volume. OPTICAL density of a MEDIUM determines the ability of the medium to refract light. Kerosene oil has higher refractive index than water. Therefore, kerosene oil is optically DENSER than water. But mass density of kerosene oil is LESS than the mass density of water. | |
| 8516. |
State two laws of refraction. |
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Answer» Solution :(i) The incident ray, the REFRACTED ray and the normal all lie in the same plane. (ii) The ratio of sine of ANGLE of incidence in the first medium to the sine of angle of REFRACTION in the second medium is a constant and is known as refractive index of the second medium with RESPECT to the first medium. |
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| 8517. |
Girls are facing the problem of stress due to such gender inequality. |
| Answer» Solution :(1) In most of the households there are many bindings on girls and excessive freedom for boys. (2) Boys do not PARTICIPATE in the domestic duties whereas girls have compulsion for the same. (3) In society too, girls have to face the problems like TEASING and MOLESTATION. This creates insecurity in the minds of girls. (4) The SOCIAL change has made women independent and equal nut still the male dominated society and the gender inequality persists causing more STRESS for young girls. | |
| 8518. |
To convert SI unit of heat into its CGS unit, conversion factor used is 4.18. |
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Answer» Solution :FALSE. As, L cal = 4.18 J, to CONVERT joule (SI unit) into calorie (CGS unit), conversion factor is `1//4.18`. |
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| 8520. |
What is meant by the orbit of a satellite? On what basis and how are the orbits of artificial satellites classified? |
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Answer» SOLUTION :The regularly repeated path of a satellite around a planet is called its orbit. Depending on the, height of the satellites orbit above the earth's surface, the satellite orbits are classified as : 1.High Earth Orbits (HEO): If the height of the satellite's orbit above the earth's surface is greater than or equal to 35780 km, the orhit is called high earth orbit.Geosynchronous satellites revolve in such orbits.Since, these satellites are stationary with reference to the Earth. they can observe a specific portion of the Earth continuously. Therefore, they are USED in applications like meteorology and for carrying signals for telephone television, radio, etc. 2.Medium Earth Orbits (MEO) : If the height of a satellite orbit above the earth's surface is in between 2000 km and 35780 km, the orbits are called medium earth orbits.Geostationary satellites revolve in suchorbits. These are, therefore, not useful in the study of Polar Regions. For this, purpose,elliptical medium earth orbits passing overthe polar region are used. These orbits are called polar orbits. In these orbits, the satellites COMPLETE one revolution in 2 to 24 hours. Some of these satellites revolve in circular orbits at a height of around 20,200 km above the earth's surface. Global POSITIONING satellites revolve in such orbits. 3. Low Earth Orbits (LEO) : If the height of the satellite orbit above the earth'ssurface is in between 180 km and 2000 km, the orbits are called Low earth Orbits.The satellites used for scientific experiments and atmospheric studies revolve in low earth orbits. Depending on the height of their orbits, they complete one revolution in around 90 minutes. International Space Station and Hubble telescopealso revolve in Low earth Orbits. 
