What is Resistance: Definition and 1000 Discussions

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. H

    How is the energy of a zero resistance circuit converted to rotational energy?

    If I have a DC induction motor coil of a zero resistance so that means that to sustain a constant magnetic field I do not need any energy. So in a DC motor how is energy of zero resistance circuit converted to rotational energy of a motor?
  2. D

    Total equivalent resistance of a combined circuit

    I attempted to solve the problem by following the positive terminal of the battery and I realized that Resistor R1 has a different path than R2+R3+R4. I came to the conclusion that R1 is in parallel with R2+R3+R4. The series connection with R2,R3,R4 would be 30 ohm total by adding the three...
  3. F

    Engineering Help me finding the current in here please (Circuit analysis)

    Hi! I've been struggling with this. Original exercise here: Find the value of Iy when R=0. And the value of Vx when R is infinite. For the first part of the question I did this since R=0: I've tried to solve this circuit and I get that Iy and I5 are 0 A, and this can't be possible since Iy...
  4. paulmdrdo

    Thevenin Resistance and the Time Constant

    Homework Statement Homework Equations Rth = R||R+R (not sure?), τ=Rth*C The Attempt at a Solution [/B] So, what I ultimately wanted to determine is the time constant of this first order op-amp circuit. I first tried to calculate the thevenin resistance seen by the capacitor by using Rth =...
  5. SaiTatter

    I need to calculate the equivalent resistance

    Homework Statement The circuit is the one in "Fig.4" I need to calculate equivalent resistance between A and B. This is what I've tried: I think that the first resistor is shorted by that wire connected between A and E. Their answer looks like this, in fig 2.2.1. I'm not sure if their...
  6. archaic

    Load resistance in voltage regulator

    Homework Statement [/B] I want to find the minimum resistance ##R_L## so as to maintain ##V_z##(voltage of the zener corresponding to the minimum current ##I_{z_0}##) across the same resistor ##R_L##. Homework Equations ##V_z##(voltage of the zener corresponding to the minimum current...
  7. Jonathan1218

    Rolling Marble + Air resistance = Displacement?

    A marble rolls down an inclined plane with an angle of elevation of 5 degrees, roughly 4.9sin(5)m/s/s, and at normal pressure temperature NPT what would I need to add to S=1/2 at^2 to include the air resistance considering the marble is a sphere with a radius of 0.85cm and mass of 20g. The whole...
  8. Adesh

    How to solve a complex equation to get the current?

    I was reading The Feynman Lectures on physics http://www.feynmanlectures.caltech.edu/I_23.html chapter 23, section 4. In it he derives the equation for current when inductor, resistor and capacitor is connected in series with an alternating voltage source, he derives this equation:-...
  9. K

    B How a Secondary Resistor affects the Transformer Primary Side?

    Let's assume a 2:1 transformer which has a 100V Source connected on the primary circuit and has no/negligible resistance, on the secondary circuit a 5 Ohms resistor is connected. Using the 'Impedance Transfer/Reflection' method, the primary circuit would act as if there was a 25 Ohms resistor...
  10. Shivang kohlii

    Reading of a voltmeter having resistance R across a resistance

    Homework Statement The potential difference across resistance R carrying current I is V = IR . Now if the potential difference is measured via voltmeter of resistance r , the reading on voltmeter is V' . Prove that V' = Ir/(R+r) . For what value of r does the voltmeter measure true value...
  11. S

    Measuring the resistance of a resistor

    Homework Statement Its a general question asking which method of measuring resistance (a 5 ohm resistor in a simple circuit) has greatest precision. The first method I varied voltage from about 5V to 10V, then measured the current each time, then averaged that current and calculated resistance...
  12. M

    Find the Norton equivalent resistance

    Homework Statement Find the Norton equivalent resistance Homework Equations Sum of resistance in a parallel circuit: 1/Rt = 1/R1 + 1/R2... Sum of resistance a series circuit: Rt= R1+R2... The Attempt at a Solution Don't know where to go from here:
  13. S

