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. D

    Why is my calculated resistance higher than the resistor used

    Homework Statement Why is my calculated total resistance of the circuit higher than the resistor used in series and the theoretical total resistance? In a series circuit I used a 100Ω resistor and measured the current at 1.0v intervals from 1.0-5.0v. At 1.0v the current was 8.70mA using a 100Ω...
  2. M

    Which side of a resistor is positive/negative?

    Homework Statement In the attached file, how do I decide which side of the resistor is positive/negative? Homework Equations N/A The Attempt at a Solution The current would go through the 6V battery starting from the positive end of the 9V battery to the negative end of the 9V battery; so my...
  3. E

    Engineering Basic circuit problem -- Resistor network and a voltage source

    Homework Statement http://www.chegg.com/homework-help/questions-and-answers/problem-2-variableh-resistor-r-circuit-fig-p224-adjusted-va-equals-60-v-find-value-r-q8083343 Homework EquationsThe Attempt at a Solution Hi, I attached a pdf file with the problem. My question is, for the lower right...
  4. B

    Energy dissipated in a resistor

    Homework Statement A resistor of resistance 10Kohms has voltage across it described by the function V(t) = 6sin(10t+pi/4)*exp(-2t) Volts Calculate the energy dissipated in the resistor between t=0 and t=0.5 Homework EquationsThe Attempt at a Solution I have done the definite integral and have...
  5. S

    Charge different entering and leaving a resistor

    Homework Statement Is a charge different upon its exit versus its entry into the lightbulb? Homework Equations PE = Vq The Attempt at a Solution Well, the answer is that the charge stays the same. Based on the equation above, since energy certainly gets reduced V must drop but I don't...
  6. T

    Why is there no voltage drop through this resistor?

    I have wired in series: + of 9V battery --- + of 1000 uF capacitor --- 660 Ohm resistor --- + of a green LED --- - of the 9V battery. Remark: the 9V battery is a bit depleted 7.8 V unconnected. Voltage drop across the capactor is 6.5V, across the LED is 1.5V but 0V across the resistor. Why...
  7. H

    Can you help me find the current through the 15 Ohm resistor branch?

    Homework Statement Homework Equations I = VR Series = current the same, voltage different Parallel = current different, voltage the sameThe Attempt at a Solution Is the 1 ohm and 15 ohm parallel? I'm still learning to differentiate it. If yes, then R = 15/16 ohm Is the R series to 5ohm? If...
  8. T

    Current at Resistor 2: How to Calculate using Capacitor Voltage and Ohm's Law

    Homework Statement In Fig. 27-66, R1= 10.0 kΩ, R2 = 15.0 kΩ, C = 0.400 µF, and the ideal battery has emf E = 20.0 V. First, the switch is closed a long time so that the steady state is reached. Then the switch is opened at time t = 0. What is the current in resistor 2 at t = 4.00 ms? This is...
  9. Syle1

    Find all resistor values in the Wheatstone bridge

    Hi, I've got a small physics problem : build an thermometer using the Wheatstone bridge, only knowing the voltage and the middle resistor of the bridge. I need help for the resistors values ; I've finished the rest, which is the relation between temperature and the resistors and the voltage. I...
  10. mkematt96

    Energy dissipated in a resistor during a time interval?

    Homework Statement Homework Equations P = I*V energy dissipated = wr = ∫ ( P *dt) ... t is from 0 to .4 seconds vs = 400t^2 = 400 * (.4^2) = 64 V The Attempt at a Solution Using KVL I said Vs ( 64 V) = 100 * i ... I found that I was 64/100 = .64 amps. I then said power is .64 amps ^ 2 *...
  11. G

    How do you find the current going through a weird circuit?

    Homework Statement Homework Equations at point C: i2 - i3 - i4 i2 = i3 + i4[/B] The Attempt at a Solution I labeled all the currents going through each resistor in the picture[/B] for loop ABC: 2000i1 = 3000i2 + 4000i3 for loop BDC: 3000i5 = 2000i4 + 4000i3 at point C: i2 - i3 - i4 i2...
  12. N

    B Solving a Circuit: Neglecting the 1 Ohm Resistor

    I want to know why in this problem in the solution, he disregarded the 1 ohm resistor and found the equivalent resistance of 6 and 3 ohms right away. https://imgur.com/a/efG11
  13. M

    Finding the time for charging Voltage

    Homework Statement 1. The characteristic decay constant for a capacitor C discharging through a resistor R is the product of R times C. If the initial voltage at time t = 0 is Vo = 13Volts and what is the voltage at time t = 2RC? 2. A capacitor C = 9microFarads is charged from 0Volts to...
  14. G

    Short circuit's effect on a voltage source and a resistor

    If I have a resistor and a voltage source in series but then I apply a short circuit in parallel to both of them would the voltage source and resistor not receive 0 V? Thus having 0 current. What would change in the circuit?
  15. T

    How does a resistor exactly reduce current flow in a circuit

    Greeting . It is clear to me that the resistor represents a physical obstruction to the passing current I do not know how exactly it works and I will try to show what I was really interested in the diagram.
  16. F

