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.
Homework Statement
Find the equivalent resistance at terminals a-b of the circuit.
Homework Equations
Resistors in parallel : 1/Req = 1/R1 + 1/R2...+...1/Rn
Resistors in series: Req = R1 + R2...+...Rn
The Attempt at a Solution
[/B]
The resistors are in ohms and the answer is 32.5 ohms. The...
Homework Statement
Hey! Problem:
A ball falls 8,5 meters, and hits the ground with 11 m/s.
The ball has a mass of 0,2 kilos.
How much work was done by Air resistance on the ball?
Homework Equations
I guess mechanical energy eqution?
The Attempt at a Solution
answer should be -4,5 joule...
hello,If anyone of you help me in finding specification(diameter of nichrome wire required) for a 2 m nichrome wire to heat up to 65 degree Celsius .Voltage applied is 12 v. I want to use it by coiling it to cylindrical mica sheet to make a smaller heating product.Temperature should not exceed 65.
Homework Statement
if a potentiometer has driver cell and wire AB ,then an unknown emf (emf<driver cell) is balanced at some length L. does the balance point change if internal resistance of driver cell is changed?
Homework Equations
V= kl K= potential gradient
The Attempt at a...
My gut instinct is that putting all the resistors in series will give max resistance, but I am not sure how to give a more rigorous either mathematical or just in words reasoning why. Or maybe I'm wrong! But it seems like the fraction introduced from parallel won't help
In any case, assume all...
I am taking an intro electrical circuits course which requires that I write extensive lab reports. I just completed a really simple lab about calculating resistance when configured in series and parallel, etc.
In my intro I'm writing a short explanation about resistance, and resistors, and...
Homework Statement
Me again. I again got confused with 2 similar things done differently on two different places. Let's say we have some arbitrary circuit and we want to replace a part of it with thevenin's generator. We also need to calculate effective Thevenin's resistance, which is where i...
Homework Statement
Find the equivalent resistance Rab for each circuit given here (resistance values have been omitted so I can focus on understanding the concept, but I can supply them if requested).
Homework Equations
This problem expects me to know how to combine resistors in...
Homework Statement
Ignore the internal resistance of the battery and assume it is merely a battery. Calculate the equivalent resistance of the circuit.
Homework Equations
1/Req = 1/R + 1/R ... (parallel)
Req = R + R ... (series)
The Attempt at a Solution
I know this is fairly simple but I...
Homework Statement
[/B]
Consider the circuit above. You are given the following measured values:
V = 1.5 V
R1 = 100
R2 = 100
R3 = 50
R4 = 50
R5 = 50
Homework Equations
Kirchhoff's Loop Rule and Junction Rule
The Attempt at a Solution
I tried setting this up using the junction and loop...
The electrons flow on the outer surface of the resistor, why then does the resistance of a resistor depend on it's cross sectional area and not on it's perimeter?
Hello,
Could you help me with the homework, please...For the conventional resistance measurement used four electrodes: two current (A, B) into the country "deserts" and the current I between two measuring (M, N) is then measured voltage AU, resistivity, which is the goal of our measurement is...
1. I'm a middle school science teacher with no science background, and I'm trying to avoid teaching any misconceptions on this topic! However, I don't know that I grasp what's going on here myself. I'm trying to explain rationale for why, on a circuit diagram, the symbol for a resistor may...
Hello everybody,
I am chemist. and I prepare ionic membrane and placed in a home made acrylic cell containing 0.1M NaCl separated into two portions by ionic membrane. I applied DC voltage of 9.6V (using 9V battery). Using multi-meter the measured DC voltage in water was 4.45V. The distance...
Homework Statement
Calculate the effective resistances between P and Q in circuit-1 and A and B in circuits 2 and 3 in each of the following circuit diagrams.
In circuits 2 and 3 the resistance R has the value 1Ω.
2. The attempt at a solution
1. Why does the AB branch get removed in circuit-1...
Homework Statement
You wish to use an LED (D1) which provides essentially zero resistance and is rated to accept either a maximum of 75 mW of power or 30 mA of current. In the following two circuits, what range values for resistor R1 will be acceptable in each case if the voltage provided by V1...
hello there i kinda need help with this, image attached in the thread
this is the ohmmmeter circuit and i have two questions :
-what is the effect of R2 when it become lower than Rm?
