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
1. Use resistors of 30 ohms, 40 ohms, 50 ohms, and 50 ohms to create a circuit with a total resistance of 95 ohms.
2. Find the amount of current going through two of these resistors if the circuit is attached to a source of 12 v.
3. What would be the voltage drops for the...
How am I supposed to calculate ohmic resistance from a non-linear electronic device component?
Say, for example, I need to calculate ohmic resistance of a pn junction of bipolar junction transistor from its forward I-V characteristics curves. (It can be either Base-Emitter junction or...
Homework Statement
[/B]Homework Equations
##F = -kx = m\ddot{x} ##
## f = \frac{2\pi}{\omega}##
## \omega = \sqrt{\frac{k}{m}} ##
##\ddot{x} + \gamma \dot{x}+\omega_o^2x = 0 ##
##\gamma = \frac{b}{m}##
The Attempt at a Solution
I'm stuck on part c of this question. Using the above equations I...
Homework Statement
So this problem is on Introduction to Electric Circuits 9th Edition (Richard C.Dorf)
This asks me to express the gain of this circuit Vo/Vs by terms of the resistance of R.
Homework Equations
KCL, KVL, some ideal OP AMP characteristics...
The Attempt at a Solution...
I have a lab to work through tomorrow morning and i need to be able to explain how the voltage, current and resistance in the compound circuit diagram below is distributed, and write an equation which can be used to measure the total resistance of the circuit. I know that when you normally try...
I passed small voltages (0-5V) through a known resistance, measured the current each time, and got different "effective resistances" for each case. However, when graphed, the effective resistances appear to approach the known resistance of the circuit as a limit at higher voltages.
What is the...
I'm (self)studying the physics of heat transfer at the moment. My book gives a relationship between heat transfer rate and thermal resistance as ##\phi=\frac {A \Delta T} {R}##. My book is not in English, so hopefully that is not the cause of this misunderstanding. I double checked that heat...
Homework Statement
An inductor is connected in series with an AC source, the rms output voltage of it is 260V and a hot-wire ammeter reads 2A. If the ratio of the voltage across the ammeter to the voltage across the inductor is 5/12, determine the resistance of the ammeter. (Neglect the...
Homework Statement
In the circuit attached below, what's the resistance between A and B?
Homework EquationsThe Attempt at a Solution
I'm finding it difficult to interpret this thing. Are resistors 1 and 2 in series or parallel? What does the loop above 1 and 2 actually do, in terms of how much...
Homework Statement
Question from OCR A Level Physics Exam 2014
(i) and (ii) = definitions
(iii) = explanation
(iv) = P.d. at 6Ohm Resistor = 0.48V
(v) Suggest why the p.d. between X and Z is zeroHomework Equations
I don't think there are any
The Attempt at a Solution
I couldn't understand...
Hi,
Silly little question about the transformer short circuit test.
When I perform it with the secondary shorted and I get Req = Power / current2
is this Req = Rpri + Rsec?
If I measured Rpri and Rsec with a multimeter?
Thanks
Homework Statement
Find the effective resistance between X and Y. I have attached the circuit to this post.
Homework Equations
V=IR
The Attempt at a Solution
I did 0.25+0.5+0.5=1.25 then flipped the fraction to get 0.8ohm. I considered as if two resistors are connected in series and rest are...
Hi everybody
Does anyone familiar with this equation?
Acceleration resistance,
= {(load MOI/mech. efficiency) + (motor MOI) x rpm^2} / {3.65 x 10^5 x acceleration time}
= {(kgm^2/ƞ) + (kgm^2) x rpm^2} / {3.65 x 10^5 x second}
= final value unit is in kilowatt (kW)
It used to calculate the...
Hello Physics Forums!
My problem is as follows. I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal...
This question is purely theoretical, so don't worry about safety or doability. Is there a way of calculating how many watts it takes to heat different metals? To be specific, how many amps and bolts it would take to get lead to its melting point. Thanks in advance.
Homework Statement
Two rocks are thrown off a cliff at the same initial speed, v. The first rock is launched at an angle, ϴ, directed below the horizontal. The second rock is launched above the horizontal at the same angle. If air resistance is negligible, the rocks would hit the ground at the...
