Resistance Definition and 1000 Threads

[Mentor's Note: Thread Moved from EE Forum] This link has the picture, for some reason it wasnt showing in this post. http://i.imgur.com/TYlb32t.jpg Here is my problem, I am supposed to use this circuit and solve for Av and Rin. My problem is that I have solved for Av but I can't solve for Rin...

Homework Statement How can I get the maximum Current Intensity by connecting 72 cells to a 3 Ohm resistor each cell has a potential difference of 1.5 Volt and internal resistance of 1 Ohm Please don't tell me to connect them all in parallel or all in series as in parallel the potential...

Homework Statement Ok, so I did this.. V=IR I=(1/R)V, gradient is (1/R) -> y=mx+c So in order to have the smallest resistance, we choose the point on the graph that has the largest gradient, which I chose B, because the tangent on the graph on point B is the largest, but the correct answer is...

Homework Statement In the circuit shown in the figure above, the ammeter reads 3.4 A and the voltmeter reads 6 V. Find the emf ɛ and the resistance R. Homework Equations Ohm's law; V= I*R EMF equations: ε=I*r+I*R ε=I*r+V The Attempt at a Solution [/B] I got the...

Hello, We know that the electric field generated by a changing magnetic field is not conservative. But, for example let' say we have an EMF source that has an internal resistor, the voltage drop across the source is equal to EMF-rI where r is the internal resistance. My question is, inside the...

Hello Forum, Most devices that are supposed to generate heat via resistance are connected to a constant voltage source. That means that the amount of power dissipated as heat is given by P= V^2/R = I^2*R This implies that the smaller the resistance the larger the current through the heating...

Homework Statement List the order of brightness of each bulb (while the switch is open) assuming the bulbs are all of the same resistance. Homework Equations Ohm's Law: Change in voltage = current divided by resistance The Attempt at a Solution I know that bulbs A,C,D,F are all equal in...

From the following diagram: Due to the velocity(##v##) of the conductor(##C##) of resistance(##R##) through the uniform magnetic field (##B##), there is an induced ##\epsilon## due to the motion: ## \epsilon = vBL## This conductor now is a voltage source, when connected to a circuit (and a...

Homework Statement I came across a problem and I was unable to understand how the effective resisitance of this circuit is to be calculated. (Please refer to image uploaded) Homework EquationsThe Attempt at a Solution Well I assumed that current tends to flow through wires without resistances...

Homework Statement The resistance to motion of a projectile, of mass m, is proportional to its speed. When falling vertically its terminal velocity is 19.6 m/s. The projectile is thrown vertically upwards with gravity acting downwards. (a) Assume that the resistance to motion can be expressed...

Can I get the derivation of the dimensions of the physical quantity ELECTRIC RESISTANCE which is given by :- A simple derivation is only required. Thanks in advance.

Homework Statement A student investigates how the resistance of a thermistor varies with temperature. Student immerses a thermistor into a 50 degrees Celsius beaker of water and measures the resistance on an ohmmeter as the water cools. Student adds ice to achieve lower temperatures. Q1. The...

Hi, I am wondering how to calculate the resistance for the current running in radial direction starting from the center of a circle? It seems there is a formula out there, and I would also like to know how to derive that formula..Thanks.

Homework Statement Homework Equations 1/R= 1/R1 + 1/R2 +... I1= R2/R1 x I The Attempt at a Solution I chose B because I thought that since total resistance in the branch of variable resistor has increased, the branch with ammeter will get a greater share of current. Since I'm not too sure...

Hey there! I'm having some real trouble deciphering this complex resistor problem. I have heard of the Kirchhoff voltage and current rules and do know how to use them to solve some problems but I'm not sure how to apply them in this context, or if they are even used to solve this. As seen the...

Homework Statement Find the equivalent resistance Homework Equations Req(series) = R1 + R2... Req(parallel)=(1/R1+1/R2...)^-1 The Attempt at a Solution I'm having problems understanding how to simplify this circuit. There should be parallel and series "loops" to simplify but I'm having...

Homework Statement [/B] What is the current between points A and B? The current I is unknown. The voltage is 12V. R1 = 3 Ohm R2 = 6 Ohm R3 = R4 = 4 Ohm Homework Equations U= R*I The Attempt at a Solution Total resistance from both branches: 1/R = 1/(R_1+R_3) + 1/(R_2+R_4) 1/R = 1/7 +...

In general I read that: R_m =\frac{l}{\mu A} But considering for example the following transformer: I don't understand why the lengths taken from the sketch by the solution's procedure are the following: For the right and left part resistance: R_r = R_l = \frac{(\frac{1}{2} + \frac{1}{2}...

Homework Statement I am trying to prove what is asked in the following problem: A particle of mass m slides down an inclined plane under the influence of gravity. If the motion is resisted by a ##f=kmv^2##, show that the time required to move a distance d after starting...

Homework Statement Find the equivalent resistance between A and B. All resistances shown are in ohm. Homework Equations The formulas for parallel and series connections. The Attempt at a Solution I have attempted to redraw the circuit and my redrawn diagram looks like this. I don't think...

Here is a typical description of motional EMF: "The figure below shows a conducting rod of length L being moved with a velocity v in a uniform magnetic field B: The magnetic force acting on a free electron in the rod will be directed upwards. As a result, electrons will start to accumulate...

This is something I have been trying to figure out lately, but I can't seem to wrap my head around it. So, according to a definition in my Physics textbook, while the electrical potential difference established between two terminals encourages the movement of charge, it is resistance that...

[Mentor's Note: Thread moved to homework forums from another forum] Figure shows a potentiometer circuit for comparison of two resistances. The balance point with a standard resistor R = 10.0 Ω is found to be 58.3 cm, while that with the unknown resistance X is 68.5 cm. Determine the value of...

