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. D

    Water resistance as a spring constant

    i am working on a project for a dynamic sculpture we want the sculpture to be able to sway and our idea includes placing the sculpture on a floating base(almost like a catamaran) , with wind forces the sculpture will sway. i would like to know how i may model the water resistance/buoyancy...
  2. A

    Question involving EMF and internal resistance

    A cell supplies a current of 2 Ampere, when it is connected to 5 ohm resistance and supply a current of 1.2 Ampere. If it is connected to resistance of 9 ohm, find EMF(electro motive force) and Internal Resistance
  3. A

    Question over the concept of Electrical Resistance

    So what actually is the cause of electrical Resistance?
  4. R

    Engineering Calculate the Resistance of the RC circuit so that LED just stays on

    In a simple series circuit there is a 12V supply battery, 12μ6 F capacitor, a Resistor, and a 2v drop LED with an imax of 30mA. frequency is 10Hz Calculate the resistance of the resistor so that the LED just stays on. Homework Equations Resistance of Capacitor Xc = 1/2∏fC P=VI V=IR...
  5. B

    Air resistance and magnitude

    If a 10 kg mass is in free fall (no air resistance), what force must be applied to slow the object down? (g = -10 m/s^2.) For this question, why is it 200 N and not 100 N? Wouldn't 100 N cancel out upward and downward forces and cancel them out?
  6. B

    Understanding Air Resistance: Explaining the Math Behind Reduced Force

    Can someone please explain the math of this problem? -If F is the force of air resistance on an object with mass m moving at a constant velocity, which of the following best describes the acceleration of the object when the force of air resistance is reduced by a factor of 4? (a) F/m (b)...
  7. R

    What are the different methods to measure the resistance of a capacitor?

    Homework Statement I was told that I can measure the "resistance" of a capacitor using 3 methods: 1. "The direct method" R = \int_1^2 \frac{\rho}{A} ds 2. "Ohm's Law" R=\frac{U}{I} U=\int_1^2 E ds E=\rho J = \frac{\rho i}{A} 3. "The analogy between electrostatics and electrokinetics"...
  8. E

    Calculating Iout & Output Resistance of BJT-MOSFET Circuit

    Hi! Here is my task: a) Calculate and sketch Iout=f(Vc2), for 0<Vc2<1.5V. (neglect Early effect) b) calculate output resistance for Vc2=Vc1. BJT's Q1 and Q2 are in forward active mode, have identical characteristics and same temperature. MOSFET M3 is in saturation. Iin=10μA, Vt=25mV...
  9. D

    MHB Find Solution to Power & Resistance w/ 10 Ohm Resistors

    Here is the question: You are given a number of 10 ohm resistors, each capable of dissipating only 1.0 W without being destroyed. What is the minimum number of such resistors that you need to combine in series or in parallel to make a 10 ohm resistance that is capable of dissipating at least 5.0...
  10. R

    Solve Haemodynamics Confusion: Peripheral Resistance, Sympathetic Stimulation

    Im not able to get this concept of haemodynamics. Constriction of blood vessels increases arterial pressure but it also increases resistance, so how does cardiac output increase? How can constriction of vessels increase venous return? It incteaes systolic filling pressure but resistance also...
  11. ?

    External AC Emitter Resistance Formula

    I have worked on an example earlier today. It's the section on BJT Amplifiers. I have been studying the sub-section on Common-Collector Amplifier. I've come across a rather peculiar formula, which has not been mentioned anywhere in my prescribed textbook besides a worked example. Here is the...
  12. E

    MOSFET amplifier input resistance

    Hi! My task is to calculate input resistance for circuit below: VDD=10V, Vtn=1V, β=1mA/V^2, VA=100V, load resistance RL=20k. Here is model for AC analysis (DC source and infinite capacitances are short circuits, current directions chosen arbitrarily): After calculationg input current iin...
  13. C

    Resistance, Current and Voltages

    When there is a current of mixed resistances (like parallel and series together), how do voltage drop and current relate throughout the circuit?
  14. V

    Resistance & Current in a wire

    Homework Statement The resistivity of gold is 2.44 x 10-8 Ω m at a temperature of 20°C. A gold wire, 0.5 mm in diameter and 44 cm long, carries a current of 380 ma. The number of electrons per second passing a given cross section of the wire, is closest to: A) 2.4 × 10^18 B)...
  15. S

    Why does gravity not create resistance?

