Resistance Definition and 1000 Threads

The French Resistance (French: La Résistance) was a collection of French movements that fought against the Nazi German occupation of France and the collaborationist Vichy régime during the Second World War. Resistance cells were small groups of armed men and women (called the Maquis in rural areas) who, in addition to their guerrilla warfare activities, were also publishers of underground newspapers, providers of first-hand intelligence information, and maintainers of escape networks that helped Allied soldiers and airmen trapped behind enemy lines. The Resistance's men and women came from all economic levels and political leanings of French society, including émigrés, academics, students, aristocrats, conservative Roman Catholics (including priests and nuns), Protestants, Jews, Muslims, liberals, anarchists, and communists.
The French Resistance played a significant role in facilitating the Allies' rapid advance through France following the invasion of Normandy on 6 June 1944. The French Resistance provided military intelligence on the German defences known as the Atlantic Wall and on Wehrmacht deployments and orders of battle for the lesser-known invasion of Provence on 15 August. The Resistance also planned, coordinated, and executed sabotage acts on the Nazi electrical power grid, transport facilities, and telecommunications networks. The Resistance's work was politically and morally important to France both during the German occupation and decades that followed. It provided the country with an inspiring example of the patriotic fulfilment of a national imperative countering an existential threat to French nationhood. The actions of the Resistance stood in marked contrast to the collaborationism of the Vichy régime.After the Allied landings in Normandy and Provence, the paramilitary components of the Resistance were organized more formally, into a hierarchy of operational units known, collectively, as the French Forces of the Interior (FFI). Estimated at 100,000 fighters in June 1944, the FFI grew rapidly and reached approximately 400,000 by October. Although the amalgamation of the FFI was, in some cases, fraught with political difficulties, it was ultimately successful, and it allowed France to rebuild the fourth-largest army in the European theatre (1.2 million men) by VE Day in May 1945.

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  1. A

    Engineering Small Signal Input Resistance of a BJT amplifier

    The diagram of the BJT amplifier small signal model is below. This is not really a homework question as I am self-learning electronics, but I was advised it may be better placed here than in the technical portion of the forum. Thus I do not have an "attempt" at a solution (which is given as RI...
  2. neilparker62

    B Troubleshooting Battery Internal Resistance Measurements

    Have been busy working with a student doing a Physics prac to determine the internal resistance of an AA 1.5 V (nominal) battery. The basic formula being investigated is: $$Vt=E_{cell}−Ir_i$$ where ##Vt## is the load (resistive only) voltage, ##E_{cell}## is the emf of the AA battery, ##I## is...
  3. C

    Can't find total resistance in a complex star circuit

    [Thread moved from the technical forums to the schoolwork forums by the Mentors] Hi i have this assignment for homework: There is only one battery for the circuit, E=10V, R=4 Ohms and L=1H it asks me to find the time constant of the circuit. i know that a time constant in a RL circuit is t=L/R...
  4. X

    Launching a Projectile with Air Resistance

    Mentor note: Moved from a technical forum section, so Homework Template is not present. Hello Physics Forums members, I am a student in AP Physics C and I was just working out the range of a projectile when air resistance is non-negligible. As of right now I'm going to use the linear model of...
  5. kalm1307

    Resistor value given capacitance and EMF with a resistance R after 3ms

    T=R/C So: 0.003s=R/100μC R=3*10^-7Ω I am really confused with the equations I have to use
  6. Joshy

    Engineering Equivalent resistance of an envelope peak detector (RF CMOS)

    Full problem: I don't normally think about circuits like these in terms of energy (Joules) so I was very much confused. What I did was find where the simplified expressions intercepts with each other to get the voltage. I scanned in my work although this text is a walk through of what I did...
  7. jaumzaum

    Understanding Increase in Peripheral Resistance & Blood Pressure

    Hello guys, can anyone help me to understand why an increase in peripheral resistance causes an increase in the blood pressure? If we assume the equation Delta P = R times Q If we assume Q is constant, the greater the resistance the greater the the decrease in pressure, so the pressure should...
  8. r4g3r4hk

    B Does air resistance have a max value?

