Understanding Voltage Distribution in AC Circuits

In summary, the conversation discusses the solution to part b of a problem involving Kirchoff's law and voltage across different points. The claim that potential at C = D = u(t) and A = B = 0 is true because by Kirchoff's law, the voltage across C1 is equal to the voltage across C2. However, it may seem impossible for there to still be a current flowing through CD if Vc = Vd. The solution also mentions that any current between two points A and B is possible as long as the resistance between them is zero. The speaker also expresses their nostalgia for the 80s, the "beautiful era" of their youth.
  • #1
phantomvommand
242
38
Homework Statement
This is the electricity problem from 1983 IPhO. I am confused about a small part of the answer, and understand the rest of the solution, so you guys do not have to go through the entire solution. I am only asking about part b.
Relevant Equations
Q = CV,
Kirchoff's laws
The problem is shown below: (I am only asking about part b)
Screenshot 2021-02-26 at 11.27.36 PM.png

^Above is the problem.

Below is the solution to part b. They have claimed that we can set potential at C = D = u(t), and A=B=0. Why is this claim true?

What I realize:
By applying Kirchoff's across ACDB, Voltage across C1 = Voltage across C2. But the claim that Voltage at C = Voltage at D seems impossible to me. How can there still be a current flowing through CD (denoted by i5), if Vc = Vd? Likewise, how can i5 exist between AB if Va = Vb = 0?

You may refer to the full solution here: https://www.jyu.fi/tdk/kastdk/olympiads/problems.html#83prob (if I have not given enough context).
Screenshot 2021-02-26 at 11.30.01 PM.png

Thank you!
 
  • Love
Likes Delta2
Physics news on Phys.org
  • #2
Thanks for posting a problem from a beautiful era, the era of my youth. 80s were the best era of my life.
Now for your question:
We can have any current between two points A and B as long as the resistance between the two points is zero. By Ohm's law we ll have $$V_{AB}=R_{AB}I_{AB}=0I_{AB}=0\Rightarrow V_A-V_B=0\Rightarrow V_A=V_B$$
 
  • #3
thanks for this... I must have been so confused :<
 
  • Like
Likes Delta2

1. What is an Olympiad AC circuits problem?

An Olympiad AC circuits problem is a type of scientific problem that involves analyzing and solving circuits that operate using alternating current (AC) instead of direct current (DC). These problems often require knowledge of complex numbers, phasors, and other advanced mathematical concepts.

2. How do I approach solving an Olympiad AC circuits problem?

The best approach to solving an Olympiad AC circuits problem is to first understand the problem and the given circuit. Then, use the principles of Kirchhoff's laws, Ohm's law, and other circuit analysis techniques to simplify the circuit and solve for the unknown variables. It is also important to double-check your calculations and use proper units for your answers.

3. What are some common mistakes to avoid when solving an Olympiad AC circuits problem?

Some common mistakes to avoid when solving an Olympiad AC circuits problem include: forgetting to account for the phase difference between voltage and current, using incorrect units, and not simplifying the circuit before attempting to solve it. It is also important to check your calculations and make sure they are accurate.

4. How can I improve my skills in solving Olympiad AC circuits problems?

To improve your skills in solving Olympiad AC circuits problems, it is important to practice regularly and familiarize yourself with the various circuit analysis techniques. You can also study and review past Olympiad problems to gain a better understanding of the types of problems that may be presented. Additionally, seeking help from a mentor or tutor can also be beneficial.

5. Are there any online resources or tools that can assist with solving Olympiad AC circuits problems?

Yes, there are many online resources and tools available to assist with solving Olympiad AC circuits problems. Some popular options include circuit simulation software, online tutorials and practice problems, and forums where you can ask for help and discuss solutions with others. It is important to use these resources as a supplement to your own understanding and not rely on them completely.

Similar threads

  • Introductory Physics Homework Help
Replies
9
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
9
Views
914
  • Introductory Physics Homework Help
Replies
2
Views
903
  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
31
Views
3K
  • Introductory Physics Homework Help
Replies
20
Views
2K
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
25
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
2K
Back
Top