Homework Statement Two conductive metal plates are bonded together. Upon bonding, an oxide layer forms between them. The oxide layer is negligible thus the overall resistance of the plates is small. However I am having trouble finding this overall resistance, i.e., trying to find Cp and Rp...

Hello! I have in my notes an expression for the sheet resistance of a uniform conductor with length L, width W = L and thickness t. It is R_{\square} = \displaystyle \frac{\sqrt{\displaystyle \frac{\pi f \mu}{\sigma}}}{1 - e^{-t/\delta}} = \displaystyle \frac{1}{\sigma \delta} \frac{1}{1 -...

Is air resistance dependent on mass? thanks!

I am sending an AC through a rectifier and need to calculate the resistance. Is there any particular method of doing so?

What's up people? I'm new in this wonderful forum. I have several questions about circuits, and they are not really common, I mean, I find them somehow complicated, but I would really come to enlightenment if you guys gave me some clues. 1.- So, let's suppose we got the simplest circuit, a...

Why does negative resistance indicate ballistic transport?

If electricity passes through a system at 12 volts, with 0.42 Amps of current, and 28.8 ohms of resistance, how do you calculate the energy lost in joules?

I would like to find a ballpark estimate of the resistance caused by an electromagnet such as this: http://www.ebay.com/itm/12V-DC-22-LB-10kg-Electric-Lifting-Magnet-Electromagnet-Solenoid-Lift-Holding-/360519627296?pt=LH_DefaultDomain_0&hash=item53f0a4f220

Homework Statement We conducted an investigation into wire length, current and resistance but kept track of the voltage rather than relying on the power pack setting. We noticed the voltmeter (measuring across the power pack) reading increased as the length of the wire increased though by only...

What is Earth resistance? What is the standard value of Earth resistance? Please help me with reference. Your co operation will be highly appriciated.

If a solenoid were wrapped around a bar magnet, and a charge were applied through the solenoid, would there be resistance?

I'm trying to solve this ecuation: Y_1=(-m)/2k((T-mg-kv^2)/(T-mg)) I'm having some truble at finding a correct formula to find the air resistance. In my research through Internet I found loads of different formulas but I don't exactly know which is the correct one. In an other discussion on this...

Homework Statement Can someone please give me insight on how to solve for the total resistance of this circuit? Thank you Homework Equations The Attempt at a Solution

I recently read that the impact of air resistance on the horizontal range increases as the launch angle increases (http://moodle.davidson.edu/moodle2/pluginfile.php/121168/mod_resource/content/2/Brancozio%20fly-ball%20paper.pdf). A graph depicting this is attached. Is there a reason for why this...

https://brilliant.org/problems/hexagonal-grid/ I've been pondering on this but not being able to solve.I mean applying Kirchoff's law here is of no use. Any ideas?

Homework Statement : [/B]Given the circuit diagram, find the equivalent resistance between points P and Q. Homework Equations : [/B]ΔVloop = 0, ΔIjunction = 0 and V = IRThe Attempt at a Solution : [/B]Eliminating the wires with no resistors and solving for resistance gives me the answer as...

I am looking for a reference to discuss the effects of resistor size on alpha, the temperature coefficient of resistivity. If we use the linear R=R0*(1+alpha*(T-T0)) alpha is a material constant, presumably for bulk-type resistors. Will alpha change as size (cross sectional area) of the resistor...

Homework Statement Hello, I am going to ask a rather simple question yet I wasn't able to solve. I have a circuit which I wanted to find out about the equivalent resistance and inductance. I know how to find the equivalent resistance of two resistors in parallel as well as two inductors in...

Hello, I have a three phase BLDC motor and I am trying to figure out its phase resistance. I have acquired the three-phase voltages and three-phase line currents of this motor. The voltage is in trapezoidal form whereas the current is in rectangular form My question is: how can I find out the...

Hello, What "path" do objects take to reach thermal equilibrium? Does heat from a hot part sitting in room temperature air like to travel through the most thermally conductive portions? My thought is that it is similar to current in a circuit taking the path of least resistance (where the most...

Hi, I shall be grateful if someone can help with this fundamental understanding, Thermal resistance (in case of conduction mode of heat tarnsfer) can be defined as; Rt = L / kA where k is the thermal conductivity Thus. thermal resistance if inversely proportional to the thermal...

Hi, Can someone please explain how to calculate the A.C. resistance of non-cylindrical conductors? All the references I can find online assume round wires and I'm not sure the same equations would apply for other geometries? Thanks, Chris

Hey all. I have been trying to calculate the input resistance of a common gate amplifier, but seem to have problems doing so. I know I have to set a test voltage (or test current) at the input, and I've been told, to ground the output. So using the Hybrid pi model for a mosfet, I did the...

I'm trying to make an ohmic contact with p-type doped silicon. Using Aluminum. Under what condition of an Al/Si contact would annealing increase the resistance of the contact? or the silicon? two regions are defined using photolithography. A brief exposure to buffered oxide etch (6:1 H2O to HF)...

Homework Statement It is known that total resistance of the circuit is dependent on the position of the wiper in potentiometer ##R##. Find the biggest and the smallest possible total resistances of the circuit. Potentiometer resistance is ##R=9r##. Homework Equations Ohm's law. The Attempt...

Homework Statement This is a standard projectile motion problem, the mass is m, the drag is F_r = - alpha *v, where alpha is a positive retarding coefficient. The origin is the ground and at time t = 0 the horizontal and vertical velocities are positive a) Write down Newton's second law for...

Homework Statement How and why does quality factor change in a series RLC circuit when the resistance in the circuit increases? I've made a small experiment circuit which looks like one in the picture: The current frequency is 1 kHz and the voltmeter should show 2V throughout the whole...