What is Resistor: Definition and 891 Discussions

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors that can dissipate many watts of electrical power as heat, may be used as part of motor controls, in power distribution systems, or as test loads for generators.
Fixed resistors have resistances that only change slightly with temperature, time or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity.
Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resistors are also implemented within integrated circuits.
The electrical function of a resistor is specified by its resistance: common commercial resistors are manufactured over a range of more than nine orders of magnitude. The nominal value of the resistance falls within the manufacturing tolerance, indicated on the component.

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  1. T

    Changing electric flux caused by a resistor

    I'm learning the basics about electromagnetism, including that a changing electric flux through an open surface causes a magnetic field. Obviously a capacitor causes this, but doesn't a resistor like a light bulb (whose resistance varies with temperature and therefore time) also cause this?
  2. R

    A device connected to a current source and then resistor

    Forgive the title, I was unsure of how to briefly describe the problem. Attached are diagrams. Homework Statement The device shown in Figure P2.5 can be modeled as a current source in parallel with a resistance. When this device is connected to a 5[mA] current source, so that...
  3. A

    Diode voltage drop (connected in parallel with a resistor)

    Hello, I am a computer engineer that specialized more in software but I am trying to remember the electronics part. In the book I read there is an exercise where a diode (forward-biased) is connected in parallel with a resistor and then both of them are connected in series with another...
  4. M

    Finding the current in a resistor

    Find the current across the 20 Ω resistor using the image. http://s1078.photobucket.com/albums/w488/maddy31595/?action=view&current=Untitled.jpg So my teacher gave us this problem and the answer, but didn't go over how to get the answer. I have no idea where to even start. Help?
  5. D

    How Fast Do Electrons Drift in a Silicon Resistor?

    Problem: An Si resistor is at 300Kelvin, and is 100μm long, 1μm thick, 5μm wide. The conductivity is 7.128 Ωcm. The resistance is 28058Ω. A voltage of 5v is applied. What is the drift velocity of the electrons, given that n = 1.01x103? Other constants: μn = 1350 cm2/Vsec μp = 450 cm2/Vsec...
  6. Q

    Resistor overheated and melted color code, how do I determine type?

    I am trying to repair this device and have determined that the issue is with this melted resistor... In order to find the correct replacement i need to determine specifically what resistor this is.
  7. J

    Measuring the White Noise Produced by a Resistor

    Hi all, I want to measure the white noise produced by a resistor in my circuit. In order to do this I did the following: 1. Ground the excitation voltage of the circuit and measure the white noise voltage produced by connecting the output of the circuit to a 8.5DVM 2. Subtract the Avg DC...
  8. T

    Use resistor simplification to find current across the 10 ohm resistor

    Homework Statement Use resistor simplification to find current across the 10ohm resistor Homework Equations V=ir p=vi The Attempt at a Solution Any help you can give me is much appreciated. When I did it i got down to a parallel circuit with a 30ohm and a 100ohm but didnt get a...
  9. L

    Equivalent resistors in resistor networks

    Homework Statement http://i134.photobucket.com/albums/q100/megajette2/Resistornetwork.png Homework Equations parallel resistors share the same nodes or terminals and simplify to (a*b)/(a+b). in series resistors values are added. The Attempt at a Solution...
  10. S

    How to use inductors and capacitors to increase power through resistor?

    i'm given a circuit that contains a 15 volt battery and a resistor that has a power rating of 1/4 watt and a resistance that must be greater than 1 kohm. I'm told that no matter how i set it up, i cannot exceed the 1/4 watt power rating of the resistor. this makes sense. i work out the max power...
  11. P

    Engineering Solving Series Circuit with 10Ω Resistor, Coil and Capacitor

    Homework Statement A series circuit consisting of a 10 ohm resistor, a coil and an ideal capacitor is connected across a 200 V, 60 Hz power supply. The current drawn is 8 A. The voltage across the coil is 120 V and its power factor is 0.8 lagging. Determine (a) the voltage across the...
  12. S

