ics physics end of physics review 9-12 science std: phys 3, 4, 5
TRANSCRIPT
Topic: The Right Tool
You must choose the right equipment to get the best scientific readings
To record sounds you would use a
To measure electrical charge, current or voltage you would use a
To measure temperature you would use a
To measure earthquake energy you would use a
Std I&E 1a
microphone
seismograph
Electrometer, ammeter or Voltmeter
thermometer
Topic: The Right Tool
Once you have your readings, you need to organize and compare your readings
You can start by putting the data into a
And once you put it into the spreadsheet, you can look at the data on a
You can take the data from the table and put it in a
Std I&E 1a
table
spreadsheet
graph
Topic: Entropy*
Entropy is a physics term that describes:
The amount of disorder is in a system
High Entropy means something is disorganized, messy and everything is behaving badly
It is a fact that Entropy is always increasing
Low Entropy means something is very organized, clean and everything is behaving nicely
Std 3f
And things will move to a less orderly state
Topic: Wave Types
Waves have 2 different shapes
The first type is a transverse wave
We made transverse waves when we were shaking a slinky
The second type is a longitudinal wave
EM Waves are transverse waves
Std 4b
Sound waves are longitudinal waves
Topic: Wave Motion
As a wave moves through something it makes parts of the material move
As a transverse wave moves by:
If you were on a surf board on the ocean
The transverse wave would make you move up and down
It makes the material (or anything that is on it) move up and down
Std 4a
Watch the little black dot as the transverse wave goes past it
Topic: Sound Waves
Sound waves are longitudinal waves
Sound waves need a material (medium) to travel through
When the molecules bump into each other, they transfer the wave energy from one molecule to the next in a direction parallel to the direction of the sound
Sound waves move through the medium by having molecules bump into each other
Std 4b
Topic: Speed of SoundSeveral things affect the speed
of sound in materials
Temperature: Higher temperature = sound moves faster
Flexibility: Lower flexibility = sound moves faster
Density: Higher density = sound moves faster
Std 4d
Sound moves faster in the desert heat than the artic cold
Sound moves faster in water or steel than in air
Sound moves faster in a stiff plastic pole than a soft plastic toy
Topic: EM Wave Spectrum
Electromagnetic Waves are a special kind of wave
Depending on the frequency (and the wavelength) of the wave, we have special names for the waves
All of these waves are transverse waves and can move without going through a material (medium)
Some of the special names are radio waves, microwaves, ultraviolet waves, x-rays and visible light
Std 4e
Topic: EM Wave Speed
Electromagnetic waves are special for many reasons
They travel faster than anything else known today
They go at the speed of light
And the speed of light is:
3 x 108 meters per second
In a vacuum (out in space) they all travel at the same speed
Std 4e
Topic: Refraction
Refraction is a bending of waves caused by a change in the speed of the wave
This can be caused by either:
Or a change in the material that causes a change in the speed of the wave
Going from one material into another material with a different wave speed
Std 4f
Topic: Index of Refraction
You can measure how much a wave will bend using the Index of Refraction (n)
The Index of Refraction is a measure of how much the velocity changes in a medium
The bigger the Index of Refraction, the slower the wave speed in the material
For light, the Index of Refraction is the speed of light in a vacuum (c) divided by the speed of light in the material (v)
Std 4e
Topic: Index of Refraction
If you compare the Index of Refraction for 2 materials…
You can tell how much the wave is going to bend
If the indices of refraction are not similar (numbers are far apart) the wave will bend a lot
If the indices of refraction are similar (numbers are close to each other) the wave will bend a little
Std 4f
Topic: Doppler Effect
The Doppler Effect is an apparent change in the frequency of a wave
The change is caused by relative motion between the source and the observer
If the sound is going away from the listener, the pitch goes down
If the sound is not getting closer or farther away from the listener, the pitch doesn’t change
If a sound wave is coming towards the listener, the pitch goes up
Std 4f
The bigger the difference in speed between the sound and the listener, the bigger the change in pitch
Topic: Sound Beats
When sound waves add together it is called interference
If two sound frequencies are close together, when they add you hear sound beats
The smaller the difference, the smaller the beat frequency
The larger the difference, the larger the beat frequency
The number of beats you hear depends on the difference in the sound frequencies
Std 4f
If there is no difference, you don’t hear any beats
Topic: Sound Limits
We know that sound is a longitudinal wave
And that all waves (except for EM waves) need to travel through something (a medium)
If you don’t have a medium, sound waves can’t travel
That is why sound won’t travel in a vacuum (in a place without any air)
So sound waves need a medium to travel through (air, water, etc.)
