Wednesday, October 26, 2011
Sunday, October 23, 2011
Wednesday, August 17, 2011
Physics Application: Electric Bell
Today's tips:One important aspect in studying physics is the ability to apply & relate each physics concept. In SPM application part is vital as it always being asked in paper 2. You are expected to explain certain physics application such as the working principle of an electric bell. Usually there are 4 marks allocated for this type of question. However to explain it, u must fully understand the physics concept being applied. In the case of electric bell, we apply the concept of electromagnet.Generally to understand basic concept of electromagnet, we must appreciate that every time current flows in a wire, magnetic field is produced. If the wire is coiled around soft iron, this causes the soft iron to be magnetized and become a temporary magnet. Once it becomes a magnet, it has the tendency to attract any magnetic materials such as iron armature in the bell.Once u understand the basic concept, then u must practise to explain the working principle of an electric bell. Why dont u take a reference book,watch this video.. try to undertand and explain how it works ..There are many other application of electromagnet such as relay switch,telephone ear piece, circuit breaker etc. Just make sure u are able to explain all of them.
Tuesday, August 9, 2011
DEFINITION
Today i'm going to discuss on SPM physics definition that can come out in paper 2 section A, B or C. Although there are a lots of definition need to be memorised, in average only 3 to 4 definition will be asked in the exam. Each definition contributes one mark only. If u are aiming for A+, u cant afford to loose too many marks. So its up to u, whether u want to grab all the marks on definition or to 'sedekah' some of them :)
Some definition can defined straight forward by referring to its formula. For example, pressure can be defined as Force acting per unit area ( P=F/A) or resistance can be defined as ratio of potential differnt over current (R=V/I).
However please be careful because not all definition can be defined based on its formula. For example u can't define potential different by using V=IR. If u say that potential different equals to product of current and resistance, u 'll lose the mark. In fact to define it, u should refer to its fundamental equation, i.e V=E/Q. Thus potential different is defined as 'energy needed to move a unit charge from one point to another'.
Some of the definition does not belong to any equation. For example elasticity is defined as 'the property of an object that enables it to return to its original shape after an applied external force is removed'
This kind of definition will be easier to memorise if u fully understand the keyword used to describe it. Basically once u can understand the physics concept being discussed, its much easier for u to memorize the definition.
Some definition can defined straight forward by referring to its formula. For example, pressure can be defined as Force acting per unit area ( P=F/A) or resistance can be defined as ratio of potential differnt over current (R=V/I).
However please be careful because not all definition can be defined based on its formula. For example u can't define potential different by using V=IR. If u say that potential different equals to product of current and resistance, u 'll lose the mark. In fact to define it, u should refer to its fundamental equation, i.e V=E/Q. Thus potential different is defined as 'energy needed to move a unit charge from one point to another'.
Some of the definition does not belong to any equation. For example elasticity is defined as 'the property of an object that enables it to return to its original shape after an applied external force is removed'
This kind of definition will be easier to memorise if u fully understand the keyword used to describe it. Basically once u can understand the physics concept being discussed, its much easier for u to memorize the definition.
Saturday, April 16, 2011
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 semiconductor is??
Hmm again..Should i give u the answer??.. may be 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.
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 semiconductor is??
Hmm again..Should i give u the answer??.. may be 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.
Tuesday, March 29, 2011
Fish & Buoyancy
Today let's revise some form 4 topics on Buoyant Force. In SPM, we learned that buoyant force depends on its volume of water displaced. The larger the volume displaced, the greater the buoyant force. Buoyant force also depends on density of the water, i.e greater water density produce greater buoyant force.
Learning physics will be interesting if u are able to blend its concept with nature & things around u. When i was a kid, i loved to keep fish as a pet and guppy was one of my favorites. Fish is very mobile in water. They are able to swim to the surface, stay in the middle of the water or sink to the bottom.
Ok how they did it.. I mean to float and sink?? Basically fish is able to do it through air filled bag called swim bladder. This bladder has nothing to do with its urine product. In fact swim bladder helps most fish to maintain its buoyancy. To swim upward a fish fills the bladder with oxygen through the gills. When the bladder is filled with oxygen, the fish has a greater volume and its bladder is expanded. This displace more water and so it experiences a greater buoyant force.
In order to sink,air is removed from the bladder that causes decrease in its volume. Thus its average weight will be greater greater than buoyant force which then pull it towards ocean floor.
