Practical assement question (1 Viewer)

[TurkStyle]

Identify the reistance in materials is increased by the prescence of impurities and scatering of electrons by lattice vibrations

-you will be provided with instructions and equipment necessary to undertake a practical activity to compare the conductivity of various conductors. You will be required to complete a full practical report including aim, method, brief, risk assesment,results in table and conclusion as well as ways to improve experiment

also were doing pendulum experiment data excercise any advice for reliability or validity on both pracs?

 

[eriito]

The main source of error in the pendulum exp. would be human error

 

[Fortify]

The main source of error in the pendulum exp. would be human error

Yep, my teacher hates it when we write 'human error'. He tells us to be more specific.

 

[study-freak]

Some suggestions for errors in the pendulum experiment:

g=9.8ms^-2 at the sea level. You did not conduct the experiment at sea level.

Thickness of crust you are standing on and mass of materials below you affect the value of g. (g=GM/r^2)

Human error - when you press buttons on stopwatch, your reaction time differs every time. Hence your time measurement differs.

T=2pi sqrt(g/l) is an approximated formula that is derived by taking limits as angle of displacement in the original expression reaches towards 0. However, your angle of displacement is obviously not zero. Thus your formula does not hold accurately. Original formula: T=2pi sqrt(g theta/l sintheta) where theta is in radians. Note that it is approximately correct for angle smaller than 10 degrees. Angle above that would give you significant error as the value of theta/sintheta changes more.

 

[eriito]

Human error - when you press buttons on stopwatch, your reaction time differs every time. Hence your time measurement differs.
.

What he said

 

[shady145]

Human error - when you press buttons on stopwatch, your reaction time differs every time. Hence your time measurement differs.

yea write something about doing multiple swings of the pendulum to minimise human error...do 10 periods or so or if u want to minimise by more do it 100 times lol

 

[eriito]

or use a data logger and motion sensor

 

[TurkStyle]

wat about the main question lolz

 

[darkchild69]

Heh, you goto Bossley Park High?

Do u know a Crystal Olivares?


Think about what resistance is (opposition to electron flow).

In conductors, lattice vibrations increase when you increase the temperature of the conductor (as you are increasing the thermal energy available to the crystal lattice). Increasing the thermal energy of the lattice, increases the amplitude and frequency of the vibrational states, meaning it will vibrate faster and further away from it's equilibrium position. So, if the positive ions in the crystal lattice are vibrating quicker and further from its equilaibrium position, then it is more likely to collide with an electron which is passing through the lattice (remember in conductors, the valence bands of individual atoms actually overlap, so all valence electrons are 'shared' amongst the ions in the crystal according to the free electron model)

This increase in a chance of a collision, means an increase in opposition to electron flow, which means an increase in resistance.

As for impurities, this is simply another thing which electrons can 'run into'. Hence, more opposition to current flow, hence higher resistance

Think about this scenario:
Think about a typical classroom, you have 5 columns of desks and a chair behind each desk. You are an electron, wanting to travel in an undistrubed straight line. The desks now start vibrating back and forth from where it is usually stationary, it is more likely that you will run into it if you travel in a straight line.
This is what happens with increased thermal energy or increased lattice vibration

Same scenario, except now the chair which was behind the desks, some of them are now in the aisle between the desks, you want to run down the aisle, but due to the chair now being in the aisle (impurity) it is more likely that you will hit something, hence more opposition to current flow, hence higher resistance.