-what is the effect of R2 when it become higher than Rm?
Rm=internal resistance of ohm-meter
R2=zero adjust...
Homework Statement
Calculate the equivalent resistance between A and B.[/B]Homework EquationsThe Attempt at a Solution
I solved this problem by using wye-delta transformation. Is there any other method to solve this? The speciality in this circuit, I noticed, two of resistances are 0.[/B]
Hi, I want to use a digital ammeter to measure the current flow though a Raspberry pi. The Pi uses about 700mA and is 5V so its got a resiatance of about 7 ohms. Therefore something like 0.5 ohm ammeter will have a large voltage drop of about 0.3V which is way too large and would lead to the...
Greetings, folks!
I have spent the past six years developing a matching pair of 13"-square heating plates to mount to the inside bottom (front and rear) of a Sun-Mar Excel NE composting toilet drum. The heating plates are necessary to keep the compost in the composting drum between 70º and...
1. Consider a closed loop which already has a current ##I## running through it while the resistance of this loop is ##R=0##. I now suddenly start tuning on a homogenous magnetic field through the loop which gives raise to an emf in the loop ##\epsilon=-\frac{d\Phi}{dt}##. What will happen?
My...
Hi everyone,
I just came across an exercise that asks me to explain how I would measure the change of resistance of a metal wire between a temperature of 0º C and 100º C. The answer to the question is below, what I don't understand is why is there a need to put ice in the water bath and the need...
Homework Statement
A total charge of 50 Ah is stored in a 12 V battery of a car. Each
of the bulbs of the four parking lights is labelled 3,6 W / 12 V.
Homework Equations
a) Find the current from the battery when only the parking lights are switched on.
b) What is the resistance of one bulb...
Well, recently I have started to deal with electronics and I've seen several new concepts such as ohm's law, parallel and series circuits, what's AC and DC and many other topics.
Ok, I have no doubt on what's direct and alternate current or what a series and parallel circuits are; rather than...
I guess i have discovered or i may say re-discovered if already existing a formula for the resistance offered to the displacement current in capacitors.
I am not talking about the capacitive reactance but, a resistance which depends on time, area and further more calculations.
What shall i do...
Do transformers change the resistance of the wires inside then when turned on? The reason I ask is because I know that transformers can be used to change the ratios between voltage a current while keeping the power sent in and power sent out roughly equal, but since V=IR this must mean that the...
Homework Statement
The copper windings in an electric motor have a resistance of 54[Ω] at 200.
Later the resistance was 60[Ω], what is the temperature
Homework Equations
$$R_1=R_0(1+\alpha t_1)$$
α=0.00393[1/0]
The Attempt at a Solution
At 00C R0 is: ##54=R_0(1+0.00393\cdot 20)\rightarrow...
Homework Statement
The book says the formula is accurate as long as t and α are small. i understand about t but why also α?
Homework Equations
Resistance R: ##R=R_0(1+\alpha t)##
The Attempt at a Solution
According to the graph (see picture) α is the slope and is suited for every material, so...
Homework Statement
Find the resistance of resistor R7 when the switch is turned on so that the power of that resistor is maximum in the circuit.
The voltage of the capacitor before the switch is turned on is Vc=200V.
Homework Equations
Thevenin's theorem
The Attempt at a Solution
I...
Homework Statement
Suppose the conductivity of the material separating two coaxial cylinders, of radius a and b (a < b) and held at a potential difference ##V##, would not be uniform. Specifically, ##\sigma(s) = k/s##, for some constant ##k##. Find the resistance between the cylinders. [Hint...
Homework Statement
Find the effective resistance between the points 'x' and 'y'. When the middle Resistance is 5 ohms.
Homework Equations
Ohm's Law - V=IR. Kirchhoff's Junction and Loop (Mesh) Rule.
The Attempt at a Solution
I drew the following diagram:
I got the correct answer when I...
Homework Statement
In metals the resistivity ρ is constant and the resistance R is fixed and doesn't depend on the current, but when i insert the equation of ρ into R i do get a dependence.
Homework Equations
Resistivity is field E divided by current to area: ##\rho=\frac{E}{i/A}##...
