## 4 SPM Form 5 Physics Mind Map Formulae List – Chapter 3

Click on the image to enlarge.

The image above shows the formulae that students need to know in Malaysia SPM Physics syllabus in Mind Map form. You may click on the image to enlarge it for a better view. You may also download and print it out for further reference.

Electromagnetism if the third chapter in SPM Form 5 Physics. Not many calculation in this chapter. Most of the calculation questions are related to transformer. Questions related to the root mean square voltage and current rarely come out in exam.

## 4 Transmission of Electricity

Q: Why the voltage is stepped up before transmitting electricity over a long distance?

A: Stepping up the voltage can reduce the current in the cable. This reduces the power loss in the cable during transmission.

### Problems Involving Electricity Transmission.

1. Power Loss During Transmission.
2. The high voltage transmission cable is very dangerous.
3. The cost of the cables is high.
4. Charge leakage may happen between cables and earth.
5. Pylons may be struck by lightning.
6. Pylons and cables may be struck by light aircraft.

## 4 Sources of Energy Used to Generate Electricity – Wind Energy

The advantages of using wind as a source of energy to generate electricity are.

1. It is renewable energy.
2. It does not pollute the environment.
3. It is suitable for the mountain area because the wind speed in the mountain area is relatively high.

The disadvantages of using wind as a source of energy are.

1. A large area is needed to build the windmills.
2. The windmills will produce a high level of noise.
3. The power generated is inconsistent due to the inconsistent of the wind speed and wind direction.

## 4 Sources of Energy Used to Generate Electricity – Biomass

1. Biomass is biological material derived from living organisms such as wood and animal waste.
2. As a renewable energy source, biomass can either be used directly via combustion to produce heat or indirectly after converting it to various forms of biofuel.
3. Heat energy produced from the burning of biomass can be used to generate electricity.

1. It is renewable energy.
2. Using biomass to generate electricity can reduce the disposal of organic waste.
3. Liquid biofuels will not pollute the air because they are lead-free and sulphur-free.

1. Large storage space is required to store the biomass.
2. Land utilization can be considerable. Can lead to deforestation.
3. The overall process can be expensive

## Nuclear Power

The advantages of using nuclear energy as a source of energy to generate electricity are.

1. The nuclear fuel such as uranium and plutonium has high energy capacity. A small amount of uranium can produce a huge amount of energy.
2. Nuclear energy does not pollute the air.

The disadvantages of using nuclear energy as a source of energy are.

1. Hazardous radioactive waste is produced during a nuclear reaction.
2. The radioactive waste will cause pollution in a very large area if leakage happens in the nuclear power plan.
3. The cost to maintain a nuclear plant is very high.
4. Building a nuclear plant involving very high technology. Only a few countries own such technology.

## Solar power

The advantages of using solar energy as a source of energy to generate electricity are.

1. It is renewable energy.
2. Sunlight is free and can be obtained easily.
3. It does not pollute the air.

The disadvantages of using solar energy as a source of energy are.

1. A large area is needed to install the solar plate.
2. The amount of sunlight at the non-tropical area depends on the season.
3. The energy collected need to be stored in a cell so that it can be used at the time sunlight is not present.
4. Its capacity is limited by the capacity of the cell. Normally a cell has relatively low capacity.

## Fossil Fuel.

The advantages of using fossil fuel such as petroleum, natural gas and coal as a source of energy to generate electricity are.

1. It is relatively easy to be collected as they are present in large amount in one place.
2. It contains high energy capacity.

The disadvantages of using fossil fuel as a source of energy are.

1. It releases a lot of carbon dioxide when it is burned. A large amount of carbon dioxide present in the atmosphere will cause an increase in the temperature of the atmosphere, known as global warming. Global warming is the most serious environmental problem that we are facing now.
2. Fossil fuels are non-renewable energy.
3. Pollute the air. Burning of fossil fuel will release particles and some hazardous gases such as sulphur dioxide and nitrogen dioxide which will pollute the air.

## 4 Sources of Energy Used to Generate Electricity – Hydroelectric

Hydroelectric
The advantages of using hydroelectric as a source of energy to generate electricity are.

1. It is renewable energy.
2. Building a dam does not pollute the environment.
3. In a lot of countries, water can be easily obtained and is free.
4. Building a hydroelectric plant does not involve very high technology as a nuclear power plant.

The disadvantages of using hydroelectric as a source of energy are.

1. Building a dam will cause a large area flooded with water, and hence seriously destroys the ecosystem nearby.
2. The flooded area causes the loss of wildlife habitat and agriculture land.
3. Dam failure happens will cause a disaster to the lower reaches area of the river.
4. The cost to build a dam is very high.

## 4 Uses of Electromagnet – Circuit Breaker

1. The figure above shows the structure of a circuit breaker.
2. A circuit breaker is an automatic switch that cut off current in a circuit when the current becomes too large.
3. When the current in a circuit increases, the strength of the electromagnet will increase in accordance; this will pull the soft iron armature towards the electromagnet.
4. As a result, the spring pulls apart the contact and disconnects the circuit immediately, and the current stop to flow.
5. We can reconnect the circuit by using the reset button. The reset button can be pushed to bring the contact back to its original position to reconnect the circuit.

## 4 Law of Electromagnetic Induction

There are 2 principal laws of electromagnetic induction:

2. Lenz’s law

1. The magnitude of the induced e.m.f is determined by Faraday’s Law.
2. Faraday’s Law states that the magnitude of the induced e.m.f is directly proportional to the rate of change of magnetic flux through a coil or alternatively the rate of the magnetic flux being cut.
3. Therefore, the induced emf can be increased by
1. using a stronger magnet
2. increase the speed of the relative motion
3. increase the number of turns of the coil

### Lenz’s Law

1. When a magnet is moved into and out of a coil, the induced current that flows through the coil can be determined from Lenz’s Law.
2. Lenz’s Law states that the induced current always flows in the direction that opposes the change in magnetic flux.
3. Lenz’s Law obeys the principle of conservation of energy. Work is done to move the magnet against the repulsive force. This work done is converted to electric energy which manifests as an induced current.
4. For a conductor in a closed circuit moving perpendicular to a magnetic field and hence cutting its magnetic flux, the direction of the induced current is determined from Fleming’s Right-Hand Rule.
5. Fleming’s Right-Hand Rule is used to determine the direction of the induced current that flows from the wire when there is relative motion with respect to the magnetic field

Physics Animation
Applet
Lenz’s Law – Molecular Expression