    If a planet is traveling through space and distorting space, why does it not slow down? If a boat travels through water and distorts the water it will slow down. I guess a better way to put it is why does empty space not resist being bent?
  16. J

    V= IR So a circuit with no resistance has no current or voltage?

    If you had a voltage v and wanted to know current, would the current be infinity ? Do we just call it 0 because it is insignifant to find such a useless number because since there is no resistance it would be too high. I figure if r=0 then I = v/0 so infinity?
  17. F

    Calculating equivelent resistance and equivelent capaictance

    Homework Statement Below is a link to the problems, A and B. http://oi62.tinypic.com/28bgqao.jpg Homework Equations For series: R=∑R_i 1/C=∑ 1/C_i For Parralell 1/R=∑ 1/R_i C=∑ C_i The Attempt at a Solution I usually don't have any problems when it comes to calculating effective resistance...
  18. P

    Resistance of a discharging capacitor

    I am trying to calculate the maximum current drawn from a capacitor that is connected to a resistor of a very low value (a few mΩ). Because the resistor does not have a large resistance as I've seen with many V/t and I/t graphs for capacitors connected to resistors, where the decay of the curve...
  19. Eagle9

    How quickly does E.coli gain resistance against antibiotics?

    As well-known, the bacteria (particularly E.coli) can gain the resistance against antibiotics. In Wikipedia its mechanism is written: I would like to know: 1) Are there any OTHER mechanisms for gaining the resistance? Can the bacteria gain resistance when it has got antibiotic, LB broth in...
  20. D

    Resistance of cylinder case a and case b

    Homework Statement what's the difference between case a (photo 1&2) and case b (photo 3 ) ? what can't i use the way of doing case b for case a? p/s : my own working for case a in photo 4 Homework Equations The Attempt at a Solution
  21. D

    Calculating Resistance for Cylindrical Conductors

    Homework Statement can anybody help me with this question? my ans is different from the ans given... i need explanation on this ! here's my attempt by the way. r=pl/a . r=resistance , p = resistivity l=length r=(1.69e-8)(2pi )(6e-2 +1.5 e-3 )(300) / (pi )(1.5e-3)^2 what's wrong with...
  22. J

    Microscopic properties of electrical resistance

    I have recently been learning about the microscope properties which dictates electrical resistance. The main equation (resistivity) in my textbook is: \rho = 2m/qN\tau where \tau is the time between collisions of electrons with the atoms, q is the charge of the electron, N is the number of...
  23. P

    Air Resistance of a Diver using Ek and Eg

    Homework Statement A 57.0 kg diver dives from a height of 15.0 m. She reaches a speed of 14.0 m/s just before entering the water. What was the average force of air resistance (e.g., friction) acting on the diver? What is the force of friction underwater if she reaches a depth of 2.5 m before...
  24. C

    Temperature Coefficient of Resistance of Two Wires in Series

    Homework Statement Two wires A and B are connected in series at 0oC and resistance of B is 3.5 times that of A. The resistance temperature coefficient of A is 0.04% and that of the combination is 0.1%. Find the resistance temperature coefficient of B. Homework Equations Rt=R0(1+α0t)...
  25. Y

    Insulation Resistance in a coaxial cable of length L

    Homework Statement Determine the insulation resistance in a coaxial cable of length L, with conductivity, as shown in Figure assume that the current density J is radial direction. The Attempt at a Solution so i was wondering if this approach is correct, consider a sequence of...
  26. Y