    I know that friction on a surface has a maximum value. When an object is pushed with a force greater than the maximum friction value, the object will move. But when a free-falling object falls from a height, does air resistance have a maximum value as well?
  9. T

    Resistance of a half ring of a given resistivity

    Lets suppose a half ring whit internal radius a and external radius b and height t. We can calculate the resistance of the half ring considering that it is made of a number of parallel resistors each one with resistance given by: R = ρ L/S where L = π·r and S = t·dr. The resistance of each...
  10. J

    Find the resistance of electrons in nanoshells

    We are given the resistivity of Gold. The length will be the outer radius minus the inner radius. We need to find the area. But I'm not sure how that would work given the spherical nature of the particle Would we need to use an integral to add up the increasing cross sectional area from the...
  11. A

    I Did Ohm, Ampere, and Volta Collaborate on Ohm's Law?

    Voltage SI unit = Volts Current SI unit = Ampere Resistance SI unit = Ohm Ohm's law : V=IR Did Georg Ohm (German), Ampere (French) & Volta (Italian) collaborated when Ohm came out with this electricity equation with units for voltage, current & resistance as per their surnames? Credit goes to...
  12. H

    Sliding resistance of eccentrically loaded block

    Summary:: What is the sliding resistance of an eccentrically loaded block on a flat surface? If a 1000kg block is placed on a flat surface (say coeff. of friction = 0.4), what force does it take to slide if it loaded eccentrically, i.e. at the far edge of the block? My thinking is there is...
  13. J

    A question about resistance in the human body

    Back in grade 10..,.( Oh my that was awhile back 😀 ) our electronics teacher passed around a multimeter and everyone measured their resistance ( a lead held in each hand, Fluke was set on infinite ). All in the class measured between 700K and 800K approx. All except me that is. I measured 1.4M...
  14. Leo Liu

    I Why does an ideal voltmeter have infinite resistance?

    Context: What I don't understand is why the little current that flows through the converted voltmeter can affect the measurement when the resistance of the resistor added to the ammeter is not infinite. Can someone please explain this to me? Thanks.
  15. samy4408

    I Why in an electric circuit with only a generator the resistance R=infinity?

    Why in an electric circuit with only a generator the resistance R=infinity? [Newbie's post edited by a Mentor to delete extraneous embellishment]
  16. guyvsdcsniper

    Finding the coefficients of a Resistance vs. Temp curve

    I am asked to find Ro, a, and b. Th problem states the values are determined by the measurements at the normal ice, steam and sulfur points. So I approached the problem by plugging the the temperature problems. For 0°C, Ro reduces to 7 ohms. Then for the other two non zero temperatures, it looks...
  17. johnsmith7565

    Engineering Current Divider Circuit (Find a Resistance)

    The resistors are all in series , with exception of R, so I added them together and then used the current divider equation to solve for R, and I got 720 ohms. The textbook says R should be 30 ohms. I’m completely lost.
  18. MrHappyTree

    Resistance in complex geometries

    For the electrical resistance ##R## of an ideal wire, we all know the formula ##R=\rho * \frac{l}{A}##. However this is only valid for a cylinder with constant cross sectional area ##A##. In a cone the cross section area is reduced over its height (or length ##l##). What is a good general...
  19. G

    B Grain direction for maximum tear resistance for a wire bound book

    Paper has a grain direction – the direction of the long fibres. For several reasons, publishers always print hardcover books with the grain of the paper in the same direction as the fold. I'm working on a book that will be 2:1 wire bound (two holes to the inch). I was wondering what the grain...
  20. Mr su

    Can this comparator accept negative voltage as its negative supply?

