## Saturday, August 27, 2011

### How to excel in Green Olympiad?

Green Olympiad is and exam conducted by TERI (The Energy and Resources Institute) to sensitize school children (Classes 8, 9 and 10) on environmental issues. Thousands of schools from India and abroad participate in this Olympiad. The paper consists of 100 multiple choice questions. Each question deals with one environmental issue or the other. The questions are set in such a way that reading the question once itself generates some awareness or thoughts related to environmental issues in the minds of children. 60% of the questions are purely on environmental affairs, 25% on the theme of the year and the rest 15% is based on current affairs.

How to Excel in Green Olympiad?

The only way to excel is to be thorough with current affairs pertaining to environmental issues and have a record of as much details as possible regarding the environment.

Some of the areas of great concern are

: Global Warming

: Pollution

: Population

: Climate Change

(Have you got some idea? Post them as comments here)

## Friday, August 26, 2011

### A too simple question paper from Physics (Magnetic effects of current and magnetism) for class XII

If you find these question easy to answer, well and good. If you don’t, please revise these portions thoroughly. These are based on just the minimum level of learning expected from a Class XII student.

1. State Gauss theorem in magnetism.

2. Define the terms retentivity and coercivity.

3. Which direction will a magnetic compass show when it is kept horizontally at the magnetic north pole of earth?

4. Determine the magnitude and direction of magnetic field to be applied in a region with a vertical electric field 1000 V/m (downwards) where a proton has to move towards east with a speed of 100 m/s without any deflection. (Disregard the presence of earth’s magnetic field.)

5. Derive expression for the force on a current carrying conductor in a uniform magnetic field.

6. Using Ampere’s circuital law, derive an expression for the magnetic field at a point due to a straight conductor carrying current.

7. The radius of the first electron orbit of a hydrogen atom is 0.5 A. The electron moves in this orbit with a uniform speed of 2.2 x 106 m/s. What is the magnetic field produced at the centre of the nucleus due to the motion of this elecetron?

8. Derive the relation mr = 1+cm (relation between magnetic permeability and magnetic susceptibility)

9. Mention the magnetic elements of earth and define each.

10. Derive expression for the magnetic dipole moment of a revolving electron.

11. Describe the principle, construction and working of a cyclotron. Why electrons cannot be accelerated using a cyclotron?

*****************

1. Gauss theorem in magnetism states that closed surface integral of magnetic field in a closed surface is zero. That is, the net magnetic flux through a closed surface is always zero.  Mathematically,

2. Retentivity is the magnetization retained by a specimen when the magnetizing field is zero. Coercivity is the reverse magnetizing force required to completely demagnetize and specimen.

3. The compass needle will not show any particular direction as the horizontal component is zero at the magnetic poles. It can rest in any direction in which it is placed just like a non-magnetic needle.

## Wednesday, August 24, 2011

### How to prepare for IIT JEE?

Surya Kant Dwivedi asks: "I am always confused in Physics that how can i do my best in Physics. It is my weakest portion in ’PCM’. Please guide me."

Excelling in Physics in IIT JEE requires systematic planned preparation. The first step is to make sure that you can solve all the exercises from NCERT text book (including the solved examples and additional exercises) confidently and completely. This ensures that you have sufficient exposure and you are up to the standard expected of you.

The next step is to get a good collection of questions asked previously in IIT JEE and solve them. If you are not able to solve a problem, you are welcome to post it here.

Recommended Books:

Fundamentals of Physics (Resnick Hallidey)

Concepts of Physics (HC Verma)

Irodov Problem in Physics

## Tuesday, August 23, 2011

### Practice problems for class 9 SA1

Try to solve these problems, it will help you score good marks in Physics in first summative assessment.

1. Calculate the force required to be imparted to a car to give it a velocity of 30 m/s in 10 s. The mass of the car is 1500 kg.

