142 Lab Final Flashcards
Where does the measured value go?
on the y-axis
Where does the control value go?
on the x-axis
How do we transform the power law into a linear relationship?
take the log of each side
How did we simplify Coloumb’s law in the first lab?
use the same magnitude of charge so the charge can be simplified to Q^2
then, we took the log of each side of the equation to make a linear relationship
and since Ke and radius was held constant, we could combine them to get log(F)=log(Q^2) +b
can take pull the ^2 outside the log(Q) as well
Relationship between Force and radius in Coloumb’s law
inverse square relationship
What did we vary in the first lab?
first, varied the amount of charge on each sphere and then, varied the distance between the charges while charge charges
What do you have to do when using the Coulomb’s law simulation?
make sure to convert the charge from microcoulombs to coulombs
Why did we get smaller force values than expected in the Coulomb’s law simulation?
in reality, the R distance would be bigger from polarization. The positive charges would have repelled each other and spread out further, but this does not happen in the simulation
since F varies inversely with R, the bigger R would give a smaller F than what we got
Why can we not make the same assumptions about electric force that we can with gravitational force?
we can neglect the radius of the earth in the simplified formula F=mg
can’t neglect the radius between two charges since we are discussing relatively smaller values
Is the electric force always pointed in the same x-direction or same y-direction in the field hockey simulation?
No. As the puck rotates around the negative charge the x and y components of the electric force are changing
Is there anything constant about the electric force in the field hockey simulation?
As the puck rotates in a circle, we know that the radius remains constant and the magnitude of the charges remain constant
therefore, the magnitude of the electric force is constant
Can you split the electric force into components?
yes
Electric fields
deal with the forces a test charge will feel due to the source charge
Electric potential
deal with the energy changes a test charge will undergo as a result of the source charge
How can you find the magnitude of an electric field at a specific point?
Find the x and y components from each source and vector sum. Make sure to include the direction/angle of field in answer
Draw all the electric fields on a specific point in space. Lines move away from + charges and towards - charges
Do you include charge signs when calculating electric field at a specific point?
no
What to watch out for when calculating electric field?
make sure coordinate system lines up and add negative signs according to vectors
What are the units on electric fields?
N/c or V/m
How to determine angle of net electric field?
use tan(Enetx/Enety)
make sure to do a drawing to determine the correct quadrant
What can you do on charges and fields phet simulation?
Can add gridlines and measurement of the net electric field at a specific point in space
When using the gridlines, make sure to check the key at the bottom to see what one block on the grid corresponds to
Why does the sensor in the middle of a symmetric square of positive charges feel no net electric field?
The sensor records the net electric field which includes magnitude and direction
The positive charges opposite each other in the square cancel each other out
What happens if you would remove one charge from a symmetric square of positive charges to the net electric field at the square’s center?
if you removed a charge from the top, a charge on the bottom of the square would have no charge to counteract it
since positive charges create electric fields away from themselves, the charge at the bottom would produce a net electric field upwards
Volt units
Joule / c
*voltage describes the effects of potential energy so makes sense that Joules are included
Equipotential curve
a circle around a source charge where every point in the circle has the same voltage