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1. Confusion about circuit schematic notations

I'm confused about the terminals in the picture above simply because I've seen the exact same thing mean 2 different things in schematics, namely: (1) it is an open circuit with voltage Vi(t) (2) The terminals are connected to some other circuit and thus have a voltage/current source, and the...
2. Best way to solve a system of complex equations?

In my circuit analysis class I consistently need to solve system of complex equations, and I can't use MATLAB or anything for it. Suppose I have the following system: (Va-Vs)/(-j15) + Va/33 + (Va-Vo)/(-j25)=0 (Vo-Va)/(-j25) + (Vo-Vs)/10 = 0 What is the best way to solve it by hand in a time...
3. (Question) Trigonometric substitution triangles

[Prefix] When we do trigonometric substitutions (such as for the integral x^3/(a^2-x^2)^2), we say something like "let x = asinp for -pi/2 <= p <= pi/2" then we carry on and solve the integral. However, sometimes our answer is ugly and we get some term in our expression like "cosp"- so we draw...
4. Current requires a closed loop to flow in DC, not AC?

It is my general understanding that according to KCL, current requires a closed loop to flow in DC. However, this is apparently not true in AC; current doesn't needa closed loop to flow. I have drawn a circuit below which causes confusion: C1 is a charge capacitor, R1 is a resistor, I1 an...
5. What exactly is moment, and when is it zero?

I've been dealing with the concept of moment this whole year, in statics/dynamics but I've never really completely understood it, just rather memorized it. What I think moment is: If some point on a body has moment, then this means it wants to rotate. So moment is essentially what causes...
6. Insights How I overcame learning challenges - comments

x86 submitted a new PF Insights post How I Overcame Learning Challenges That I Faced Studying STEM Continue reading the Original PF Insights Post.
7. If current doesn't flow in an open circuit, how are capacitors charged?

When answering a related question on physics forum, I found something I seemed to be confused about: Suppose we have a battery connected in series to a capacitor with no charge. A capacitor with no charge on it acts like an open circuit. I know what happens next: the battery charges the...
8. Is the tangential acceleration component always zero(wheel?)

If a wheel is rolling down a hill without slipping then we know the contact point has zero velocity. Is it also true that the tangential acceleration of this point is zero too?
9. Finding the phase angle of current through a capacitor?

Homework Statement Calculate the current in the capacitor shown in the figure below if the voltage input is V(t) = 29cos(377t-30) V, C = 1 micro Farad Homework Equations i = C dv/dt The Attempt at a Solution I essentially differntiate V(t) and multiply by 1 * 10^-6. I then get a negative...
10. Engineering Solving unkown impedance in circuit

Homework Statement Homework Equations V=IZ The Attempt at a Solution So my plan is as follows: Find the current through the 1 ohm resistor, multiplying this by the combined impedance of the capacitor & 1 ohm resistor. Now I know the voltage across the unkown impedance Z. Subtract this...
11. Engineering Solving phasor circuit with unknown dep. current src

Homework Statement Homework Equations V=IR The Attempt at a Solution I try to simplify the circuit by combining the capacitor and 2ohm resistor in parallel, Z = 1-j. Then I add the inductor to get Z = 1. Knowing the current across the resistor, 2(0d) I find the voltage across the 5 ohm...
12. Engineering Phasor circuit analysis

Homework Statement (Note, my answer below is also wrong. I've attempted this problem for about 1 hour now and I can't figure it out.) Homework Equations KCL (Kirchoffs Current Law) Z for the capacitor, Z = 1/(jwC)[/B] The Attempt at a Solution I'm using KCL at V1 with the following...
13. Circuit analysis complex numbers

Homework Statement I'm going crazy. I've done this problem nearly 20 times and keep getting the same answer. I've read my textbook so many times too! What am I doing wrong? Homework Equations Zcapacitor = 1/(jwC) Zinductor = jwL Zresistor = R The Attempt at a Solution Z for the...
14. Solving a first order circuit

Homework Statement We are given K1 = 0. So the answer should be in the form of V(x) = K2e^(-t/z) Homework Equations V=IR V(x) = K1 + K2e^(-t/z) V(infinity) = K1 V(0+) = K1 + K2 z = RC The Attempt at a Solution I draw the circuit for t = 0- and find the voltage across the capacitor...
15. Question about resistors (parallel and series)

Here is a picture of a circuit: I have two questions: (1) Are all resistors connected in one of two ways? I.e., resistors can be connected in parallel and in series, but is it possible for them to be connected as NOT parllel and NOT series? For instance, the two circled resistors don't...
16. Is electrical engineering just rote memorization? Or am I

For instance, I was introduced to thevenin and norton theorems about 1-2 weeks ago and it seems like we're expected to rote memorize the algorithms on solving problems. There is no proof/logic explained in different circumstances. For instance, we're told what these theorems are and how they...
17. Determining Rth from a simple circuit

Homework Statement Homework Equations V=IR[/B] From my textbook: If the circuit contains both independent and dependent sources, the open‐circuit terminals are shorted and the short‐circuit current between these terminals is determined. The ratio of the open‐circuit voltage to the...
18. Engineering Solving a weird circuit using nodal analysis?