    Comparison horizontal distance in presence of resistance

    Homework Statement A particle of mass m kg is projected under gravity with horizontal and vertical components of velocity U and V. There is horizontal resistance of magnitude mku, where k is constant and u is horizontal component of the velocity at t seconds. No vertical resistance present. (i)...
  14. S

    Help with some sort of formula to determine resistance to heat

    I am not that smart when it comes to math. But I was wondering if there is a formula calculator or something online that would help me with the example of a problem. For instance if the attic is 130 degrees and I have a 14 inch round metal duct to my air conditioner in the Attic is there a way...
  15. E

    At what resistance does current cease to flow

    Howdy, Pretty elementary question, I think. Looking at Ohm's law, current is I=V/R For a given voltage (let's use 120 for typical U.S.A household) at what resistance will current actually cease to flow (equal zero)? To clarify and expand on that: I am confused about whether a system with an...
  16. P

    Auto/Motor How can I calculate the resistance force for an electric Go Kart?

    Hello to all, I am trying to design an electric Go kart as part of a personal project. I am now in the preliminary design phase, trying to find some literature regarding to the resistance force (Rolling resistance + aerodynamic drag). I was able to find a document in which some guys did some...
  17. H

    Varying Gravity and Air Resistance in projectile motion

    Salutations, I have been trying to approach a case about projectile motion considering variation of gravity acceleration and air resistance: A spherical baseball with mass "m" is hit with inclination angle $\theta$ and launching velocity $v_0$, then, the wind has a drag force equals to ##F=kv##...
  18. Luxucs

    Faraday's Law with Zero Resistance Current Loop

    Hi there, I was recently helping a friend of mine with a fairly standard electromagnetic induction problem (a basic sketch of the set-up is attached) where we have a current loop with resistance ##R## moving through a magnetic dipole and had to roughly sketch out the current induced in the loop...
  19. Rayanna

    Introduction of antibiotic resistance gene to a bacteria

    Why would anyone like to intoduce a antibiotic gene in a bacteria if it will make it resistant to antibiotics which is not of any advantages to humans?
  20. V

    A few questions concerning voltage, current and resistance

    [ mentor note: post adjusted to conform to homework template and some spellings fixed ] 1. The Problem I have some few questions that connect voltage, current and resistance. Imagine that we have a circuit that consists of a battery (5V), 2 resistors. Now once we close the circuit, battery...
  21. Shivang kohlii

    Why is resistance of similar cases calculated differently?

    Homework Statement 1.In the WE-11 resistance is calculated by integrating and that too by taking length as dr and area as the CSA of the small cylinder .. Shouldn't length be l and area by 2πrdr..? I also don't understand why can't we simply use Dl/A formula , Where A =π((2R)^2 - R^2) 2)...
  22. Peter Alexander

    Engineering Computing resistance in given circuit with BJT

    Hi, before you proceed with reading this question, I would like you to know what I do not expect anyone to solve this task for me. I have a problem with a single step in the solution and I'm only asking you to help me with this one step. 1. Homework Statement Compute ##R_B## so that Q-point of...
  23. M

    Low voltage across low resistance for heating elements

    I am planning some low power heating devices in the 10 - 20 watt range and have been considering the usual high resistance alloys: nichrome, kanthal, and stainless steels (304, 316, 630). I have noticed that all of these materials are expensive. Is there some reason I could not just use steel...
  24. archaic

    Equivalent Resistance of Parallel Resistors

    I did this for fun, if you want to do it in an unconventional way, this would be useful in programming. For ##n## resistors in parallel: $$R_{total}=\frac{\prod_{i=0}^{n-1} R_{i}}{\sum_{i=0}^{n-1}(\prod_{j=0}^{n-2} R_{i+j \mod n})}$$
  25. J

