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. J

    Finding current for each resistor at different times

    Homework Statement For the circuit given that R1=10 W, R2=20 W, R3=30 W and L=30 mH, determine the current through each resistor a) at the moment the switch is closed b) a long time after the switch is closed After the switch has been closed a long time it is reopened, determine the...
  2. S

    Is a series resistor necessary when charging a capacitor?

    I'm using 250V 2200uF capacitor to discharge high instantaneous current into an inductor as shown in the attached image. I'm using a 12 Volt battery fed into an inverter that output 220 VAC which then is fed into a rectifier which outputs 220VDC. My question; Can I connect the 220 VDC...
  3. H

    Measuring current with o'scope using shunt resistor?

    I am having a hard time understanding how to measure current safely in the following circuit. The circuit consists of an isolated step up transformer. 50V 1kHz pulsed dc on the primary and 500V 1kHz pulsed dc on the secondary @ 10mA max. I am wanting to measure current on the secondary side of...
  4. kartikwat

    What happens when charge enters the resistor?

    What happens when charge enters the resistor?
  5. A

    Help identifying a burnt resistor WB27X10438

    Hi guys, I was wondering if you could take a look at a resistor that burnt from my microwave pcb. I've had good luck in the past with replacing capacitors and other failed components but I am having a hard time seeing the colors of the resister...
  6. B

    Engineering Thevenin equivalent of resistor only circuit

    Homework Statement Find thevenin equivalent of resistor circuit Homework Equations The Attempt at a Solution This may be a dumb question, but does a thevenin equivalent NEED to have a voltage source? On my final exam there was a question that asked for the thevenin equivalent of...
  7. Hardik Batra

    What is the Correct Color Code for a 1KΩ ± 10% Resistor?

    I want to know color code for this resistor ---> 1KΩ \pm 10% I have check in two sites. This sites showed me different color code for this resistor value. Which one is right i don't know i am confused! http://www.digikey.com/us/en/mkt/calculators/4-band-resistors.html (this...
  8. A

    How is current same on both sides of a resistor

    How come that the current is equal on both the sides.The resistor should decrease the rate of flow of electrons i.e. current.
  9. J

    Mastering a Tricky Equivalent Resistance Problem for the Physics C Exam

    Please don't say this is homework because it is not. I am simply studying problems for the physics c exam and I can't figure out this textbook problem. Please show me how to do this! The equivalent resistance part in the most depth because I don't understand. Is it right to say no current...
  10. G

    Potential Difference and Power in Resistor Circuit

    Homework Statement I attached a screenshot of the problem(s) that my professor gave in a practice exam. Homework Equations ∑I = 0 at each junction ∑V = 0 at each closed loop P = I2R = V2/R Rseries = R1 + R2 +... The Attempt at a Solution Part A: I think the current I in the center...
  11. A

    A resistor, an inductor, and a capacitor are connected in series?

    Homework Statement A resistor, inductor, capacitor are connected in series to an AC source. The AC source is operating at the resonance freq. Which are true? 1.The current is in phase with the driving voltage. 2.The peak voltage across the capacitor is greater than the peak...
  12. R

    Using resistor and DC motor acting as generator as a brake

    how would you calculate the resistance required for a resistor which is in series with a generator (DC motor in reverse) to achieve a certain torque from the generator? Eg, there's a torque of 30kN acting on a 100kW generator while it moves at 50RPM. The is the same mechanism as electric...
  13. B

    Issue finding change in voltage across a resistor

    Homework Statement Determine the voltage drop across R1 R1 = 770 , R2 = 630 , and R3 = 470 . The equivalent resistance is 816Ω Homework Equations V = IRThe Attempt at a Solution 1.) I find the total current of the circuit: V = IR -> I = V/R I = 12v/816Ω = 0.015A 2.) I then find the...
  14. V

    Does it matter if the resistor is on top or below a voltage source

    Does it matter if the resistor is on top or below a voltage source after doing a source transformation? According to this picture from wikipiedia, the resistor is on top of the voltage source: But even if the resistor (Z) was on the other side of the voltage source, it would still be...
  15. T

    Maximun power delivered to a resistor

    Homework Statement Find the maximun possible power delivered to the resistor. Given current through a power line. And the length of the loop that will receive the induced emf. Homework Equations B= uo*I/2pi*ρ Vemf= -d/dt ∫B*dS The Attempt at a Solution Here's my attempted solution...
  16. C

    If you stop cooling a resistor and stop current simultaneously?

