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Syllabus

what is modulation? what is its need.

(1) $\frac{F}{2}$ towards right

(2) $\frac{F}{3}$ towards left

(3) $\frac{2F}{3}$ towards right

(4) Zero

What is meant by grating element?

(1) (2, 1)

(2) (2, 2)

(3) (1, 0)

(4) (0, 1)

why skywave not used in the transmission of tv signals?

What is the difference between point to point and broadcast communication modes. Give one example

Q). A sphere of radius 25 cm and mass 1 kg is hung by a string of negligible mass and length 40 cm, then tension in the string is :

(1) 10.81 N

(2) 18.4 N

(3) 10 N

(4) 8 N

define sky wave propogation(1) $\frac{1}{3}\mathrm{tan}\theta $

(2) $\frac{1}{3}\mathrm{sin}\theta $

(3) $\frac{2}{3}\mathrm{tan}\theta $

(4) $\frac{2}{3}\mathrm{sin}\theta $

why ar microwaves used in RADAR?

(1) $\overline{)\overline{)\mathrm{A}}.\overline{)\mathrm{B}}}=\mathrm{A}+\mathrm{B}$ (2) $\overline{)\overline{)\mathrm{A}}+\overline{)\mathrm{B}}}=\mathrm{A}.\mathrm{B}$ (3) $\overline{)\overline{)\mathrm{A}.\mathrm{B}}}=\mathrm{A}.\mathrm{B}$ (4) $\overline{)1}+\overline{)1}=1$

when modulation index is kept less than 1 distortion dosent occur.......how and why???? plxzzzzzzz reply briefly........nd fastly.......

Q.32. If a carved black utensil is heated to high temperature and then brought in dark then :

(1) Both utensil and its carving will shine

(2) Only carving will shine

(3) Only utensil will shine

(4) None of the utensil and carving will shine

draw a block diagram of a simple amplitude modulation.explain briefly,how amplitude modulationis achieved.

State two factors by which the range of TV signal can be increased??

Explain why high frequency carrier waves are needed for effective transmission of signals?

Q. Two spheres of radii in the ratio 1 : 2 and densities in the ratio 2: 1 and of same specific heat, are heated to same temperature and left in the same surrounding. Their rate of falling temperature will be in the ratio:

(1) 2 : 1 (2) 1 : 1 (3) 1 : 2 (4) 1 : 4

what is square law device? what is the function of this?Please suggest me any me hurry up!

i am wating your reply?

$\mathbf{8}\mathbf{.}\mathbf{}\mathrm{A}\mathrm{disc}\mathrm{rolls}\mathrm{down}\mathrm{a}\mathrm{plane}\mathrm{of}\mathrm{length}\mathrm{L}\mathrm{and}\mathrm{inclined}\mathrm{at}\mathrm{angle}\mathrm{\theta},\mathrm{without}\mathrm{slipping}.\mathrm{Its}\mathrm{velocity}\mathrm{on}\mathrm{reaching}\mathrm{the}\mathrm{bottom}\mathrm{will}\mathrm{be}:-\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\left(1\right)\sqrt{\frac{4\mathrm{gL}\mathrm{sin}\mathrm{\theta}}{3}}\left(2\right)\sqrt{\frac{2\mathrm{gL}\mathrm{sin}\mathrm{\theta}}{3}}\left(3\right)\sqrt{\frac{10\mathrm{gL}\mathrm{sin}\mathrm{\theta}}{7}}\left(4\right)\sqrt{4\mathrm{gL}\mathrm{sin}\mathrm{\theta}}$

1) 4 J

2)8 J

3)12 J

4)16 J

why do we need to modulate the frequency?

What's the process required to make the transmission of audio signals possible???

Are there any types???

what are the limitations of amplitude modulation?

explain detection of amplitude modulated wave

What is meant by detection of modulated carrier wave? Explain briefly steps for detection?

what is ground wave propagation

Solve this:Two identical bodies are made of a material for which the heat capacity increase with temperature. One of these is at 100

^{o}C, while the other one is 0^{o}C. If the two bodies are b ought into contact then, assuming no heat loss, the final common temperature is :(1) less than 50

^{o}C but greater than 0^{o}C (2) 0^{o}C(3) 50

^{o}C (4) more than 50^{o}CWhich mode of propagation is used by short wave broadcast services having frequency range from a few MHz upto 30MHz? Expain diagrammatically how long distance communication can be achieved by this mode.Why is there an upper limit to frequency of waves used in this mode?

Sir plz..give the answer fast!!!!

^{8}Hz?Why do we use manganine wire in potentiometer?(1) 10 kg-${m}^{2}$

(2) 30 kg-${m}^{2}$

(3) 40 kg-${m}^{2}$

(4) 25 kg-${m}^{2}$

write two factors justifying the need of modulating a signal.

Q10. An object of mass M starts from rest at the bottom of a fixed incline of height H. A person decides to push the object up the incline in one of two ways with an applied force shown in the diagram. In each of the trials, the object reaches the top of the incline with speed V. How would the work done by the person on the block compare for the two trials ? Assume the same constant non-zero coefficient of kinetic friction between the incline and the object for both trails.

(A) More work would be done in Trial 1

(B) More work would be done in Trial 2

(C) It is impossible to determine for which trial there would be more work done without knowing the value of the speed V.

(D) It is impossible to determine for which trial there would the more work done without knowing the value of the coefficient of kinetic friction.

what is square law device?

The block diagram of AM transmitter and AM receiver

Sir, Why moon cannot be used as a communication satellite?

radius 3 R from O in which a hole of radius R is cut whose centre is at 2R distance from centre of large circular plate.