Std 4f
And in space, no one can hear you scream……
Topic: Wave Energy
All waves transfer energy when they move
Some waves need a medium to move, some don’t
We saw this when we did the lab with the string telephones
If a wave needs a medium, the medium ends up in the same place where it started after the wave goes past
Std 4a
The sound waves moved through the string but it didn’t move the string
Topic: Wave Energy
So what happens to this energy?
Sound waves can cause things to move
When they rub against each other, friction causes them to heat up
So if you had a loud enough sound wave, you could heat up water!
And when things move they rub against each other
Std 4d
Topic: Electrostatic Force
Electrically charged particles can be either positive (+) or negative (-)
Charged particles can push or pull on each other (force)
The amount of charge (+) or (-) – more charge = more force
The distance between the charges – more distance = less force
The amount of force depends on 2 things:
Std 5eIf the distance gets big enough, the force goes to 0 (goes away)
Topic: Electrostatic Force
When you have 2 charges, they can either pull or push on each other
If the charges are the same (alike) they push against each other
So remember that opposites attract and alike repel
If the charges are opposite (different) they pull towards each other
Std 5e
Topic: Electrostatic Force
When we draw Electrostatic Forces, we show the amount of force a special way
If we draw a small number of lines we have a small force
If we draw many lines we have a big force
So more lines = more force
If we draw more lines we have a bigger force
Std 5m
And the closer the lines are to each other = the stronger the force is
Topic: Electrostatic Force
How much does the force change?
This is the equation for the amount of force between charges
The amount of charge = q The distance between the charges = r
Std 5e
2x the charge = 2x the force
3x the charge = 3x the force
2x the distance = 1/4x the force
3x the distance = 1/9x the force
A change in the distance between the charges has more affect because the distance is squared in this equation
Topic: Right Hand Rule
When an electric current goes through a wire
It makes a magnetic field around the wire
Wrap your right hand around the wire
Point your thumb in the direction of the current
The direction of the field depends on the Right Hand Rule
Std 5h
Your fingers wrap in the direction of the magnetic field
You can see this if you put a compass next to the wire
Topic: Magnetic Induction
When you move a magnet next to a wire…
The magnet will induce (or make) a voltage in the wire
So if you move a magnet next to wires in an electric circuit, you will cause electric current to flow
When you have a voltage in a wire that is part of a electric circuit…
Std 5h
Electric current will flow through the circuit
Topic: Transistors
When transistors were invented in the 1940’s
They made many changes in electronics
They could be made cheaper
They could be made smaller
And they used less energy
Std 5d
With all these changes they quickly replaced bigger vacuum tubes
Topic: Transistors
Transistors are designed to do 2 things….
The 1st is to be a switch to turn on and off current
The 2nd is to add energy to a weak input signal
The first function is used in a computer
The second function is used in an amplifier
Std 5d
Topic: Transistors
Transistors have changed modern electronics because:
They can amplify small inputs into larger output signals
They don’t break easily like old vacuum tubes
They are smaller than vacuum tubes
So – the computers, radios and cell phones we use today are much smaller and tougher
Std 5d
Topic: PlasmaPlasma is the 4th state of
matter (solid, liquid, gas…)
It happens when you take a gas and either heat it to a very hot temperature or put a large voltage on it
A plasma is atoms of gas that have had their electrons pulled off so they are made of positive ions and free electrons
Because they have ions and electrons they are good electric conductors
You can find plasmas in the sun (very hot) or in a fluorescent light bulb (large voltage)
Std 5i
Plasma is like a gas, but a gas can’t conduct electricity