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Senin, 07 Maret 2011

Rangkaian Listrik


Pengenalan Listrik dan Rangkaian Listrik

Electricity Tutorial

This tutorial is a brief introduction to the concepts of charge, voltage, and current. This tutorial is not as long and tedious as a college textbook, yet it contains more information than students are likely to find in an elementary schoolbook.

The Atom

A drawing of an atomOn the left is a conceptual drawing of an atom. Atoms are the building blocks of matter. Everything is made of atoms, from rocks, to trees, to stars, to even yourself. An atom consists of a tightly packed nucleus containing one or more protons (colored red in the picture), and usually an equal number of neutrons (gray). Electrons (blue) surround the nucleus, forming an electron cloud. The number of electrons in an electrically stable atom is always equal to the number of protons in the nucleus.


Electric Charge

Opposite charges attract. Like charges repel. A curious thing happens between protons and electrons: a proton and an electron are always attracted to one another, while a proton will repel other protons, and an electron will repel other electrons. This behavior is caused by something called the electric force. Protons are said to have a positive electric charge, while electrons have a negative electric charge. Two objects with the same type of charge push away from each other, while two objects with opposite charges attract to each other. Since a proton and an electron have opposite electric charges, they are attracted to each other. Two protons, however, move away from each other because of their equal electric charges. The same is true of two electrons, which push away from each other because of their equal negative charges.

Electric Balance

Electric balance Most matter contains an equal number of protons and electrons. The negative electrons balance out the positive protons, and the matter has no overall electrical charge. The word overall is important, since the charges are still there, bouncing around inside the matter. Electrical charges are everywhere, but we just can't sense them because they are in balance. In fact, if you take chemistry, you'll learn that the electric force is the very thing that holds matter together. The next time you pick something up, just think that whatever you are holding is literally filled with electric charge. This is an important fact that many people miss when they study electricity.

Static Electricity

A drawing of two ions Let's say we steal an electron from one atom and give the electron to another atom. One atom will have an overall positive charge and the other will have an overall negative charge. When this happens, the two atoms are called ions. Because ions have an overall electric charge, they can interact with other charged objects. Since like charges repel and opposite charges attract, a positive ion will attract negatively charged objects, such as electrons or other ions, and will repel positively charged objects. A negatively charged ion will attract positively charged objects, and will repel other negatively charged objects.
The same is true for larger objects. If you take electrons from one object and place them on another object, the first object will have an overall positive charge while the second will have an overall negative charge. Depending on the types of objects and the amount of charge involved, the electric force may be enough to cause the objects to stick together. This phenomenon is often referred to as "static electricity."
There are several ways to steal electrons from one object and give them to another. Some of the ways include chemical reactions, mechanical motion, light, and even heat. If you rub a glass rod with silk, the electrons in the glass rod will be knocked off and collected on the silk. The glass rod gains an overall positive charge, and the silk gains an overall negative charge. In a battery, chemical reactions are used to force electrons from the positive terminal and place them on the negative terminal.

Measuring Charges

The amount of overall electric charge possessed by an object is measured in coulombs. One coulomb is roughly equal to the amount of charge possessed by 6,000,000,000,000,000,000 (six billion billion) electrons. While this may seem like a huge number at first, it is not really that much, since electrons are so tiny. Just to give you an idea, one coulomb is roughly the amount of charge that flows through a 12-watt automotive light bulb in one second.
If the amount of charge possessed by two objects and the distance between them are known, it is possible to calculate the amount of force between the objects using a formula known as Coulomb's law. This law was discovered by Charles Augustin de Coulomb in 1784, and states that the force between two charged objects varies directly as the charges of the objects and inversely as the square of the distance between them. Coulomb's law is given below in formula form:
F=kqq'/r^2
F is the force, in Newtons.
q and q' are the charges of the two objects, in coulombs.
r is the distance between the objects, in meters.
k is a constant equal to 8.98755×109 N m2 C-2

