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Description

In this lab, you will analyze data from two non-ohmic circuits: 1) R-C circuit, and 2) p-n junction Diode.

Just like last week, you will watch the videos I have recorded for the two cases. Unlike the last week, I will provide the data sets for the two cases. All you will have to do is to carefully analyze the data.

RC series demonstration (Links to an external site.)

Zener diode I-V data (Links to an external site.)

For data associated to each of the above video clips, check the Lab Files section. You will be able to find excel spreadsheets named after the two experiments.

For additional help on the two circuits, use the links below:

https://en.wikipedia.org/wiki/RC_circuit

(Links to an external site.)

https://en.wikipedia.org/wiki/Zener_diode

this is two video link

PHY192: Lab 10 (Non ohmic circuits)
Current Electricity III
Name:
Materials
A computer with internet and Excel
Objective
To confirm Ohm’s law and understand
non-ohmic conductors.
————————————————————I will add instruction videos for this lab, and will discuss
the details in the lecture.
Activity 1 (RC series circuit data)
Verify Ohm’s law with real circuit components. Watch the uploaded video and collect data on
the basis of what you see on screen. Then plot the current vs. voltage and confirm Ohm’s law.
Find the equivalent resistance of the circuit. Your report should have the data and plot that you
have generated from excel.
Analysis
1. Plot the current vs. time and voltage vs. time for the resistor and the capacitor data.
2. Use a suitable fit for the data. Then try to find the time constant of the circuit from the data.
3. There is a theoretical value of the time constant in the RC circuit. Find that value from the
resistance and capacitance values (ask your instructor if you are unsure). You may also look up
the internet for your research.
4. Compare the measured (value from the fit) and the theoretical time constants.
5. Find the percentage error. You have already done it in Lab 9.
Activity 2 (A non-ohmic I-V data)
We will work with a non-ohmic circuit in this activity. There are many ways we can make non
ohmic circuits. Suggest a way based on what you have seen in 192.
We will measure the voltage across and current through such a circuit and check if the I-V plot
still looks like a straight line. You will collect data from the screen capture video (or I will share
the data) I will share and use it to complete the report. Your report should have the data and
plot from excel.
Analysis
1. Plot the current vs. voltage for forward and reverse bias data. Plot them separately.
2. Use a suitable fit for the forward bias data.
3. Discuss what you have found interesting in this I-V data. Mention an application where this
kind of I-V response could be useful. You may look up in the internet for this part.
Mini-Lab #5: Acceleration
Day 1: Acceleration Due to Gravity (Free Fall)
Purpose: To measure the acceleration due to gravity for various objects of differing mass. This
system measures acceleration due to effectively one force acting on the objects. In this
laboratory, we will observe a falling ball and measure its position with Capstone. From this data,
we will determine the acceleration due to gravity, and compare the theoretical acceleration to the
measured acceleration.
Experimental Procedure (performed by staff)

We begin by getting both a ping-pong ball and a tennis ball.

We take one, hold it at a specified height, and record it as it falls and comes back up.

We then switch to the other ball, and repeat the procedure.
Plots to Make
There are no plots to make for this lab (there are some plots you will be making during the lab to
take data, but this will not need to be in your lab report.)
Things to Discuss

Describe the forces that are acting on the balls. Describe which ones are responsible
for their acceleration.

What is the physical meaning of the slope of the velocity vs. time graph? Is the slope
constant or not constant and what does that imply about the motion?

How can one tell from a position vs. time graph that an object’s velocity is constant?

How could one tell from a position vs. time graph that an object’s velocity is changing?

Note that the mass is not given in this lab. Is it needed?
Calculations to Perform

In Capstone’s windows, produce plots of the ball’s position vs. time and velocity vs.
time.

In the velocity vs. time graph, find the region that corresponds to the up-and-down trip
and use the cursor to click-and-draw a rectangle around the region that is relatively
straight. From the “Fit” menu in the graph window, select “Linear”. Record the slope and
include the value in your lab report.

Compare the accelerations you found to the predicted acceleration (what is the predicted
acceleration for free fall?). Your values should be close to each other. Calculate the
percent error.
Day 2: Acceleration Due To Gravity (Inclined Plane)
Purpose: To measure the acceleration of an object experiencing multiple forces and compare it to
our theoretical predictions for its acceleration. The object in today’s lab will be the cart on the
inclined track.
Theory

The cart will be initially at rest, and you will measure both the displacement 𝛥𝑥⃗ and the
time 𝑡 it takes the cart to travel that said displacement. From these measurements, you
will calculate the cart’s acceleration. The following steps elaborate further:

Write down the definition of acceleration as a derivative of the velocity.

Assume that the cart’s acceleration is constant. Solve the equation for the cart’s
velocity as a function of acceleration (HINT: It is the antiderivative of the
acceleration equation.)

Write down the definition of velocity as a derivative of the position.

Now solve for the equation for the cart’s position (HINT: It is the antiderivative
of the velocity equation.)

Note: the above steps are essentially the same steps shown in Example N3.2 in the
book, see equation N3.6 to double check your work.

Rearrange this position equation for the theoretical acceleration. You will use
the displacement and time measured as mentioned above to help find this
theoretical acceleration.
Experimental Procedure (performed by staff)

We set up an incline track at an angle 𝜃.

We release the cart from rest at the top of track, and observe as it falls towards the bottom
of the track, not allowing the cart to crash.

We then repeated the procedure for carts of varying mass.
Calculations to Perform

Measure the actual acceleration of the cart using Pasco Capstone (there are multiple ways
of doing this.)

Compare your measured accelerations to the predicted acceleration for all three trials.
Your values should be very close to each other.
Plots to Make
No plots to make for this lab.
Things to Discuss
Describe the forces that are causing the cart to move down the track. Describe which ones
are responsible for the cart’s acceleration.
Lab Writeup Details
Note: Combine parts 1 and 2 into a single mini-lab writeup.
Introduction and Theory

Include a basic description of what this lab is all about. Remember, you want to ease your
reader into what’s going on.

Provide what equations we are working with, as well as any assumptions we are making
in this lab.

Describe the forces that are acting on the cart and balls. Describe which ones are
responsible for their acceleration. For Day 2, please show the derivation of the constant
acceleration equation used for the theoretical calculation.
Data Analysis

Reference what equations you used to calculate acceleration (could write the equations
here, or reference equations already written in the Introduction and Theory section).
Day 1

Produce tables comparing the theoretical acceleration to the experimental
acceleration, as well as the percent error.
Day 2

Produce three tables (one for each video) comparing the theoretical acceleration
to the experimental acceleration, as well as the percent error.

Discuss whether or not the experimental acceleration was close to the theoretical
acceleration for each day. If not, you must list a few reasons as to why you believe it did
not hold (what went wrong?) If it did, point to specific values that show the theoretical
acceleration matched the experimental acceleration.
Style

Report is neat and formatted nicely

Figures/Tables have descriptions

Significant Figures make sense
Link to rubric: Mini-Lab #5: Acceleration

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