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| 8522. |
In coelenterates, …………. , are useful for capturing the prey whereas …………. Inject the toxin in the body of prey. |
| Answer» Solution :In COELENTERATES, tentacles are useful for capturing the prey WHEREAS CNIDOBLASTS inject the toxin in the BODY of prey . | |
| 8523. |
Simple microscope, Compound microscope, Astronomical tlelscope, Terrestrial telescope. |
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Answer» |
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| 8524. |
person indulging in selfie has a very active social life. |
| Answer» Solution :False-Person indulging in SELFIE is not aware about the WORLD AROUND and the risks and has a very SEDENTARY SOCIAL life. | |
| 8525. |
Particles of masses 1g, 28, 3g ..., 100g are kept at the marks 1 cm, 2 cm, 3 cm ... , 100 cm respectively on a meter scale. Find the moment of inertia of the system of particles about a perpendicular bisector of the meter scale. |
Answer» Solution :Given Masses of 1g, 28, 3g ....... 100 g are 1, 2, 3 ...... 100 cm on a scale.  i) Sum of masses`Sigma m=underset(i=1)overset(n) "NI"` Sum of n natural numbers S `=(n(n+1))/(2) = (100xx101)/(2) = 5051` `therefore` Total mass M = 5051 gr = 5.051 kg ` to (1)` ii)Centre of mass of all these masses is given by `X_(CM) = (m_1x_1 +m_2x_2 + .....)/(Sigma m)` `(1xx 1+2xx 2 +3xx3 + ........+ 100 XX 100)/(M)` = `(1^2 + 2^2 + 3^2 + ......+ 100^2)/(M)` But sum of squares of 1st n natural numbers is `S = (n(n+1)(2n+1))/(6)` `therefore CM = (n(n+1)(2n+1))/(6xxn(n+1)) "use " M = (n(n+1))/(2)` `therefore CM = 201/2= 67 CM `to (2)` iii) M.O.I = m_1 r_1^2 + m_2r_2^2 + m_3r_3^2 + ......+ m_100 r_100^2` `therefoer 1 = 1xx 1xx 1+ 2 xx 2^2 + 3xx 3^2 + ....... + 100 xx 100^2` `= 1+2^3 + 3^3 + ......+100^3 xx 10^(-7) kgm^2` `(because 1g = 10^(-3) kg & 1.CM =10^(-2) m)` Sum of cubes of 1st n natural numbers is `S = (n^2(n+1)^2)/(4)` `therefore I = (100^2 xx (101)^2)/(4) g.cm^2` `= 2.550 xx 10^7 g.cm^2 = 2.550 kg.m^2` (From one end of scale) M.O.I about C.M = `I_G - I - MR^2` `= 2.550 - 5.05xx 0.67xx 0.67` `= 2.550 - 2.267 = 0.238 kgm^2` iv) Perpendicular bisector is at 50 CM. so shift M.O.I from centre of mass to `x_1` = 50cm point from x = 67 CM `therefoer` Distance between the axis `R= 67- 50 = 17cm = 0.17 M` M.O.I about this axis `I = I_G + MR^2` ` = 0.283 + 5.05xx 0.17 xx 0.17` `= 0.283 + 0.146 = 0.429 kgm^2` `therefore` M.O.I about perpendicular bisector of scale= `0.429 kg -m^2` |
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| 8526. |
How is sound produced? |
| Answer» Solution :By touching a RINGING bell or a musical INSTRUMENT while it is PRODUCING music, we conclude that sound is produced by vibrations. | |
| 8527. |
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object ? Alsi, find the power of the lens. |
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Answer» <P> Solution :Since the image is real and same size. The position of image should be at 2f. It is given that the image of the needle is formed at a distance of 50 cm from the convex LENS. Hence, the needle is PLACED in front of the lens at a distance of 50 cm.Object distance, `u = -50 cm` Image distance, v = 50 cm Focal LENGTH = f According the lens formula, `(1)/(v)-(1)/(u)=(1)/(f)` `(1)/(f)=(1)/(50)-(1)/((-50))=(1)/(50)+(1)/((50))=(1)/(25)` f = 25 cm = 0.25 cm Power of lens, `p=(1)/("f (in METERS)")=(1)/(0.25)=+4D` |
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| 8528. |
A satellite goes along an elliptical path around earth. The rate of change of area swept by the line joining earth and the satellite is proportional to |
| Answer» ANSWER :D | |
| 8529. |
How many 176Omega resistors (in parallel) are required to carry 5A on a 220 V line ? |
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Answer» Solution :I = 5A V = 220 V `Rp= (V)/(I) = (220)/(5) = 44 OMEGA` Now, if n resistors, each o.f resistance 176 `Omega` are connected in parallel to GIVE EQUIVALENT resistance of 44`Omega`, i.e. `R_(p)` `R_(p)= (R)/(n)` `44=(176)/(n)` `n=(176)/(44) = 4` |
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| 8530. |
In Fleming's right-hand rule the fore finger points in the direction of________ and the direction of induced current is indicated by_____________. |
| Answer» SOLUTION :MAGNETIC FIELD, central (middle) FINGER | |
| 8531. |
Two lamps, one rated 100W at 220 V, and the other 60 W at 220 V are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220V ? |