    Power dissipated by a resistor

    hi just needed to know if the power dissipated by a resistor is equal to the total voltage. I am having a hard time understanding a problem i was given, and i know the formulas to find power dissipated, but i can't use P = I squared * R or P = V squared / R for this question... " A 10 ohm...
  13. C

    Transmission Parameters of Single Vertical Resistor

    Hello every body... Consider two port system having a resistor (can it be called two port system?)... ____---->I1________________I2_<----_________...
  14. D

    Resistor Heat Dissipation (with imaginary numbers)

    Friends: I am wondering about heat dissipation when you have imaginary numbers. Lets say a current I = (3 + 4j) Amps is going through an impedance Z = (2 + 3j) Ohms. What is the amount of heat dissipated by the impedance? I think that you take the magnitude of the current, |I| = 5 Amps, and...
  15. N

    STK 4191 amp. burning resistor

    STK 4191 amp. burning resistor :( I just built a STK 4191 amp. when i supply power a 100Ω resistor (1w) near the IC starts smoking. there're no short circuits across the ICs pins or anywhere on the board and i took all precautions when soldering the IC on (was done with heatsink + 40mm fan...
  16. T

    Help with resistor power dissipation homework

    This question is in reference to the diagram here: http://imageshack.us/f/17/ecediagram.jpg/ Find the average power dissipated on the resistor. Assume Vth for the diodes is 1V, N1 = 1000, N2 = 100, the transformer is ideal (non-lossy), and V(t) is a purely sinusoidal voltage with frequency...
  17. A

    Fix Headlight Problem on 2008 VW Rabbit

    Long story short, I am college student with limited capital. My high beam went out on my 2008 VW rabbit and melted the headlight enclosure. The cost to fix the unit is $500 which I do not want to spend for a head light. The bulb is a 12v 55w unit. There is a bulb out light I would like to get...
  18. C

    Calculate Current Through Resistor - Kirchhoff's Rules

    Homework Statement Calculate the current through the resistor of resistance for circuit B. Express your answer in terms of EMF, R1, and R2. http://imageshack.us/photo/my-images/163/screenshot20111112at110.png/" Homework Equations Kirchhoff's Loop and junction rules The Attempt at a...
  19. C

    PGRE | Resistor Combination Circuit

    Homework Statement Hello forum, please see the attached image. This problem amounts to finding the equivalent resistance for the circuit and using Ohm's law to solve for the current. Homework Equations V=IR The Attempt at a Solution What I really need help with is learning how...
  20. M

    Power over current source and resistor in series

    Problem description: The problem is Kotitehtävä 7 in the attachement. The idea is to calculate the output power (both P and Q) of the current source. Attempt: I know the current through the current source (obviously) and want to calculate the voltage over it to get the power. I have...
  21. E

    Why Is the 0.7 Volts Diode Drop Used in Calculating R2 Current?

    This isn't a homework question but it is a formula from a book I have been using to study, so I'm posting it here. Here is the circuit and formula - I don't understand why the voltage drop of 0.7 volts across the diode is being used as part of the formula to work out the current...
  22. S

    Work done by the magnetic field on the resistor

    Homework Statement A magnetic field, B= 0.8 T, is directed out of the page in a region containing a rectangular up-side-down "U-wire" having width W = 0.5 m, as shown. A resistor of mass m and resistance R = 6 Ω, which is free to slide without friction on the vertical rails, is released from...
  23. E

    Find voltage across a resistor using Loop Analysis

    Homework Statement http://i.imgur.com/H20el.png Homework Equations KVL The Attempt at a Solution When I solved the equation for V0, I got V0=2V. Is this correct? If it's not, I'll upload my work. Thanks!
  24. J

    Archived How Does Closing a Switch Affect Capacitors and Resistors in a Circuit?

