## Work and its types

Work: In physics work is said to be done when a force acting on a body displaces it through a certain distance. The work by a constant force is measured by the dot product of force will displacement.

i.e. W = F.S or W = F S cosq …(1)

where F = force and S = displacement

And q = angle between F and S.

From eq.(1), we have W=F cosq x S. Therefore, work done by a force is equal to the product of the component of the force in the direction of displacement of the body and the distance through which the body moves. Continue reading “Work and its types”

## Poynting theorem and derivation

Poynting Theorem

Statement. This theorem states that the cross product of electric field vector, E and magnetic field vector, H at any point is a measure of the rate of flow of electromagnetic energy per unit area at that point, that is

P = E x H

Here P → Poynting vector and it is named after its discoverer, J.H. Poynting. The direction of P is perpendicular to E and H and in the direction of vector E x H Continue reading “Poynting theorem and derivation”

## Applications of optical fibers

Last time I have discussed the various losses and their reasons in optical fibers. Toady we will discuss the various applications of fibers.

Optical Fibre Communication System

Optical fibers are mainly used in communication systems due to  rapidly increasing demands for telephone communications throughout the world, multiconductor copper cables have become not only very expensive but also an inefficient way to meet these information requirements. Continue reading “Applications of optical fibers”

## Reasons for losses in optical fibers

When a signal passes through an optical fiber, then signal intensity losses may occur. This is called attenuation. There are many reasons for losses in optical fibers.

This loss is generally expressed in decibel (dB) and is defined as the ratio of injected optical power Pi into the fibre to the received optical power P0 from the fibre, i.e., attenuation  = 10/L Log (Pi) / (P0)  dB / km where L is the length of the fibre in km. Continue reading “Reasons for losses in optical fibers”

## Best journals of Energy of 2011

Now a days lots of result is done in the field of energy science. Energy science may include biodiesel, solar energy and other many energy resources. I have compiled the list of best or top 20 journals of energy science. If you are researcher in this field you can search these journals and try to contribute their articles for the same. The ranking is done on the basis of impact factor of journals. Continue reading “Best journals of Energy of 2011”

## Earth and Cosmological Events

Cosmology is a science related with the space. It can be divided into two parts. one is the physical cosmology and other is the modern cosmology. Physical cosmology deals with the origin, evolution and future of the universe. There are various cosmological events which can affect the earth. The events like speed bump, black hole, asteroids ( a large one) and supernova can affect the life on earth.

Supernova is a stellar explosion, can result in a burst of explosion and can outshine the entire galaxy. During a small interval supernova supernova is expected to radiate a large amount of energy which is equal to energy radiated by the sun in his whole life.

Literally black hole means where gravity prevents anything to escape even the light.  It is called black because it reflects nothing.

This cosmological events can definitely affect the earth. If you know more events, then please share with us.