SPM Physics: Semiconductor Diode

In SPM, u must be able to describe semiconductor diode. How to describe it??

• When p-type & n-type semiconductor is joined together, a semiconductor diode is produced.
• At p-n jucntion, a depletion layer is formed when the electron from the n-type fill in the hole in the p-type.
• Connecting p-type to the +ve terminal and n-type to the -ve terminal causing the electron in the n-type to be pulled and filled in the holes across the junction. This movementof electron allow current to flow, thus the diode is forward biased.  
• When the connection is reversed i.e p-type to -ve terminal & n-type to the +ve terminal, the diode is reverse biased. Electron is pulled away from crossing the jucntion, thus no current is flowing.
• This shows that diode allow current to flow in one direction only.

Then u must appreciate the function of diode as rectifier. What is rectifier???

Diode as rectifier can convert AC current into DC current.

The process of conveting AC to DC current is known as rectification. There are two type of rectification that u need to understand in SPM. For each case u must hafal the waveform and its circuit connection. Lets analyse both of them;

1. Half wave rectification (refer to your book, then watch this!)

2. Full wave rectification (refer to your book, then watch this!)



After knowing the different waveform produce for those rectifiers..u also need to draw the waveform appear due to capacitor smoothing effect. Make sure u refer them back in your reference book.

Finally Its SPAIN!

I' m glad the World cup is over..now  i can have enough sleep :).. What also delighted me is that one of my favorate team was crowned as the champion . The way they played simply outclassed the Dutch . All their players were so calm & confidence in passing the ball. These players deseved the trophy coz they have a winning mentality.

Now the world cup is over, and its time to look forwrd for your trial & SPM preparation. For me, if u wanna score A+ in any subject, u must formulate the same winning mentality as what the SPain team did. U must be strong mentally..and always learn from your mistakes. The Spain team was beaten in a group stage, but they came back like an iron steel to reclaim their place as a favorate to win the trophy. They learned their mistakes, and always looked forward to win. In the end, they won it with flying colors. So..if u wanna really achieve an excellent SPM results..u must have this kind of positive attitude.

As usual i've observed some physics stuff being discussed among the commentators through out this word cup.If u noticed, in earlier campaign, the commentator kept saying the ball in South Africa bounced a bit higher than other places. For your info, most of the the stadium in 2010 world cup is located at a higher altitude.Thus it is observed that the ball bounce higher than usual .
Hmm...can u explain why the ball bounce higher as the altitude increase???

SPM Physics: Semiconductor

Basically,this topic wont be too difficult if u took chemistry in SPM.
As usual, u need to understand the meaning of semi conductor..

Lets start with the word 'semi' &  'conductor'..do u really understand what is conductor???Do u have any idea the word 'semi' is?? If u dont, i m not gonna give u the answer..take out a dictionary & start searching on your own..dont be lazy to THINK!!

So what is semiconductor??
Hmm again..Should i give u the answer??.. may b not!. coz its all in the text book or any reference book! I'm sure your parents have spent some money to buy a reference book for u..so why dont u learnt to USE IT!! I can bet most of your reference book, or exercise book are still looked neat & tidy as if u just bought it yesterday. So i think its time to do some 'conteng-conteng' on those books.Learning physics will be easier if u are not the type who is too lazy to think and  to reason logically ..but if u are the lazy type,frankly speaking its hard for u to get even a 'B'.
I might sound a bit harsh ..However dont take it too personal, bukan apa just to wake u up from your 'ignorance' attitude... at the same time i m trying my best to guide u to learn physics effectively.

Alright, lets get back to this topic..
How to describe semiconductors in terms of resistance & free electrons???
Usually pure semiconductors or intrinsic semiconductors are made from silicon or germanium. It conducts electricity when it has more free electrons especially under high temperature. However at low temperature, semiconductor produce few free electrons which makes it hard to conduct electricty. Thus the semiconductor acts as an insulator, i.e it has higher resistance.



So in simple words , semiconductor is actually a substance with its resistivity is between a conductor and an insulator. However u must bear in mind that its conductivity is not as good as conductor. So the question is,how are we going to make it a better conductor??

