7B-DL05

.pdf

School

University of Alabama *

*We aren’t endorsed by this school

Course

678

Subject

Electrical Engineering

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by AdmiralGerbilPerson1003

Physics 7B DL 5 Overview DL 5 Unit 5: Flow, Transport and Exponential Change DL 5 Model: Steady-State Energy Density Activity 5.12: Series and Parallel Resistors (complete unfinished work from DL 4) Activity 5.13: Equivalent Resistance and Power Ratings (FNTs from DL 4) Learning Goals: ! Practice using the construct of equivalent resistance in simple parallel and series circuits. ! Understand household wiring in terms of the basic concepts. ! Understand the parallel nature of household circuits and why this leads to “constant” voltage. ! Develop a deeper understanding of electrical power and power in general. ! Develop an understanding of electrical power in household circuits. ! Practice finding equivalent parallel and series resistance. Activity 5.14: Non-steady State Flow Learning Goals: ! Understand what defines a flow which is not steady-state. ! Understand how a liquid which is flowing out of a pipe behaves with time. ! Make plots of how current changes as a function of time is a non-steady state flow. ! Understand how heat flow is an example of non-steady state flow. ! Make connections between the liquid flow and heat flow problems.

Physics 7B Activity 5.13 DL 5 Unit 5: Flow, Transport and Exponential Change DL 5 Equivalent Resistance and Power Ratings A) Equivalent Resistance FNT 1: Share your individual responses to this FNT with the other members of your group. 1) On the board, draw the circuit that results after replacing ࠵? ! and ࠵? " with their equivalent resistor. Indicate the value of this equivalent resistor on your diagram. Call this equivalent resistor ࠵? !" . 2) Next, draw the circuit that results after replacing ࠵? # and ࠵? !" with their equivalent resistor. Indicate the value of this equivalent resistor on your diagram. Call this equivalent resistor ࠵? #!" . 3) Use your second diagram (the one with ࠵? #!" ) and Kirchhoff’s loop rule to determine the current “drawn from” the battery. Is this also the value of the current in ࠵? # and ࠵? !" in your first diagram? Explain. 4) Use your first diagram (the one with ࠵? # and ࠵? !" ) and Kirchhoff’s loop rule to determine the voltage drop across ࠵? # and ࠵? !" . 5) What does the voltage drop across ࠵? !" tell you about the voltage across ࠵? ! and ࠵? " ? 6) Determine the currents in ࠵? ! and ࠵? " . What must be the relation of these two currents to the current through the battery you determined in 3)? Why? Whole Class Discussion B) FNT 2: 1) Share your individual responses to FNT 2 with the other members of your group. 2) Does your answer depend on the value of either resistor #2 or #3? 3) Describe, in simple terms, what it means for a component to be short circuited. 4) If the resistors represent light bulbs, how would the brightness of each light bulb change after the wire is added? Whole Class Discussion C) Power: FNTs 3 – 7: Share your individual responses to FNTs 3 - 7 with the other members of your group. Come to a consensus on the answers to each FNT, as well as the reasons behind your answer. Put up on the board any of these FNTs your DL instructor tells you to. Be prepared to explain your response for each FNT, as well as the reasons for your response, if called upon in the whole class discussion. Whole Class Discussion

Physics 7B Activity 5.14 DL 5 Unit 5: Flow, Transport and Exponential Change DL 5 Non-Steady State Flow A) Leaking pipe Shown here is a narrow pipe open to the atmosphere at the top. Initially, there is steady-state flow in the pipe, until the pipe breaks on the right side of the horizontal portion, and the fluid starts to flow out. Assume that only the horizontal portion of the pipe has high resistance. Explain what happens once the fluid starts to flow out into the atmosphere by answering the questions below: 1) Explain why this is no longer a steady-state flow system. 2) Obtain an expression for current by applying Bernoulli’s equation from the top of the pipe to the location of the leak on the bottom right. Assume there is always liquid in the horizontal portion of the pipe. 3) Bernoulli’s equation assumes that the current ࠵? is always positive. Recall that current is the rate of change of volume with time. In this case, does the volume decrease or increase with time? Based on your answer adjust the sign in front of ࠵? . Then, express ࠵? in terms of the rate of change of volume. 4) Express volume in the equation from 3) in terms of height and area. 5) The equation you found in 4) should relate the rate of change of height to the height itself. Can you think of a function that satisfies this relation? Whole Class Discussion 6) Write down an equation for height as a function of time using your result in 4) and 5) . 7) Make a plot of height as a function of time. How would your plot change for a pipe with a larger area, assuming resistance stayed the same? What about if the resistance was higher, but area stayed the same? Do your answers make sense? 8) What does 6) tell you about how current changes with time? Sketch a plot for ࠵? vs time. Whole Class Discussion B) A heat flow situation For the horizontal pipe in Part A) the current depends on the pressure difference across the pipe, which is varying with time: ࠵? = − ࠵?࠵? ࠵? . Similarly, heat flow rate from a location of higher temperature to lower temperature depends on the temperature difference: ࠵? = − ࠵?࠵? ࠵? , where R is the thermal resistance to heat flow. Continue to Next Page h R A

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version