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. justin___

    Finding an open-cicuit voltage, why is resistor in series ignored?

    I found how to get the solution to this question (the answer is 200V), but I don't understand why we ignore the 30kOhm resistor when using analysing the circuit. Because it is in series with the open voltage, wouldn't there be some voltage drop across the resistor that would affect the...
  2. student_man

    Engineering Current change after inserting thin conductive foil into resistor

    I tried splitting it up into 4 individual resistors, adding them up (each side serially and then both sides with each other as parallel) and then using V=IR but it ended up being the same current as the original. (The answer should end up being (9/8)* the original current)
  3. guyvsdcsniper

    Graphing the Power dissipated in a resistor

    I am solving #5 in the attached image. So I am graphing the power dissipated by a series circuit which : (a) Contains a constant voltage source and a variable resistor, R (b) Contains a constant current source and a variable resistor. It makes sense to me to just use the power equation that...
  4. Lay1

    Voltage Variation w/ Variable Resistor: Correct?

    In this figure, I suppose the maximum voltage is when R2=1kohm and the minimum voltage is when R2=0kohm, which means R2 is a variable resistor. Is the way I think is correct or not? Please give me suggestions. Thank you.
  5. J

    How does the presence of a cube resistor affect current flow in a circuit?

    I would think that it is 2 A (6/3 because there are three wires the current can go to), but this does not seem to be correct.
  6. G

    Power dissipated by a resistor on a coaxial cable

    I need help with part c. My solution: Is there an other way to do this other than dimensional analysis? P.S "dr an infinitesimal radius", it ofcourse should be dz.
  7. P

    Engineering What is the Relationship Between Resistor Values in an Attenuator Circuit?

    Greetings, fellow travelers. I gave been digging into some of my old (1970s) Electronic maths textbooks and for my amusement and time wasting refreshing some old knowledge. Have got through a fair but but have to keep coming back to this problem. I do have the answers but I cannot regardless of...
  8. greg_rack

    Current flowing through resistor in RLC circuit (C in parallel with L)

    Hello guys, LRC circuits with an AC source are having the best over me... had some confusion in class with respect to which method is best using(phasors diagram, reactances or complex impedances) which I am trying to desperately sort out before my exam; here I will show you my best attempt on...
  9. kalm1307

    Resistor value given capacitance and EMF with a resistance R after 3ms

    T=R/C So: 0.003s=R/100μC R=3*10^-7Ω I am really confused with the equations I have to use
  10. bluesteels

    Power formula for circuit when another resistor is added in

    On Chegg they solve for V using P=V^2/R using 36W and R1= 25Ω, which is equal to 30V then they add R1+R2 = 40Ω and they plug in P=V^2/R and solve for P which is 22.5W I'm confused on why they didn't use P=I^2*R cause you know the system is in series so I is the same and solve for I then...
  11. S

    Why is it important to classify circuits as series or parallel?

    The answer sheet assumes that the resistors in both circuits are in series and that we need to use the equation Req = R1+R2+R3.. to find the Req in both cases. How come the resistors are in series, when there are multiple resistors in a single row? Also, why does the following work yield the...
  12. Hazel Appraiasal

    Solving the Missing Resistor Problem in a Parallel Circuit

    Summary:: How de you find the missing resistor (R6) in this problem. I assume you take the current flow of the parallel circuit to find the resistance of R6 but I feel like there is still some missing information
  13. Y

    Questions About Choosing a Shunt Resistor

    I'm trying to do a power analysis on my target, which runs on 3.3 volts. Without the resistor, the average current while running is roughly 140mA. I used a 10Ohm resistor as a shunt resistor with a 5V power source. The voltage difference between VCC PIN and GND was measured using a shunt...
  14. A

    Engineering Calculating the voltage at a certain Resistor

    Hello! Consider this circuit; Now the value are given as follows; U = 10V; R1 = 150 Ohm R2 = 470 Ohm R3 = 330 Ohm; I am susposed to calculate the voltage at R1 when S1 clossed;so when there is a current flowing through it. I did that using the loaded voltage divider,since I can see that R2...
  15. N

    Using delicate 5V IC to toggle 12V device with MOSFET, Diode, resistor

    Hey all, I have a 5v IC that is triggered by a sensor to unlock the 12v lock, I am using a NPN transistor as a switch with the 5v VCC as the gate, I need it to sink back to the GND of the IC without blowing it, is this safe? If not what changes would you suggest, it has been years since I've had...
  16. guyvsdcsniper

    Trouble finding the current through this resistor in the circuit

    I was following this problem up until they say we can they state I3= I1-I2. I understand why we can say that but I don't see how I can use that to get the system of equation in terms of I1 and I2 at the bottom. Could someone show me how this was done?
  17. E

    How to find the heat energy produced in a resistor?

    i found current to be 2/5 A. then 2/5A multipled by 6s = 2.4C. and since one joule per coulomb is equal to the unit of p.d, i get 2.4J. I don't get 4.8J(supposed answer)
  18. cemtu

    Engineering Shunt Resistor, Grain Boundaries & Solar Cell Circuit

    In the circuit equivalent of a solar cell, shunt resistor is described as "The irregular polycrystalline lattice grain boundaries that resist to the flow of electrical current in the silicon material." If this explanation is correct, shouldn't it be "lower shunt resistance increases the current...
  19. P

    Can I replace a 4 ohm speaker with a 4 ohm power resistor?

