
The
useful N-Level Notes site for all Sec4 Normal and Sec4E/5N students taking
O-Levels as the topics here are also tested in O-Levels.
This site is published by Lee Hong Rui from Bukit View Secondary School. Any
comments or Suggestions should be forwarded to me directly.
For GCE O-Level Notes, visit RAY-Notes 2008




The object will roll away after being displaced(Hit/pushed)
Note that when drawing the lines/arrows, it must always be from the North to South direction!!




| Iron | Steel |
-When magnetised, is a stronger magnet ![]() | When magnetised, not as strong!![]() |
| Easily Magnetised & Demagnetize. | Difficult to Magnetise & Demagnetise |
| Electromagnets: Good Temporary magnets | Electromagnets: Good Permanent Magnets. |

| V=RxI | Voltage=Resistance x Current | V R | I |
| P=VxI | Power=Voltage x Current | P V | I |
| E=PxT | Energy=Power x Time | E P |T |
| E P |
Electrostatics 
(Static Electicity)
a)Current Electricity is the type of electricity where charges are flowing.
b)An electricity is actually an external flow of electrons(Negative) from the negative pole to the positive pole.
c)Direction of electron flow is opposite the direction of the conventional current.
2. Insulators-Materials that electricity cannot flow through.
Conductors-Materials that allow electricity can flow through.
3) Current is measured as the amount of electricity Charge flowing in unit time.
Thus an electric current is the rate of flow of charges
4) Unit of Charge: Coulomb (C).
5) Formular of current,charge and time:
Current=(Charge Time)
-Express in Symbols, Q= IXS
6) Current of 1 ampere(A)= Charges flowing at the rate of 1C/S.
7) Instrument used to measure current is Ammeter,Connected in series.
2 Properties of Charges:
1) 2 types-Positive(+ve),
Negative(-ve)
2) Like Charges repel while unlike charges
attract.
**Only Negative
Charges(-ve) moves.
Applications:
-Lightning Rods
-Electrostatic
-Spray painting
le-1.6X10-19C
=1/1.6X10-19 1C
Calculator method:
1 Divide 1.6 EXP +/- 19
=6.25X1018

Current
Electricity
Current is the rate of flow of
charge.
I = Q / t
I = Current
Q= Charge
t = Time
*Quest: Which of the
following is a unit of current?
(a) J/S
(b) C/S
(c) S/C
(d) Volts
Ans: C/S
Current direction
-->+ve to -ve (Positive-Negative)
*Note: Ammeter can be measured from
any part of the circuit!
Ammeter;
-connection
-Ideal ammeter-zero resistance!
1(a) Current electricity is the type of electricity where the charges are flowing/moving.
(b)An electric current is actually an
external flow of electrons (Negative) from the negative pole of the
battery to the positive pole of the battery
However, the direction of
conventional current is taken to be the direction of flow of Positive
charges.
(c) Thus, the direction of electron
flow is opposite to the direction of conventional current.

2. Insulators are materials
that do not allow electric current to flow through them while conductors
allow electric current to flow through them.
3. Current is measured as the amount
of electric charge flowing in unit time. Thus an electric current is the
rate of flow of charges.
*4.The unit of charge is the Coulomb(C). 
5.The quantities current, charge and time a reconnected by the equation:
Express in symbols, Q= .
6. A current of one ampere (A) means charges are flowing at the rate of 1 C/s.
7. The instrument used to measure
current is called the Ammeter and it is connected in series to a
circuit.
-In a series circuit, there is only
one single conducting path or loop.
Resistence,Voltage, Current.
SI UNIT:
Resistence-R
Current- I
Voltage- V=RI
Resistence is measured in "Ohms".
1000Ohms=1Kilo-ohms OR 1K.
Current is measured in "Ampheres"(A)
1000miliAmpheres=1Amphere OR 1A.
note:"/" = Over.
examp: 1/2 = half
Measuring resistence:
Types of Connection:
In series:
R1+R2+R3....= .
In Parallel:
1/R1 + 1/R2 + 1/R3= .
Example:
1/20 + 1/10 + 1/5 (change to same denorminators first)
=1/20 + 2/20 + 4/20
=7/20
resistence=20/7
***Important note!
When resistors connected in parallel, the total resistence of the resistors will always be smaller than the smallest value resistor!!!
Voltage- measure using Voltmeter (connected in parallel)
Current- measure using Ammeter (connection in series)
In a series circuit, the higher the resistence of the resistor, the higher the voltage flowing across it.
