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Answer» Solution :The resistance of 100 W lamp, `R_1 = V^2/P_1 =(220^2)/(100) =(220xx220)/100 =4840/10 Omega = 484 Omega` The resistance of 60 W lamp, `R_2 = V^2/P_2 = (220^2)/60 = (220xx220)/60 = 4840/6 Omega= 806.7 Omega` When, these LAMPS are connected in PARALLEL, their equivalent resistance `R_p` is given by `1/R_p =1/R_1 + 1/R_2= (R_2 + R_1)/(R_1 R_2)` `:. R_p =(R_1 R_2)/(R_1 +R_2)` `=(484 xx 806.7)/(484 + 806.7) = (390442.8)/1290.7 = 302.6 Omega` The CURRENT DRAWN from the line, `I = V/R_p =220/302.6 = 0.7270 ~~ 0.73A` |
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| 8532. |
How does a solenoid behave like a magnet ? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet ? Explain. |
| Answer» Solution :When current is passed through a solenoid coil, magnetic FIELD produced due to each turn of solenoid coil is in the same direction. As a result, the resultant magnetic field is very STRONG and uniform. The field lines inside the solenoid are in the form of parallel straight lines along the axis of solenoid. Thus, the solenoid behaves LIKE a bar magnet. One END of solenoid behaves as a magnetic north pole while the other end behaves as the south pole. We can determine the magnetic poles formed in a solenoid. The end of the current-carrying solenoid, which attracts north pole but repels south pole of a bar magnet, is behaving as the south magnetic pole. The other end, which attracts south pole of a bar magnet but repels the north pole, is behaving as north magnetic pole. | |
| 8533. |
The apparent position of a star in the sky is ………… . |
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Answer» SLIGHTLY LOWER than its ACTUAL POSITION |
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| 8534. |
State whether the following statementare true or false : Themagneticfield linesatcentreof a longcircularcoil carrying s current are parallel straightlines . |
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| 8535. |
Where do plants get each of the raw materials required for photosynthesis ? |
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Answer» Solution :i) Carbon dioxide : AIR, through STOMATA. II) Water : Soil through roots. iii) Sunlight : From the SUN, prestnt in green PARTS of the body absorbed by chlorophyl molecules plant body. |
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| 8536. |
You know that as we go higher than the sea level, the boiling point of water decreases. What would be the effect on the melting point of solid? |
| Answer» SOLUTION :As we go HIGHER than the sea level, the melting point of solids ( i) that expand on melting is lowered due to a DECREASES in pressure (ii) that contract on meltingis raised due to a DECREASE in pressure. | |
| 8537. |
When the projectile hits the parent nucleus, it is converted into an ___________ nucleus. |
| Answer» SOLUTION :UNSTABLE | |
| 8538. |
Consider a thin spherical shell of radius R with its centre at the origin, carrying uniform positive surface charge density. The variation of the magnitude of the electric field | vec(E) (r ) | and the electric potential V (r ) with the distance r from the center is best represented by which graph, Fig. |
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Answer» ltimg SRC="HTTPS://d10lpgp6xz60nq.cloudfront.net/physics_images/PR_XII_V01_C01_E01_319_O01.png" WIDTH="30%"gt |
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| 8539. |
Explain the changes taking place in the cilary muscles when we focus on a nearby object and far-off objects. |
| Answer» Solution :The human eye has the ability to adjust its focal length according to the distance of object, which is known as power of accomodation. While viewing distant objects, CILIARY muscles of the eye relax which makes the eye les thinner. This INCREASES the focal length of the eye LENS so that a clear image of the object is formed on the RETINA. While viewing NEARBY objects, ciliary muscles contract which increases the curvature of the eye lens. This decreses the focal length of the eye lens so that a clear image of the object is formed on the retina. | |
| 8540. |
What is regelation? Why is it observed? |
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Answer» Solution :i. The PHENOMENON in which the ICE converts to liquid due to applied pressure and then re- converts to ice once the pressure is removed is CALLED regelation. ii. a. Due to applied pressure, melting point of ice is lowered below `0^(@)C`. b. As a result, ice gets converted into water at ` 0^(@) C`. c. When the applied pressure is removed, the melting point is RESTORED to `0^(@)C` and water gets re-converted into ice. |