    Also would a passive filter add much resistance to the circuit and rob the speaker of power? Here is the 2 way lowpass filter I was thinking of. I don't need 2 of these obviously but they seem to come as a pair. https://www.amazon.com.au/dp/B07R613YSK/
  20. sodoyle

    Can I use individual capacitor IR for parallel circuit balancing resistors?

    I am going to have several series/parallel capacitors so need balancing resistors. I understand that for series capacitors, it is wise to use voltage balancing resistors so mismatch in individual series capacitors leakage current can flow through the resistors which prevents individual...
  21. Andrei0408

    Calculate the voltage across a resistor using Thevenin's Theorem

    I'm thinking I should apply Thevenin's Theorem to find the voltage, but I need to find I_D in order to be able to calculate U_S.
  22. Tim86

    DC current through a resistor circuit

    Summary:: Current through a certain resistor in a mixed dc circuit. Hi, Sorry if this is the wrong forum. I'm trying to work out the current through R1.The answer I need is 2 Amp, which I have confirmed with a simulation software. I have calculated the source current as 8A, the current past...
  23. Joshy

    Active LPF or Integrator w/feedback Resistor

    Summary: Why would you choose a RC with a non-inverting op-amp instead of an integrator with feedback resistor for an active LPF? I was at an interview not long ago and one of the classic questions popped up: Draw me an active LPF with gain. I've seen it plenty in my book (Sedra and Smith) and...
  24. greg_rack

    Current flowing through a resistor in an RRL DC circuit

    DISCLAIMER: don't answer in terms of integrals, I haven't covered those yet :) Hi guys, I'm having a few troubles understanding RRL circuits, and have a few questions for you. A "normal" RL circuit will have a current growing inversely exponentially, starting from 0 and going to ##V/R## as...
  25. H

    The greatest power will be dissipated in the resistor if R =?

    Since the power generated by both primary coil and secondary coil would be the same in a transformer, so I used the relationships stated above to deduce the resistance R in secondary coil. P1 = N2^2 *100 = 100^2 * 100 P2 = N1^2 *100 = 500^2 * R R = 4 Let me know if my thoughts here are...
  26. B

    What is the value of the load resistor?

    But I think the answer is 32, is it correct?
  27. X

    Engineering Find di(0+)/dt and dv(0+)/dt of circuit containing resistor, inductor

    Dear PF, I am trying to solve practice problem 8.1 and I am stuck on part b which asks us to find di(0+)/dt and dv(0+)/dt. Down below in the picture is my attempt. Before t=0 it is quite intuitive since the inductor acts as short circuit to steady-state DC and a capacitor acts as open circuit...
  28. icesalmon

    Engineering Find the Average Power absorbed by the 20k Resistor

    I wrote the following equations using node voltage, my issue is that I'm confused about why the RC branch at the output doesn't effect the value of the Gain for the amplifier; the equation involving VA / ( 20k - j12k ) is omitted in the solution. IAC = IAB + IBC V- = V+ = VB = VS ( VA-VC...
  29. cianfa72

    Circuit theory - Resistor function for dynamic non linear circuits

    Hi, I'm reading the following paper (L. Chua) about the state-of-art of dynamic non linear circuit analysis -- Chua_Dynamic_Circuits I've a doubt about Theorem 2 on section 3.2 On the Existence of the Resistor Function that establishes sufficient conditions for the existence of network...
  30. J

    Understanding Complex Circuit Configurations

    Having more difficulty understanding the concept, thus I am not showing values. What is causing me confusion is the line in the middle. The first aR and bR are obviously in parallel, but the second aR and bR confuse me. I tried calculating the equivalent resistance from the first aR and bR and...
  31. greg_rack

    Electric potential difference at the ends of a resistor

    So, having two parallel resistor ##R_{1}## and ##R_{2}## , the current flowing through the equivalent one will be ##I_{eq}=I_{1}+I_{2}##. Now, it comes the point I'm not totally getting: why is ##V_{eq}=V_{1}=V_{2}##? These V's are the difference of potential measured between which points...
  32. greg_rack

    Current in a resistor with Kirchhoff's laws

    So, I started by writing down conditions imposed by Kirchhoff's laws, coming up with a system of 3 equations with the 3 unknown currents: $$ \left\{\begin{matrix} 9V-8\Omega I_{8}+6V-4\Omega I_{4}=0 \\ 6V-4\Omega I_{4}+3V-2\Omega I_{2}=0\\ I_{2}+I_{8}=I_{4} \end{matrix}\right.$$ But...
  33. S

    Engineering Find Current Through 40 Ohms Resistor Using Thevenin

    Find the current through the 40ohms resistor using the Thevenin? I have calculated the Zth = 10 ohms. And I couldn't find the Vth.
  34. PhysicsTest

    Why is the Voltage Drop Across a Resistor -Ve to +Ve?

