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Electrostatic – Hazards and Applications of Electrostatics

1. An electric field is a region where an electric charge experiences an electric force.

2. The direction of the field is the direction of the force on a small positive charge.

3. Some hazards of electrostatic charging are lightning and electrostatic discharge.

4. Some uses of electrostatic charging are the laser printer, photocopier and electrostatic precipitators.

From O level Physics Tutor

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O Level Chemistry Tuition Singapore/Chemistry O Level Tuition/Tutor

Chapter 16 – Energy Changes

What are the characteristics of exothermic reactions?

When an exothermic reaction occurs,

a) heat is liberated and is transferred from the chemicals to the surroundings, and

b) the temperature of the reaction mixture rises. The container feels warm.

Examples of exothermic reactions

• Combustion of fuels
• Rusting of iron
• Corrosion of metals
• Reaction between acid and alkali neutralisation),
• Respiration

What are the characteristics of endothermic reactions?

When an endothermic reaction occurs,

a) heat is absorbed and is transferred from the surroundings to the reactants, and

b) the temperature of the reaction mixture falls. It feels cold.

Examples of endothermic reactions

• Photosynthesis

• Action of light on silver bromide in photographic film

• Thermal decomposition
Example CaCO3 —–> CaO + CO2

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Chemical Bonding FAQ 2

FAQ: Why does a stream of chloromethane (polar substance) running from a burette be deflected towards a negatively charged rod?

The polar molecules will align themselves such that the d+ ends of the molecules will face the negatively charged rod. The electrostatic force of
attraction causes the stream to be deflected towards the rod.

FAQ: Explain the trend in the boiling points of the halogens.

The halogens from F2 to I2 are non-polar so that the intermolecular attraction between their molecules is due to instantaneous dipole–induced dipole (id−id)interactions.

The number of electrons of the halogens increases down the group from F2 to I2.\ Ease of polarisability of electron clouds and strength of id–id interactions also increase down the group, with I2 having electron clouds which are most easily polarised resulting in greatest id–id interactions.
Since boiling involves overcoming intermolecular forces, the boiling points of halogens increases down the group.

Ease of donation of lone pair of electrons on Y
FAQ Why must Y be N, O or F?

To interact strongly with the d+ H on H-X, Y needs to be highly electronegative and the lone pair of electrons on Y must not be too diffuse in space. Hence, Y also needs to be small
must be N, O or F.

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A-Level Economics Tuition Singapore/H2/H1 Economics Tuition

Hi J2 H1/H2 Economics Tuition Students

The Singapore’s Economy

Important Characteristics
1. Small
2. Open
3. Market-oriented economy

Important Macroeconomic Policy Framework of Singapore
1. Exchange Rate Centered Monetary Policy – To maintain price stability.

i) Reading 1

2. Free Trade Policies, geared increasingly towards emerging economies – To achieve economic growth and healthy BOP

i) Reading 2

3. Supply side policy centered on labor market flexibility, labor quantity/quality (Interventionistic) and market privatization/deregulation (market-oriented) – to boost productive capacity and competitiveness, achieving sustainable growth and price stability.

Linking characteristics to policies:

1. Why exchange rate centered monetary policy and not interest rate centered monetary policy?
2. Why free trade policies and not protectionism? Why increasingly geared towards emerging economies such as G3, ASEAN and China?
3. Why supply side centered fiscal policy and not demand side centered?
4. Why supply side policies involving labor market flexibility, labor quantity/quality, deregulation and privatisation?

Additional Readings:

1. Monetary Policy Framework in Singapore, by Monetary Authority of Singapore, Economic Policy Department, Pages 3-6.
2. Global Demand Growth from Singapore’s Perspective, by Ministry of Trade and Industry, Economic Survey of Singapore 2010.