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| 8541. |
Which electricity generation process is eco-friendly and which not ? |
| Answer» Solution :Electricity generated through solar ENERGY and wind energy are TRULY eco-friendly. Though it is said that hydroelectricity is non-polluting and eco-friendly, it is not true. Hydroelectric project CAUSE destruction of biodiversity and dispplacement of the local people. Thermal energy, nuclear energy and energy OBTAINED through natural GAS are not at all eco-friendly. | |
| 8542. |
Which of the following options is not the formula for heat energy (in joule) produced when a current is passed through a conductor? |
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Answer» `H =I^2 RT` |
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| 8543. |
Bring out any two physiological activities of abscisic acid (ABA). |
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Answer» Solution :(a) ABA promotes the PROCESS of abscissin (SEPARATION of leaves, FLOWERS and fruits from the branch) (b) During water strees and drought conditions ABA causes stomatal CLOSURE. |
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| 8544. |
Electrical resistivity of a given metallic wire depends upon |
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Answer» its length |
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| 8545. |
What are the limitations of can be shown in single me energy from : (i) The wind (ii) Waves (iii) Tides |
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Answer» Solution :(i) Limitations of extracting energy from the wind: Wind FLOWING with a SUFFICIENT speed is not available everywhere and all the time. (ii) Limitations of extracting energy from ocean waves : Wave energy would be commercially viable only at places where the waves are STRONG. The energy produced from waves has to be transmitted through LONG distances at the possible of use. (iii) Limitations of extracting energy from tides : There are very few sites suitable for harnessing tidal energy. The rise and fall of WATER during tides is not very large. So, large scale generation of electricity is not possible. |
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| 8546. |
The figure shows elliptical orbit of a planet m about the sun S. the shaded area SCD is twice the shaded area SAB. If t_(1) be the time for the planet to move from C to D and t_(2) is the time to move from A to B, then: |
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Answer» SOLUTION :According to KEPLER's `II^(nd)` law, AREA VELOCITY for the palnet is constant `:. ""(A_1)/(t_1)= (A_2)/(t_2), A_1=2A_(2)` `:. ""(2A_2)/(t_1)= (A_2)/(t_2)` `t_1= 2t_2`. |
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| 8547. |
Silver amalgam is used for filling dental cavities. |
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Answer» Solution :(1) SILVER is a soft metal and wears off on CONSTANT usage particularly due to abrasion. Silver amalgam is an alloy of silver with mercury. (2) It is a hard substance. It is nontoxic. Besides these properties it is a lustrous shining substance. It MELTS at a COMPARATIVELY low, temperature and can therefore conveniently fill in the cavities. Hence, silver amalgam is used for filling DENTAL cavities. |
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| 8548. |
The radiations from the radio isotopes can be used to kill the ________ and ___________. |
| Answer» SOLUTION :INSECTS, PARASITES | |
| 8549. |
Doctor has presecribed a lens having power + 1.5D. What will be the focal length of the lens ? What is the type of the lensand whatmust be the defect of vision ? |
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Answer» To FIND: Focal length (f) Formula: `P=(1)/(f(m))` Calculation: From formula, `f=(1.5)=+0.67 m` The prescribed lens is convex lens as the focal length is positive. Convex lens has positive focal length and it is used for the correction of farsightedness or HYPERMETROPIA. Thus, the defect in vision is hypermetropia (farsightedness). |
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| 8550. |
In a power plant based on natural gas the natural gas burs in the presence of air in the _________ . |
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Answer» CONDENSER |
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