Social Studies Revison:
Updated on 26 Augest 2007 (Sat)
Sustaining Singapore's Development In The 21st Century
External Factors that affect singapore:
Economic Slowdown
-Singapore is highly dependent on her trade with other countries so if there is a slowdown in other country, singapore will be affected.
eg. When there is a currency crisis in Southeast Asia,
S'pore was affected.
Social-Political unrest in other countries
-S'pore have to bear the blunt of war even if they were not started by Singapore.
Environment Crisis.
-Air and Water pollution that drift towards S'pore will affect the lives of people and operation of business.
eg.Haze from the Indonesian forest fires cause the people living in Singapore to fall ill and also increased the prices of vegetables from Malaysia as their plantation agriculture products were affected.
Economic Strategies for Sustaining Development
>>Movement towards a Knowledge-Based Economy
Improving Worker's Employability
-Workers are encouraged to upgrade their skills to remain employable.
-NTUC pays 80% of the training costs for retrenched Union workers.
-Workers are encouraged to be well-equipped with Information Technology (IT)
Importing of Foreign Technologies
-Encouraging Multinational Cooperations to operate in S'pore as they can share technology with the local companies.
Attracting Foreign Talents
-Attracting foreign talents can help S'pore build up her network talent around the world
Promoting R&D
-Necessary because S'pore needs to develop her own tlent pools and create her own technologies.
Creation of IT Infrastructure
An up-to-date IT Infrastructure will enhance the competiveness and efficiency of Singpore.
Environment Strategies
Improving Infrastructure for waste deposal
-There are six plants for treatment of human waste.
-They are compact and covered structures build by the government and helps to save space and reduce foul smells.
Using improved Technology and Processes
-They provide a cleaner environment
-eg. Nature gas with lesser pollutants are used in power stations.
Preserving Nature Sites
-5% of the land in S'pore are preserved as nature sites.
-These sites house a wide range of natural habitat which can be used for recreation, eduacational and scientific research
Summarised Notes for Sri Lanka
Reasons for Sri Lankan Conflict:
Citizenship Rights
-After Sri Lanka gained independence, the Tamils lost citizenship and became stateless.
-Granted Citizenship only to those born in Sri Lanka or grandfathers were born there.
-Indian Tamils were denied basic
rights such as voting and yet they continue to work and contribute
for the Sri Lankan Economy.
Jobs in the Government Service
-English-educated Tamils could enter the government service and get promoted.
-The Sinhalese who does not know english could not enter.
-To improve position of the Sinhalese,the Sri Lankan Government made Sinhala the only language of administration.
-The Tamils were given 3 years to learn Sinhala or be dismissed.
-Tamil is then made the language of administration in the Northern & Eastern Provinces where there are more tamils.
University Criteria
-There was an equal number of Sinhalese and Tamils in the same courses, numbers are not proportionate to the population in the country.
-Changes were made to the criteria to allow more Sinhalese students to enter these courses.
-Tamils were unable to obtain necessary academic qualifications needed to secure jobs.
Consequences of Conflict:
Armed Conflict
-Tamils turned violent when their demands were still not met and still be treated as second-class citizens.
-Tamil United Liberation Front was formed as demanded for separate state called Tamil Eelam.
-Demands Rejected>> Tamil youths form Tamil Tigers and started attacking the Tamils who did not support them then the Sinhalese.
Economic Problem
-Bread winners in families are killed in riots.
-Massive
unemployment among the factory and plantation workers.
-Fall
in tourist arrival which led to unemployment
-Loss
of foreign investment; Investors not confident.