For complete lesson notes, please contact 9863 9633 or 9679 0479

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A-Level Economics Tuition Singapore/H2/H1 Economics Tuition

Hi J1 H1/H2 Economics Tuition Students

We are starting new class – J1 H2/H1 Economics this Sunday 21 Apr.
Timing 9 am to 11 am
For enquirers please contact Hp 9863 9633 or Hp 9679 0479
———————————————————————

Microeconomics Topic 1.3 : Firms and How They Operate 1

H2 Syllabus :

• Objectives of firms
o Profit Maximisation
o Alternative Objectives

• Costs of production
o Short run vs Long run
o Fixed cost vs variable cost

H2 Learning Outcome :
• Understand the concept of profit as the difference between total revenue and total cost
• Understand that firm make price and output decisions based on the marginalist principle

1.1 Production

Production is the process of combining inputs to make goods and services.

Recall that the Production Possibilities Curve (PPC) tells us combinations of the maximum quantity of outputs that an economy can produce at a given technology.

For a firm, its Production Function gives the maximum quantity of output it can produce over some period of time for each different combination of inputs.

When a firm uses many different inputs, production functions can be quite complicated. This is true even of small firms. For economic analysis, we often assume firms use only two inputs i.e. Capital and Labour.

Different Combinations of Inputs
Production Function
Different Quantities of Output

1.2 Short Run Vs Long Run

When a firm changes its level of production, it will want to adjust the amounts of inputs it uses. But these adjustments depend on the time horizon the firm’s managers are thinking about. Some inputs can be adjusted relatively quickly. Most firms, for example, can hire more labour and purchase more raw materials within a few weeks or less. But at many firms, there are some inputs that can be adjusted only after a long time interval. For example, it may take a year or longer before an automobile firm can purchase and install new, fully equipped assembly lines, or
acquire additional factory space.

For complete lesson notes, please contact 9863 9633 or 9679 0479

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A-Level Physics Tuition Singapore/H2 Physics Tuition/JC Physics Tutor

Hi All A-Level/JC/H2/H1 Physics Students

Exam based questions – Quantum Physics

1. Show an understanding that photoelectric effect provides evidence for a particulate nature of electromagnetic radiation.

Electromagnetic radiation is considered as a stream of photons.
Photoelectric effect provides the evidence for the particulate nature of electromagnetic radiation.

2. What evidences show that light has wave and particulate natures?

Diffraction and interference of light is the evidence for its wave nature.
Photoelectric effect is the evidence of its particulate nature.

3. What are the 4 results of the photoelectric effect experiments?

Result 1: Current is proportional to intensity. This result can be explained using wave nature and particulate nature of light.

Result 2: For every material of cathode irradiated, there is a limiting frequency fo or threshold frequency, below which no electrons would be emitted from the cathode regardless of the light intensity.
This result can be explained using particulate nature of light only.

Result 3: The maximum kinetic energy of emitted photoelectrons depends only on the frequency of the incident radiation, and not its intensity.
This result can be explained using particulate nature of light only.

Result 4: The emission of photoelectrons starts with no observable time lag, even for very low intensity of incident radiation.
This result can be explained using particulate nature of light only.

4. Explain photoelectric phenomena in terms of photon energy and work function energy.

Work function energy is the minimum energy required to remove an electron from the surface of the metal.

If the photon energy is less than the work function energy of the cathode, no photoelectron will be emitted. Hence, to emit photoelectrons, photon energy must be equal or greater than the work function energy of the cathode.

For more exam based questions, please contact Mr Ong @9863 9633

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A-Level Mathematics Tuition Singapore/JC Maths/H2 Math Tuition and Tutor

Hi A-Level/H2 Math Students

J1 – Practice Exam questions on Mathematical Induction and Series and Sequences

J2 – Teaching Binomial Distributions and continue practice exam questions on probability.

From A Level Math Tutors

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A Level GP/General Paper Tuition Singapore

Balance in Essays

What’s the point?

A good argumentative essay always addresses the alternative viewpoints held by people who disagree with the writer. This shows that the writer is mature enough to handle opposition, and intelligent enough to see the issue from different perspectives, even if he does not agree with some of these perspectives. It also allows the writer to refute the opposition, thereby showing the opposing view to be flawed or limited, and strengthening his own position.