The answer is by having a DOPING process....hmm..What is DOPING????
It is a process to increase the conductivity of a pure semiconductor by adding an impurities.
In the end extrinsic semicondutors are produced.

There are two type of doping:

1. P-type

• p type is made by adding trivalent atom such as Boron
• trivalent atom has 3 electron in outer shell, one less than silicon.
• an extra hole is provided and this holes act as majority charge carrier for p-type

2. then we have a n- type :

•  it is made by adding pentavalent atom such as phosphorus
• pentavalent atom has 5 electrons in outer shell & 4 of them used to make covalent bond with silicon
• an extra unused electron  act as free electron which is the majority charge carriers for n type.

Sembang bola, sembang fizik

Senario 1:
Datang seorang anak kecil, hazim berumur 4 tahun menyapa pakngahya, Zahid:
Angah-angah..agak-agak siapa yang layak masuk 'final' world cup ni... hazim nak sangat tgk argentina masuk smpai final..
"Oh! sebelum masuk final, kena ada semifinal dulu..hazim"..sapa Zahid

Hmm tapi kenapa mesti ada "semifinal"..nama pun "semi"..lepas tu ..final".."semi" tu apa pakngah???
Terkedu sekejap zahid dengar soalan tersebut..lalu dgn spontan dia menjawab;
"Ala...'semi' tu semi lah..dah memang nama dia "semi"..ish byk tanyalah budak ni..Dah! pergi tidur"

Begitulah pertanyaan yang diaju oleh adik hazim...hmm kdg2 tidak terlayan telatah kanak-kanak yg sgt berfikiran kritis ..hampir semua perkataan ingin diketahui maknanya...NAMUN... 

Senario 2:
Pada keesokkan harinya, dgn mata kuyu zahid pergi ke sekolah dan dimulai dengan kelas fizik. Datang cikgu Tiara sambil mengedar kertas nota untuk diamati semua pelajar.
Sesudah itu cikgu Tiara bersuara:
Ok murid-mmurid, hari ini kita nak sambung berkenaan topik semalam iaitu applikasi semikonduktor dalam 'diode'. Saya harap awak masih ingat perbincangan semalam.."Baiklah,sekarang..buka muka surat..."
..sebelum sempat cikgu Tiara sambung bicara, Zahid bangun sambil bertanya dengan gaya 'blur'nya"..

Cikgu kejap..."semikonduktor" tu apa cikgu???
Dgn  geram..cikgu Tiara menjawab;
Kan saya dah terang semalam..semikonduktor tu datang dari 2 perkataan.."semi + konduktor"
Zahid jadi bertambah 'blur'..tapi cikgu 'semi' tu apa???

Ya Allah!...'semi' tu 'semi' lah zahid,.. budak sekolah rendah pun faham..takkan itu pun awak tak tau.Awak terlebih tengok "semifinal" ke malam tadi ???

Terus zahid tunduk tersipu-sipu dengan sindiran tajam cikgu Tiara.."Aduh, kalau lah aku tengok kamus bila hazim tanya, mesti aku tak jadi macam orang 'BLUR' pagi ini"..

Timbul rasa malu malu  kerana Hazim sekecil itu mampu meneroka kapasiti otak sampai  timbul rasa faham secara 'natural'...tapi aku ???? begitulah rungut hati zahid terhadap sifat "malas nak ambil tahu" yang semakin membarah, walaupun 'SPM' makin dekat...
Sambil merenung jauh, Zahid memujuk hatinya,
"Aku yakin mesti ada jalan..cuma aku mesti kena cuba, dan cuba..dan cuba !

CRO:Measuring Voltage & Frequency

Ok, today i'm gonna continue our discussion on Cathode Ray Oscilloscope. In last post i did mention one of the purpose using CRO is to measure voltage & frequency of a waveform.
To do this, we must understand the function of 'Y-gain & Time base'

Y-Gain:
- it is used to set the scales for the y-axis. Let say if u set the button at 10V/division..it means the y-axis has a scales of 0V,10V,20V,30V .....i.e each division has 10V.

Time base:
-meanwhile timebase is used to set the scales for x-axis. If the timebase is set to 10ms, i.e each division has 10miliseconds.

Now lets look at this video example,