2. For how long should a force of 200N act on a body of mass 2o kg so that it acquires a velocity of 100 m/s?

3. A force of 4 kg wt acts upon a body of mass 9.8 kg. Calculate the acceleration . Given g=9.8 m/s2

4. A 2000kg vehicle moving with a speed of 20 m/s is brought to rest in a distance of 50 cm. (i) find the acceleration (ii) Calculate the unbalanced force acting on the vehicle.

5. A motor car is moving with a velocity of 108 km/h and takes 4 s to stop after the brakes are applied. Calculate the force exerted by the brakes on the motor car if its mass along with passengers in the motor car is 1000 kg.

6. A bullet of mass 50 g is fired from a gun of mass 4 kg with an initial velocity of 35 m/s. Calculate the initial velocity of recoil of the gun.

7. A bullet of mass 20 g is fired horizontally from the pistol of mass 2 kg with a horizontal velocity of 150 m/s. What is the recoil velocity of the pistol?

8. Two persons with equal muscle power  manage to push a motor car of mass 1200 kg at a uniform velocity along a level road. The same motor car can be pushed by three persons with equal muscle power to produce an acceleration of 0.2 m/s. With what force does each person push the car?

## Friday, August 19, 2011

### REVISION MATERIAL FOR CBSE CLASS 9 SCIENCE (PHYSICS) FOR SA 1

PHYSICS (MOTION)

Points to remember:

• A body is said to be at rest if it does not change its position with respect to its surroundings

• A body is said to be in motion i i changes its position with respect to surroundings

• we can perceive the motion of certain bodies directly such as a cycle moving on road.

• we can perceive the motion of certain other objects by indirect evidences.Motion of air can be observed from movement of dust particles and the branches of trees.

• rest and motion are relative terms.a body appearing to be at rest to one person may appear to be in motion of another person

• Speed is the ratio of distance covered to the time taken.speed is scalar quantity

• Speed is never negative and is zero when the body is at rest

• Velocity is the rate of change of displacement with time.It is a vector quantity

• Velocity may be zero,negative or positive even when tho body is moving. Its S I unit is m s -1

• Acceleration is the rate of change of velocity of a body.Acceleration is a vector quantity. Its  S I unit is m s -2.

• Motion . A body is said to be in motion  if it changes it position with respect to surroundings

• Uniform motion. Motion is said to be uniform if body covers equal distance in equal intervals of time however small these intervals may be.

• Non uniform motion.Motion is said to be nonuniform if the body covers unequal distances in equal intervals of time.

• Distance covered by body is the actual length of path covered by the body. It is measured in metre (in SI). Its CGS unit is centimetre (cm). Distance can never be negative. It is a scalar quantity.

• Displacement is the distance covered by a body in certain direction from starting point to final point. Displacement is a vector quantity and may be positive, negative or zero.

• Speed is the ratio of distance covered to the time taken

## Thursday, August 18, 2011

### Harvard graduate successfully running a tea stall

Amuleek Singh Bijral is a graduate of Harvard Business School and moreover he is a successful chai boy. He runs a tea stall in Basavanagudi, which is a hub of South Indian filter coffee fans. He is among the unconventional entrepreneurs and founder and CEO of Mountain Trail Foods Ltd. Despite starting his first tea stall just one and a half year ago, he has now 10 outlets in the city. His team has also enlarged and he now has 50 people include other IITians and IIM graduates.

### Now a dream to become a Pilot will go through stages of Fire

Pilot aspirants will have to pass an entrance exam where their aptitude would be tested before being allowed to join a flying school. The number of times an aspirant can appear for the exam will be scanned by Directorate General of Civil Aviation (DGCA) followed with the introduction of biometric ways like iris scan to ensure that candidates’ don’t send anyone else in their place to appear for the exam.

### Indians hit English at their Language

In a surprising report of Educational Testing Service (ETS), it has been found out that Indians beat the British in their own language. ETS conducts Test of English as a Foreign Language (TOEFL) and found out that those students with Konkani as their native language topped the rankings.