    Resistor instead of a step-down transformer

    As a quick and dirty/cheap solution, can a resistor be used instead of a step-down transformer ( stepping down from 230V AC mains to 3 V AC) to drive some simple electronic circuit such as a few LEDs or transistor radio etc ?
  17. P

    Understanding Resistance and Circuits for Homework Assignments

    Homework Statement My problem is that I don't know how to deal with this kind of questions. Homework Equations V=I*R[/B]The Attempt at a Solution I thought that the overall resistance would increase since there is a hindrance after the lamp doesn't function anymore, but don't know what to...
  18. G

    Semiconductor resistor in series with a capacitor -- Energy gap

    Homework Statement Consider a circuit that consists on a resistor of an intrinsic semiconductor R and a capacitor C in series. The voltage between the terminals of the circuit is U, which is an alternated sinusoidal voltage. U1, which is the voltage in the capacitor as a phase difference of 30...
  19. D

    Engineering Calculate the maximum power of the resistor in a circuit

    Homework Statement In an AC circuit of periodic current we know: ##E=6[V]##, ##R_g=50[Ω]##, ##L_g=\sqrt3 [nH]## and ##ω=50*10^9[s^{-1}]##. Calculate: a) All available power of the ##E## b) The resistance of ##R## so that the average power is max c) That average power from part b) Homework...
  20. L

    What is the current in these 3 circuits right after the switches are opened?

    Homework Statement What is the current through the resistor marked 'R' in all three circuits just after the switch is reopened after being closed for a long time? The Attempt at a Solution The explanation that we were given for (1) is that I = V/2R and (2) I = V/3R and (3) I = V/(R/2) but I...
  21. S

    Resistors in Series - Lab data confusion

    Homework Statement (see my attached photo to better understand where I am coming from!) So after some research, I've discovered that the current at different points in a simple series circuit is supposed to be the same value, and that the voltage is supposed to be different values. I...
  22. S

    Resistors in Series - Lab data confusion

    Hi guys! (see my attached photo to better understand where I am coming from!) So after some research, I've discovered that the current at different points in a simple series circuit is supposed to be the same value, and that the voltage is supposed to be different values. I performed a lab on...
  23. L

    Navigate the Res-Monster Maze: Find R's Current

    Homework Statement Res-monster maze. In Fig. 27-21, all the resistors have a resistance of 4.0 and all the (ideal) batteries have an emf of 4.0 V. What is the current through resistor R? (If you can find the proper loop through this maze, you can answer the question with a few seconds of mental...
  24. S

    How do I calculate voltage drops and currents in a resistor circuit problem?

    Relevant equations: V=IR Attempt at solution: When the switches are open, R1, R2 and R3 are in series so the current in that case would be 12 V/ (2 ohms + 3 ohms + 3 ohms) = 1.5 A. When the switches are closed, the current across R3 is still 1.5 A, so the voltage drop across R3 is 1.5 A * 3...
  25. C

    Resistance of a cylindrical resistor

    Homework Statement Homework EquationsThe Attempt at a Solution Can someone tell me what formula to use? Is it p=RA/L? but what about the mass? Thanks~
  26. C

    Resistor and current in a circuit

    Hello , I have to teach a group of 9th grade students role of resistor in a circuit and how it affects the current in the circuit . This will be their first exposition to circuits .So I need a good and simple analogy so that students can grasp these concepts easily . This is what I plan to...
  27. prakhargupta3301

    Will there be a difference between the readings of V1 and V2

    I= Current flowing V1= Voltmeter 1 V2= Voltmeter 2 My question is that if there would be any difference between the readings of V1 and V2? We know that: By Ohm's law: V= I.R also: Combined resistance of R1 and R2 will be: 1/RCombined Resistance of R1 and R2= 1/R1+1/R2 The reading in V2...
  28. prakhargupta3301

    Find the current flowing through the 3 ohm resistor.

  29. V

    Power consumed in a resistor

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] The first and foremost thing which I do not understand in this question is that there are many resistors present in the circuit , so how is it that we could relate power dissipated in one resistor to the power supplied by...
  30. C

    Could someone me identify a burned-up resistor

    hi, I am am hoping someone maybe able to help me identify a resistor the middle is slighty ( fell off) from heat i suspect i will add photos the only coulors left are very end cream then a gold band then cream then middle no there any more then we have a dark brown band then light brown hope...
  31. Manoj Sahu

    How grounding resistor and reactor have no effect in 3 phase fault?

