# What is Loops: Definition and 274 Discussions

Froot Loops is a brand of sweetened, fruit-flavored breakfast cereal produced by Kellogg's and sold in many countries. The cereal pieces are ring-shaped (hence "loops") and come in a variety of bright colors and a blend of fruit flavors (hence "froot", a cacography of fruit). However, there is no actual fruit in Froot Loops and they are all the same flavor. Kellogg's introduced Froot Loops in 1963. Originally, there were only red, orange and yellow loops, but green, blue and purple were added during the 1990s. Different methods of production are used in the UK where, due to the lack of natural colourings for yellow, red and blue, Froot Loops are purple, green and orange, and the loops are also larger in size. Although the marketing side of Kellogg's misleadingly sold the idea that each individual loop color was a different flavor, Kellogg's has acknowledged that all share the same fruit-blend flavor.

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1. ### Is This a Series or Parallel Circuit?

Consider the problem below I used Kirchoff's loop/junction rules to correctly arrive at answer C (1.3A). Before using Kirchoff's rules I tried to get ##V_3## by treating this as a Fermi problem using the following lines of logic, but there is a flaw somewhere, can someone identify the flaw...
2. ### I Renormalization Scale in Loop Feynman Amplitudes

I want some clarification on what is done about the ##\mu^{2\epsilon}## renormalization scale parameter in loop amplitudes. I am under the impression that it shows up to restore the mass dimension of an amplitude when the loop momentum integral is reduced from 4 to ##4-2\epsilon## dimensions. As...
3. ### I DC current flows in a wire when two loops are brought close by?

Hi all, I have a question on the DC current flows, when two loops are close by. Consider a battery driving a loop with a finite resistance. There are charges on the surface of the loop, which exerts forces to direct the flow of the DC current. The changes also produce an electrostatic field...
4. ### Stewart platform and closed loops

Hello! (I am not asking for someone to do this for me. I am only asking a qualitative question.) Suppose one knows the lengths of all six links that are involved in the Stewart platform. Is that enough to define the position and orientation of the top (assuming the base is fixed) I would...
5. ### A Retrieving the loops on spinfoams

I am looking for a paper i read several yeais ago. is was on a graphical way to see all the closed loops associated to an oriented spinfoam. there was a set of lines on each edge. do you see what i mean? thanks
6. ### What are these loops on this jet's wing?

I was watching a video about a herpetologist's trip to Thailand to study monitor lizards and there was a short part of the youtube video showing a part of the wing of an aircraft this guy was riding in. It's obvious it was a jet plane, but there was these weird loops that appear to be welded to...
7. ### I Simpler Brunnian "rubberband" loops?

The standard configuration of Brunnian "rubberband" loops shows a series of unknots each bent into a U-shape, with their ends looped around the middle of the next unknot. (See for instance http://katlas.math.toronto.edu/wiki/%22Rubberband%22_Brunnian_Links). This connection requires 8...
8. ### How do for loops work in python?

str1="hello" for stringElement in str1: print("str1","=",stringElement) Strings are arrays in python and they are represented like this. Now I want to understand how the for loop is working here. My dry run-: for h in str1 print h for e in str1 print e and so on till...
9. ### The magnitude of the magnetic field at the center of the loops is....

I calculate like this and I think the answer is E not D. N( µoI/2a + µo2I/2*2a) = 2µoNI/2a = µoNI/a
10. ### Confusion when dealing with loops and surfaces with Maxwell equations

DISCLAIMER: in Italy, we talk about "circuitazione" of a field through a closed loop ##\gamma##, for the physical quantity $$\Gamma_\gamma(\overrightarrow{E}) = \sum_{k}\overrightarrow{\Delta l_k} \cdot \overrightarrow{E_k}$$ but after some research, I haven't managed to find the correspondent...
11. ### I Why do representations label the edges in LQG?

Hi Pfs Marcus wrote a huge bibliography during many years about LQG. but i do not see where to find an answer to a question. Penrose draw diagrams with edges labelled by numbers. What is the reason why later number were replaced by SU(2) representations?tÿ
12. ### I When swapping roots of a polynomial, how to prove discriminant loops?

I was looking at this discussion of swapping roots of a polynomial causing the discriminant to loop around the origin. https://www.akalin.com/quintic-unsolvability Although it appears to be the case, has this mathematical fact ever been proven? It seems that the formula for the discriminant...
13. ### Motional EMF for loops of wire vs conducting plates

I'm in an intro E&M class, and I'm trying to distinguish between Motional EMF for loops of wire and conducting plates. This question might be kind of silly, but are Eddy currents pretty much the same thing as induced currents in a loop of wire? More specifically, what I am trying to ask is if...

15. ### Engineering Kirchoff's voltage law applied to this circuit with three loops

I'm stuck straight out of the gate any help is really appreciated
16. ### Does the order in which you run two 'for' loops matter?

