Resistance Definition and 1000 Threads

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 [FONT=Georgia]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...

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...

Homework Statement An office worker uses an immersion heater to warm 250 g of water in a light, covered, insulated cup from 20 degrees C to 100 degrees C in 4 minutes. The heater is Nichrome resistance wire connected to 120V power supply. Assume wire is at 100 degree C during 4 minute time...

Homework Statement In a simple RC circuit the current as a function of time behaves in the following manner: I(5s) = 8.823 I(10s) = 7.788 I(20) = 6.065 I(30) = 4.724 I(40) = 3.679 I(50) = 2.865 I(60) = 2.231 I(70) = 1.738 I(80) = 1.353 I(90) = 1.054 I(100) = 0.821 I(110) = 0.639 Assuming...

For a school project, I need to know how much less wind resistance a round skyscraper will have compared to a standard rectangular one. You can assume the skyscraper will simply be a generic elliptical shape, somewhat similar to an egg. Answer doesn't have to be extremely specific, I just need...

Homework Statement Ok, so I am attempting to solve a projectile motion problem involving air resistance that requires me to find the total x-distance the projectile traverses before landing again. Given: \\ m=0.7\text{kg} \\ k=0.01 \frac{\text{kg}}{\text{m}} \\ \theta=30 \degree Homework...

I have a problem understanding the concept of potential difference. I get the picture of seeing it as a height difference for example (rock or water that would fall down) but what confuses me is that many times the order of elements in a circuit does not matter. To explain myself better: if I...

Homework Statement Find the Thevenin's equivalent with respect to points A and B Homework Equations 3. The Attempt at a Solution [/B] The resistance i found to be ##R_t=(R_2+R_1)||R_3+R_4## and that is the correct expression but for the voltage source the book gives...

Homework Statement This is the second problem from our test preparation cycle and i partially solved and understood it. The circuit in the picture is in the state of switch being open (STATE 1: SWITCH OPEN). Calculate ##E1## so that the change in the electrical energy of the capacitor is...

Homework Statement This is one of the problem i had had some help in solving but some things remain unclear to me and i will highlight them by posting the exact question in the brackets next to the line of solution so that you can see what bothers me. Hopefully you can help me better understand...

Homework Statement I'm currently working on the "cavendish" experiment and wish to use/develop a method separate from the casus we've been provided. Now I've nicely calculated and derived everything I need to know, including all the corrections that have to be made for the mass of the rod, the...

Homework Statement I am trying to develop simulation for a falling object subject to air resistance. Object is similar to Samara seed. object is considered to be under steady vertical descend. know variable : surface area of object (A) weight of object (W) cd: drag coefficient object rotates...

Hi PhysicsForums, Why would a parallel circuit(or in blood) decrease resistance? Here is my thought experiment and where I got stuck: Say from aorta to one arteriole, the resistance is super high on that flow(this big amount of flow is entering a tinier area), but add more arterioles and we...

Homework Statement In the figure given what is the Thevenin resistance between the nodes of the capacitor?? Homework Equations The Thevenin resistance is the open node resistance between two points. The Attempt at a Solution The way I see it, R2, Rf and R1 are in series and that combination...

Homework Statement Determine the Thevenin and Norton equivalents at terminals a-b of the circuit in Fig. 4.125. The figure is uploaded. Homework Equations We know that the Thevenin resistance is the resistance between the terminals when the independent sources are turned off. The Attempt at a...

Homework Statement (##R_5=8\Omega##) a) Calculate the current ##I_{g2}## so that the power of the generator ##I_{g1}## equals ##P_{ig1}=6.25W## b) What is ##I## then? Homework Equations 3. The Attempt at a Solution [/B]...

How is the constant used to measure resistance? I can't find a clear answer anywhere. The constant is h/e^2 but that doesn't really help in seeing how it is linked to resistance other than the units being the same in base units.

i connected one probe of digital mutimeter to the Earth terminal of domestic ac supply and held the other probe. it showed resistance of 1.8Mohm . but when i touched that end (one i'd held) to the floor. it displays 1( beyond 200Mohm ). why so ? shouldn't resistance be lesser?doesnt any current...