    Homework Statement A charge Q is placed on a capacitor of capacitance C. The capacitor is connected into the circuit as shown in the figure below, with an open switch, a resistor, and an initially uncharged capacitor of capacitance 3C. The switch is then closed and the circuit comes to an...
  25. S

    Engineering Determine whether each circuit element is a source or a resistor

    Homework Statement In the circuit as shown in Figure 4, there are three independent sources and five ordinary resistors. (a) Determine which of the circuit elements are sources and which are resistors? (b) Determine the value of the resistance for each of the resistors...
  26. Twinflower

    Determine resistance in a cone formed carbon resistor

    Homework Statement I have to determine the resistance of a cone shaped resistor with the following dimmensions: Height at the first end: 1mm Lengdt: 250mm Height at the last end: 0.5 mm Rho: 14.5^10-6 Ohm*m Homework Equations \Omega = \frac{\rho \times L}{A} The Attempt at a...
  27. D

    Finding required resistor to reduce voltage

    Homework Statement Your task is to design a "dummy" indicator light for your car. The cheapest bulb available is a #47 incandescent lamp rated at 6.3V for 150 mA. The problem is, your car produces 13.5 V when it's on. Choose the nearest 10% resistor that will reduce the voltage across the...
  28. W

    Solve Resistor Cube Problem: Find Voltage Across Current Source

    Homework Statement So I need to find the total voltage across the current source. Looking at the attachment, I took front square: B_______C ......|.....| ......|.....| ......A_______D back square: E_______H ......|.....| ......|.....| ......F_______G Homework Equations node analysisThe...
  29. P

    On non linear resistor and how to calculate a fixed resistor.

    Homework Statement The current in amperes through a certain type of non-linear resistor is given by I=0.05V^3, where V is the potential difference in volts across the resistor. This resistor is connected in series to a fixed resistor and a constant voltage source of 9V is connected across...
  30. A

    Potential across a Resistor for an Ideal Battery

    Homework Statement An ideal battery with an emf of = 14.0 V is connected to a network of resistances with R1 = 6.00 , R2 = 12.0 , R3 = 4.00 , R4 = 3.00 and R5 = 5.00 . What is the potential difference across R5? __R1__ __________R3__ __R2__ __R4_____R5__ __emf battery__...
  31. N

    Physics Uncertainity + resistor calculations

    Homework Statement I am given a resistor, 40KΩ + or - 20%. I know the uncertainty formula but it involves two variables, but not how to combine these together to get an answer. Not to mention, isn't the uncertainty formula redundant since I know the 20% over or under? Homework Equations...
  32. R

    How to calculate the voltage on a resistor at a power cable

    hallo everyone, i have here a simple problem that i cannot solve. This is the problem: A resistor of 46 Ω is connected to the end of a power cable. The voltage a the begin of the cable is 230 V. The length of the cable is 25 m The copper area is 1.0 mm2 The specific resistance of...
  33. O

    Charge density in a resistor issue

    Homework Statement given simple circuit with V the voltage connected to a resistor with area A, length d and electrical conductance: b*e^-2x/d after my computations the resistance R=d*(e^2-1)/(2bA) Homework Equations what is the electrical field E in the center of the...
  34. D

    Equivalent circuits resistor problem

    Homework Statement Find Req. Homework Equations Series: R1 + R2 + ... Parallel: 1/(1/R1 + 1/R2 + ...) The Attempt at a Solution There's no solution for this one in the book but I'm thinking that I can break this up into two parallel sets. Parallel1...
  35. B

    Entropy of running water around a resistor

    Homework Statement An electric current of 10A runs for 1 minute through a 20 ohm Resistor which is maintained at 10 degC by being immersed in running water. What are the entropy changes in a) the resistor b) the running water c) the universe Homework Equations P = I2R dS = dQ/T...
  36. D

    Find the Current Through a Resistor with a Constant Current Source

    Homework Statement Hey everyone. I might be overthinking this one, but I thought I'd post it. (sorry for the crappy MS Paint sketch!) I need to find the current through R3 Homework Equations V=IR \SigmaV=0 (around a closed loop) \SigmaI=0 (going into a junction) The Attempt...
  37. A

    What ohm resistor should I use for my transformer's extra capacity?

    This will (maybe) be an easy question to answer. Here is my situation: I have a 12v 200mA capacity transformer (wall wart) that I am using to power up a relay which takes about 5mA and has an input voltage range of 5-24v. Basically I need to burn off the other 185mA or so of the transformer's...
  38. D

    Amount of charge flowing through a resistor?

