mythbuster experiment

Can warm water freeze faster than cold water?

Surprisingly, yes it can. Warm water can freeze faster than cold water, provided the proper conditions are in place. When it does happen, it is known as the Mpemba Effect.

To demonstrate it yourself you will need:

• two identical containers of the same size and shape
• access to cold water
• A kettle
• A freezer large enough to hold both of your containers

1. Fill each container with the same amount of water, but make sure that the initial temperature of the water in each container is slightly different - starting temperatures of 70 degrees centigrade and 30 degrees centigrade, respectively, work well. You could use water from the cold tap that has been allowed to stand at room temperature for 5 minutes and water that has been boiled in the kettle and allowed to cool for 3-5 minutes.

2. Put both containers in the freezer.

3. As the water in the containers cools, you will find that the container with the warmer water (70 degrees) will freeze faster than the container with the cooler water (at 30 degrees).

This defies immediate logic and even scientists are not in agreement about exactly how it happens. The main factors that are broadly agreed on are that freezing the hotter water affects its scientific properties. Some of it evaporates so there is less to freeze, the way heat moves through it changes, the gases in it change, it affects its surroundings in the freezer and also experiences a phenomenon called supercooling, which means that it can freeze at a slightly higher temperature than colder water.

For such an everyday substance, water is surprisingly complex and it doesn't always behave as expected. But at least we can prove one myth about it is true!

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Ngah aku boring2 kt umah, aku telah mempelajari sesuatu yg berfaedah iaitu kotak rubik..hehe..boring yg teramat sgt smpai aku merajinkan diri aku mempelajari cara menyelesaikan kotak rubik..

hehe..ni le kotak rubik 2

So..first step adalah menyelesaikan muka pertama..pusing nye pusing jd le cmni

selesaikan muka pertama dlu ye jd cmni

Setelah jd cm di atas, kita selesaikan lapisan di dibawah muka pertama..pusing2 kan lg smpai le jd cmni..

wt lk lapisan pertama bawah muka yg dh sip 2..jd le cmni ek

Dh siap cmni..wt lk lapisan kedua bawah muka yg dh siap 2..pusing lg dan pusing lg smpai jd cmni..

hehe..lapisan kedua lk dh siap setelah dipusing2

At last..setelah penat memusingkan kotak rubik ni..ia akan menjadi seperti ini..makne nye stage terakhir sebelum kotak rubik ini siap

ini adalah stage terakhir sebelum kotakini siap

Dan ahkir sekali ni le kotak rubik yg dh siap..hehe..sebelum ni aku dpt wt 1 muka je..pstu aku biar kn je r..hehe..

dh siap pn..hehe..pndai x aku..haha..

don't know what it is...

sebenarnye aku pn xtau ape makne semua nye ni..tapi aku ngok cm interesting je permainan ni..so aku post je le ek..

•A: hot

•B: loves people and sex

•C: good kisser

•D: a very good galfren or boyfriend anyone ever had

•E: has gorgeous eyes

•F: loves people wild and crazy

•G: very outgoing

•H: stick to one

•I: is really sweet & romantic

•J: is very sexual

•K: crazy

•L: is a very good kisser

•M: Makes dating fun

•N: is a very good kisser too!

•O: has one of the best personalities ever

•P: popular with all types of people

•Q: a hypocrite

•R: funny

•S: makes people laugh

•T: a smile to die for

•U: is loved by everyone

•V: not judgmental

•W: very broad minded

•X: never let people tell you what to do

•Y: is loved by everyone

•Z: can be funny and dumb at times

so ape characteristic korg bagi setiap huruf nme korg kn..hehe..try it..hope you'll enjoy it

have fun!

klo nama aku..ia akan jd seperti ini:

ISZAM

I: is really sweet & romantic
S: makes people laugh
Z: can be funny and dumb at times
A: hot
M: Makes dating fun

hehe..untuk seronok bermain ok le..tp klo jgn le percaya ngat benda2 cmni..hehe..

aku post pn tuk sesuka je..hehe..enjoy k..

bipolar junction transistor (BJT)

A bipolar junction transistor (BJT) is a type of transistor. It is a three-terminal device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons and holes.

Although a small part of the transistor current is due to the flow of majority carriers, most of the transistor current is due to the flow of minority carriers and so BJTs are classified as 'minority-carrier' devices.