### Common Entrance test (CET) for Medical exams from next year onwards

The Medical Council of India (MCI) has decided to conduct an all-India level examination for admission to post-graduate medical courses across the country early next year. Such an examination will be held for the first time. The syllabus for the National Eligibility and Entrance Test (NEET-PG) will be the same as that of the MBBS. CET for admission to Medical Post-graduate Courses across the country shall be held in January-February 2012 for admissions in the academic year 2012-13.

### Counseling sessions for IIT Delhi freshers

After the suicide of 19 years old student Dinesh Ahlawat, the management at Indian Institute of Technology (IIT), Delhi, is leaving no stone unturned to bring back the campus ambience. Students have been counseled and senior students are also assisting in the process in various sessions. A strong system of student counselors is helping out to provide support to first year students within the first 15 days of joining.

### Handover answer sheets of students under RTI: Supreme Court

Supreme Court has permitted the disclosure of answer sheets of any examination conducted by any agency in India under the Right to Information Act (RTI). The bench of justices made it clear that the bodies conducting examinations could not retain the answer sheets. The bench of justices also upheld a Calcutta High Court order, permitting students to inspect and photocopy their answer sheets in any educational or professional examination.

## Tuesday, August 16, 2011

### Prime Minister's Speech on India's Independence Day 2011

Read the Indian President's Speech Here

### IIMs CAT to test knowledge too, not just aptitude

The CAT format will be changed to test the candidate's knowledge too and will not just limit on aptitude. In the new-format test, students will get 140 minutes to answer 60 questions spread equally over two sections, down from the earlier three. Candidates cannot move on to the next section till 70 minutes are over, unlike last year, when they had 135 minutes to attempt the same number of questions without any section-wise time restriction. The section-wise time allocation will end race against time in the exam which always puts speed at a premium.

### Tamil Nadu has reported a marginal fall in the number of admissions

Tamil Nadu has reported a marginal fall in the number of admissions in technical courses— down from 112,000 last year to 104,000 in 2011 — even though the number of seats on offer has gone up by nearly 30,000. This is an evidence that students have become choosy and they are looking for institutions and courses offering better placements and facilities. The quality of Faculty and infrastructure are also among the many reasons causing this drop out.

## Sunday, August 14, 2011

### A Numerical Problem from Projectile Motion

A short is fired from a gun on the top of a hill 90m high with velocity 80m/s at an angle of 30 degree with the horizontal. Find the horizontal distance between the vertical line through the gun and the ponit where the shot strikes the ground? (Shilpa asked this question)

Take Sy= -90m

ay= -g=-9.8m/s2

uy= u sin(30) =80 x 0.5 = 40m/s

Substitute in the eqn

s = ut + 0.5 at2

and find t

The horizontal distance Rx = horizontal velocity x time =  U cos (30) x time

Substitute for u and t and get the answer

## Friday, August 12, 2011

### JUNO -NASA's mission to Jupiter launched

NASA launched JUNO as part of its Jupiter mission.
Juno will study Jupiter's composition, gravity and magnetic fields as well as attempt to answer how the planet formed and whether it has a rocky core.

The \$1.1bn Juno probe was launched today from Cape Canaveral, Florida, at 12.25 p.m. local time and will now begin a five-year journey to the planet.

### Does transformer have any resistance?other than ohmic resistance?

Does transformer have any resistance,other than ohmic resistance? (Ajay Asked)

Waiting for response from students and visitors

## Thursday, August 11, 2011

### Two atoms entangled using microwaves for the first time

Physicists at the National Institute of Standards and Technology have for the first time linked the quantum properties of two separated ions (electrically charged atoms) by manipulating them with microwaves instead of the usual laser beams, suggesting it may be possible to replace an exotic room-sized quantum computing "laser park" with miniaturized, commercial microwave technology similar to that used in smart phones. Read More

## Wednesday, August 10, 2011

Download the free suppliment to Physics WOrld online at the following link. This supplement focusses on the challenges in Vacuum and the solutions.

• Vacuum Technology : Basis for innovation and Process Optimization

• Testing Equipment for space

and more articles related to vacuum.