    Calculating Coaxial Cable Insulation Resistance for Radial Current Density

    Homework Statement Determine the insulation resistance in a coaxial cable of length L, with conductivity, as shown in Figure assume that the current density J is radial direction. The Attempt at a Solution so i was wondering if this approach is correct, consider a sequence of...
  27. A

    Resistance between two points in complex circuit

    Homework Statement I have attached a circuit scheme from old textbook. Basically, there are 17 resistors which every has resistance R and we need to find the resistance between points A and B. (I added numbers to each resistor so it would be easier to communicate). Extra question of mine - is...
  28. A

    Height of ball bounce with air resistance

    Homework Statement Ball with mass of 0.7 kg and radius 0.15 m is dropped from top of the building 30 m tall. Force of air resistance which acts on ball is given with the equation: F_r = \frac{1}{2} c S ρ v^2 where c = 0.5 S = r^2 ∏ ρ = 1.29 \frac{kg}{m^3} v = current speed. How tall will...
  29. P

    What is the Resistance of an Electric Iron with a Label of 240V, 2kW?

    Homework Statement An electric iron labelled "240V,2kW". Find the resistance in the electric iron. Homework Equations P=V^2/R R=V^2/P The Attempt at a Solution R=240^2/2000=28.8 ohm
  30. C

    Purpose of sheet resistance in thin film devices

    In optoelectronics and other nanotechnology applications (like organic photovoltaics, organic LEDs etc) most layers need to be electrically characterized among other types of measurements. Thus, sheet resistance is measured. An example are the 4-point-probe resistivity measurements. Yet, what...
  31. patrickmoloney

    Drag Force - Air Resistance Question

    Homework Statement A skydiver drops o¤ an outcrop at the top of a sheer face on a mountain and falls vertically downwards. Let v(x) be the velocity of the skydiver at a vertical distance x below the drop-off point. As the skydiver falls he will experience a drag force of magnitude...
  32. R

    Find resistance, inductance, and the time constant for an RL circuit.

    Homework Statement A 5.0V battery is attached to an RL circuit. The current is given by the formula: I = V0/R(1-e-t/τ), where I0 is the steady-state current, and τ is the time constant for the circuit. Using the data table provided, determine τ, R, and L for this circuit. I(mA) | t(μs)...
  33. Entanglement

    Ohmic Resistance: What Causes It?

    Where does ohmic resistance arise from, is it from the collision of the current with the electrons of the wire or is it from the electric field of the electrons of the wire's atoms that cause repulsion force against the flowing current ??
  34. S

    Power to overcome bearings resistance

    Hello, I have a pair of bearings (NSK Super Precision Angular Contact Ball Bearings) and was wondering whether I would be able to estimate the power it takes to overcome the bearings resistance when the shaft spins with some given rpm. Are you aware if this is possible to estimate. Thanks!
  35. N

    High resistance or low resistance for induction cooktops?

    Induction heating relies on an ac current to produce a changing magnetic field and hence a conductor will experience a changing magnetic flux. This induces an emf and then a current and thus heat. Heat generated is P=I^2 * R From this, it would appear that a very high resistance would lead...
  36. Y

    Equivalent resistance, using node voltage analysis

    Homework Statement (I added in the R values for reference) Homework Equations GV=I KCL The Attempt at a Solution I am not concerned with the MATLAB portion of the problem, only the setup. I think what the problem wants me to do is: 1) connect a 1A test current from the...
  37. Maxo

    Projectile with air resistance

    Grεετings! :smile: I have some questions about a physics problem. I would appreciate some help with understanding this. Homework Statement The task is to plot some graphs for a projectile at different angles, first when neglecting air resistance and then including a formula for air...
  38. A

    Solving for the resistance in a Voltage Regulator

    Homework Statement Create a 15V regulated power supply capable of providing a maximum load current of 25 mA. Circuit looks like this: http://i.imgur.com/fMtscbG.png?1ILmax (maximum load resistance) = 25mA Izt (test current) = 20mA Izk (knee current) = 25mA rz = 11 Ω Vz (nominal zener voltage...
  39. Y

    Does Air Resistance Cause a Ball to Take Longer Falling Down Than Rising Up?

