Physics Form 4: Chapter 2 - Hooke's Law

• Elasticity is the ability of a material to return to its original shape/length when the stretching force or the compressing force is no longer acting on it.
•  Hooke’s law states that the force applied is proportional to the extension of spring,  provided the elastic limit is not exceeded.

Gradient = spring constant 

Area under the graph = elastic potential energy

• Spring constant quantifies the stiffness of a spring.
• Steeper gradient of graph F against x, extension has a stiffer spring.
• Spring A is stiffer than spring B.

Physics Form 5: Chapter 3 - Moving Coil Meter

Moving coil meter only measures direct current. It has a linear scale because the pointer deflection is directly proportional to the size of the current.

How moving coil meter works:

1.  With the switch open, there is no current flow  through  the meter coil.

2.   With no current flowing, the coil generates no magnetic field and the pointer stays at zero reading.

3.  Close the switch and a current flows through the coil.

4.  The current creates a catapult magnetic field and a turning force acts on the coil.

5.  The turning force rotates the coil and the pointer deflects across the scale until the hairspring produces an equal and opposing turning force on the coil.

As the current through the coil increases, the magnetic field generated around the coil increases. The stronger the magnetic field, the larger the turning force of the coil to move the pointer.

 Function of the hairspring: 

With the use of hairsprings, the coil will return to its initial position when there is no current. The springs will also tend to resist the movement of the coil when there is current through the coil. When the attraction between the magnetic fields (from the permanent magnet and the coil) is exactly equal to the force of the hairsprings, the coil will stop moving toward the magnet. 

Other features are used to increase the accuracy and sensitivity of this meter movement such as. 

• An iron core is placed inside the coil to concentrate the magnetic fields. 
• Curved pole pieces are attached to the magnet to produce a radial magnetic field to ensure that the turning force on the coil increases steadily as the current increases. 
• Using stronger magnet.
• Increasing the number of turns in the coil.
• Increasing the area of the coil.
• Using a weaker hairspring.

Methodists to open private schools as public standards fall

The Malaysian Insider news

KUALA LUMPUR, May 29 — The Methodist Church in Malaysia believes private schools are a solution to the declining academic standards in public schools, and have begun building them in areas where there is an absence of government schools. The Methodist Church, together with other Christian denominations, has been involved in education since the 1800s when the British first came to the Malay Peninsula. The Church has 26 secondary and 42 primary schools assisted by the government, six private schools and a private college.

Bishop Dr Hwa Yung said the Methodist Church’s mission now was to build a “string of private schools” so that Malaysian youth would have the best possible education. “We have now also begun building private schools which seek to contribute towards raising academic standards in this country, something which unfortunately seems to have gone into freefall in the last few decades,” Yung said in his foreword of the Methodist Boys’ School Penang’s 120th anniversary souvenir programme.

The Penang school celebrated its anniversary yesterday in a dinner attended by Penang Chief Minister Lim Guan Eng. Hwa Yung lamented the fact that most mission schools were now under government control and run according to policies which were not too “sympathetic” to this category of schools. However, he said the Methodist Church had begun setting up schools for rural folks who have no access to government schools, and that one of these “private schools” has been recognised by the local education department and its students have been allowed to sit for year six and form three exams.

“We are seeking more human and financial resources to begin work in other areas of special needs, whether they be poverty, physical or developmental disabilities,” the bishop added. According to the Church, its sixth-form college, the Methodist College here, is aspiring to reach university college status by the next decade.

Physics Form 4: Chapter 2 - Principle of Conservation of Energy

• The principle of conservation of energy shows that energy cannot be created or destroyed but can change from one form to another.
• The principle of conservation of energy states that the total quantity of energy in an enclosed system is always the same.
  

For example:  Energy transformation on a roller coaster

• At the top of the hill, the cars possess the maximum quantity of potential energy. Potential energy  is dependent upon the mass of the object and the height of the object. The car's large quantity of potential energy is due to the fact that they are elevated to a large height above the ground. 

• As the cars descend the first drop, they lose much of this potential energy in accord with their loss of height. The cars subsequently gain kinetic energy. Kinetic energy is dependent upon the mass of the object and the speed of the object. 

• The train of coaster cars speeds up as they lose height. Thus, their original potential energy (due to their large height) is transformed into kinetic energy (revealed by their high speeds). As the ride continues, the train of cars are continuously losing and gaining height. 

• Each gain in height corresponds to the loss of speed as kinetic energy (due to speed) is transformed into potential energy (due to height). Each loss in height corresponds to a gain of speed as potential energy (due to height) is transformed into kinetic energy (due to speed).

Conclusion:

1. Potential energy convert to kinetic energy and vice versa
2. Total energy in the system is still the same.

Chemistry Form 4: Chapter 5 - Electrical Conductivity of Ionic Compound

In solid state, ionic compound does not conduct electricity. It is because there is no freely moving ions in solid state. The negative ions and positive ions are strongly held together by electrostatic forces in a crystal lattice structure as shown below:

But, when ionic compound is heated up until its boiling point, the sufficient heat energy able to break up the strong electrostatic forces between positive ions and negative ions. This causes negative ions and positive ions to move freely in molten state. Thus, ionic compound can conduct electricity in molten state.

When ionic compound dissolves in water, the crystal lattice structure collapses and thus releases positive ions and negative ions. This causes negative ions and positive ions to move freely in aqueous state to conduct electricity.

Click on the diagram below to play!

Physics Form 4: Resolving Forces Into Components

Addition of vector 

Click on the diagram below to play!

Click on the diagram below to play!

Any force can be resolved into the addition of two mutually perpendicular forces which are called components of force. The components of force are resolved along the x-axis = horizontal component and the y-axis = vertical component.

 

For example:

 

Come Back to Penang, Overseas Students Told

The Star, Friday 20 May 2011
PENANGITES studying overseas should return home after they have completed their studies since Penang is going to be the most happening place in Malaysia with many “exciting” projects.Chief Minister Lim Guan Eng said the graduates could contribute their expertise to make the state an intelligent and international city.

“We want Penang to be your ideal home and we need you to make it happen,” he said at the presentation of excellence awards to 64 students who achieved excellent results in the STPM examination last year. A total of 70 awards, including six special awards, were given to the students who scored a Cumulative Grade Point Average (CGPA) of 4.0.

The students were from eight schools on Penang island and nine schools on the mainland. Lim said there was a great improvement in the results as 42 students received the awards in 2009 and 41 students the year before. The students each received a certificate and RM400 for each award

Physics Form 5: Chapter 3 - Alternating Current Motor

• The permanent magnets used have curved surfaces at its poles to create a radial magnetic field which has a uniform strength.
• The uniform magnetic field ensures that the force acting on the rectangular coil is uniform.
• A pair of slip rings is used to ensure that the rotation of the rectangular coil is always in the same direction

Click on the diagram below to play!