Homework Statement
When an external resistor of resistance R 1 = 14 Ω is connected to the terminals of a battery, a current of 6.0 A flows through the resistor. When an external resistor of resistance R2 = 64.4 Ω is connected instead, the current is 2.0 A. Calculate the emf and the internal...
Hi,
The Circuit I am referring to is a simple series circuit with the resistance of the wire is negligible.
I am confused about the fact that if we increase the resistance of a resistor in a circuit, the PD across the component will also increase. From my understanding I thought increasing the...
Hi, I want to measure the motor resistance of a gear DC motor by experimentation and Ohm's Law. Should I measure the current without the gear head, with the gear head, stall current (with gear head) or stall current (without gear head)?
I am trying to obtain values for Equation 4 in...
Homework Statement .
[/B]
An 11kv motor is fed by cables from a transformer via switchgrear, having a phase impedence of 0.3 + j0.3 ohm. The Earth return path to the transformer neutral has a resistance of 0.42 ohm. Determine a suitable value of neutral resistance if the voltage rise at...
Homework Statement
There is a figure, I'll try my best to draw/describe.
1. All three resisters are in parallel
___R____
!___R____!
!___R____ !
2. 2 resisters are parallel and one in series, after the parallel (ignore the dots)
___R___
... _____R___
!___R___ !
3. 2...
I would like to know the sheet resistance of a metal mesh that consists of 3 larger busbars (W=0.0025 cm L=0.3 cm) and 10 smaller fingers (W= 0.0002 cm L= 0,16416 cm) which are all connected by a big collection bar. The thickness of the whole layer is 0.00. This collection bar has been...
Homework Statement
Homework Equations / 3. The Attempt at a Solution
Here is my attempt from the homework assignment. It doesn't appear that I got any points for this question and was hoping to get a little help in correcting my issues or pointed in the right direction to start over. [/B]
Helo,
I am in an electronic course and we just started studying diodes. I am stuck on the following problem:
Place a 100 ohm resistance in series with a diode, and plot current versus voltage across the series combination.
I am also given the following values for the diode:
n = 1, Is =...
Hello Experts,
I am a physics newbie with big ideas. I have a question.
I am thinking about how to produce a zero Resistance Current.
We know we can do this using super-conductors in sub zero temperature, but maybe there's another way.
My assumptions (which could be wrong):
1) Resistance in a...
If we continue to draw a specific amount of power from a cell (re-chargable), how will the internal resistance of the cell vary? Is there any particular mathematical relation between them? Please help me understand
Homework Statement
What is the average resistance force F acting on the satellite during its flight, m = 3000kg, h=300km.
Homework EquationsThe Attempt at a Solution
If it is llow orbit, so it inhibits the resistance of the atmosphere. In 300 km is no air, so no resistance ...?
If air resistance increases with velocity, then if a ball is thrown upwards, does air resistance decrease as the upward velocity of the ball decreases or does it only increase and remains constant when the upward velocity of the ball decreases?
There are two circuits, each consist of a cell and two bulbs, in one circuit they are in parallel, and in the other they are in series. What's the best way to remember which lamp has the greatest pd, current and resistance when one bulb is brighter than the other in the series and parallel circuit?
Hello, I'm a physician with special interest in cardiovascular physiology. I'm trying to comprehend the basic physics of the cardiovascular system. Here's my thought process -
Simply stated - the heart muscle contracts, thereby causing a reduction in the cardiac chamber volume and release of...
I am working in an industry where my technicians have to short the bus bars on regular basis (manually) for some maintenance purposes.
I want to add high neutral grounding resistance to the incoming supply transformer to limit the Line to ground fault. Presently the neutral has been solidly...
This thought occurred to me when reading about class D amplifiers, which essentially "emulates" amplification by very quickly switching on and off.
Could one use the same principle to eliminate for example heat losses during impedance matching? IIRC, in the perfect condition of matched...
Homework Statement
I need to calculate EMF and internal resistance from the given resistance and voltage.