    If you stop cooling a resistor and stop current simultaneously then what happens to the temperature of the resistor in the next few moments? My question is actually about whether a computer CPU will continue to heat up at all when the computer is switched off (Stopping any power to the CPU, so...
  17. gfd43tg

    Engineering Solving Old Midterm Problem: Voltage Across 9kΩ Resistor

    I am working on the second problem of an old midterm, and I cannot figure out how they got that answer for the voltage across that 9kΩ resistor. I said the current going through the resistor is the same as that going through the inductor, so I figured I would find the current as a function of...
  18. B

    Finding current through resistor (Kirchhoff's Laws)

    Homework Statement Consider the circuit shown in the diagram below, for R1 = 5 Ω, R2 = 8 Ω, R3 = 8 Ω, R4 = 8 Ω, and V0 = 8.0 V. Calculate the current through R4. Homework Equations Loop rule: The sum of all potential changes around a closed loop is zero Junction rule...
  19. R

    Finding the current in each resistor - Kirchhoff

    Homework Statement Find the current in each resistor of this circuit. Homework Equations Kirchoff's Current Law The Attempt at a Solution I just need a nudge in the right direction. I am fairly sure Kirchoff's Current Law comes into play, and have counted 6 loops and 4...
  20. N

    Precharge resistor circuit

    please help me with plotting of graph between "current versus time" for precharge resistor- 2.2 kΩ 20W. this is placed across a contactor,which is linked to a motor controller with capacitors of value:6768μF. closing time of resistor is calculated as 2.97 sec!
  21. T

    Largest resistor value such that BJT remains in active mode

    Homework Statement We are given that the transistor has β = 30. The BJT is shown below (along with the solution). Every value in the figure is given with the exception of the equation I circled in red: The Attempt at a Solution What I don't get is how they got the inequality Vc - Vb >...
  22. G

    Calculating Energy Dissipation in a Resistor with Closed Switches

    Homework Statement In the circuit shown in the figure, both switches operate together; that is, they either open or close at the same time. The switches are closed a long time before opening at t=0. (Figure 1) How many microjoules of energy have been dissipated in the 12 kΩ resistor 22ms...
  23. F

    Find the current in the 2Ω resistor marked A

    Homework Statement I attached the image, but it's asking me to find the current in the 2Ω resistor marked A. Homework Equations V=IR Loop Rule Junction Rule: I(in)=I(out( The Attempt at a Solution I have no solution. I just conceptually don't understand how my professor...
  24. KingCrimson

    What EXACTLY does a resistor do ?

    according to my understanding of a resistor , all it does is limit the number of charges flowing according to the potential energy possessed by each unit of charge , as the potential energy / charge * aka volts * increase , their ability to * move in large numbers through resistors * increase ...
  25. L

    Potential Difference Across Resistor in Parallel with Inductor

    If we have a resistor and inductor in parallel, how does the resistor maintain a potential difference equal to our emf? Am I correct in saying that for the inductor to maintain a voltage difference, there has to be some change in current, so that the current going through the resistor is also...
  26. S

    What is the equivalent resistor seen from two terminals on the left?

    Homework Statement R1 = 1K Ohm R2= 50K Ohm gM = 100mA/V I should find the equivelent resistor seen from the two terminals on the left Homework Equations Nodes equations, Ohm's law. The Attempt at a Solution So, I started by putting a test voltage source on the left but I end...
  27. PinguZaide

    Engineering Mesh law in a resistor circuit with current and voltage sources

    Hello everyone. Hope somebody can help. Homework Statement We are given the following circuit. http://puu.sh/70uaQ.png We need to find the currents i1, i2 and i3 by explicitly using the mesh law. Homework Equations There are no relevant equations.The Attempt at a Solution So, I draw these 4...
  28. O

    Choosing the Right Resistor for Your Project

    Hello I need to buy 100k and 1k resistor.. but how do i know what watts do i need? 1 watt or 2 watts hope help
  29. D

    Disparity between resistor power rating and rated voltage?

    Hello there, I am wondering why the resistor maximum voltage is not simply the square root of the product of its wattage and its resistance. According to the attached datasheet (pdf) for example, the maximum voltage of a 2.2 mega ohm, 0.25W resistor, is 250V (instead of 742V as calculated)...
  30. N

    Fourier series / calculate power over resistor

    Homework Statement V(t) = 4 for 0<t< 1 and 0 for 1<t<3 and repeats itself for all t (negative and positive) Find the first 5 harmonics of the Fourier series in cosine form and find the power if this is the voltage over 100 ohm resistor The Attempt at a Solutionpower = d_dc ^2 / R + .5sum...
  31. G

    Controlling the power output of a power resistor

    Homework Statement Hi, I am working on a temperature control system which involves using a power resistor to heat a block of aluminium and a thermocouple to measure the temperature. Both the thermocouple and the power resistor will be controlled using the NI USB-6008 and Labview. As my...
  32. A

    Engineering [Circuits] Calculating the power absorbed by a resistor

    Homework Statement Homework Equations The Attempt at a Solution Attached to this post. I have calculated the power absorbed for the 6S and 5S resistors but not the 3S resistor.
  33. N

    Two current sources in series with a resistor.

    hello, forum members. I'm new so pardon if any error. IS the question in this pic solved correctly.
  34. M

    Is the electric field stronger in resistors with higher resistance?