## Monday, August 8, 2011

### Due to High Cutoffs, Application for US Student Visas Increased by 20%

Due to high cut-offs in top colleges in India, student visa applications for US have increased by as much as 20%. It is obvious that students have started looking west to do the course of their choice, instead of settling for second-best or third-best courses in their list.

### DUSU Elections to be held on Sept. 9

The Delhi University has announced the schedule for Delhi University Students’ Union elections. The elections will be held on September 9, however, the date of declaration of result has not been announced. The last date for receipt of nomination papers will be August 29. The papers will be scrutinized after 3 pm and the list will be published around 5 pm. The venue, date and time for announcement of election result have not been decided yet.

### Telephone Hotline and Virtual Information Hub for Students Soon

In the wake of the constant raids and charges of fraud on various universities, U.S Embassy has said that Indian students must choose the college with caution. The suggestion was given after authorities in Annandale, Virginia, a suburb of Washington, raided on charges of fraud the offices of a university with 90 percent of the 2,400 students from India and a majority of them from Andhra Pradesh. Therefore to prevent from falling into such traps U.S authorities are planning to set up a Virtual Information Hub and Telephone Hotline for students.

### Four Bhopal students Qualify in the National Talent Search Examination

Four students from the Bhopal made it through in the National Talent Search examination organised by the NCERT (National Council of Education, Research and Training). 33 students cleared the exam from the state. Bhopal's Chinmay Talegavkar, Kritika Upadhyay, Charles Rajan and Parth Singh were selected in the exam. Rajan came second in the state and earned the 49th rank all over India. The exams are given by school students studying in class VIII.

### New Fraud Cases Comes to Light in AIIMS Entrance Exam

The Central Bureau of Investigation (CBI) has registered four new cases with regards to AIIMS (All-India Institute of Medical Sciences) Entrance Exam manipulation for admission to various courses. The first case is related with rigging of results of the all-India post-graduation entrance examination conducted in January 2010. According to the agency, optical mark recognition answer sheets of seven candidates were interpolated in that examination. As a result, all the seven candidates got through in different colleges.

### Five-Year Term Proposed for BDS Course

In fresh developments, The Dental Council of India (DCI) has made a proposal to the Central government to increase the term of the BDS (Bachelor of Dental Science) course from four years to five. This will include a year of internship, on the lines of MBBS. The information was given by President of DCI Dr. Dibyendu Mazumdar.

### BA Sociology Answer Sheets Vanish from Delhi University

Shock waves went through Delhi University's Janki Devi Memorial College, after the examination department of the university misplaced 20 answer scripts, belonging to the students of BA (hons) Sociology. The 20 students, who had taken the second year exams, were informed by DU that the answer scripts of the paper, ‘Sociology of Contemporary India,' had been misplaced and in order to be marked, students were required to re-take the exam.

### Variation of Time with altitude

Time shown by a clock at a height more than that of the mount everest will be ahead of the time shown by the clock at ground level? Or it will be same? Or there will be a difference but very small.?

If it is a pendulum clock, the time period will vary with altitude. As the time period of oscillation depends on acceleration due to gravity and the value of g decreases with altitude.

## Friday, August 5, 2011

### How is doping related with depletion layer of diode?

"How is doping related with depletion layer of diode and how it increases the conductivity of semiconductor" - Nilotpal Arjun Asks

Answer: As doping is increased, the width of depletion layer decreases as there will be enough electrons and holes available in a narrow region. The conductivity increases

## Wednesday, August 3, 2011

### Selected Physics questions for SA1 for Class 9

1. Velocity time graph of a body is shown in the diagram below.

What conclusion can be drawn about the velocity of the body from the graph?

2. The value of G on earth's surface is 6.67 x 10 -11 Nm2/kg2. What is its value on the surface of moon?

3. A person weighs 600N on the surface of earth. Find his weight and mass on the surface of earth. Take g = 10 m/s2

4. Derive the relation between force and acceleration. Define the unit of force.

### Physics Portions for SA1 Class IX CBSE

Motion, force and work

Motion : Distance and displacement, velocity; uniform and non-uniform motion along a straight line; acceleration, distance-time and velocity-time graphs for uniform motion and uniformly accelerated motion, equations of motion by

graphical method; elementary idea of uniform circular motion.