Homework Statement Homework Equations V=IR Kirchoffs Current Law The Attempt at a Solution I picked the middle node (the one surrounded by 3 resistors) as my reference. V1 and V2 are my other two nodes. I'm also assuming that V1>V2, V1<reference Using Kirchoffs Current Law: (Node 1)...
19. Whats the difference between q and q_v in thermodynamics?

In thermodynamics, (delta internal energy) = (delta) U = q + w But it is also known that (delta U) = q_v = integral of (C_v) dT So if C_v is constant, then we have (delta U) = q_v = C_v (delta T) But the confusing part for me is what follows. For instance, in an adiabatic process, for...
20. Power learning - 16 hours a day

I have big plans for summer (note: I still plan on exercising, eating healthy, and showering regularly. Of course, my goal is 12-16 hours per day, 5-6 days a week), 10 math books to finish in 4 months of moderate to very hard difficulty (for me, not in general. I plan on learning all the...
21. Inclined plane normal force varies by coordinate system?

Suppose we have a block on an inclined plane. If we choose the x-y axis to be parallel and perpendicular to the inclined plane, then we have Fy = N - mgcos30 = 0 But if we choose our trivial x-y coordinate system, where y is parallel to the force of gravity, then we get: Fy = Ncos30 - mg =...
22. Friction between two boxes

Homework Statement Homework Equations F=ma Ff = N u The Attempt at a Solution Pretty much, I did the same thing in the solution. For box A: N = mg Ffs = mg*uk = 9.81*20*.4=78.48N I note that Ffs > 60 N, so the boxes will move with the same acceleration Now there are two ways I can...
23. Conservation of momentum in a system, direction changes?

We all know that momentum is conserved in a system. But I am confused of one thing. Suppose we have a system containing a wall with very large mass and a ball and use a classical x-y coordinate axis. If I swing the ball at an angle of 45 degrees from the horizontal, upwards to the huge wall...
24. Momentum textbook problem

Homework Statement The 75kg boy leaps off the cart A with a horizontal velocity of v' = 3 m/s to the left measured relative to the cart. Determine the velocity of cart A just after the jump. If he then lands on cart B with the same velocity that he left cart A, determine the velocity of cart...
25. Does the potential energy of a spring do work on the both

Suppose we have two boxes, A and B with different masses, the spring is fixed to block A. Then we take block B and press it against block A so that the spring compresses. Afterwards, we let go of both boxes. If we were to model this using the conservation of energy, then it is known that...
26. Momentum, why can we change the system?

Here is our momentum equation for when two separate masses m1 and m2 collide with each other and couple together m1v1 + m2v2 = (m1+m2)v3 In the LHS of our equation, we have two systems. m1 and m2. But in the RHS of our equation, we use a totally different system. m3, the combination of m1...
27. Exactly what is there to understand in physics? Its memory?

I notice a lot of people say that physics is all understanding. But to me it seems like useless memorization of formulas (as opposed to say real analysis). I will give an example over here, with my thought process. Perhaps someone who disagrees with me can tell me their thought process, and...
28. Physics/chemistry kicking my butt

Hi guys, first year computer engineering student here. I am looking for advice to ace physics/chemistry classes that I have to take. Last semester, I did poorly in statics (class average, got a B-) despite spending the majority of my time doing practice problems/studying for this class. (didnt...
29. Why is the voltage across one resistor the same as supply?

People say that the voltage across one resistor is equal to the voltage supplied. I've drawn a picture of a simple circuit with two points near the positive terminal. Apparently, if we take the potential difference of these two points, it will equal 9V according to the above saying (which can...
30. Treating multiple objects as the same system

Throughout my limited physics career (high school, first year university) I was introduced to concepts such as potential energy, kinetic energy, and work. Naturally, I was taught about potential energy using the whole gravity analogy. A brick at height h has more potential energy than a brick...