Voltage

Whenever electrons are taken from one object and placed on another object, causing an imbalance of charge, we say that a voltage exists. That is what somebody means when they say that something has so many volts of electricity. They are describing a difference of charge in two different places. A standard AA battery has a difference of 1.5 volts between its positive and negative terminal, while car battery has a difference of 12 volts between its two terminals, and the everyday type of static electricity that causes things to stick together and occasionally gives you a jolt when you touch a metal object is usually measured in thousands of volts.
Two parallel charged plates.Another way to understand voltage is to think of an "electric field." Imagine a plate with positive charge next to a plate with negative charge. If I place a positive charge between these plates, the plates’ electric field will attract the charge to the negative side. Imagine that I place a 1 coulomb positive charge next to the negative plate, and then pull it towards the positive plate. Because the electric field creates a force in the opposite direction, moving the charge requires energy. The amount of energy depends on the distance between the plates and the strength of the electric field created by the plates. We call this energy the electric field’s "voltage." One volt is the amount of energy in joules required to move 1 coulomb of charge through an electric field. Mathematically, 1Volt = 1Joule / 1Coulomb.
Volts are useful, because they neatly describe the size and strength of any electric field. Visualizing the electric field between two simple plates is easy, but visualizing the field in a complicated circuit with batteries, motors, light bulbs, and switches is very difficult. Voltage simplifies circuits like these by describing the entire electric field with a single number.

Electric Current

Current in motion animaiton. The word current comes from the Latin word currere, which means to run or to flow. An electric current is nothing more than the flow of electric charges. Electric charges can only flow through certain materials, called conductors. Although the electrons in most materials are confined to fixed orbits, some materials, including most metals, have many loose electrons which are free to wander around through the material. Materials with this property act as conductors. When a conductor is placed between two charged objects, these loose electrons are pushed away by the negatively charged object and are sucked into the positively charged object. The result is that there is a flow of charge, called a current, and the two object's charges become balanced. The amount of current flowing through a conductor at any given time in measured in amperes, or amps for short. When you read that something uses so many amps, what you are being told is the amount of current flowing through the device. One ampere is equal to the flow of one coulomb of charge in one second.

Batteries and Current

Batteries and current In the previous paragraph, we looked at how current flows from one charged object to another, canceling out the charges of the two objects. Once the charges were canceled, the current stopped. If current were always this short-lived, it would be very impractical. Imagine a flashlight that only lasted a fraction of a second before needing to be recharged! While current does tend to cancel out charges on two objects and then stop flowing, if a charge can be placed on the objects faster than the current can drain the charge, it is possible to keep a current flowing indefinitely. That is what happens in a battery. Chemical reactions within the battery pump electrons from the positive terminal to the negative terminal faster than the device connected to the battery can drain them. The battery will continue to supply as much current as the device requires until the chemicals within the battery are used up, at which point the battery is dead and must be replaced.

Resistance

All conductors offer some degree of resistance to the flow of electric current. What happens is this: As electrons travel through the conductor, they bump into atoms, losing some of their movement in jiggling the atom. The result is that the current flowing through the conductor is slowed down, and the conductor is heated. The amount that a given conductor resists the flow of electric current is measured in ohms.

Power

Whenever current flows, work is done. A conductor may be heated, a motor may be spun, a bulb might give off light, or some other form of energy may be released. There is a simple law that tells exactly how much work may be done by a flowing current. The amount of work done is equal to the voltage of the supply times the current flowing through the wire. This law is expressed in the form P=IV, where P is the power in watts, I is the current in amps, and V is the voltage in volts. For example, if we find that a light bulb draws half of an amp at 120 volts, we simply multiply the 120 volts by half an amp to find that the bulb draws 60 watts of power.