Many students often do not see the relevance of including balance in their essays. They argue that even acknowledging the existence of any alternative viewpoint weakens their argument and is therefore not only unnecessary, but also detrimental to their essays. They fail to understand that this is true only when they are unable to handle the necessary task of rebuttal in a competent manner, or when they deliberately choose a very weak opposing viewpoint and then refute it in the belief that this strengthens their argument. It is needless to say that a poor rebuttal does not enhance the argument in any way, and may, in some cases, weaken it. However, using this as an excuse for not dealing with alternative viewpoints is as ridiculous as trying to argue that it is pointless to try to write an essay at all, since there is always a chance the arguments may be faulty. Furthermore, failing to address alternative views shows a lack of intellectual rigour and courage, and makes the writer appear narrow-minded at best, and ignorant at worst. This weakens an argument as much as, or perhaps even more than, a poor rebuttal. Similarly, picking a very weak opposing view simply makes the writer look like an intellectual coward who does not dare to engage with the issues that really matter.

Clearly, the most sensible thing to do is to make sure that the alternative views raised can be addressed adequately in the rebuttal. This requires careful thought and planning, because the key to the challenge of dealing with balance lies in highlighting the right alternative views. On the one hand, the writer has to draw attention to ideas that are significant enough to matter. On the other hand, these alternative ideas cannot be so strong that they become impossible to refute satisfactorily. This is a delicate balancing act that must be thought through very carefully in the planning stages of the essay.

You can refute the opposing view by showing that
1) it is a good point, but so is yours;
2) it is a good point, but yours is better; or
3) it is untrue.

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Electrostatic – Key Concepts I

1. There are two types of charges—positive and negative.

2. Like charges repel, unlike charges attract

3. Charge is measured in coulombs (C).

4. Electrostatic charging by friction involves a transfer of electrons.

5. Electrical insulators (e.g. rubber) do not conduct electricity because their electric charges (electrons) are not free to move about.

6. Electrical conductors (e.g. copper) are able to conduct electricity because their electric charges (electrons) are free to move within them.

7. Charged insulators can be neutralised by heating and humid conditions.

8. Conductors can be charged by induction.

From O level Physics Tutor

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Electrostatic – Key Concepts I

1. There are two types of charges—positive and negative.

2. Like charges repel, unlike charges attract

3. Charge is measured in coulombs (C).

4. Electrostatic charging by friction involves a transfer of electrons.

5. Electrical insulators (e.g. rubber) do not conduct electricity because their electric charges (electrons) are not free to move about.

6. Electrical conductors (e.g. copper) are able to conduct electricity because their electric charges (electrons) are free to move within them.

7. Charged insulators can be neutralised by heating and humid conditions.

8. Conductors can be charged by induction.

From O level Physics Tutor

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O-Level Additional Mathematics Tuition Singapore

S3 – Teaching Binomial Theorem

S4 – Teaching Application of Integration

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Factorization

Some useful identities

a^2 + 2ab + b^2 = (a + b)^2

a^2 – 2ab + b^2 = (a – b)^2

a^2 – b^2 = (a+b)(a-b)

a^3 + b^3 = (a+b)(a^2-ab+b^2)

a^3 – b^3 = (a-b)(a^2+ab+b^2)

From O-Level Elementary Mathematics Singapore Tutor

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A-Level Economics Tuition Singapore/H2/H1 Economics Tuition

Microeconomics Topic 2.2 : Government Intervention in the Market : Taxes and Subsidies

H2 Syllabus :
• Methods by which government intervene in markets and the impact on market outcomes

H2 Learning Outcome :
• Examine the various methods by which governments intervene in markets

H1 Syllabus :
• Policies to correct market failure : Taxes and Subsidies

H1 Learning Outcome :
• Analyse how governments intervene through imposition of taxes, subsidies.

1. Taxes

1.1 Definition
Taxes are money that the government takes from households and firms in order to pay for its own functioning and public projects.

1.2 Types of Taxes
Taxes may be direct or indirect :
• Direct Taxes – Taxes on income and wealth. Examples include personal income tax,
corporate tax.
• Indirect Taxes – Taxes on expenditure. Examples include excise duties on alcohol, petrol etc.
Indirect Taxes may be imposed on consumers or on producers although in most analysis, the focus is indirect taxes on producers.