    I check the datasheet of LM 319 high speed comparator online. I was wondering if LM 319 can accept negative supply voltage(-10V) and its possible to produce a 10V to -10V square wave which oscillates along origin rather than just 10V to 0v as shown below.
  21. G

    Equivalent Capacitance and Resistance of this Circuit

    NOTE: THE C1 that is 120 microfarads is meant to be C3. What I did first was find equivalent capacitance of C2 and C3 by doing (40)*(120)/(40+120)=30. Then I found Ceq by doing (20)*(30)/(20+30)=12. For the resistance I did 6*3/(6+3)=2, for R2 and R1. Then to find Req I did (5)*(2)/5+2= 10/7 Am...
  22. godiswatching_

    Engineering Resistance of a wire around the Earth

    Hey! I had a question about this problem. I did (1) Using $$R_{0}=\rho\frac{l}{A}$$ For (2) I assume the question means that the radius increases by a meter. So I used $$\bigtriangleup L = 2\pi (r_{E}+1) - l$$ and then I used that L to find the new R. Then I said $$\bigtriangleup R = R-R_{0}$$...
  23. Purpleshinyrock

    Does element x present a linear resistance?

    ANSWER: element x does not present a linear resistance because it isn't constant as i and v increases. Is my answer correct?
  24. J

    I Car acceleration if resistance forces don't exist

    Let imagine that car with constant 500HP accelerate but resistance forces don't exist (aero drag,internal friction in engine and transmision,tyer rolling resistance etc etc..) neglect fuel loss over time.. From 0-100km/h take in 4sec and burn 200mL petrol Will car accelerate from...
  25. A

    Find the equivalent resistance of this 5-resistor circuit

    I have a question about an exercise I don't understand, I don't want the solution, only the first element to begin. I have tried with kirchhoff law, but I failed. thanks
  26. Ugnius

    How to Calculate the Resistance of Nichrome in a Series Circuit with Graphite?

    I don't really have any equations or idea how to solve this. I searched for relevant equations and only R=Rref(1+α(T-Tref)) pops up. I wasn't given any temperatures so I guess there must be some other way to solve this. Maybe anyone has idea how to approach this?
  27. es4

    Constant frictional resistance & retardation

    What the question mean by "constant frictional resistance" in terms of formula? I suppose they meant... "resistance force (f)" which is, >> f = m * a. So, here is my try... m = 1.15 ton or 1150 kg vi = 20 m/s vf = 0 d = 800 m v^2 - u^2 = 2ad 0 - 20^2 = 2a* 800 - 400 = 2a* 800 - 400 /...
  28. RalphZ

    Automotive Does vehicle weight have an effect on torque capacity of the gearbox?

    Hi, This has long been in my head, I've seen it work out in reality, but I have no idea about the forces involved in this. As I don't have an engineering degree or mathematical knowledge in automotive engineering, I've come here for help. Sorry if I've used some terms where they do not fit, as...
  29. np115

    How to solve for EMF and internal resistance in a circuit?

    I know the answers are 9 V and .5 ohms but I have no idea how to get there. Originally I solved for Delta V in the open circuit through (1.636)(5) which gave me 8.18V. Then, I solved for Delta V in the closed circuit through (1.565)(1/((1/5)+(1/10)) which gave me 5.51 V. I used these voltages...
  30. ergospherical

    B Resistance Between Two Small Conducting Spheres

    Here's a little snack; what is the resistance between two small conducting spheres, each of radius ##r##, separated by a distance ##d \gg r## within a material of resistivity ##\rho## (of infinite expanse)?
  31. S

    Does Resistance change wrt temperature include effect of size change

    Changing the temperature of a metal changes the resistivity. But It also changes the size of a sample under test. Does the change in size have an additional effect on the resistance or is that already factored in ?
  32. Astronuc

    Some 'lucky few' have 'resistance' or immunity to SARS-Cov-2 (Alpha?)

    Back in June 2020, in São Paulo, Brazil, Thais Andrade has avoided infection with Covid-19 though her husband, Erik Soares de Araujo, fell seriously ill and had to be hospitalized. https://www.statnews.com/2021/08/23/lucky-few-seem-resistant-to-covid19-scientists-want-to-know-why/ Scientists...
  33. S

    Current and resistance in the power loss of a transformer

    a) Output voltage = 2 x 6 = 12 V Current in R = 12 V / 13.5 kΩ = 8.9 x 10-4 A That is the correct answer based on the solution but I don't understand why when calculating the current in R, the resistance of secondary coil is not considered. I thought it should be like this: Current in R = 12...
  34. P

    How does mirror symmetry for resistance work?