    Amount of charge flowing through a resistor? the current through a resistor is 3 mA. What charge will flow through it in 200 seconds? if the resistor has a resistance of 2.0 kΩ what will be the power dissipated in it? for the first one, i have no idea. i can't seem to find any formula...
  39. R

    Current through resistor, with heat. What happens to the current?

    Homework Statement Suppose a current of 1 A is flowing through a resistor. If this makes the resistor heat up, will the current through the resistor increase, decrease, or remain constant? Assume the voltage applied to the resistor is constant. Homework Equations The Attempt at a...
  40. N

    Entropy, resistor in a temperature bath

    Consider a resistor with current running through it for some time in a constant temperature bath. I understand that the change in entropy of the resistor is zero because there is no change between the initial and final thermodynamic state. However, I am trying to come up with a reversible...
  41. Redbelly98

    Circuit breaker with parallel resistor

    In my battery-powered lawnmower there is a circuit breaker. I have replaced the breaker, and when I cut apart the old one I found a 68 Ω resistor in parallel with the breaker switch. My question is, what is the purpose of this resistor? Here is the basic mower circuit: (Imagine that...
  42. R

    Resistor values for a series circuit

    Suppose we have a bulb or a forward-biased LED (or any other component) which needs no more than say 3 V across it to operate. And we want to connect it in series with a voltage source of say 12 V, and a resistor. So without this resistor, the LED would quickly burn out and be destroyed. I've...
  43. Y

    Potential drop across each resistor

    Homework Statement Two resistors, R1 and R2, are connected in series across a potential difference, ΔV0. Express the potential drop across each resistor individually, in terms of these quantities. The Attempt at a Solution R1 + R2 = Req I = V0 / Req drop at V1 = V0 / (req) * R1 V2...
  44. E

    How to calculate the Resistor Values for an op amp circuit

    I need help calculating the R values for this circuit from the following article: AN HIGH RESOLUTION RESISTIVE PROBE FOR NONLINEAR ANALYSIS OF TWO-PHASE FLOWS L. Cantelli, A. Fichera, A. Pagano This is only a section of the circuit, there is more but I'm only interested in this part of...
  45. L

    Resistor value for Enable/Disable

    How is the resistor value for an IC Enable/disable pin decided. I always use 10K. But not sure how to calculate it . Do you connect Enable bar directly to ground or thru a resistor.
  46. R

    Find the resistance through a resistor

    Homework Statement For the following questions, use the schematic below, where R1 = 3.0 Ω and R2 = 17.0 Ω. (a) What is the equivalent resistance between points A and B for this combination of resistors? 3.83 Ω (b) A 8-V emf is connected to the terminals A and B. What is the current...
  47. P

    Equivalent resistor of 2011 resistor web

    1. let's have 2011 point each pair connected by a resitor R. what is the equivalent resistor between each pair of points conneced by R? 2. due to the symmetry the equivalent resistor between two arbitrary point connected by R is always the same. let's take two of this contigouspoins. the...
  48. J

    UV LED circuit - how many and which resistor?

    Many years having passed since I last looked at an electrical circuit, I been asked to design an electrical circuit at work. We make tonic water, and the idea is to create a holder for bottles with a built-in UV light rigging. Due to the relative efficiency, robustness, cheapness etc, I am...
  49. Femme_physics

    Understanding Vout: How to Properly Calculate and Discount Resistors

    In trying to figure out what's Vout, do I discount R4? I don't believe any current will flow through there. http://img825.imageshack.us/img825/7236/vinvout.jpg
  50. I

    Platinum Resistor: Measuring Temperature with High Accuracy

    Homework Statement A Pt-resistance thermometer is used to measure temperatures in the range 0°C to 100°C. The electrical resistance of the thermometer is 2 Ω at 20°C and 6 Ω at 100°C. It is necessary to measure the temperature to an accuracy of ± 0.1 K. How accurately must the electrical...
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