## Wednesday, February 29, 2012

### Calculating charge on a body with excess of electrons

How would I calculate the charge on a small sphere with an excess of 5.0 x 10 14 electrons?

We know that charge on an electron is (-) 1.6 x 10-19 C

If the sphere has 5.0 x 10 14 electrons in excess then the body has a net negative charge and is given by q = ne

Charge on the sphere = 5.0 x 10 14 x (-) 1.6 x 10 -19 = 8 x 10 -5 C

## Tuesday, February 28, 2012

### CLASS 11 PHYSICS - PRACTICE PAPER FOR ANNUAL EXAM

SESSION ENDING EXAMINATION

CLASS XI

PHYSICS

M.MARKS:70

TIME 3 HRS

General Instructions:

• All questions are compulsary

• There are 30 questions in total. Questions 1 to 8 carry 1 mark each. Questions 9 to 18 carry 2 marks each. Questions 19 to 27 carry 3 marks each and questions 28 to 30 carry 5 marks each.

• Use of calculators is not permitted.

******Choices are avoided as this is a question paper meant for practice ***********

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

### Some important questions for class 12

• A charged particle enters a magnetic field region in a direction perpendicular to the direction of the magnetic field. Will there be any change in the particle’s (i) kinetic energy (ii) momentum

Ans:

In the presence of a magnetic field, the particle experiences a magnetic force in the direction perpendicular to the directions of the moving particle and the magnetic field. The magnitude of
velocity of the particle remains the same while its direction changes. Hence, kinetic energy of the particle will not change while its momentum will change

• Write the undesirable effects and their causes during signal transmissions.

Solution:

There are four undesirable effects during signal transmission. The following table lists these effects with their respective causes.

1. Attenuation   Decrease in signal strength due to energy loss

2. Distortion     Due to wave form perturbation

3. Interference    Due to contamination of extraneous signals
4. Noise      Due to random electrical signals

# What problems do you face in implementing CCE?

CCE Stands for Continuous and Comprehensive Evaluation.

Many complain that there are various problems in proper implementation of CCE.

Let's discuss and find problems and the possible remedies.

Teachers, students, educational administrators and parents are requested to participate and post their opinions, details of the problems and possible remedies.

A few problems identified are posted below.

• Lack of time: The teachers get around 35 to 409 minutes for a class and it is insufficient to meet the requirements of CCE

• Lack of infrastructure

• Student Pupil ratio

## Sunday, February 19, 2012

### Why roads at mountains are serpentine?

Why roads at mountains are serpentine?

This is to reduce the effort. It follows the principle of a screw which in turn is a modified form of inclined plane.

See the pic on left. Though we have to do a greater work (against friction) the average force or effort is less and the risk or danger of accident is less.

## Tuesday, February 7, 2012

### PhysicsFans – A Website for Physics Lovers

We are happy to announce a new website – www.physicsfans.com dedicated for all those who love Physics.

It aims at bringing together the like minded, the people around who like Physics. There is no compulsion that the members be studying Physics; if you are fascinated by the wonders of Physics, you can join it.

The website will publish latest discoveries and inventions as well as the developments in the scientific world. www.PhysicsFans.com is expected to grow as an online place for getting the prime information for students and public as long as it is related to Physics in some way or the other.

The contents of the site are accessible without a membership. But if you want to get benefited from the Physics Online Community and want to publish your own blogs and participate in discussions you must be a member.

Social networking is also being enabled at the site for members so that they can interact online through messages and chat.

there are sections on

1. Emerging Theories in Physics
2. Latest Discoveries in Physics
3. Physics News
4. Physics Videos
5. Physics Jokes
6. Biographies of Great Physicists
7. Book Review Section
8. Polls

……………………….. and more.

The idea began with a group in Facebook - https://www.facebook.com/groups/askphysics/, which was started as a group for all those who love Physics. The huge response received from the members of the group resulted in this website where the members will get greater freedom to express themselves freely as they can write at length, post images, videos, post to forums and more.

The site is developing some ground rules for members.

1. Memberships are activated only after verification of identity.
2. Members are prohibited from any kind of spamming or promotion of violence or pornography.
3. The members must be active, by visiting the site quite often and participating in discussions and posting blogs etc. Members inactive for more that one month will be black listed and will be deleted if no response obtained on contacting/warning

If you like the concept and like Physics, you can join the move at http://www.physicsfans.com/user/register

## Thursday, February 2, 2012

### CBSE 2012

CBSE (Central Board of Secondary Education) has started online counselling for students and parents for Board Exams.

The first phase of this pre-exam counselling will start from Wednesday Feb 1,2012 and will continue until April 16 2012, for those appearing for board examinations this year.

Toll Free Number 1800-180-3456 is allotted to talk with experts. Anyone can call between 8 a.m. to midnight from Feb 1 to April 16, 2012.

This year, approximately 67 experts, including principals, trained counsellors from CBSE affiliated government and private schools and few psychologists are participating in tele-counselling.

## Wednesday, February 1, 2012

### How was your Physics Practical Examination?

Hello students!

It's the time of AISSCE Practical Examination.

How was your Physics Practical Examination and Viva?

Which questions were asked to you?

Which were the experiments and activities you were asked to perform?

How farely did you do it?

Share your experience here as comments to this post. Your responses will be a boon for the others.

You can post the questions you were asked during Viva so that others can find the answers to them and learn for the Viva during their turn.