    The question is to find the resistance between AF (top 2 points). Let the far right unlabelled vertex of the pentagon be B. Why can we say that points O and C are at the same potential? I get that both points O and C appear to be at 'half the path' if you consider AOF and ABCDF, and so potential...
  35. Evo

    COVID Lambda variant shows vaccine resistance

    Well, if the Delta variant wasn't enough, now this seems to be rearing it's head. Also continued https://news.yahoo.com/delta-infections-among-vaccinated-likely-192553854.html
  36. E

    What does negligible resistance mean?

    why is answer for (6a)6J?
  37. I

    Input Resistance of this BJT Amplifier

    Hi i got a question ,how do i calculate the input resistance ,of the RS resistor ,so i would get half of the voltage of the voltage source (500mA) .I've created the circuit in ltspice and found out that its around 95K ohms to get 250mA,but how would i calculate it . Ive also attached my...
  38. Dario56

    Internal Resistance of the Battery - Ohmic Resistance

    When current starts flowing in a circuit, voltage of the battery drops from EMF value. There are three sources of this however here I am only interested in ohmic resistance of the battery. EMF of the battery is created because of electrochemical processes on both electrodes which create...
  39. Viona

    B The resistance of an ohmic conductor

    I know that the resistance of an ohmic conductor increases with length because the electrons going through the conductor must undergo more collisions in a longer conductor. But why decreasing the cross-sectional area of the conductor also increases the resistance of a conductor?
  40. P

    Understanding diode (LED) resistance at V=0

    I'm working with some bare chip diodes for an application where I need extreme luminosity. These are the diodes here: https://www.irtronix.com/leuv-v625a6 I notice that some of the diodes have very significant resistance (on the order of megaohms) from anode to cathode and some have very small...
  41. E

    Resistance Differences: Nichrome vs. Copper Wire

    i don't understand the answer: Nichrome has a higher resistance than copper wire. There is a greater potential difference across the nichrome than the copper wire. From ,the resistance of nichrome is low enough such that there is significant power output. ^ i feel like the bold parts contradict...
  42. Pouyan

    Complex circuit and its resistance

    The true answer is : The voltage between P and Q is 1.5 V. I got stuck finding the total resistance. My question is: Is B parallel to both A and C? Is C parallel to D ? I tried many ways to find the total R but failed! My first attempt: I say the system ABD is in serie with C...
  43. Wrichik Basu

    How do you calculate the series resistance for this Triac control circuit?

    Disclaimer: Some of you might easily recognize that the components and circuit I am talking about are related to one of my projects, on which I had posted some months ago. Actually, the circuit is the same as the one in my project, but the one I am posting in this thread actually uses high...
  44. Istiak

    Is My Delta to Wye Conversion Calculation Correct?

    I was following these [steps](https://www.allaboutcircuits.com/textbook/direct-current/chpt-10/delta-y-and-y-conversions/). I was calculating resistance for left side circuit. $$R_1=\frac{2 × 2}{2+2+4}=0.5\Omega$$ $$R_2=\frac{2 × 4}{2+2+4}=1\Omega$$ $$R_3=\frac{2 × 4}{2+2+4}=1\Omega$$ Then...
  45. I

    Two Stage Amplifier -- Find the Input Resistance

    Am trying to find Effects of Feedback - Input resistance of this circuit. Is this the formula that in need to use to find the input resistance of this circuit ?
  46. P

    Why Can't Current Flow Between Two Same Voltage Nodes?

    The question is to find the resistance between points A and F. I understand that the resistor between OC can be removed. From this point onwards, resistor OC has been removed. Let the far right point of the diagram, where i5 and i7 exit from, be B. Is it possible to detach the remaining...
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