R = 3 ohms
U = 3,6 V
EMF- ?
I0 - ?
r - ?
Homework Equations
I = U/R
EMF = A/q
I = EMF/R+r
I0 = EMF/r
The Attempt at a Solution
I = 3,6/3 = 1,2 A
I = EMF/R+r
1,2= EMF/3+r
^ I hit a wall...
Homework Statement
[/B]
Calculate the internal resistance of V & A based on methods A & B below:
Method A
Voltmeter = 1.46 V
Ammeter = 0.24 A
E (emf of battery) = 1.48 V
Method B
Voltmeter = 1.48 V
Ammeter = 0.24 A
E (emf of battery) = 1.48 VHomework Equations
Ohm's Law: V = I*R
The...
Homework Statement
Homework EquationsThe Attempt at a Solution
I attempted all of the parts:
I think I did the right things for a-b-c-d, but I am pretty unsure about e & f. Can someone verify if my logic is right? Thanks.
Homework Statement
The question wants to know why th current should be small through a wire when using an ohmmeter.
Homework Equations
None
The Attempt at a Solution
I can't think of a solution, and looking online doesn't give any answer.
There is this debate in car audio forums of this question whether it is better to connect your amp ground to the frame of the car or the battery.. basically they haven't came to a conclusion so I was curious what you guys think...
Basically what I mean is that when you hook up an amp in the...
Homework Statement
We need to find the total resistance of this circuit but I'm not sure whether the circuit will shorten or not.
(I don't even have any idea on where I should start cause it looks so different from the other ones.)
Can someone also give me tips and tricks in simplifying ladder...
Hi all, I will be doing an experiment in which I will be rolling a basketball down an elevated ramp. After leaving the ramp, the basketball will free fall for 1.25m before reaching the ground. I was looking to come up with a theoretical trajectory for the motion of the ball, the issue is that I...
Homework Statement
I am practicing questions from the book in preparation for an exam, and I am having trouble with this one
Homework EquationsThe Attempt at a Solution
According to my professor, the answers are: R1=12ohm, R2=9ohm, L=34.28 H
So far this is what I have done:
Voc = 6V
τ = 20/7...
I'm a computer science student. I'm currently learning electronics so that I can program embedded devices effectively. I'm reading from the free book at allaboutcircuits.com.
Why is the voltage between two points on a wire in a closed circuit equal to zero? Note that between these two points...
Hey guys!
Any answers will be much appreciated!
The following is a deep conceptual issue I have. The diagram is a bit crude but will suffice I think.
Note: Had drawn the circular 'electric field' at the time, to just help myself over my confusion. Feel free to ignore it.
As per Ohm's law V...
Homework Statement
If we have object with mass 10 kg traveling at starting velocity of 50 km/s and one force of resistance that is equal to v^2 of object's velocity how can we calculate distance and time in which that object travels until it gets to velocity of 10 km/s.Homework EquationsThe...
Homework Statement
Homework Equations
I = nqVA
J = E/ρ
J = I/A
The Attempt at a Solution
The underlying assumption was that current was constant across all 3 bits of the conductor, and thus answer is b.
The concept I can't grasp is this: Why is current constant? Shouldn't a smaller A mean...
Homework Statement
In the following picture, the absolute value of the difference in electric potential, between points A and B is:
A)5V
B)4V
C)3V
D)1V
E)0V
Homework Equations
E =qV
V = iRThe Attempt at a Solution
I have no idea where to start on this one, just started my electric circuits...
Homework Statement
Two resistors are connected in parallel. The total resistance of the combination is 6.0 ohms. If one of the resistors is 10 ohms, what is the value of the other?
Homework Equations
1/RT= 1/R1+1/R2
The Attempt at a Solution
I got 15 just by doing trial and error, and I'm...
Homework Statement
In this problem we are asked to calculate the total power of the resistors in the circuit below.
Homework Equations
##P=I^2R##
The Attempt at a Solution
My solution goes like this:
PT=PR1+PR2+PR3+PR4+PR5
I can find PR1 and PR5 immediately from the given current...