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# Monthly Archives: March 2012

## The total force on charge q on the vertex

Consider the charges q,q and -q placed at the vertices of an equilateral triangle. What is the force on each charge?
I actually didn’t understand the total force on charge -q at the vertex C of the equilateral triangle. How is it equal to root3Fn where n is the unit vector along the direction bisecting the angle BCA (Why?).

Thejaswini posted the question

## Why is it dangerous to stand in the upper deck of a double decker bus?

Why is it dangerous to stand in the upper deck of a double decker bus?

“a body is said to be more stable when its CENTER OF GRAVITY is kept as low as possible. In a double decker bus , the c.g. of our body is obviously at higher place than the lower deck.In addition , if we stand the c.g. goes the higher , which will lead for a great imballance to be followed by a severe fall off. Moreover,when the bus moves or jerks,in lower deck,the moment of deflecting force is tolerable . But in the upper deck,it’s tremendously high”

## What physical phenomenon is there that a black hole has a high gravity?

What physical phenomenon is there that a black holehas a high gravity?

## Heat! Heat! Heat!

A glass ball at -10 degrees C is placed in 500 ml of water at 20 degrees C. The final temp is 15 degrees C.
A. How much heat is lost by the water
B. what is the heat capacity of the water
C. How much heat is gained by the glass ball
D. What is the heat capacity of the glass ball
E. what is the ratio of the heat capacities of the water and the glass ball
F. What is the ratio of the temp changes of the water and glass ball
G. How are the answers to e and f related

## Difference between Dielectric Break Down and Corona Discharge

HOW IS CORONA DISCHARGE DIFFERENT FROM DIELECTRIC BREAKDOWN IN THE CASE OF VANDEGRAFF GENERATOR

• Corona (egrejeen.wordpress.com)

## Photon and Antiphoton

I heard that photon is its own antiparticle. If so, what is the different between these two photons

Photons also have their antiparticles, but antiphotons are photons themselves.

http://arxiv.org/abs/1009.5119

http://van.physics.illinois.edu/qa/listing.php?id=1153

http://www-3.unipv.it/fis/tamq/Anti-photon.pdf

## Conversion of Galvanometer to Ammeter problem

A galvanometer can be converted to ammeter by connecting a low resistance, called shunt in parallel with it. If a galvanometer of resistance 45 Ω is shunted by a resistance of 5 Ω what fraction of main current passes through the  Galvanometer? What is the current which flows through the shunt?

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