ICS Physics

End of Physics Review

9-12 Science Std: Phys 3, 4, 5

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