(1) R/4

(2) R/5

(3) R/2

(4) none of these

I need to prepare project on Communication System ...can someone help me on it

It is based on the CBSE....and i need it for submission for the partial fullfilment for the requirement for studies in Physics 10+2.

please help me select toic or to prepare.

your help is heartly welcome at: thomasofjnv@gmail.com

before 06 november, 2012.

What is space wave propagation?

(1) double

(2) four times

(3) half

(4) remains same

explain about downlink and uplink????

Q.12. A cube of edge length 10 cm is just balanced at the interface of two liquids A and B as shown in figure and B has specific gravity 0.6 and 0.4 respectively, then mass of cube is

(1) 240 g

(2) 360 g

(3) 480 g

(4) 540 g

A TV tower has a height of 100m. How much population is covered by the TV broadcast if the average population density around the tower is 1000 persons per sq km?

Q.6. On account of the rotation of earth about its axis :-

(A) the linear velocity of objects at equator is greater than that at other places

(B) the angular velocity of objects at equator is more than that of objects at poles

(C) the linear velocity of objects at all places on the earth is equal, but angular velocity is different

(D) the angular velocity and linear velocity are uniform at all places

what is the necessity of modulation?

Q54. A small sphere rolls down without slipping from the top of a track in a vertical plane. The track has an elevated section and a horizontal part. The horizontal part is 1.0 m above the ground level and the top of the track is 2.6 m above the ground. Find the distance on the ground with respect to the point B (which is vertically below the end of the track as shown in the figure ). Where the sphere lands.

1) 3.00 2) 2.13 m 3) 4.00 m 4) 10 m

why is an FM signal less susceptible to noise than AM signal ?

What is the principle behind the working of stethoscope? Kindly answer sir/mam.

^{}^{2}in the SI system. what is the value of the moment of inertia in a system of units in which the unit of length is 5 cm and the unit of mass is 10 g?What is amplitude modulation?

an audio signal is not transmitted directly by converting it into an electromagnetic wave of same frequency.give 2 reasons.

KINDLY PROVIDE THE SOLUTION OF PHYSICS CLASS 12 SET 55/3 OF BOARD 2013 SOON?

Q.11. What percentage of power of AM wave is carried by the side bands for modulation index m = 1 ?

pls explain modulation and demodulation???/

draw a plot of variation of ' amplitude ' versus 'w ' for an amplitude modulated wave. hence explain the need for keeping the broadcast frequencies sufficiently spaced out ?

Solve this:A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is :

$[Latenheatoficeis3.4\times {10}^{5}J/Kgandg=10N/Kg]$

(1) 34 km (2) 544 km (3) 136 km (4) 68 km

what is html?explain in detail?

Q). Two thermometers are used to record the temperature of a room. If the bulb of one is wrapped in wet hanky

(1) the temperature recorded by both will be same

(2) the temperature recorded by wet-bulb thermometer will be greater than that recorded by the other

(3) the temperature recorded by dry bulb thermometer will be greater than that recorded by the other

(4) none of the above

what is downlink and uplink ?

define frequency modulation ? write the advantages of frequency modulation over amplitude modulation ?A TV tower has a height of 80m. What should be its height if it is to triple its coverage?

What is meant by coverage in this questionRANGEor AREACOVERED??what does line of sight communication means???

sir i am not able to understand topic4 of communication systems.please help me with some formulae...

the topic is :AMPLITUDE MODULATION.I AM UNABLE TO UNDERSTAND EVEN A BIT OF IT.PLEASE HELP.

Why do long distance radio broadcasts use shortwave bands?

A message signal of frequency 10kHz and peak voltage 10 V is used to modulate a carrier of frequency 1 MHz and peak voltage of 20V.Determine

a) Modulation Index

b) the side bands produced

What is sky wave propagation ?

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250 pico farad in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it

Q13. A solid sphere of mass m and radius R is rolling without slipping on a rough horizontal surface with angular acceleration $\alpha $. Centre of mass of sphere lies at a distance $\frac{\mathrm{R}}{\sqrt{2}}$ from the centre of sphere. Find the normal force applied by sphere on the surface at an instant when line joining centre of mass of sphere and centre of sphere makes an angle 45° with vertical and angular velocity of sphere at this instant is $\mathrm{\omega}$.

$\left(\mathrm{A}\right)\mathrm{mg}+\frac{\mathrm{mR}}{2}\left(\mathrm{\alpha}\u2013{\mathrm{\omega}}^{2}\right)\left(\mathrm{B}\right)\mathrm{mg}-\frac{{\displaystyle \mathrm{mR}}}{{\displaystyle 2}}\left(\mathrm{\alpha}+{\mathrm{\omega}}^{2}\right)\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\left(\mathrm{C}\right)\mathrm{mg}+\frac{{\displaystyle \mathrm{mR}}}{{\displaystyle 2}}\left(\mathrm{\alpha}\u2013{\mathrm{\omega}}^{2}\right)\left(\mathrm{D}\right)\mathrm{mg}+\frac{{\displaystyle \mathrm{mR}}}{{\displaystyle 2}}\left(\mathrm{\alpha}+{\mathrm{\omega}}^{2}\right)$

Difference between transducer and transmitter?

Solve this:On a new scale of temperature (which is linear) and called the W scale, the freezing and boiled points of water are 39

^{o}W and 239^{o}W respectively. What will be the temperature on the new scale, corresponding to a temperature of 39^{o}C on a Celsius scale ?(1) 200

^{o}W (2) 139^{o}W (3)78^{o}(4) 117^{o}Wwhat are logic gates??