    Hi, I was reading a paper on circuits, electric field and resistance.Now i have a question , the paper says that in a resistor or part of circuit which has higher resistivity the electric field is higher than in those parts were there is low or lower resistance, now is that true, it seems to...
  35. C

    Engineering Find the average power absorbed by a specific resistor in circuit

    Homework Statement http://imageshack.us/a/img850/788/yk72.jpg Find the average power absorbed by the 2Ω resistor in the circuit (pictured above) Homework Equations Average power = (1/2)(Imax)(Vmax)(cosø) x=rcosθ y=rsinθ current division, voltage division The Attempt...
  36. C

    Average power absorbed by resistor:

    Homework Statement http://imageshack.us/a/img4/5259/wn5b.jpg Find the average power absorbed by the resistor in the circuit if v1(t) = 10cos(377t + 60°)V and v2(t) = 20cos(377t + 120°)V Homework Equations average power = (1/2)Vmax*Imax*cosø x=rcosθ y=rsinθ mag = (r2 +...
  37. M

    Why would voltage decrease over a resistor?

    What happens to a circuit over a resistor that causes measured voltage to drop? If voltage is related to a charge imbalance creating electric potential between two points, then what does electrons moving through a resistor have to do with a reduction of that charge imbalance? Series circuit...
  38. Y

    Electric circuit resistor combinations

    Hello friends, I have problems in simplifying electrical circuits. I've attached 2 (of the many) questions I have trouble with. According to the question, superposition must be used to solve these. In the first question, supposing the voltage source doesn't exist, how do you simplify the left...
  39. L

    Metal chassis resistor power dissipation

    I need some information on power dissipation of metal chassis resistors. I have 47 ohm, 50W resistors. (digikey part #A102169-ND) I hooked them up to 24V. So current flowing is about 0.51A But the resistors get too damn hot to touch(48-55 deg C, just after a few mins(~5mins). The power...
  40. A

    What happens to the power dissipated in a resistor when the voltage ac

    What happens to the power dissipated in a resistor when the voltage across it is changed?
  41. M

    Electricity circuit question, amplitude resistor?

    Homework Statement The ac circuit has 3 components in series: a Capacitor C=120μF, an Inductor L=100mH, and a resistor R=7Ω. A) Find the amplitude of the voltage across the resistor R in the LCR circuit below, when operated at a frequency of 45 Hz? B) What is the phase difference...
  42. F

    Finding current through a resistor

    1. Problem statement. 2. Known equations Kirchoffs law, logic 3. Attempt I believe there are 4 currents, as shown above. i1 and i2 are coming from the 9 volt battery in a clockwise direction and i3 and i4 are from the 24v battery in a anti clockwise direction. I just apply kirchkoffs law...
  43. B

    Resistor series proof and the Y-Δ transform

    If you have resistors in series ---\/\/\/\/---\/\/\/\/\/--- then the equivalent resistance of this system will merely be the sum of the individual resistors in the series. But the proof of this result is based on the fundamental assumption that the currents going through the two resistors (as...
  44. J

    Current flowing through the resistor

    I'm just stuck on a question that I've been given as a quick test, it's really stumped me. I was wondering if anyone could assist me. Here's the question: Thank you.
  45. D

    Determine VPS, quiescent value, and resistor value

    Homework Statement 1) What is the VPS voltage source value in Volts a) 1 b) 2 c)2.5 d)4 e) 5 2) Determine the Resistor value a)1.75k b) 2 k e) 2.5k d)2.285 k e) 5k 3) What is the ID quiescent value approximately in mA’s? a)...
  46. I

    Simplifying a Resistor Circuit

    Is it possible to simplify this circuit using just parallel and series definitions ? * A circuit is parallel to another circuit or several circuits if and only if they share common terminals; i.e. if both the branches touch each other's endpoints * Resistors can be connected...
  47. S

    Find V3 to Make I in 10Ω Resistor Zero

    Homework Statement In the circuit, find the value of V3 such that the current through the 10Ω resistor is zero. Homework Equations V=IR The Attempt at a Solution I am not sure how to apply Kirchoffs loop rule to this situation. If I want the current through the resistor to be zero...
  48. N

    FET common source analysis with source resistor

    Hi everyone, I have attached an image of fet amplifier in common source configuration. I want to have the ac analysis of this circuit. I am able to figure out the input impedance and the voltage gain. But I can't formulate for output impedance. According to me, while calculating output...
  49. L

    Cube of Resistor Problem - Nice one

    Homework Statement Asymmetrical Cube - Determine the equivalent resistance between points A and C’ of the circuit below. Homework Equations U = R.i The Attempt at a Solution This problem was my professor that created. I know how to solve it, but I would like to know if other...
  50. I

    Optimal Placement of a Resistor in a Circuit

    Am I correct in thinking that it would not matter if I place the 100ohm resistor after the 220nF capacitor (as shown in the picture), or before the capacitor?
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