To float at certain level, the bladder is filled with air until it displaces a volume of water to produce a buoyant force that equal to its weight. In this case, the weight & buoyant force are in equilibrium. Thus it stays at that level. The same concept is applied in submarine except submarine needs a ballast tank to increase or decrease its buoyancy by adding or removing sea water inside it.
Learning physics will be interesting if u are able to blend its concept with nature & things around u. When i was a kid, i loved to keep fish as a pet and guppy was one of my favorites. Fish is very mobile in water. They are able to swim to the surface, stay in the middle of the water or sink to the bottom.
Ok how they did it.. I mean to float and sink?? Basically fish is able to do it through air filled bag called swim bladder. This bladder has nothing to do with its urine product. In fact swim bladder helps most fish to maintain its buoyancy. To swim upward a fish fills the bladder with oxygen through the gills. When the bladder is filled with oxygen, the fish has a greater volume and its bladder is expanded. This displace more water and so it experiences a greater buoyant force.
In order to sink,air is removed from the bladder that causes decrease in its volume. Thus its average weight will be greater greater than buoyant force which then pull it towards ocean floor.
To float at certain level, the bladder is filled with air until it displaces a volume of water to produce a buoyant force that equal to its weight. In this case, the weight & buoyant force are in equilibrium. Thus it stays at that level. The same concept is applied in submarine except submarine needs a ballast tank to increase or decrease its buoyancy by adding or removing sea water inside it.
Wednesday, March 9, 2011
HOW TO BUILT A SOLAR CAR MODEL
BASIC CONSTRUCTION OF THE MODEL CAR
1. The completed model racing car is shown below. The ‘underneath’ view shows the motors fixed top a polystyrene base, held to it by insulation tape. The front plastic wheel has a 2mm axle which is taped to the card base. The sequence / stages involved in the construction of the model car are shown on the pages to follow.
SEQUENCE DRAWING OF MANUFACTURE
1. Cut out the shapes for the card base and bodywork.
2. Shape / form three art straws to the frame of the model car. When folding/bending the straws, place the straws on top of the card base to ensure that the straw frame matches it in size. Then sellotape the art straw frame to the card base.
3. Cut a rectangular slot at the front of the card base, using a craft knife. This must be accurately cut as the front wheel should fit precisely in position. If the rectangle is too large the front wheel will move from side to side when the finished model is tested. This will make the model move in circles rather than a relatively straight line.
4. Solder short red and black wire to the motors. Check that red is soldered to the positive terminal and black to the negative terminal of each motor. Fix the motors on to the polystyrene motor base, using insulation tape.
5. Turn the polystyrene motor base over and connect the red and black wires to the electrical connectors as shown in the diagram opposite. Then connect a further long red and black wires to the opposite side of the connector.
6. Sellotape the motor base to the straw frame/card. Be careful hoe the model car is picked up as it is not a strong structure. Lift the model by the motor base otherwise the model could be damaged.
7. Carefully turn over the model and use insulation tape to fix the axle to the card. Then turn over the model again so that it stands on all four wheels.
8. Cut out the bodywork card and draw a design that reflects the theme of a racing car. The card can be pushed into the art straw frame quite easily. In fact the bodywork can be interchanged so that the model has different bodywork each time it runs/races.
9. Finally connect the solar panels and, if in England, wait for a sunny day. ‘Flick’ the switch and the model car will move either forward of backwards. Switch the wires at the solar panels terminals to alter the direction.
1. The completed model racing car is shown below. The ‘underneath’ view shows the motors fixed top a polystyrene base, held to it by insulation tape. The front plastic wheel has a 2mm axle which is taped to the card base. The sequence / stages involved in the construction of the model car are shown on the pages to follow.
SEQUENCE DRAWING OF MANUFACTURE
1. Cut out the shapes for the card base and bodywork.
2. Shape / form three art straws to the frame of the model car. When folding/bending the straws, place the straws on top of the card base to ensure that the straw frame matches it in size. Then sellotape the art straw frame to the card base.
3. Cut a rectangular slot at the front of the card base, using a craft knife. This must be accurately cut as the front wheel should fit precisely in position. If the rectangle is too large the front wheel will move from side to side when the finished model is tested. This will make the model move in circles rather than a relatively straight line.
4. Solder short red and black wire to the motors. Check that red is soldered to the positive terminal and black to the negative terminal of each motor. Fix the motors on to the polystyrene motor base, using insulation tape.
5. Turn the polystyrene motor base over and connect the red and black wires to the electrical connectors as shown in the diagram opposite. Then connect a further long red and black wires to the opposite side of the connector.
6. Sellotape the motor base to the straw frame/card. Be careful hoe the model car is picked up as it is not a strong structure. Lift the model by the motor base otherwise the model could be damaged.
