Now have more fun at www.askphysics.com

Ask Physics is now more dynamic and Social Networking enabled. Members enjoy a lot of facilities like face book integration, making friends online, sending private messages, forums and groups and many more. Visit ask physics to find out the new additions and facilities.

Though anyone can ask a question and get the answers by email, joining the site as a member adds to the fun. Members can post questions directly to forums, join groups of their interest, like or unlike the posts and activities by other members, add members as friends, send messages to friends and a lot more are in the making.

Teachers can also join the site and start posting answers to the questions as well as taking part in online discussions at forums.

Future Plans

Ask Physics is planning to start a separate section for Physics Classroom Videos.

Work From Home Opportunity

If you are an expert in Typing and can edit documents with complex formatting and diagrams with MS Word, you can apply for an online job.

There is no application fee. Just use the form below to apply. You will be contacted with further details if you get through the initial screening. This is an excellent opportunity to earn from home utilizing your spare time.

http://spreadsheets.google.com/embeddedform?formkey=dF9LZjAxOWpiYzBwVFZxZlo2V0pWYmc6MQ

Work From Home Opportunity

If you are an expert in Typing and can edit documents with complex formatting and diagrams with MS Word, you can apply for an online job.

There is no application fee. Just click the link below to apply. You will be contacted with further details if you get through the initial screening. This is an excellent opportunity to earn from home utilizing your spare time.

http://spreadsheets.google.com/viewform?formkey=dF9LZjAxOWpiYzBwVFZxZlo2V0pWYmc6MQ

Communication Systems : Revision Test

One mark questions

1. What is the meant by the term attenuation ?


2. Why ground wave transmission is restricted to 1500 kHz?


3. Define critical frequency in sky wave propagation.


4. What type of modulation is required in TV transmission?


5. Why AM radio reception is affected by electrical disturbances while FM radio reception is not?


6. What should be the length of a dipole antenna for a carrier wave of frequency 3 x 10⁸ Hz


7. Draw a block diagram showing the basic communication system.


8. What is the range of frequencies used for FM radio transmission?

Two marks Questions

1. Distinguish analog and digital transmission


2. Write the functions of transducer and repeater in Communication systems.


3. Distinguish amplitude modulation and frequency modulation.


4. Draw a block diagram showing a simple amplitude modulator


5. Explain how a message signal is extracted from Amplitude Modulated signal.


6. Distinguish Sky wave propagation and Space wave propagation.


7. Name the different layers of earth’s atmosphere.


8. Mention two ways in which the range of transmission can be increased.


9. Explain the term modulation index and describe its significance.


10. List four devices used for communication each of which differ from other in the mode of communication.

Three marks questions

1. Explain the need for modulation


2. Derive an expression for the range of transmission from an antenna of height h.


3. Describe the demodulation of AM wave using waveforms and circuit diagrams.

Affordable Web Hosting and Domain Registration

World's Largest Registrar - GoDaddy.com

Wordpress & Go Daddy Hosting - A Winning Combination For Your blog!

 

GoDaddy Auctions: The smart choice for buying & selling domain names.

GoDaddy.com Hosting Plans from $1.99 per month! Now with Unlimited Bandwidth!

Uttar Pradesh To Hold State-Level Common Entrance Test For Admission To PhD Programs

The Vice-Chancellors of the universities in Uttar Pradesh have resolved to hold a state level Common Entrance Test for admission to the PhD (Doctor of Philosophy) degree course. Besides, all the state universities will have a common syllabus, making it easier for the students to select their teachers under the 'virtual class' system as well as a common time-table to hold entrance tests, examinations, and to declare results.

Bangalore University Will Hand Over Its 11 Hostels To Department Of Social Welfare

Persistent hostel problems and ongoing strikes and protests by hostel inmates against hostel reforms imposed by the newly appointed warden have forced the Bangalore University to take a tough stand. The university syndicate has decided to end the matter by handing over its 11 hostels to the state Department of Social Welfare. The wardens appointed by the varsity will be withdrawn and the social welfare department’s staff will soon take over.

Number Of International Students In US Colleges And Universities Is On A Rise

According to the Open Doors 2010 Survey published by the Institute of International Education (IIE), there has been a whopping rise of 30% in Chinese students in the United States while there has been just a 2% rise in Indians studying there. Thus, China has replaced India as the leading place of origin for international student population in the US. By far, the United States is the leading destination for study abroad students from India with nearly 105,000 Indian students enrolled in higher studies. It is followed by the UK, which hosts 36,000 Indian students; and Australia, which hosts about 21,000 Indian students.

First Management Aptitude And Skills Test Will Be Held On Feb 20 Next Year

The Management Aptitude and Skills Tells (MAST), launched by the All India Management Association (AIMA), will be first held on Feb 20, 2011. This innovative computer-based test for B-school graduates will evaluate them on general ability, personality traits, and domain knowledge. It has been launched to help students find best-suited job opportunities and the recruiters to find the right candidates based on the skills, talents, and aptitudes of management graduates.