    Homework Statement If a ball is thrown upwards and lands in the same spot, would it take longer to reach max height or drop back down from the max height? Also use air resistance. Homework Equations The Attempt at a Solution I believe that it would take longer for the object to...
  40. D

    MHB Max distance when an angle for a projectile is pi/4 neglecting air resistance

    We know that the angle of \(\frac{\pi}{4}\) causes a projectile to travel its max distance when air resistance is neglected. When we consider air resistance is the \(\frac{\pi}{4}\) still the angle that produces the max distance? With air resistance, the projectile with of course travel less...
  41. A

    Equivalent Resistance of Circuit System

    I'm having trouble with this problem. Any advice would be appreciated. I know I can't group all resistors together in one loop, but I'm not sure where to draw my loops. Should I choose the 200 ohm and 300 ohm for one parallel and the 400 ohm and 80 ohm for the other parallel? I have a...
  42. S

    How does air resistance change with weight and surface area?

    Homework Statement This isn't exactly homework...but I'm not sure where to post it. I was reading a textbook, and got myself in a mental predicament. I understand the reasons the book gave, but I want to *really* understand. So my question: "Why does air resistance decrease as the...
  43. JasonHathaway

    Equivalent resistance between two nodes help

    Homework Statement Homework Equations Parallel-Series resistors combinations. The Attempt at a Solution Using an approach much like the one used to find the Thevinin resistance: 1- Open circuit between A and B (R1, R2, R3), and short circuit the voltage source. 2- (R4//R5)+R6=170 3-...
  44. S

    Calculating E.M.F and Internal Resistance of a Cell in Series Circuit

    Homework Statement A cell of unknown e.m.f. , ε , and internal resistance, r, is connected in series with a variable resistor. A voltmeter is then connected across the terminals of the resistor. When the resistor has a value of 16.0 Ω the voltmeter reads 1.20 V. When the resistance is...
  45. M

    Chemical kinetics, reaction order, resistance

    X + Y + Z -> A + C+ + B- Initial Concentrations Z= 4.1 X 10^-3M, X=2.3 X 10^-1M, Y= 1.2 X 10^-1 M. http://s121.photobucket.com/user/marykaywest420/media/81386cf6-e132-4578-8fb5-1024a2a3f3d5_zpscc804723.jpg.html?sort=3&o=0 3. So my attempt included graphing -R/(R∞-R) vs. time. which produced...
  46. L

    Ideal Batteries' Internal Resistance

    Homework Statement A circuit is constructed with five resistors and one real battery as shown above right. We model. The real battery as an ideal emf V = 12 V in series with an internal resistance r as shown above left. The values for the resistors are: R1 = R3 = 59 Ω, R4 = R5 = 79 Ω and R2 =...
  47. znaya

    Finding the voltage in a resistance

    Homework Statement Given the circuit in the image (with a current source of 2A and several resistors), what's the voltage in R3? http://postimg.org/image/yl6czh9u7/ The answer options are: 1.1V 0.77V 50V 0.55V Homework Equations Ohm's law. V=RI The Attempt at a Solution I...
  48. C

    Does a flashlight battery have internal resistance?

    Homework Statement Does a flashlight battery have internal resistance? Explain. Homework Equations V = ε - Ir The Attempt at a Solution Yes, they do have internal resistance. This results in the open circuit ε being different than the voltage measured across the terminals if a current is...
  49. H

    Internal Resistance of a battery

    Homework Statement When a 10 ohm load is placed across the terminals of a battery, the terminal voltage is 11.0V. When a 100 ohm load is used instead, the terminal voltage is 11.9V. What is the internal resistance of the battery? Homework Equations V=IR The Attempt at a Solution...
  50. F

    Circuits - Calculating Effectice Resistance

    Sorry for my crude drawings but I thought it was easiest and quickest this way to post the question. Homework Statement Calculate the effective resistance for the circuits below. A. B: Homework Equations R_{series}=\sum\limits_{i=1}^n R_i \\...
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