    A typical monthly utility rate / Current and resistance

    Homework Statement A typical monthly utility rate structure might go something like this: $1.60 for the first 16 kWh, 7.05 cents/kWh for the next 34 kWh used, 5.02 cents/kWh for the next 50 kWh, 3.25 cents/kWh for the next 100 kWh, 2.95 cents/kWh for the next 200 kWh, 2.35 cents/kWh for all in...
  26. bornofflame

    RC Circuit - Rate energy is dissipated in the resistor

    Homework Statement 1. A 2.01 uFcapacitor that is initially uncharged is connected in series with a 6.51 kΩ resistor and an emf source with 74.6 V and negligible internal resistance. The circuit is completed at t = 0. a) Just after the circuit is completed, what is the rate at which electrical...
  27. Kevin J

    What is the resistance of a wire if its diameter is doubled?

    This was a MCQ question on one of my Cambridge IGCSE Exams, the answer key said that the resistance would decrease by 16 folds (1/16 less then the previous one), I don't know how they got 16 from? (Apparently, I answered 1/4 and it was wrong)
  28. R

    Equivalent resistance with a capacitor

    Homework Statement So I need to find the equivalent resistance for the following RC circuit to calculate the time constant, but I got stuck in terms of finding out the equivalent resistance. Homework Equations V = IR The Attempt at a Solution So the thing I am not sure on is how do you...
  29. M

    The dropping of two identical balls without air resistance

    I was thinking about this and couldn't really figure it out. You are standing on a cliff and you have two identical balls. In this case, air resistance is to be ignored. The only thing different is that you throw the ball horizontally at different speeds. Let's say you threw ball one at a speed...
  30. B

    Effective Resistance (Fluid Mechanics)

    Imagine you have a vertical pressure head 2m tall with water flowing down to height 0m and emptying. Through this length we have 3 identical tubes of resistance R and length L. Assuming I know the volumetric flow rate(Q) as a function of height, how can I calculate the resistance of each tube...
  31. H

    The resistance of a wire without a voltage bias

    When a bias is applied to a wire, due to the resistance of a wire, the electrons colliding with the atoms make the wire warmer. However, we know that without any bias the electrons also move with very large velocity (of the order 10^5 m/s). How about the collision of these rapid electrons with...
  32. F

    Calculate the total resistance

    Homework Statement Homework Equations [/B] The Attempt at a Solution [/B] Could anyone check my answer please ?
  33. Celso

    Power waste (conceptual doubt)

    I'm currently in a undergrad level course of eletromagnetism and my professor found it useful to remember quickly of some relationships that we see in high scool, among them power waste. I got the formulas, since they're simple and are direct derivated from the definitions of electric current...
  34. Safder Aree

    Engineering Finding Internal Resistance through Circuit Analysis

    Homework Statement Given this following circuit: What is the internal resistance of the meter movement ( R_I). This is part of a project I'm doing and I know the equation that gives you the internal resistance in this circuit. $$R_I = \frac{R_sR_p}{R_s - R_p}$$. However, I have no idea how...
  35. R

    Temperature profiles and thermal resistance

    I heated two different materials with a laser beam for about 10 seconds and these are the measured temperature profiles: From the various solutions to the general heat conduction equation, temperature rise seems to increase with increasing thermal resistance of the material. The total...
  36. X

    Free falling ball with and without air resistance

    Homework Statement A 2 kg ball (k factor of 0.02 m-1) is in free fall. The initial downward velocity of the ball is 12 m/s. Find the difference in displacement after 1s both with and without air resistance. Homework Equations vf = vi + at y = yi + 1/2(vi+vf)t y - yi = vit + (1/2)At2 - (1/3)Bt3...
  37. H

    A Metal or Insulator: Examining Resistance in Multiple Directions

    Generally, a material is metal or insulator is simply determined by the gap. But if we view it in another way, to measure the resistance in different direction, says x and y, and there are usually different. And then measure the resistance change with temperature. Usually, the resistances goes...
  38. K