Number Of Seats In All IIMs Increased To 2600; Number Of CAT Applicants Dropped By 15%

The intake capacity of all the 11 IIMs put together is about 2600 seats. These include the six older Indian Institutes of Management - Ahmedabad, Calcutta, Bangalore, Indore, Kozhikode and Lucknow as well as the five new ones - Shillong, Rohtak, Ranchi, Raipur, and Trichy. With the Supreme Court directives in place, IIMs have to accommodate 27% of Non-creamy layer Other Backward Classes (NC-OBC) category students, 15% seats for SC students, 7.5% for ST, and 3% seats for Differently Abled students. Thus, seats for general category students have only increased to 1235 from 1043, previously available. However for NC-OBC students, there are 700 new seats to compete for.

Mysore And Karnatak Universities To Be The First Innovative And Restructured Universities In India

In a historic decision, the state cabinet has decided to declare the University of Mysore and Karnatak University (Dharwad) as the Innovative and Restructured Universities under the new legislation Karnataka State Universities Bill, 2010. The universities will now have a new form of governance with more autonomy for Academia and Administration, flexi working hours and research project for all faculty members, more freedom to students to switch their subjects within certain limitations, twinning programs with Indian and foreign universities, and induction programs with free classes on soft skills.

The Young Innovator From IIT Kharagpur Bagged First Prize At IIT-Delhi Fair

Indian Institutes of Technology (IITs) have always encouraged innovation and entrepreneurship. Shwetank Jain, studying BTech at IIT Kharagpur proved it by winning the first prize at the India Innovation Initiative (i3) National Fair by presenting his P2 Power Solutions – an Intelligent Power Conditioner with Hybrid System Integrator that economizes use of energy and enhances power quality. The fair was held at IIT Delhi and was organized by the Department of Science and Technology, Government of India, Agilent Technologies, and the Confederation of Indian Industry (CII).

Nanotechnology in Ancient India (!)

Did you know that the Ancient Indian Acharyas applied Nanotechnology too!

 

Concept of reduction in particle size of metals is explained as well as practiced from the time of Charaka. The methods are explained in Charaka Samhita (1500 BC)

The different Bhasmas prepared in Ayurveda are actually utilizing the applications of nanosized metals like iron, calcium, zinc, gold etc. Bhasmas are biologically produced nanoparticles.

Nanoparticles are produced industrially now in big amounts for various purposes including medicine. But the ancient technology which provided an economical way of creating nanosized particles used for curing various ailments are really commendable.

Read more at http://nopr.niscair.res.in/bitstream/123456789/10656/1/JSIR%2069(12)%20901-905.pdf

Get Complete solutions to Irodov Problems

Irodov Problems in Physics is a set of high standard problems in Physics

FInd the solutions to these problems here

http://irodovsolutions.blogspot.com/

Solutions to Irodov Problem 1.81 and 1.82

The body mpushes the body Mbackwards. As the bodyM is pushed backwards,m is forced to slide down the incline on M. Let the tension in the string be T and let the normal reaction between the surfaces be N. Further let the acceleration of body M be and let the acceleration of body m with respect to an observer on body Mbe along the direction down the inclined plane.
Relation between and : The relation between the two acceleration can be seen in the figure below. As seen in the figure,AB and CD are two section of the string before and after the pulley. After the mass M and hence the pulley moves back by x units the length CD shortens to C'D = CD-x. Since, the total length of the stringAB + CD is to remain constant AB must extend to A'B' = AB + x. In other words if the mass M moves x units towards the wall, the massm slides the same x units on the inclined plane. Thus, we have,

Forces on mass m : We will resolve the forces acting on m in the parallel and perpendicular direction to the incline. This mass experiences two kinds of i) accelerations, as it rides along with mass M and ii) its acceleration as it slides on the incline relative to M. The net acceleration is the summation of these two accelerations. From (1) however, the magnitude of both these accelerations is the same.
In the direction perpendicular to the incline, there are twp forces acting on the body, i) the component of gravity and ii) the normal reaction N from the surface of mass M. The component of the net acceleration of mass m along the perpendicular direction is given by, as shown in the figure. Thus we have,

In the direction parallel to the incline, there are two forces acting on the mass m, i) the tension in the string T and ii) the component of force of gravity pulling it down the incline. The component of net acceleration along this direction is given by as shown in the figure. Thus, we have,

Forces on mass M : For this problem we need consider only the forces acting in the horizontal direction - this is shown in the figure.
There are three forces acting on the mass M that effect its motion in the horizontal direction, i) the normal reaction from mass mand ii) the tensions of magnitude T in the parts of the string after and before the pulley directed along the direction of the string. The component of tension in the part string connecting the mass m and the pulley is given by . The mass M accelerates at a rate w towards the wall. Thus we have,

Now we have all the information needed to solve for w.
From (2) and (4),

From(3) and (5) we have,

Irodov Problem 1.81

In the system, as body 1 moves backwards, body 2 will slide down along the inclined plane. Let the acceleration of body 1 be and let the acceleration of body 2 with respect to an observer on body 1 be along the direction down the inclined plane. Further let the normal reaction between the two bodies be N.
Forces acting on body 2 : We shall resolve all forces in directions parallel and perpendicular to the incline of body 1. There are two forces acting on this body in the perpendicular direction.

