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Showing posts with label Website. Show all posts

Wednesday, 30 January 2019

January 30, 2019

Chinese new Year

                   Chinese new Year:



 . Chinese new year is a holiday that celebrates the beginning of a new year according to the chinese lunar  calender.Is is considered to be one of the most important holidays for chinese families.
. The holidayis celebrated with big family gatherings, Gift giving, Eating of the symbolic foods and display  of the festive decorations all focused on bringing good  luch for the new year and celebrating
the coming of spring.In china the lunar calender  is still used to determine traditional holidays like chinese new year.
. Since the lunar calender is based on the phases of the moon which has a shorter cycle then the sun,
chinese new year is never on the same day each year, buy typically falls some  January 21 where  between and Febrary 20.The celebration can actually last up to a month.  Here are some traditions accociated with chinese new year.

Cleaning Houses and New Cloths

. Prior to the first day of the new year it is customary for families to thoroughly clean thrie houses.
Doing this is said to clean out any bad luch from the previous year and make the house ready to accept good luck for the coming year.
. All cleaning must be finished before the new year day so there is no chance of accidentally
throwning out the good fortune of the new year.Wearing black is not allowed due to its association with  death,however,wearing red is encouraged as the colour is associated with warding off bad spirits.

Decorating The house
. Buying flowers for the home is also common place since they symbolize the coming of spring and a new beginnering.

New Year EVe Dinner
. It is typical for a chinese family to make einght to nine dishes for the new year eve
dinner because in chinese language the word einght means "Proserity" and the word nine
means "long-lasting".

Giving Good Luck Gift

. It is a traditional practise for adults to give childern little red envelopes filled
with money in order to sumbolize wealth and proserity for the coming year.
. It is also common for elders to present red packets to inmarried memebers of the family
Envelops are not to be opened until the recipent has left the home of the giver.

Honouring The Animal

. Every year is associated with one of the twelve animals of the chinese zodias.
These animals are often represented in decorations. some people believe that those
born during the year of a particular animal may have the character trailts of that
animal.

Note

. thanks for the year that passes, and reinvigorate themselves for the coming year.





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Monday, 28 January 2019

January 28, 2019

Lenz Law


In 1834 Russian PhysiclstHelnrich Lenz Found that the polarity
of induced emf always leads to an induced current that oppose
the change which induces emf.

statement:

The direction of indues current is always such as to oppose the change which causes the current.

Condition For Its Application:

we can apply Lenz law directly to closed loop because is refers to induced currents and not to induced emf.however if the loop is not closed, we imagine as if it is closed and then from the direction od induced current, we can find the polarity of induced emf.

Explanation:
                       As current carrying coll behaves as a bar magnet due to the magnetic effect of current. One face of the coll acts as the north pole while the other one as the south pole. Then by Lenz Law, if the coil is to oppose the motion of bar magnet then the face of the coil wards the magnet must become a north pole, as shown in the figure. The two north poles repel each other. By right-hand role, The induced current must be in anti-clockwise direction from the side of bar magnet.
According to Lenz Law the push of magnet is the change which produces the induced current which tends to oppose push. similarly, if we pull the magnet away from the coil, the induced current oppose the pull by creating the south pole towards the bar magnet.

Lenz law of Conservation of Energy

Let us consider the experimental arrangment in which a rod of lenth L is placed on a conducting rail as shown in figure.

Force acting on rod when it moves to ringht

when the rod moves towards ringht, emf is induced in it and induced current flows through the loop in anti-clockwise direction. Now the rod becomes a current carrying conductor moving in the magnetic field, so it experiences a force given by,
According to ringht hand role, the direction of f is opposite to v. so, it tends to stop the rod, as shown in fingure.
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