Resistance Definition and 1000 Threads

Well, I am confused on insulin resistance and cellular signaling. Know... Below is my understand: Insulin resistance happens either when the paceraes does not produce enough of the protein insulin and another way resistance occurs is when the receptor is not functioning properly. Are there...

Homework Statement Homework Equations For R, current I=E/R and for X, I=E/X... both are separate cases. The Attempt at a Solution [/B] Why does the balancing change? The potential difference across each resistor is E Itself right? I tried by assuming an arbitary internal resistance r...

The question it's easy. Suppose to have a black box circuit, it will have an input resistance ##R_{in}## and an output resistance ##R_{out}##, all the books and texts argue that it's good to have a big ##R_{in}## and a low ##R_{out}##, but why?

Homework Statement In a book discussing a simple electrical circuit it said "If a thick wire is used in the experiment, the current will be extremely high for a very low voltage. The wire can get very hot very quickly". This got me thinking about fuses in plugs. Is the fuse in a plug a thick...

Hello, Please I would like to know how the resistance of the plates of a capacitors work? Is it the same as a resistor? If yes, is there electric field like inside a resistor? Thank you

Here is my problem: when trying to find Rth for a circuit with dependent sources, I excite the circuit a voltage Vo, and then proceed to find the resulting current Io. Finally, I use the equation Rth = Vo / Io, with a plus (+) sign. The way I see it, Io enters the positive side of Vo, so the...

Homework Statement The circuit has identical light bulbs. A fourth identical light bulb is added to the circuit. How does the brightness of the original light bulbs change? a)All of them get dimmer b)X,Z get dimmer, Y brighter c)X,Z brighter, Y dimmer d)X,Y dimmer, Z brighter e)X,Y brighter, Z...

Homework Statement This is a sample problem. I'm trying to figure it out before I do the actual homework. The issue is, the way to figure it out is not included in our notes. I'm absolutely lost (math isn't my strong point) I've also included my attempt at how I think it should be done below...

Homework Statement What amount of heat will be generated in a coil of resistance R due to a charge q passing through it if the current in the coil decreases down to zero uniformly during a time interval ##\Delta t## Homework Equations ##dH=i^2Rdt## ##i=\frac{dq}{dt}## The Attempt at a...

Homework Statement The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 70.00 Ω, R2 = 50.00 Ω, and R3 = 62.00 Ω. The voltage is V = 15 V. With this information, what is the value of...

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...

is it really ok to assume that internal resistance of a cell is absent in a circuit ?

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...