Force and Newton's laws: Force and motion, Newton's laws of motion, inertia of a body, inertia and mass, momentum, force and acceleration. Elementary idea of conservation of momentum, action and reaction forces.

Gravitation : Gravitation; universal law of gravitation, force of gravitation of the earth (gravity), acceleration due to gravity; mass and weight; free fall

Practicals

1. To determine the melting point of ice and the boiling point of water.

2. To study the third law of motion using two spring balances.

## Tuesday, August 2, 2011

### IGNOU Launches Courses for Nurses, Teachers, Parents

The Indira Gandhi National Open University (IGNOU) on 27th July 2011 launched three courses focusing on raising more educational opportunities for Medical, Nursing and Teaching personnel, an official said. According to a varsity official, the two certificate courses and one diploma programme will be offered by the university through distance education mode. The Adolescent Health and Counselling course will prepare teachers and parents to help adolescents to develop a healthy lifestyle and handle stress, he said.

### Apex court rules in favour of 5 Entrance Tests

PGDM institutions across the country are free to accept CAT, XAT, MAT, ATMA and JMET scores and even conduct their own GD PI, the Supreme Court ruled on 26th July 2011. An interim order to the effect which was passed on March 17, 2011 has been extended till the next academic year – 2012-2013. In the circular, the AICTE had sought for its respective state machineries to take control of the fees and curriculum of all AICTE-approved PGDM courses. While passing the interim order, Supreme Court (of March 17, 2011) had asked the AICTE to file a counter affidavit within 10 days.

### Sports Authority of India to Recruit Scientific Officers

Gearing up for the London Olympic Games, Sports Authority of India (SAI) has decided to recruit scientific officers to posts, which have been lying vacant for more than 19 years. The Sports Authority has a sanctioned strength of 25 junior scientific officers; however 19 posts are still lying vacant. A post each of scientific officer and senior scientific officer too is vacant. The recruitment process will be completed in the next 4-5 months.

### High Cut-Off Marks is Due to Demand-Supply Mismatch: Sibal

HRD Minister Kapil Sibal has said that the 100 per cent cut-off marks this year, for admission in certain streams in Delhi University is due to the demand-supply dynamics and a solution lies in expanding the educational infrastructure. Mr. Sibal said that the demand is far greater than supply and thus the cut-off is bound to be high. The HRD minister also asked that if there is one Sri Ram College of Commerce and everybody wants admission there, what solution can be given to students.

### CAT 2011 Highlights

Indian Institutes of Management (IIMs) have announced the Common Admission Test 2011 (CAT 2011) highlights. Prometric, a provider of market-leading test development and test delivery solutions is IIMs' partner in developing and delivering CAT 2011. The first section will consist of Quantitative Ability & Data Interpretation. Whereas, the second section will focus on Verbal Ability & Logical Reasoning. These two sections will be implemented sequentially with separate time limits.

The examination will be 140 minutes. Within each section, candidates will have 70 minutes to answer 30 questions which will have an on-screen countdown timer.

### Electric Current and Conductor

I have a question based on current as we all know that current flows due to the movement of electrons in substance. Now suppose a conductor having electrons randomly in motion so we study that current flow due to flow of electrons in a substance so this have to produce electric current. Then why a substance (conductor) doesn't make current; but when connected to a socket it give current..
Thanks

Sachin

## Monday, August 1, 2011

### A few problems from Current electricity

1. A carbon resistor of 47 k ohms is to be marked in the colour code . Write the sequence of colours .

2. A toaster produces more heat than a light bulb when connected in parallel to the 220 V mains . Which of the two has greater resistance ?
3. A 0- 50 amp ammeter has been guaranteed accuracy of 2% of a full reading scale . The limiting percentage error when the meter is measuring 10 ampere is …… ?

[Posted by  George]