7. Carefully turn over the model and use insulation tape to fix the axle to the card. Then turn over the model again so that it stands on all four wheels.
8. Cut out the bodywork card and draw a design that reflects the theme of a racing car. The card can be pushed into the art straw frame quite easily. In fact the bodywork can be interchanged so that the model has different bodywork each time it runs/races.
9. Finally connect the solar panels and, if in England, wait for a sunny day. ‘Flick’ the switch and the model car will move either forward of backwards. Switch the wires at the solar panels terminals to alter the direction.
COMPONENTS REQUIRED TO MAKE THE SOLAR POWERED MODEL CAR
A solar powered model racing car can be made quite easily using very basic equipment, tools and materials.
1. A pair of scissors insulation tape, sellotape and a craft knife, for holding some of the components to the straw frame.
2. Two 3 to 6v motors are needed to drive the back wheels and a piece of 2mm compressed polystyrene or PVC. The motors will be taped to the polystyrene using insulation tape
3. Two rubber wheels with a 1.5/2mm hole through the centre. The wheels will be pushed straight on to the shafts of the motors (friction fit).
4.One /two jumbo art straws, 400mm in length. These will be used to make the basic frame of the vehicle.
5. A plastic wheel will be used for the front of the vehicle. A small 2mm steel axle is also required.
6. A line of electrical connectors are used to connect the wires from the motors to the solar panels and ON/OFF switch.
7. A small electrical screw driver, wire cutters, wire strippers, long nose pliers and soldering iron, for working with the electronics aspect of the project.
8. Cheap solar panels (photovoltaic panels). These will provide the electrical power required to drive the model solar car forward.
9. An A3 piece of card with the size of the card base and bodywork clearing marked out. If a number of model solar powered cars are to be made, simply photocopy the as many times as necessary.
10. A range of drawing equipment will be needed to add a design and colour scheme to the bodywork of the model car.
1. A pair of scissors insulation tape, sellotape and a craft knife, for holding some of the components to the straw frame.
2. Two 3 to 6v motors are needed to drive the back wheels and a piece of 2mm compressed polystyrene or PVC. The motors will be taped to the polystyrene using insulation tape
3. Two rubber wheels with a 1.5/2mm hole through the centre. The wheels will be pushed straight on to the shafts of the motors (friction fit).
4.One /two jumbo art straws, 400mm in length. These will be used to make the basic frame of the vehicle.
5. A plastic wheel will be used for the front of the vehicle. A small 2mm steel axle is also required.
6. A line of electrical connectors are used to connect the wires from the motors to the solar panels and ON/OFF switch.
7. A small electrical screw driver, wire cutters, wire strippers, long nose pliers and soldering iron, for working with the electronics aspect of the project.
8. Cheap solar panels (photovoltaic panels). These will provide the electrical power required to drive the model solar car forward.
9. An A3 piece of card with the size of the card base and bodywork clearing marked out. If a number of model solar powered cars are to be made, simply photocopy the as many times as necessary.
10. A range of drawing equipment will be needed to add a design and colour scheme to the bodywork of the model car.
Sunday, March 6, 2011
An Electric current
Figure 1
1. Hi guys...have you ever seen an instrument such as shown in Figure 1 ? What is the name and purpose of this instrument? It is an ammeter. Ammeter is used to measure an electric current.
Figure 22. Now look at Figure 2. The reading of the ammeter is 3 Amperes (3A). It shows that the current flow is 3A. What does it mean? It is the indication of the amount of electric charges that flow every second. It is because electric current, I, is the rate of flow of electric charges, I = Q/t, where Q is the amount of electric charges flow in Coulomb (C) and t is the time taken for the electric charges to flow in second (s).
3. The unit of an electric current is Ampere(A) which is equivalent to Coulomb/second
Friday, February 25, 2011
The Electromagnetic waves
1. The Electromagnetic wave consist of vibrating electric field and magnetic field perpendicular to each other and perpendicular to the direction of wave propagation as shown in the animation below. Blue wave represent the vibrating electric field and red wave represent the vibrating magnetic field.