Indirect taxes may be specific tax or ad valorem tax :
• Specific Tax – sometimes known as Lump-Sum Tax is a fixed amount of tax per unit of good or service. E.g. tax per litre of petrol, tax per litre of wine.
• Ad Valorem Tax – tax based on a percentage of the price or value of the good or service. E.g. Goods and Services Tax.

For complete lesson notes, please contact 9863 9633

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Concept Lesson #3

Types of Macro Policies and Transmission Mechanism

I) Fiscal Policy

(1) POSSIBLE Definitions

(i) Fiscal policy in general refers to the use of government spending and
taxation to influence the pattern of economic activities, and also the level of output, employment, aggregate demand and aggregate supply. The
objectives is to achieve various economic goals, both micro and
macroecnomic.

(ii) An expansionary fiscal policy in general involves the discretionary increase in government spending in selected areas and/or reduction in selected tax rates. The effect is to raise the AD and boost output and employment, thus helping to achieve actual growth and fall in cyclical unemployment. Such a policy can have an effect on both the SRAS and LRAS as well.

(iii)A contractionary fiscal policy in general involves the discretionary decrease in government spending in selected areas and/or increase in selected tax rates. The effect is to reduce the AD which can control demand pull inflation through fall in output, thus helping to achieve the objective of stable prices

(2) Transmission Mechanism for EFP
See Diagram 1

(3) Evaluation/Limitations for EFP
(a) Budget Deficit and Debt to GDP Ratio
(b) Crowding Out Effect
(c) Consumer Pessimism and increase household savings
(d) Ricardian Equivalence and increase household savings
(e) Investor Pessimism and increase in corporate savings
(f) High export dependence and
(g) Small multiplier and high leakages
(h) Demand-Pull Inflation (Trade-off between growth and price stability)
(i) Philips Curve (Trade-off between inflation and unemployment)
(j) Opposing income and substitution effects on work efforts due to lowering of taxes
(k) Irreversibility of fiscal spending on welfares, infrastructures
(l) Zombie industry and allocative inefficiency
(m) Market Failure and Allocative Inefficiency
(n) Positive Effects on LRAS
(o) Positive Effects on SRAS
(p) Positive Effects on Sustainable Growth and Comparative Advantage

For complete concept lesson, please contact 9863 9633

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Chemical Bonding FAQ 1

What are Chemical bonds?
– Binding forces of attraction between particles (atoms, ions or molecules) resulting in a lower energy arrangement.
– The formation of a bond involves the re-distribution of the outer electrons of the atoms concerned.

What is the Octet Rule?
Atoms tend to lose, gain or share electrons until they are surrounded by eight valence electrons. Atoms try to achieve the same number of electrons as the noble gases closest to them in the Periodic Table.

Explain which of the following ionic compound has the stronger ionic bond.
(i) sodium fluoride or sodium chloride
Sodium fluoride has stronger ionic bond as fluoride is smaller than chloride so that the shorter distance between Na+ and F– resulted in stronger ionic bond.

(ii) sodium fluoride or magnesium fluoride
MgF2 has stronger ionic bond as Mg2+ is more highly charged than Na+, resulting in greater electrostatic attraction in MgF2.

Why is it that both NCl3 and PCl3 exist, but only PCl5 exist and not NCl5?
Such expansion of octet is observed in some compounds formed by elements of Period 3 (and beyond) This is due to the availability of vacant, low-lying orbitals. The energy required to promote an electron from 3s or 3p to 3d is not very large.

However elements in Period 2 (e.g. O and N) do not have low-lying vacant orbitals for expansion of octet. Promotion of electrons to the next quantum shell requires too much energy and hence Period 2 elements can accommodate only a maximum of eight valence electrons.

Point to note
A single covalent bond consists of one s bond.
• A double covalent bond consists of one s bond and one pie bond.
• A triple covalent bond consists of one s bond and two pie bonds.

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