i) the component of force of gravity and ii) the normal reaction N between the surfaces. The only acceleration experienced by the body in this direction is the component of its acceleration as it rides on body 1 - as shown in the figure. Thus, we have,

In the direction parallel to the inclined plane, there is only one force acting on the body - the component of force of gravity that's pulling it down the inclined plane, . The net acceleration of the body along this direction is sum of two accelerations it is being subject to, i) its acceleration as it rides on body 1 - and ii) its acceleration relative to an observer on body 1 along the inclined plane . Thus, we have,

Forces acting on body 1: We shall consider only the horizontal direction for this part. There is only one force acting on the body - the component of normal reaction that is responsible to accelerate the body at a rate . Thus, we have,

From (1) and (3)

ALICE experiment announces first results from LHC’s lead-ion collisions

In the first measurement, scientists counted the charged particles that were produced from a few thousand of the most central lead-ion collisions—those where the lead nuclei hit each other head-on. The result showed that about 18,000 particles are produced from collisions of lead ions, which is about 2.2 times more particles than produced in similar collisions of gold ions at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider.

With the LHC’s lead-ion collisions taking place at more than 13 times the energy of RHIC’s gold-ion collisions, predicting a big increase in the number of particles produced would seem to be a no-brainer. Surprisingly, however, the opposite was true. The majority of theories predicted a number lower than that measured by ALICE, because of a strange property of the world of quarks and gluons, the fundamental particles that make up a lead nucleus.

Read More

Must Read - A Costly Quest for the Dark Heart of the Cosmos

The experiment, if it succeeds, could help NASA take a giant step toward answering the question of what the universe is made of. It could also confer scientific glory on both the International Space Station and a celebrated physicist reaching one last time, literally, for the stars. If it fails, it will validate critics who think it a scandal the experiment was ever approved.

Read More

Antimatter atoms have been trapped for the first time ?!

Researchers at Cern, home of the Large Hadron Collider, have held 38 antihydrogen atoms in place, each for a fraction of a second.

Antihydrogen has been produced before but it was instantly destroyed when it encountered normal matter.

The team, reporting in Nature, says the ability to study such antimatter atoms will allow previously impossible tests of fundamental tenets of physics.

The current "standard model" of physics holds that each particle - protons, electrons, neutrons and a zoo of more exotic particles - has its mirror image antiparticle.

 

Read More

Nobel error?!

Nobel prize committee under fire

A high-profile graphene researcher has written to the Nobel prize committee for physics, objecting to errors in its explanation of this year's prize. The award was given to Andre Geim and Konstantin Novoselov of Manchester University, UK, for their work on graphene, a two-dimensional carbon structure that has huge potential in the field of electronics.

Due to the Nobels' prominence, it is not unheard of for disgruntled researchers to criticize a prize committee's decision. But this complaint focuses instead on the quality of the scientific background document issued by the committee to explain why it awarded the prize. "The Nobel Prize committee did not do its homework," says Walt de Heer of Georgia Institute of Technology in Atlanta.

Read More

How is the new appearance and added facilities here?

We have changed the design and added some features on trial basis. DO you like them?

If you have any suggestions or face any problems in using them, please post them as comments to this.

Is the current design better than the previous one? Please respond….

Transcript of my chat with a student on DARK MATTER

Mani is online.

hi sir..gud aftrnun

hello

sir..hav u heard of dark matter?

ya

itz said dat its present evrywher in d universe...does it possess mass?

Not Everywhere, Darkmatter is matter which is not seen because they donot emit or reflect any detectable radiations or matter. Their presence is felt by gravity. Just like a blind find that things are there by feeling it. It possesses mass and that is how it is felt

bt its nt made of atoms..so hw can it b influencd by gravity??

Whatever be the elementary constituents, if there is matter there is gravity. Matter which cannot be detected, it may either be 100% absorbent or 100% transparent.

in either case, its presence is not "seen"

it constitutes about 90% of all substances in d universe..so it shud possibly b present everywer..even in our body..

If you find any discrepancy between your observed mass and felt mass (inertia) then there is a possibility

bt d felt mass cant b measured though..sir..so if dark matter is present..den the mass of every object is subjectd to vary..right?

darkmatter is not "seen" because of the absence of any radiation from it. It has gravity

 

yes..bt since it has mass..it wud add up to the mass of the matter in wich it is present..

By the way who said 90%? http://upload.wikimedia.org/wikipedia/commons/a/a5/080998_Universe_Content_240.jpg

It is not an easy task to explain everything via simple text chat. I recommend you go through the  following links to understand dark matter and dark energy better.

http://en.wikipedia.org/wiki/Dark_energy

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/dark_energy.html

http://physicsworld.com/cws/article/print/19419

http://hubblesite.org/hubble_discoveries/dark_energy/