Ohm's Law

V=IR Let's say you have a six volt battery and you need to draw two amps of current. What resistance should you make the conductor? Or let's say you have a three volt power supply and a thousand ohm resistor. How much current would flow through the resistor if you were to connect the resistor to the power supply? In order to find the answers to these questions, all you need to do is to use a simple mathematical formula called ohm's law. Ohm's law states that the amount of current flowing through a conductor times the resistance of the conductor is equal to voltage of the power supply. This law is often expressed in the form V=IR, where V is the voltage measured in volts, I is the current measured in amps, and R is the resistance measured in ohms.

***sumber : internet tentang ilmu listrik 

doraemon

File:Doraemon volume 1 cover.jpg

Gunung Meletus

Gunung berapi atau gunung api secara umum adalah istilah yang dapat didefinisikan sebagai suatu sistem saluran fluida panas (batuan dalam wujud cair atau lava) yang memanjang dari kedalaman sekitar 10 km di bawah permukaan bumi sampai ke permukaan bumi, termasuk endapan hasil akumulasi material yang dikeluarkan pada saat meletus.
Lebih lanjut, istilah gunung api ini juga dipakai untuk menamai fenomena pembentukan ice volcanoes atau gunung api es dan mud volcanoes atau gunung api lumpur. Gunung api es biasa terjadi di daerah yang mempunyai musim dingin bersalju, sedangkan gunung api lumpur dapat kita lihat di daerah Kuwu, Grobogan, Jawa Tengah yang populer sebagai Bledug Kuwu.
Gunung berapi terdapat di seluruh dunia, tetapi lokasi gunung berapi yang paling dikenali adalah gunung berapi yang berada di sepanjang busur Cincin Api Pasifik (Pacific Ring of Fire). Busur Cincin Api Pasifik merupakan garis bergeseknya antara dua lempengan tektonik.
Gunung berapi terdapat dalam beberapa bentuk sepanjang masa hidupnya. Gunung berapi yang aktif mungkin berubah menjadi separuh aktif, istirahat, sebelum akhirnya menjadi tidak aktif atau mati. Bagaimanapun gunung berapi mampu istirahat dalam waktu 610 tahun sebelum berubah menjadi aktif kembali. Oleh itu, sulit untuk menentukan keadaan sebenarnya daripada suatu gunung berapi itu, apakah gunung berapi itu berada dalam keadaan istirahat atau telah mati.
Apabila gunung berapi meletus, magma yang terkandung di dalam kamar magmar di bawah gunung berapi meletus keluar sebagai lahar atau lava. Selain daripada aliran lava, kehancuran oleh gunung berapi disebabkan melalui berbagai cara seperti berikut:
  • Aliran lava.                                                 
  • Letusan gunung berapi.
  • Aliran lumpur.                                              
  • Abu.                                                         
  • Kebakaran hutan.
  • Gas beracun.
  • Gelombang tsunami.
  • Gempa bumi.                      

Tanda-tanda Kiamat

Tanda-tanda besar

  • Hijaunya bumi arafah.
  • Lahirnya ramai anak anak zina dari perkahwinan tidak sah atau perceraian tidak diluluskan mahkamah.
  • Keluar sejenis binatang dari perut bumi yang digelar Dabbatul Ardhi.
  • Keluar asap tebal dibumi hijaz.
  • Munculnya nabi palsu yang ke 40.
  • Diangkat al-Quran dan Ilmu addin dari manusia.
  • Berlaku perang besar dikawasan kaukasus
  • Runtuhnya Ka'abah diserang oleh orang habshah
  • 3 kali gempa bumi
  • Keluarnya suku Yakjuj dan Makjuj.
  • Bermulalah kekuasaan Dajjal.
  • Munculnya Imam Mahdi.
  • Turunnya Nabi Isa a.s.dan azannya mematikan yakjuj makjuj.
  • Matahari terbit dari ufuk barat.
  • Terdengar tiupan sangkakala pertama

