Resistance Definition and 1000 Threads

Our professor has asked us why would a photo diode when shined with light, produce no negative resistance. So far, the only thing I can come up with is because it is in photo conductive orientation (as opposed to photo voltaic) increasing Dark Current thereby eliminating the negative...

In the given circuit we have to find the output voltage , the voltage drop across resistance RL (RL = 10KΩ) and the current through the zener diode having zener voltage VZ = 50V By this question I want to be clear about the way to solve circuits with zener diode...please explain the...

Homework Statement I am currently doing the phy project on length vs resistance of wire. to reduce the power loss in transmission wire, the length of wire must be short, as power loss = (I^2) R... in my experiment , I fixed I (current) , now i am asked to find the application of low...

Homework Statement Model the trajectory of a projectile with an initial velocity v_0 that is subject to the force of drag.Homework Equations F_{\text{d}} = \frac{1}{2}C_{\text{d}}\rho\text{A}(v(t))^2 v_x(t) = v_{0x} + \int_{t_0}^t a_x(t')\mathrm{d}t' The Attempt at a Solution I really...

Hi, What I have been trying to achieve is learn about signal processing ,particularly filters. Newbie to DSP,so far! I have 2 signals with me.Voltage and current signals. Both are unfiltered. I have managed to filter out these two signals to remove most of the noise. Now,I want to find the...

Homework Statement There are two wires: Wire one looks like --=========-- Wire two looks like --------------- Do they have the same resistance? So this isn't actually one of my homework problems, but I'm just debating this with a friend and neither of us can come to an agreement. So...

Homework Statement The question asks for resistance R of a disk with radius r and fixed width w, whose cross sectional area is variable. Unlike in the picture below, the resistor is not connected to the circuit on the flat ends, but on the cylindrical sides. Homework Equations...

Please explain the below: Resistance@95 =R@35 x (1+α*(95x(I/Io)²+20))/(1+75x α) at the actual current A (I Act).

I am stumped by an exercise in using Laplace transforms to analyze the voltage and current in simple LC tank. My issue is with the correct sign of the voltage across the capacitor ...let me pose the problem. A circuit consists of a voltage source V, 2 switches, a cap C and an inductor L. The...

Homework Statement A coconut, with ##m = 2.30 kg##, falls from rest from a tree which is ##h = 35.0 m## high. Take ##g = 9.78 m/s^2##. 1. What speed does the coconut hit the ground? Ignore air resistance. 2. If it actually hits the ground with a speed of ##23.9 m/s##, how much work was...

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...

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

So what actually is the cause of electrical Resistance?

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...

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?

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)...

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"...

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...

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...

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...

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...

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...

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

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)...

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?

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?

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...

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...

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...

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

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...

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...

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...

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)...

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...

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...

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...

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...

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

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...

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...

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)...

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 ??

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!

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...

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...

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...

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...

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...

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...