    Understanding Resistance: Exploring the Limits of Wire and Hose Capacity

    If you have wire that has 100 ampere current but your load is only 0.5 ampere.. how come the load won't be destroyed by the powerful 100 ampere source? Or let's take the case of hose. If you have water running so fast inside a 10 inches diameter hose.. and you put a small hose between it.. the...
  39. G

    Explaining a signal converting circuit

    i have a drawing of a circuit that converts a signal in range [-5,5] V to a range [0,1.2]V . i wish to understand how it works.. i have basic knowledge of electricity as an undergraduate in general physics but a bit rusty , thus i am here looking for answers...
  40. A

    Resistance of a non-ohmic device from its I/V graph

    What is the resistance of Device Q when a current of 200mA flows through it? Wouldn't the resistance of the device be approaching 0 Ω as its characteristic resembles one of a diode (gradient = 1/R)? Apparently, the answer is just using V = I R, and solving for the resistance. Is there...
  41. M

    I can't figure out what resistance values to use....

    I started an electronics program recently and I am a month into it so I am quite new at this. I have a problem involving a potentiometer and I don't understand how to compute the voltages because I don't know what I am supposed to use for my resistance values. I know that in series the total...
  42. E

    Voltage drop in the internal resistance of a voltage source

    In this circuit,first there will be voltage drop in the internal resistance of the voltage source.Mostly,the voltage source is assumed ideal in circuits,however,here a practical voltage source is assumed. So,there will be voltage drop in the internal resistance of the voltage source which will...
  43. M

    How to determine the change of resistance from I-V graph?

    1. Homework Statement How to determine the change of R of a non-ohmic conductor from different parts of I-V graph? Please see the sketch attached. Homework Equations R=V/I The Attempt at a Solution For the part that passes through the origin, it is obvious that the...
  44. Souhardya Nandi

    Can we calculate the rolling resistance coefficient theoretically?

    I was wondering that if rolling resistance is basically caused by slight deformation of a body, we must have formulas in place to relate it to the physical and material properties of a body. But when I went ravaging for it in library or internet, everything was experimental. I wished to know...
  45. J

    A 2-d and 3-d model for contact resistance of M/n-Si (book?)

    Hi, We're studying Contact resistance and the professor has given assignments on contact resistance. But I can't find any books to refer to. Here is one sample question: The books I'm referring to are ones by Donald Neaman, SMZ, Kanos. but none of them have any mention of 1-d or 2-d model for...
  46. Islam Sabry

    The equivalent resistance for the resistors in this circuit?

    Homework Statement If the circuit of parallel and series resistors , is as follows , what's the equivalent resistance for the group? Homework Equations neglecting the battery internal resistance... irrelevant to the question. The Attempt at a Solution I tried to do the following R1=8+12=20...
  47. S

    Air resistance in projectile motion

    In lower-division physics classes, air resistance is usually ignored to make the mathematics of projectile motion easier to understand. When air resistance is included, it's often stated that at lower velocities, air resistance is proportional to the velocity of the object, Fair ∝ kv At...
  48. C

    Air resistance - freefall and horizontal projectile motion

    We have two identical balls sitting at the same height. One of them is released without applying any force (it falls freely) and the other one is given a non-zero horizontal velocity. Which of them will hit the ground first? The force of air resistance is proportional to the square of the...
  49. Mzzed

    Calculating Q-Factor and Resistance for Series LC Filters

    I am trying to calculate the correct component values to use in a simple series LC filter, however I am not sure which value of resistance is to be included in these equations. When talking about a series LC filter, is the resistance required for calculating q factor the resistance of the...
  50. A

    I''What is the optimal resistance for maximizing battery terminal voltage?

    Homework Statement A battery has an emf of V and an internal resistance of r. What resistance R, when connected across the terminals of this battery, will cause the terminal voltage of the battery to be ? A. r= R B. R= 4r C. R= r/4 Homework Equations V=IRThe Attempt at a Solution Req= r+R =...
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