Tanda-tanda kecil

Didapati kini bahawa seluruh tanda-tanda kecil telah muncul dan terbukti seperti yang dinyatakan dalam hadis. Kebanyakan hadis-hadis ini dapat ditemukan di dalam Sahih Muslim, Sahih Bukhari dan Riwayat Tarmizi.
  • Penaklukan Baitulmuqaddis
Dari Auf b. Malik r.a., katanya, "Rasulullah s. a. w. telah bersabda:"Aku menghitung enam perkara menjelang hari kiamat." Baginda menyebutkan salah satu di antaranya, iaitu penaklukan Baitulmuqaddis." - Sahih Bukhari[1]
"Dan tinggallah manusia-manusia yang buruk, yang seenaknya melakukan persetubuhan seperti himar (keldai). Maka pada zaman mereka inilah kiamat akan datang." - Sahih Muslim
  • Pemimpin yang terdiri dari orang yang jahil dan fasik[perlu rujukan]
Pada akhir zaman akan terjadi tanah runtuh, rusuhan dan perubahan muka."Ada yang bertanya kepada Rasulullah; "Wahai Rasulullah bila hal ini terjadi?" Baginda menjawab; "Apabila telah bermaharajalela bunyi-bunyian (muzik) dan penyanyi-penyanyi wanita" - Ibnu Majah
Di antara tanda-tanda telah dekatnya kiamat ialah manusia bermegah-megahan dalam mendirikan masjid" - Riwayat Nasai.
  • Munculnya kekejian, memutuskan kerabat dan hubungan dengan tetangga tidak baik[perlu rujukan]
Tidak akan datang kiamat sehingga banyak perbuatan dan perkataan keji, memutuskan hubungan silaturahim dan sikap yang buruk dalam tetangga." - Riwayat Ahmad dan Hakim
  • Ramai orang menuntut ilmu kerana pangkat dan kedudukan[perlu rujukan]
Tidak akan datang hari kiamat sehingga Allah mengambil orang-orang yang baik dan ahli agama dimuka bumi, maka tiada yang tinggal padanya kecuali orang-orang yang hina dan buruk yang tidak mengetahui yang makruf dan tidak mengingkari kemungkaran - Riwayat Ahmad
Di antara tanda-tanda semakin dekatnya kiamat ialah dunia akan dikuasai oleh Luka' bin Luka'(orang yang bodoh dan hina). Maka orang yang paling baik ketika itu ialah orang yang beriman yang diapit oleh dua orang mulia" - Riwayat Thabrani
  • Mengucapkan salam kepada orang yang dikenalnya sahaja[perlu rujukan]
"Sesungguhnya di antara tanda-tanda telah dekatnya hari kiamat ialah manusia tidak mahu mengucapkan salam kepada orang lain kecuali yang dikenalnya saja." - Riwayat Ahmad
  • Banyak wanita yang berpakaian tetapi hakikatnya telanjang [perlu rujukan]
Diriwayatkan dari Abu Hurairah r.a.
"Di antara tanda-tanda telah dekatnya hari kiamat ialah akan muncul pakaian-pakaian wanita dan apabila mereka memakainya keadaannya seperti telanjang."
Di antara tanda-tanda telah dekatnya hari kiamat ialah menggelembung (membesarnya) bulan sabit." - Riwayat Thabrani
  • Banyak dusta dan tidak tepat dalam menyampaikan berita
Pada akhir zaman akan muncul pembohong-pembohong besar yang datang kepadamu dengan membawa berita-berita yang belum pernah kamu dengar dan belum pernah didengar oleh bapa-bapa kamu sebelumnya, kerana itu jauhkanlah dirimu dari mereka agar mereka tidak menyesatkanmu dan memfitnahmu" - Sahih Muslim
  • Banyak saksi palsu dan menyimpan kesaksian yang benar
Sesungguhnya sebelum datangnya hari kiamat akan banyak kesaksian palsu dan disembunyikan kesaksian yang benar" - Riwayat Ahmad
  • Negara Arab menjadi padang rumput dan sungai
Tidak akan datang hari kiamat sehingga negeri Arab kembali menjadi padang rumput dan sungai-sungai." - Sahih Muslim
  • Banyaknya sifat bohong dan ia menjadi perkata biasa[perlu rujukan]
  • Jarak-jarak antara pasar menjadi dekat (menunjukkan banyaknya kegiatan perdagangan)[perlu rujukan]
Banyaknya sifat bohong, pendeknya waktu, dekatnya jarak-jarak antara pasar-pasar." - Riwayat Bukhari
  • Manusia mewarnai rambut di kepalanya dengan warna hitam supaya kelihatan muda[perlu rujukan]
Pada akhir zaman akan muncul suatu kaum yang mencelupi rambut mereka dengan warna hitam seperti 'bulu merpati' yang mereka itu tidak akan mencium bau syurga." - Sahih Abu Daud & Nasai
  • Kekayaan umum dikuasai segelintir orang tanpa kebenaran dan tanpa rasa takut, termasuk rasuah dan mengambil harta secara tersembunyi.
-hadis bawah-
  • Akan terdapat banya pengkritik, pembawa-cerita, penikam-belakang dan pengejek dalam masyarakat.
-hadis bawah-
  • Orang akan mendirikan hubungan dengan orang tak dikenali dan memutuskan hubungan dengan yang rapat dan disayangi.
-hadis bawah-
  • Orang akan melakukan homoseksual.
-hadis bawah-
  • Akan terdapat ramai anak luar nikah.
- Abdullah Ibn Mas'ood (R.A.)
  • Berkurangnya sifat amanah
-hadis bawah-
  • Terasa berat untuk menjalankan syariah (zakat dijadikan hutang)
-hadis bawah-
  • Lelaki mentaati isterinya tetapi menderhakai ibunya
-hadis bawah-
  • Lelaki berkasar dengan bapanya tetapi beramah dengan rakannya
-hadis bawah-
  • Suara manusia meninggi (menjerit dan berteriak) di masjid-masjid
-hadis bawah-
  • Pemimpin suatu kaum adalah keji dan pemimpin suatu suku adalah fasik
-hadis bawah-
  • Lelaki dihormati bukan kerana budi dan kebaikan tetapi kerana takut akan kejahatannya