2. The Electromagnetic wave is a TRANSVERSE WAVE. It can be polarised.
3. The Electromagnetic Spectrum.
4. The Electromagnetic Spectrum Song.
2. The Electromagnetic wave is a TRANSVERSE WAVE. It can be polarised.
3. The Electromagnetic Spectrum.
4. The Electromagnetic Spectrum Song.
Friday, February 11, 2011
FACTS ABOUT WAVES
1. Waves transfer energy without transfering the matter.
2. Transverse wave's particles vibrate perpendicular to the wave direction.
3. Longitudinal wave's particles vibrate parallel to the wave direction.
4. The amplitude of a wave determines its energy. Higher amplitude has greater energy.
5. Damping of wave causes decrease in amplitude & energy.
6. Waves' wavefront is always pependicular to the direction of the waves.
7. Waves undergo all of these phenomena; reflection, refraction, diffraction & interference.
8. Water,light & electromagnetic waves are transverse waves.
9. Coherent waves have same frequency & in phase.
10.As the frequency of a wave increases its energy increases and its wavelength decreases.
11.Shorter waves with higher frequencies have shorter periods.
FACTS ABOUT LIGHT WAVES
1. Light is a transverse wave
2. Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher refractive index(n).
3. Medium with higher refractive index has higher optical density.
4. At the critical angle a light wave will be refracted to 90 degrees.
5. Blue light has more energy,a shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
6. Monochromatic light has one color, frequency & wavelength.
FACTS ABOUT WATER WAVES
1. Water waves moves faster at deeper region. This change in speed causes refraction of water waves.
2. Water waves has longer wavelength at deeper region.
3. Deeper region is less dense than shallow region.
4. Water waves bended towards normal as it moves from deeper to shallow region.
5. After diffraction, water waves amplitude decrease thus its energy decrease as well.However its speed, wavelength & frequency remain constant.
FACTS ABOUT SOUND WAVES
1. Sound is a longitudinal waves.
2. Sound wave is produced through vibration of an object, like guitar string.
3. Vibration frm the object causes air molecules to be pushed & pulled forming a COMPRESSION & RAREFACTION region.
4. Series of COMPRESSIOn & RAREFACTION produce sound.
5. Louder sound has bigger amplitude.
6. Sound with high pitch has higher frequency.
7. The sound that we hear is known as 'audio sound' that has freuency between 20-20khz.
8. Those sound below 20hz is known as infrasound. While sound with frequency beyond 20khz is known as ultrasonic.
9. Sound require medium to travel. It travels fastest in solid> liquid> gas.
10.Sound can't be heard in vacuum....Starwars' outer space sound effect was a myth :)
2. Transverse wave's particles vibrate perpendicular to the wave direction.
3. Longitudinal wave's particles vibrate parallel to the wave direction.
4. The amplitude of a wave determines its energy. Higher amplitude has greater energy.
5. Damping of wave causes decrease in amplitude & energy.
6. Waves' wavefront is always pependicular to the direction of the waves.
7. Waves undergo all of these phenomena; reflection, refraction, diffraction & interference.
8. Water,light & electromagnetic waves are transverse waves.
9. Coherent waves have same frequency & in phase.
10.As the frequency of a wave increases its energy increases and its wavelength decreases.
11.Shorter waves with higher frequencies have shorter periods.
FACTS ABOUT LIGHT WAVES
1. Light is a transverse wave
2. Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher refractive index(n).
3. Medium with higher refractive index has higher optical density.
4. At the critical angle a light wave will be refracted to 90 degrees.
5. Blue light has more energy,a shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
6. Monochromatic light has one color, frequency & wavelength.
FACTS ABOUT WATER WAVES
1. Water waves moves faster at deeper region. This change in speed causes refraction of water waves.
2. Water waves has longer wavelength at deeper region.
3. Deeper region is less dense than shallow region.
4. Water waves bended towards normal as it moves from deeper to shallow region.
5. After diffraction, water waves amplitude decrease thus its energy decrease as well.However its speed, wavelength & frequency remain constant.
FACTS ABOUT SOUND WAVES
1. Sound is a longitudinal waves.
2. Sound wave is produced through vibration of an object, like guitar string.
3. Vibration frm the object causes air molecules to be pushed & pulled forming a COMPRESSION & RAREFACTION region.
4. Series of COMPRESSIOn & RAREFACTION produce sound.
5. Louder sound has bigger amplitude.
6. Sound with high pitch has higher frequency.
7. The sound that we hear is known as 'audio sound' that has freuency between 20-20khz.
8. Those sound below 20hz is known as infrasound. While sound with frequency beyond 20khz is known as ultrasonic.
9. Sound require medium to travel. It travels fastest in solid> liquid> gas.
10.Sound can't be heard in vacuum....Starwars' outer space sound effect was a myth :)
Saturday, February 5, 2011
Thursday, February 3, 2011
Thursday, January 27, 2011
Saturday, January 22, 2011
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