It's a simple question, and I feel like the order in which you run two loops would not matter in regards to how long it would take to run the script. You'd still have to run through ##m \cdot n## cells no matter the order. If you check column-wise, you will have to check all m entries in each of...
17. ### Help with Understanding Ground Loops

Hello, When connecting different circuits together, the reference electric potential ##V_{ref}## (the ##0 Volt##) for each circuit should be the same electric potential so the potential at all other points is the same. If circuit 1 has reference ##V_{ref1}## and circuit 2 has ##V_{ref2}##...
18. ### Ampere's law -- application with two conducting loops

I am trying to get more confidence on the direction of current using Amperes law, the problem statement is Loop1: My first task was to assign the direction of current. If I wrap around the my right hand fingers in the direction of integration the thumb is pointing up hence Positive Y direction...
19. ### Calculating effective action at two loops

Does this mean that the expression for the above vertex is $$-\frac{g}{2}\epsilon^{abx}\epsilon^{cdx}\int d\tau \langle A_{a} (\tau) A_{c} (\tau)\rangle \langle Y^{i}_{b} (\tau)Y^{i}_{d}(\tau) \rangle$$
20. ### Average current around a magnetic loop that changes its shape

To find out what the induced loop current was i used the formula: V=R×I To find out what the value of V was i used the formula that links electromotive force (fem) to angular speed: Fem=ω×B×A The only thing that's missing is the loops area but considering that it's a semicircle and that the...
21. ### Magnetic field due to two loops

My attempt is the magnetic field due to loop1 and loop2 should get added The magnetic field due to loop1 is B1 =(μ0 * Φ * i)/(4*π*r) = (4*π*(2*π)*0.004) /(4 *π*0.015) = 1670nT. I assumed this value should be less than 100nT. What is the reason? The other question is "Loop 2 is to be rotated...
22. ### How can I fix a ValueError when trying to terminate a while loop in Python?

Please help! I am trying to create a Python program for an assignment that will convert Celsius to Fahrenheit and vice versa depending on the input from the user. The numeric conversion portion of the code is working, however, if the user inputs "exit" the while loop is supposed to terminate...
23. ### A What is the explanation behind loops as O(h) corrections in tree level diagrams?

tree level diagrams are classical, and loops are corrections of order h. what is a good derivation or explanation of this?
24. ### Current in coupled loops (transformer design)

I think I know the answer,but just to make sure. I have two coupled inductors through a core that provides better flux permeability, aka a transformer, I provide say 5v and 1000 amps AC to the primary loop, in my secondary loop I have a capacitor in series with the loop (of sufficient...
25. ### Influence of Core Change on Current in Solenoid Loops

How does changing the core of the solenoid affect the current induced in the loop?
26. ### B Closed Timelike Curves vs Time Loops: What's the Difference?

What's the difference between Closed Timelike Curves seen in physics and the time loops in movies where a character relives a period of time over and over, but retains memories? I'm just curious about this stuff.
27. ### B Is it possible to experience time loops?

I haven't been on here in a while and have forgotten a lot of my physics knowledge, which is annoying. I just want to know, are time loops possible? Like the ones that appear in movies where a character relives a period of time. Is this allowed by the laws of physics? I know it's not really a...
28. ### Induced EMF in closed loops around bar magnet

I wonder if there is a way to calculate induced EMF in closed loops around bar magnet, which is traveling with constant velocity v to the right as depicted?
29. ### B Closed Time-Like Curves: Principles & Observations

Hi, If I understand correctly, closed time like curves (CTC) are world lines that close upon themselves. What would an observer measure to demonstrate a CTC?
30. ### Magnetic field and coplanar loops

Homework Statement Homework EquationsThe Attempt at a Solution The current in the inner loop should flow in anticlockwise direction so as to resist the increase in flux of the external magnetic field . But how do I deal with the outer loop since there is smaller loop inside it ? I think...
31. ### B Exploring the Possibility of Causal Loops and Time Travel: Can They Coexist?

A causal loop is when an object has no definite starting point, eg: if you threw a ball into a wormhole, and when it comes out it hits itself, making itself go into the wormhole. This sequence keeps going. Is this kind of stuff possible if we ever have a time machine?
32. ### I Computing Polyakov Loops in Lattice QCD (Basic Question)

Hi PhysicsForums, I have a pretty basic question about extracting physical parameters from lattice QCD simulations. As described in "Quantum Chromodynamics on the Lattice" by Gattringer and Lang, it seems we should be able to extract the static quark/anti-quark potential by considering the...
33. ### Kirchhoff's First Law to solve a circuit with 2 loops

Homework Statement I've recently watched a video which explains Kirchhoff's first law however, I'm not sure about his calculations. I got the same answer just wanting to make sure I am doing it right. the guy wrote L1: -75I2 +3V=0 ⇒ I2= -3/-75=0.04A He calculated L2 like -12V -125I3 +75I2=0 ⇒...
34. ### Induced current in two connected loops