Senin, 21 Februari 2011

A Lonely Road
Crossed Another
Cold State Line
Miles away
From those I Love
Purpose hard to Find

While I Recall all the World
You Spoke to me
Can't help but wish that
i Was There
back Where I'd love to be..

oh yeah..



Dear God
The Only think I ask
of you is
to hold her when
i'm not around
When I'm Much
too Far away

We all
Need the person
who Can be
True to you
But I left her when
I found Her
And Now i wish
i'd Stayed

'Cause i'm Lonely
and i'm Tired
i'm Missing You
again Oh No..

Once Again

There's Nothing
Her For Me on
The Barren Road
There's No One
Here While The
City Sleeps
and all the shops
Are closed

Can't Help but
think of the times
i've had With You
Pictures and some
Memories will have
to help me through

Oh Yeah..

Dear God
The Only think I ask
of you is
to hold her when
i'm not around
When I'm Much
too Far away

We all
Need the person
who Can be
True to you
But I left her when
I found Her
And Now i wish
i'd Stayed

'Cause i'm Lonely
and i'm Tired
i'm Missing You
again Oh No..

Once Again

Some Search,
Never Finding away
Before Love They
Waste away
I found You
Something told Me
to stay

I gave in,
to selfish ways
and how i Miss
Some One to Hold
When hope Begins
to Fade

A Lonely Road
Crossed Another
Cold State Line
Miles away
From those I Love
Purpose hard to Find

Dear God
The Only think I ask
of you is
to hold her when
i'm not around
When I'm Much
too Far away

We all
Need the person
who Can be
True to you
But I left her when
I found Her
And Now i wish
i'd Stayed

'Cause i'm Lonely
and i'm Tired
i'm Missing You
again Oh No..

Once Again