Homework Statement I understand part a, but not part B. Homework EquationsThe Attempt at a Solution For part b) the PD across the resistor is 2V, but we don't know the current so we can't calculate using ohm's law eqn. And because the new resistor's resistance is unkown, how do we actually...

Homework Statement I am asked to calculate the missing resistance(R5) when only given the voltage drop of of 14v across it Homework Equations current and divider rule ohms law The Attempt at a Solution [/B] i tried finding the current of the 6+10 ohm series resistor that is parallel to R5...

hi everyone, i need some help with my project that is DC rice cooker. i have the same problem for my calculation and logic cause my rice cooker use 12V and 100Watt. is that mean i need to use 8.3333Amp for the current? or i need to design a circuit that can reduce the amount of current needed...

Hi everyone, so I'm trying to achieve IV curves based on how this website had done below: http://www.voltaicsystems.com/blog/solar-charger-tutorial-part-2/ But whenever I increase the resistance, the amperage increases rather than decreases! For example, when I use a 500 ohm resistor the...

Hallo, I have a question which elements are responsible for the increase of tangent delta in a X Capacitor and the reduction of its insulation resistance?

graphite has high conductivity , so i though of making a touch button out of a pencil drawn pattern on the wall.the pattern is shown below. when not touched -resistance between ends of the pattern >200Mohm (exceeds dmm limit) when fully pressed - resistance between ends of the pattern = 1.3...

If this is not ok to post then let me know, but I have a question that I feel can only be answered here. Question: Would it be possible to heat a 50' semi trailer frame to roughly 400F through electrical resistance, I know it would require a lot of power but the reason I ask is because I am...

If an object is heavier.. it has more resistance to inertia.. during seismic movement.. when the ground shakes or accelerates.. does it mean bigger foundation would be more resistant and move less.. and smaller foundation can move more?

Hi. A simple model explains resistance in metals with collisions of the electrons with the stationary atomic cores. So I assume more collisions result in a higher resistance? But for the dissipated power we have ##P=U^2/R## , which is large for small resistance. I have difficulties combining...

If a pendulum consisting of a string and a bob is allowed to swing in a vacuum vs in air, which has larger period?

Homework Statement Homework Equations R=V/I The Attempt at a Solution Would it be 10ohms? Since PQ is between two 10ohms resistor.

Homework Statement Homework EquationsThe Attempt at a Solution (a) [/B]We can assume for ideal op-amps that there is: infinite input impedance low output impedance the potential for infinite amplification (b) Non-inverting op amp (c) This is the part I have trouble with. There is three...

Homework Statement We have 1Ω, 2Ω, 2Ω, 4Ω, 5Ω and 6Ω resistors. We have to make a circuit with all of them and total resistance must be 1 ohm. Homework Equations Parallel: 1/R1+1/R2=1/R In series: R1+R2=R The Attempt at a Solution I have only made a circuit from 4 resistors: 1 ohm and 2 ohms...

Hello, Circuit: 1. Homework Statement Determine the net resistance between points a and c and a and b. Assume R' ≠ R. Homework Equations ε - IR = 0 V = IR The Attempt at a Solution http://i.imgur.com/Y2KPI20.jpg I applied an emf between the points a and c, and tried to solve using...

Hi. Is the resistance of a charged cable different compared to a cable with zero net charge? If it is charged negatively, one could argue that now there are more carriers for the current, so the resistance should be smaller (similarly to water that becomes more conductive if ions are added). On...

I'm not entirely clear what shunt resistance is, it's fairly hard to find things on google which refer to it in the context of LEDs. So we did an experiment in which we measured the IV characteristics of InAs at different temperatures, and observed the gradients of these graphs (apparently those...

According to relativity gravity is just an illusion caused by wrapping of space-time fabric by mass, right? So, what is the elasticity of of space-time? There must be some king of resistance for the wrapping, otherwise even a tiny mass would plunge in the space time for eternity.