Homework Statement Homework EquationsThe Attempt at a Solution Call the middle point where the two loops meet O . The induced EMF in the right wire should be anticlockwise and in the left loop should be clockwise . But there can be only one current in the wire . The induced EMF in the...
35. ### Magnetic field of circular loops and solenoid

I don't understand something. At the center of N circular loops, the magnetic field is μ_0NI/2a. And that for a solenoid is μ_0nI. Why are they not the same when the number of loops is large and the length for the solenoid is long?
36. ### Pressure Drop in a fire fighting network with loops

Hello Everyone, Can someone please explain to me how I would go about verifying the External Static Pressure of a pump that feeds a pressurized fire fighting network with loops in it. An image of the network is attached. I'm not being able to grasp the concept of pressure drop in a pressurized...
37. ### Art My Video Art (fractals, video feedback loops, etc)

Hey, I just thought I would share some of my video art. They are meant to be visuals going alongside Techno / House music in the nightclubs of Berlin. However I got a lot of ideas from reading up on physics, like diffraction patterns, fractals, polarization of light / materials, lenses, video...
38. ### EMF in bigger loops kept on both sides of a small loop

Homework Statement Modification: Take two big loops kept on both sides of the small loop at a distance a from the corresponding end of the small loop. Homework EquationsThe Attempt at a Solution The flux through the bigger loop is equal to the flux through the smaller loop, provided that the...
39. M

### B Exploring Time Loops: The Possibility of Repetition in the Universe

I was just wondering, if time can be dilated by gravity, can it actually loop and repeat itself (like movies), and if anyone was there it somehow witness it, they would see everything repeated? Sorry if this sounds silly, but I'm curious.
40. E

### I Will Increasing Tension of a Two Loop Standing Wave Change its Frequency?

Hello all, I am doing this question where it asks if I increase the tension of a two loop standing wave without changing the frequency, what kind of standing wave will I get? I came to the conclusion that it would become a one loop standing wave as f= 2L/(n) as I plugged in 2 for n and I got...
41. ### B Knot theory: closed loops in n dimensions

I'm not a math machine, but I dabble in dimensional stuff. I think this falls under knot theory. I have built several prototypes of a tesseract. Each of them sits in a little case in my office. One of them is made from truncated cubes, held together with elastic cord: In theory, the...
42. P

### Hardy Cross method with open loops

Hi. I am using the Hardy Cross method to simulate the gas flow inside a multiple hearth furnace (as shown in figure A). Figure B is a representation of the furnace's body as a pipe network. The segment A-AH represents the actual hEarth's, while segments B-AI and C-AJ represent the exhaust ducts...
43. ### I Weak gravity conjecture and strings vs loops

“If the weak gravity conjecture is right, loop quantum gravity is definitely wrong,” said Nima Arkani-Hamed, a professor at the Institute for Advanced Study who co-discovered the weak gravity conjecture. source...
44. ### Physics Behind Time Loops In Movies?

I was just wondering if there is any physics behind the time loops in the movies Groundhog Day or Edge of Tomorrow.
45. ### Does a wire loops' magnetic field affect it's current?

When you run current through a circle formed wire it generates a magnetic field. Will this field affect the current in the wire that generates it? I mean if it does wouldn't the calculations for the created magnetic field be rather circular? The magnetic field depends on the current which in...
46. ### If-else statements in for loops

I've come across a rumor that states that if-else statements can make the loops go slower. Well, it's not rumors since the writer offered numbers (times) to support the statement. http://blogs.sas.com/content/iml/2012/02/13/avoid-unnecessary-if-then-statements-in-loops.html I was wondering...
47. ### Electromagnetic induction in current loops

would be really grateful if someone could help throw some light on this - its probably really simple but I am typing myself up in loops! I have a piece of wire which is placed in an external AC magnetic field which is varying sinusoidally. The wire is folded to make two rings of radii r1 and r2...
48. ### Python How Can I Improve Nested For Loops in Python for Combining Cut Expressions?

Hello, well I am not sure how to search for this online, but I raise this question here: Suppose that I have several bins of let's say cuts, here I list 3 but the main idea is to make their numbers tunable by the user: cut1 = { "p10" : "p <= 10" , "11p20 " : "10<p && p<=20" ...
49. ### A How Do Nested Conducting Loops Interact Electromagnetically?

Hello, As a heuristic tool for a complex problem, I'm trying to understand a series of nested conducting loops each with a initial identical current on it. These perfectly conducting loops are in the same plane each with that current in either direction. Each nested loop is perfectly...
50. ### Is there a possibility that time loops exist?

I'm filmmaker, currently I'm writing movie about time loop. My question is, is it possible for time loop to happen? What can cause it? and is there any scientific explanation behind it?