    Really very elementary one, if i refer the circuit below For the source in the direction of current the polarity is -Ve to +Ve that is understood which is conventional current, but in the case of resistance in the direction of current the voltage V_R polarity is -Ve to +Ve. Why for resistance...
  35. K

    Comp Sci Need help finding the resistor size for a circuit (Ohm's law)

    I know there is a serial and parallel circuit I know R1 = 2k, R3 = 1k and i know Vout which is 1V. And i know 5V is coming from supply. I need to calculate the size of resistor R2. I can calculate : 1) IR1 = 5-1V/2000ohms = 2mA 2) UR1 = 0,002A*2000ohms=4V voltage drop on R1 How do i go on...
  36. willDavidson

    Capacitor-balancing resistor sizing

    I understand that when sizing balancing resistors you should consider the power rating of the resistors. The resistance and power rating has to be high enough so that they do not overheat. Even with a large enough power rating, I know that they will effect your overall efficiency since that's...
  37. archaic

    How Does a Resistor Affect the Heating Time of Water?

    1)$$R=\frac{\Delta t(\Delta V)^2}{Q}=\frac{\Delta t(\Delta V)^2}{mc\Delta T}=8.33\,\Omega$$2)$$\Delta t'=\frac{mcR\Delta T'}{(\Delta V)^2}=\frac{\Delta T'}{\Delta T}\Delta t=59.4\text{ min}$$3) I surfed the net a bit and have found a post on physics.stackexchange in which it is mentioned that...
  38. jisbon

    Engineering Computing the Maximum Power delivered to a Resistor

    Hi all, Checking my answers here as it doesn't seem to match with the answers given to me. Would appreciate if anyone could point out the mistakes I made. First I will compute Rth. Offing all independent sources, applying a known voltage across R (in this case 1v) and using mesh analysis...
  39. stiwi_xyz

    Need Help With These Resistor Network Problems Please

    Consider the resistor network shown in Figure 1-1, where 𝑅1=2𝑘Ω and 𝑅2=5𝑘Ω. (a) Calculate the numerical value of the single equivalent resistance, in 𝑘Ω, as seen from the terminals 𝐴−𝐴′. Express your answer to two decimal places.Next, consider the circuit shown in Figure 1-2, where 𝑉=30𝑉 and...
  40. M

    Engineering Calculating Power Lost in a Resistor (within Transformer Circuit)

    Hi, I have a simple question that I don't have a fundamental understanding of: do resistors dissipate reactive power (in addition to active power)? For context, when we are looking at a transformer (single phase) equivalent circuit (similar to the one in the image attached), we are asked to...
  41. Abdullah Almosalami

    Couple Questions about this Resistor Datasheet

    So I have these 10k 5% resistors from Stackpole Electronics and just because I never actually took the time to look at a resistor datasheet beyond nominal resistance, tolerance, and power rating specs, I decided to look them up. Came across a couple things I wanted to ask about: 1) Maximum...
  42. B

    Equivalent resistor of a simple circuit

    Hi. Anyone knows how to calculate the Req of this circuit? n tends to infinite.
  43. Prabs3257

    Heat dissipated in a Resistor-Capacitor circuit

    I tried to conserve the charge on the left plates of both the capacitors as intially the total charge on both is 48 and at t=t0 the total charge is 36(on c1) +4V(V is the potential across c2) so i got V=3 and then i conserved the energy Initial energy on both capacitor = final energy on both +...
  44. B

    Finding the value of this load resistor

    Question: I first knew that this would be a series circuit setup, there the current all around the circuit would be the same. It's given that when it's a open circuit, p.d. across the output is 4000V hence the emf is therefore 4000V. When it gets connected to a load resistor, the voltage...
  45. B

    Value of the shunt resistor in this circuit

    Here are a couple of questions that I have been trying to answer and had a go at it. Not sure if I answered some incorrectly so was hoping to get some guidance For this one I have tried to make use of Kirchhoff's 2nd law to help me, but this is what I have ended up with when using it...
  46. B

    Calculating the current through this load resistor

    Hi everyone I have drawn what I think what the setup should look like, and worked out the equivalent resistance of the parallel connected resistors Not so sure where to go next with this problem? Any help would be greatly appreciated!
  47. B

    Finding the resistance of this shunt resistor

    How would I go about this question? Here is my attempt at it but I haven't really gone anywhere with this :oldconfused: Any help would be really appreciated!
  48. E

    B Hydraulic resistor as a constriction in a pipe

    Earlier I was trying to explain to one of my siblings why current is constant in a series connection (invoking that if it weren't we would have an accumulation of charge, etc.), however to give a more intuitive picture I tried to describe the hydraulic model of electric circuits, representing a...