Homework Statement
Students are given some resistors, a battery with internal resistance, and an ammeter. They are asked to determine the emf e and internal resistance of the battery using just this equipment. Working with the circuit shown at right, they insert each resistor into the circuit...
recently, I did a experiment about insulating coating on a powder.
and I measured resistance with various voltage.
according to Ohm's law, the resistance is constant
however, my sample showed different resistance with difference V.
At every voltage, I checked the currents and the resistance...
The question is to solve the current through a resistor after a pn junction. (photo attached)
As far as I'm aware the voltage source in the pn junction is (in this orientation) of opposite polarity to that of the 0.8V voltage source.
From my understanding the answer goes like:
V=IR
I=V/R...
Hi, I've had an idea for a school physics project but I'm not sure if it will work.
I want to measure the volume of water in a fixed shape container by passing an electrical current though it and monitoring how the resistance changes (with a potential divider circuit). My idea is that if I...
Hello Forum,
It is well known that the electrical power dissipated (in the form of heat) by a resistor of resistance R connected to a battery of voltage V is:
P_diss = (V^2)/ R or equivalently P= (I^2)*(R)
Clearly the smaller the resistance R, the more the dissipated power because R is at...
When you increase the resistance of a filament bulb more work is done on the bulb which means its temperature increases. This causes the ionic lattice to vibrate with a greater amplitude (since it has more kinetic energy). The conduction electrons now encounter more collisions, hence the...
1. Homework Statement
Find the equivalent resistance
Homework Equations
Is=I1=I2=...
Vs=V1+V2+...
Rs=R1+R2+...
Ip=I1+I2+...
Vp=V1=V2=...
1/Rp=(1/R1)+(1/R2)+...
The Attempt at a Solution
Sorry the picture is sideways! Is this the correct method for finding the equivalent resistance? The part...
1. Consider the group of resistors in the figure, where R1 = 12.3 and R2 = 7.95http://www.webassign.net/images/omegacap.gif. The current flowing through the 7.95[PLAIN]http://www.webassign.net/images/omegacap.gif resistor is 1.22 A. What is the voltage of the batter...
Hi everyone,
I am trying to simulate a circuit containing resistors, inductors and capacitors. When i calculate the Impedance of the circuit i find it to be for example 150+100j for a frequency of 5Hz. When i run the same simulation for a frequency of 15 Hz i find it to be 162+134j. I understand...
In this clip the mythbusters are investigating projectile motion at a firing range:
Using the fact that the bullet fell approximately 1 inch as it traveled 100 feet, I predicted it should travel 600 feet down the firing range before hitting the ground from a height of 36 inches. Instead, it...
Homework Statement
Hi there. I have to solve this problem, and I'm having some doubts.
It is desired to build an electric engine of 0.9[HP], which will be connected to 220[V]. This will be done by a Cu wire with a cross section of 1.2 [mm²]. Supposing an efficency of 90% compute how long...
1. A parachutist of mass 62 kg is falling at 55 km/h when her parachute open. She then falls 24 m in the next 2.0 seconds. Find the force of air resistance acting on the parachute during those 2.0 seconds.2. Could I just find the force of friction?3. I found out what the force would be if not...
Homework Statement
two 8 ohm resistors and a battery of emf 12.0V and internal resistance of 8ohms are connected in series. Calculate the power delivered to each external resistor and then calculate the power wasted due to internal resistance.
I keep coming up with the answer 18 but apparently...
I am working on my graduation design project, and I am responsible for making the power supply circuit. It is a lower power source, and acts like a current source that can supply current in the range of 30 mA to 130 mA.
My power supply circuit has a source impedance of 85 ohm. Our load, a...
Does anybody understand the fundamentals of what is happening in this circuit?
Tungsten welding info is all about high current... but this is a low current scenario.
AC input, CDI Coil generated 20Kv (estimated) suffers voltage drop over 100mm of tungsten rod.
The larger the diameter... the...
Homework Statement
Why is the resistance lower in a bulb which is turned on? (Compared to when it has been off)
One bulb which is off has a measured resistance of ##27.0 M\Omega##
When it is on it has a measured resistance of #380.9375 \Omega##
Homework Equations
##\rho (T)=\rho_o(1+\alpha...