Author: admin

Part One:
What you will need to answer these is this :”‪‪Charges and Fields‬ 1.0.63‬ (colorado.edu)”
1.Based only on your observations from the previous section, what would you guess the mathematical relationship is betweenthedistance from a point charge andelectric field strength?
2. Using the ruler tool and the electric fields sensors, find the electric field at 10 different
distances from the charge and enter them in the table below.
Distance
Electric Field Strength
3. Plot these points in excel and find the appropriate trendline. Make sure to label your
axes and units and put the equation on the graph. Print the graph as a whole page
and attach it to your lab.
4. Based on your graph, what is the mathematical relationship between distance from a
point charge and its electric field strength? Did you predict correctly in question 1.
Relationship between charge and electric field
1. Based only on your observations from the previous section, what would you guess
the mathematical relationship is between charge and electric field strength?
2. Using the ruler tool and an electric field sensor you leave in one place, find the
electric field strength as you add more and more charges and enter your data in the
table below.
Charge Electric Field Strength
3. Plot these points in excel and find the appropriate trendline. Make sure to label your
axes and units and put the equation on the graph. Print the graph as a whole page
and attach it to your lab.
4. Based on your graph, what is the mathematical relationship between charge and it
electric field strength? Did you predict correctly in question 1.
III. Multiple Charges
Predict and observe the electric field vectors for two equal charges.
1. What pattern would you expect for the electric field produced by a pair of charges
which are equal in size and have the same sign? (Do not set up the simulation until
after you have made your prediction!) Draw your prediction of the electric field
directional arrows you would expect. Show at least a dozen arrows at evenly
spaced intervals covering the entire area of the box, including the area between the
charges.
2. Check your prediction.
a. In what ways is the pattern similar to your prediction? In what ways is it different?
b. Looking at the simulation, where is the field strongest? Where is it weakest?
Predict and observe the electric field vectors for two opposite charges.
3. What pattern would you expect for the electric field produced by a pair of charges
which are equal in size and have the opposite sign? (Do not set up the simulation
until after you have made your prediction!) Draw your prediction of the electric field
directional arrows you would expect. Show at least a dozen arrows at evenly
spaced intervals covering the entire area of the box, including the area between the
charges.
4. Check your prediction.
c. In what ways is the pattern similar to your prediction? In what ways is it different?
d. Looking at the simulation, where is the field strongest? Where is it weakest?
Make up your own charge distribution and predict the electric field lines.
1. Clear the screen and set up an arbitrary charge distribution (Do not set up the
simulation until after you have made your prediction!) Draw your prediction of the
electric field directional arrows you would expect. Show at least a dozen arrows at
evenly spaced intervals covering the entire area of the box, including the area
between the charges.
2. Check your prediction.
e. In what ways is the pattern similar to your prediction? In what ways is it different?
f. Looking at the simulation, where is the field strongest? Where is it weakest?
V.CONCLUSIONS
1. Based on your results from part II (field of a point charge) and without looking it up, please guess a mathematical relationship (you do not need specific numbers or constants, just an approximate proportionality) between electric field, charge and distance from a charge. Justify your answer in a couple sentences. 2. How does the equation you came up with in question 1 relate to Coulomb’s Law for
force between two point charges (remembering that Coulomb’s Law is 𝐹 = 𝑘 q1q2/r)? Give a relationship between E and F and justify your answer.
Part Two:
You will need to partner with someone in your house to do this experiment. (A third person is helpful as a timer if available but not essential). Face that person and hold each other’s hands so that you are both capable of squeezing each other’s hand. The first person is instructed to squeeze the left hand of the other person with their right hand. As soon as the other person feels the squeeze, they can squeeze the first person’s left hand with their right hand. Then you will continue the cycle. As soon as the first person feels the squeeze on their left hand, they squeeze the second person’s left hand and on and on. In this way you have now made a loop of conduction (basically a human circuit).
What is the neural signaling process involved in this? Tactile detectors in the left hand detect a squeeze, a neural impulse travels from their hand up their arm and to their dorsal root ganglia (clusters of neurons) next to the spinal cord where it connects to (synapses with) another set of neurons that send signals up the spinal cord to the brain, where various things happen (including activating the memory instruction to now squeeze with the right hand), neural signals commence to orchestrate the appropriate muscle movement and several synapses later the right hand squeezes the hand of the other person. Draw a sketch of this process in the space below.
After several rounds of practice, we now measure the total time for the squeeze-squeeze effect to propagate for 10 full cycles (20 people worth because each cycle goes through two people), from you to the other person and back again. Once you have this time, divide by 20 to get the time that it takes the signal to travel through one person (since there are two people, in 10 cycles the signal passes through a body twenty times). This will be how long it takes for each individual to detect the incoming sensory signal, execute the needed analyses and decisions, and produce an outgoing muscle response.
Time for the squeeze-squeeze effect: ______________ seconds
Now, rather than hold hands, each person places their right hand on the left shoulder of the other. The instruction is the same, but instead of squeezing, tap the next person’s shoulder. Again, the first person will begin the process by tapping the left shoulder of the second person with their right hand; that person, as quickly as possible, taps the shoulder of the first person; and so on. After several rounds of practice, we now measure the total time or the tap-tap effect for ten full cycles. Again divide by 20 to get the average time for the signal to propagate through each body. Time for the tap-tap effect: ______________ second
Question: If things go right, the total time for the tap-tap effect will be less than the total time for the squeeze-squeeze effect. What is that difference?
Squeeze-Squeeze Time – Tap-Tap Time = ΔT = ______________ seconds
Question: Why do you suppose there should be a difference between the squeeze-squeeze and the tap-tap case?
In the squeeze-squeeze case, there is an additional arm’s length (from left hand to left shoulder) that must be transmitted by a neural signal as compared to the tap-tap case. Using the simple speed equation (without acceleration), determine the easy equation you would use to find the nerve conduction speed in a human arm using the difference in time between squeeze-squeeze and tap-tap that you determined above. Write the equation below.
If you did step 5 correctly, then you should know that in order to calculate the conduction speed you will need to know the average arm lengths of you and your partner, shoulder to the tips of the finger. Find these lengths using a ruler and input the info below for each person. Then add them and divide them by two to find the average. Using your equation from step 5, calculate the conduction speed of the human body below:
Conclusion:
Free nerve endings associated with touch and pressure are known to have conduction speeds between 3-30m/s. Do your results fall into this range? Describe in thorough detail at least one source of error that could have disturbed the accuracy of your results. Describe specifically how it would have affected your results. Would it have made the magnitude greater? Less? Why?
Using what you learned in lecture, estimate the resistance of your full arm, finger to shoulder. Note: Your exact values will differ since you all have different arm sizes. You just want to get the right order of magnitude.
The voltages associated with nerve conduction are usually on the order of 70 mV. Using this fact and the answer to the last question, give a rough estimate for the current traveling through your arm during standard nerve conduction. Describe in thorough and clear detail how electric signals are propagated through nerve cells. In other words, describe an action potential and how such a signal is then transferred onto the next neuron and so on. Use pictures and words if necessary.