An NPN transistor can be considered as two diodes with a shared anode region. In typical operation

• the emitter–base junction is forward biased
• the base–collector junction is reverse biased

In an NPN transistor, for example, when a positive voltage is applied to the base–emitter junction

• the equilibrium between thermally generated carriers and the repelling electric field of the depletion region becomes unbalanced
• allowing thermally excited electrons to inject into the base region
• These electrons wander (or "diffuse") through the base from the region of high concentration near the emitter towards the region of low concentration near the collector
• The electrons in the base are called minority carriers because the base is doped p-type which would make holes the majority carrier in the base.

The base region of the transistor must be made thin, so that carriers can diffuse across it in much less time than the semiconductor's minority carrier lifetime, to minimize the percentage of carriers that recombine before reaching the collector–base junction. To ensure this

• the thickness of the base is much less than the diffusion length of the electrons

The collector–base junction is reverse-biased, so little electron injection occurs from the collector to the base, but electrons that diffuse through the base towards the collector are swept into the collector by the electric field in the depletion region of the collector–base junction.

A BJT consists of three differently doped semiconductor regions

• the emitter region
• the base region
• the collector region

These regions are, respectively, pn type and p type in a PNP, and n type, p type and n type in a NPN transistor. Each semiconductor region is connected to a terminal, appropriately labeled:

• emitter (E)
• base (B)
• collector (C)

The diagram shows the schematic representation of an npn transistor connected to two voltage sources. To make the transistor conduct appreciable current (on the order of 1 mA) from C to E, V_BE must be above a minimum value sometimes referred to as the cut-in voltage. The cut-in voltage is usually about 600 mV for silicon BJTs, but can be different depending on the current level selected for the application and the type of transistor.

In the diagram, the arrows representing current point in the direction of the electric or conventional current—the flow of electrons is in the opposite direction of the arrows since electrons carry negative electric charge. The ratio of the collector current to the base current is called the DC current gain. This gain is usually quite large and is often 100 or more.

As the applied collector–base voltage (V_BC) varies, the collector–base depletion region varies in size. An increase in the collector–base voltage, for example, causes a greater reverse bias across the collector–base junction, increasing the collector–base depletion region width, and decreasing the width of the base. This variation in base width often is called the "Early effect" after its discoverer James M. Early.

Narrowing of the base width has two consequences:

• There is a lesser chance for recombination within the "smaller" base region.
• The charge gradient is increased across the base, and consequently, the current of minority carriers injected across the emitter junction increases.

Both factors increase the collector or "output" current of the transistor in response to an increase in the collector–base voltage.

In the forward active region the Early effect modifies the collector current (i_C) and the forward common emitter current gain (β_F) as given by the following equations:^{[citation needed]}

Where

• V_CB is the collector–base voltage
• V_A is the Early voltage (15 V to 150 V)
• β_F0 is forward common-emitter current gain when V_CB = 0 V

pn junction diode

do you know how actually pn junction diode work?

here i have the theory how it does..hehe..actually soalan ni ditanya masa aku g interview kt NS aritu..huhu..

In a p-n junction, without an external applied voltage, an equilibrium condition is reached in which a potential difference is formed across the junction. This potential difference is called built-in potential V_bi.
In an equilibrium PN junction (Figure 1.0), electrons near the PN interface tend to diffuse into the p region. As electrons diffuse

• they leave positively charged ions (donors) on the n region
• Similarly holes near the PN interface begin to diffuse in the n-type region leaving fixed ions (acceptors) with negative charge
• The regions nearby the PN interfaces lose their neutrality and become charged, forming the space charge region or depletion layer

Figure 1.0: A p-n junction in thermal equilibrium with zero bias voltage applied.

The electric field created by the space charge region opposes the diffusion process for both electrons and holes. There are two concurrent phenomena:

• the diffusion process that tends to generate more space charge
• and the electric field generated by the space charge that tends to counteract the diffusion.

The carrier concentration profile at equilibrium is shown in Figure 1.1 with blue and red lines. Also shown are the two counterbalancing phenomena that establish equilibrium.

A PN junction in thermal equilibrium with zero bias voltage applied. Under the junction, plots for the charge density, the electric field and the voltage are reported.

pn junction diode have 2 bias which are foward bias and reverse bias

• Forward-bias occurs when the P-type semiconductor material is connected to the positive terminal of a battery and the N-type semiconductor material is connected to the negative terminal. This reduces the width of the depletion zone.

• Connecting the P-type region to the negative terminal of the battery and the N-type region to the positive terminal, produces the reverse-bias effect. Therefore the depletion region widens