    How would you justify the above question? Please elaborate in detail with diagrams (if applicable). It will be really helpful. Thank you.
  32. B

    HOW TO: Stop efficient LEDs from lighting up when off

    Saw an old thread, "Led Lights Burn With Power Off" and it was closed... so let me check out an issue with you all: in this same situation and I don't want the lights softly glowing, could I put a 100 ohm 1/4 watt resister in line to block the teeny tiny induced current? Would it behave well...
  33. M

    Calculating the V, I and R of resistor components

    Hi there, The problem asks me to calculate the Voltage, Current and Power of each component within the circuit. I have already calculated the following: V total = 12 Volts R total = 259.54 Ohm I total = 0.046 Amps I am confused as to how I am supposed to calculate the voltage drop across each...
  34. TheBigDig

    Using Nodal Analysis to determine current in a resistor

    Homework Statement Homework Equations ##V = IR## ##\sum_{k = 0}^{n} I_k = 0## The Attempt at a Solution [/B] I set the bottom node as the reference node and worked from there to find the three equations for the loop. When I try to eliminate ##I_4## by using ##I_4 = I_2 - I_3## I run into...
  35. nothing909

    IGBT gate resistor for switching application

    Homework Statement I have a 560 ohm gate resistor on an IGBT. Usually an IGBT doesn't require a gate resistor as it already has a high impedance of its own, but I'm told that for switching applications a gate resistor can be beneficial. The attempt at a solution If there is a gate resistor...
  36. Additya

    B Can a wire be called a resistor?

    Can a wire be called a resistor? Also do all circuits require a resistor? If no then give an example of a circuit which doesn't have a resistor. Please thanks
  37. S

    Understanding Reactive Power Measurements with a Smart Meter

    Hi, I was doing some test with the load bank today and I obtain a value which I don't quite understand. I supply a 400V Line to Line, 50Hz to a smart meter and to the resistor load bank. The measured value by the smart meter was 500W and -40Var with a current of 0.71A. As the current increases...
  38. S

    Voltage drop and current through each resistor

    Homework Statement Determine the voltage drop and current through each resistor. *This is just my sketch of the problem since I couldn't take a clear picture of it. Homework Equations Ohm's law V= IR Parallel total resistance Req=1/R1+1/R2+1/R3+... Series total resistance Req=R1+R2+R3+...
  39. J

    Potential Divider Circuits (resistor + LED)

    Homework Statement Attached to this thread is the question and mark scheme. Homework EquationsThe Attempt at a Solution I got most of the question right but I have no idea about the explanation part of why to include the 100 ohm resistor which is required for the higher level. It says in the...
  40. Kelsi_Jade

    Find the Current Flowing through each resistor

    Homework Statement Homework Equations / 3. The Attempt at a Solution Looking to solve mistakes to study from homework. Here's what I had so far[/B]
  41. Bassa

    Diode - Resistor Combination

    Helo, I am in an electronic course and we just started studying diodes. I am stuck on the following problem: Place a 100 ohm resistance in series with a diode, and plot current versus voltage across the series combination. I am also given the following values for the diode: n = 1, Is =...
  42. nothing909

    Resistor value at the gate of a JFET

    Homework Statement Referring to the diagrams below, what would a suitable value for Rg and why? I have did a lot of research and can't get a clear answer, can someone clear it up for me?
  43. R

    Length and Area of Cylindrical Nichrome Resistor

    Homework Statement You must complete the circuit of (Figure 1) in such a way that it draws a current of 0.450 A from the battery. The battery maintains a potential difference of 10.0 V with no load, but has an internal resistance of Rbatt = 15.0 Ω . The only material you have is 20.0 mm^3 of...
  44. K

    Charging a capacitor through a resistor -- final voltage?

    Why does capacitor charges up to full voltage as the emf of the battery even if there is a resistor is connected in series? I know that having a resistor means it will take longer to charge the capacitor but shouldn't some energy need to be lost in the resistor as well?
  45. clamatoman

    Solving for RMS current of a resistor, help?

    Homework Statement A resistor connected across an AC power supply has a current given by I=(1.35A)cos(300t) when connected to a power supply with emf 120 V rms. Find the RMS current. Homework Equations IRMS=Imax/√2 The Attempt at a Solution IRMS=Imax/√2 IRMS=0.477 A INCORRECT Not exactly sure...
  46. S

    Value of resistor for full scale deflection with 10A

    Homework Statement In order to provide full scale deflection the coil current required in a galvanometer is 190μA and the resistance of the coil in the galvanometer is 35Ω - What is the value of the resistor to be connected in parallel with the meter so that full scale deflection is obtained...
  47. Hamood97

    Find the two figures and the get value of the resistor and current

    Homework Statement finding the resistor and current which is following through the circuit[/B]Homework Equations kirchhoff law The Attempt at a Solution almost as fig 1 ( 9v=3.458 mA and 12v=11.122 mA) fig 2 (9v=1.472 mA and 12v=12.882 mA) i3=2.48 mA
  48. solour

    Current Through A Resistor That Is In Parallel With A Capacitor

    Homework Statement [/B] My question is regarding part C of the question. Homework Equations V = IR V(t) = V(1-e^(-t/tau)) The Attempt at a Solution My idea is to use Kirchoff's Voltage Law and find the voltage of the capacitor as a function of time, then since the voltage across capacitor is...
  49. nothing909

    Calculating resistor for IGBT and choosing flyback diode

    Homework Statement On the circuit I've drawn up, how do I calculate a current limiting resistor for the gate of the IGBT? The IGBT being used is a stgp6nc60hd. Also, how would I go about choosing a flyback diode for the motor?
  50. G

    Finding resistance of single resistor

    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...
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