Resistors Definition and 48 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. P

    Resistance of a Pentagon

    The question is to find the resistance between points A and F. I understand that the resistor between OC can be removed. From this point onwards, resistor OC has been removed. Let the far right point of the diagram, where i5 and i7 exit from, be B. Is it possible to detach the remaining...
  2. M

    2-Resistor, 2-Capacitor Circuit with Switch

    I already did part a and got the correct answer of 4.8 microC. However, I am unsure how to approach part b, where the switch is closed and apparently the two capacitors end up with different charges. For part b, since there is a path between the two capacitors, I don't know if I am able to...
  3. SaiTatter

    I need to calculate the equivalent resistance

    Homework Statement The circuit is the one in "Fig.4" I need to calculate equivalent resistance between A and B. This is what I've tried: I think that the first resistor is shorted by that wire connected between A and E. Their answer looks like this, in fig 2.2.1. I'm not sure if their...
  4. Kevin J

    Why does current choose the short circuit path?

    I've seen answers saying that electricity takes path of least resistance, I know this and there is no need to explain this for me. A forum's answer told me that the electrons initially flow through to the path with resistance and eventually becomes congested (redirecting the remaining electrons...
  5. R

    Equivalent resistance with a capacitor

    Homework Statement So I need to find the equivalent resistance for the following RC circuit to calculate the time constant, but I got stuck in terms of finding out the equivalent resistance. Homework Equations V = IR The Attempt at a Solution So the thing I am not sure on is how do you...
  6. A

    Combination Circuit Help (pic)

    Could somebody help me out with this combination circuit? The answer that I get is 62K but that is not one of the answers. At first, I thought the 10kohm and 20kohm wherein series and the other side as well. Then I thought they are all in parallel because of the different current flow they all...
  7. archaic

    Basic current question

    Hey guys, in the picture below, the current flowing through R1 is the same flowing through R3 right? And hence we have R1 and R3 in series? In this second picture R2 is going to cancel out because apparently that's what happens when you have a branch containing components parallel with a wire...
  8. G

    Weird circuit board with only resistors

    Found this. What could it be? So many resistors and nothing else?
  9. D

    How to calculate the resistance in a combined circuit

    Homework Statement Work out the total resistance of a combined circuit. - picture of circuit layout Homework Equations Rt=R1+R2+Rn... R=V/I 1/RT=1/R1+1/R2+1/Rn... The Attempt at a Solution RT=R1+R2 =100+150=250Ω for the resistors in series...
  10. A

    How to calculate voltage drop

    So I have two formulas for calculating voltage drop. The first is: Vdrop = Vin * R1 / ( R1 + R2...). This let's me calculate the voltage drop on the first resistor in a series of 2 resistors. You can also extend this to more resistors in series just by summing all the resistors. However, I do...
  11. T

    Engineering How can I simplify this mixed resistors circuit

    Hi I am to calculate Rab of the circuit and I have no idea on how to approach this problem. It would have been all nice and eaasy if it weren't for the vertival 30 ohm resistor. Because of this I'm in a dark spot. I will appreciate any help.
  12. P

    Engineering Resonance and RCL circuits

    Homework Statement I'm just really lost on this topic and honestly don't have too much of an idea. (a) Using Kirchoff's loop rule, find the differential equation satisfied by the charge q(t). (b) Verify that q(t) = q_max e^-(a/t) cos(ωt) satisfies the differential equation for particular...
  13. 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...
  14. 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...
  15. W

    How would you solve the following cuircut problem?

    Homework Statement You are tasked with designing an electrical circuit with a motor, a battery, and several 1ohm and 2ohm resistors. The motor is designed to run at a current of 20A and a voltage of 10V, but your battery supplies 15 V. The motor can then lift a 4kg mass 2.25 meters in...
  16. Ali Zain

    Rank in order, from largest to smallest, the resistance (eq)

    Homework Statement There is a figure, I'll try my best to draw/describe. 1. All three resisters are in parallel ___R____ !___R____! !___R____ ! 2. 2 resisters are parallel and one in series, after the parallel (ignore the dots) ___R___ ... _____R___ !___R___ ! 3. 2...
  17. Vanessa Avila

    Finding the current through the battery

    Homework Statement I am confused what to do but I have to find the current through the battery: Homework Equations V=IR The Attempt at a Solution I decided to find the equivalent resistance and do V/R = I using the 14V, but I believe my Req is wrong. What is throwing me off is the...
  18. egio

    I Not sure what I can make into equivalent resistors

    Could I combine the two resistors together in parallel to make an equivalent resistor, and then use that equivalent resistor in series with the capacitor? It would be great if there was some rule of thumb that I can use to know what I can make into an equivalent resistor/capacitor down the line...
  19. 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
  20. franktherabbit

    Engineering Transformation of resistors in a circuit

    Homework Statement From the circuit diagram ( ) calculate the net charge flown through the capacitor 2. Homework Equations 3. The Attempt at a Solution [/B] I actually don't need to solve the full problem as i understand how, what i have trouble with is the...
  21. C

    A circuit with multiple sources of voltage

    Homework Statement Solve this circuit: a) Mark all currents b) Write a system of equations allowing you to solve for the currents 2. The attempt at a solution Part a) in attachment. Part b) \epsilon_1 = i_1 r_1 + (i_1 + i_2 + i_3) R \epsilon_2 = i_2 r_2 + (i_1 + i_2 + i_3) R \epsilon_3...
  22. M

    Engineering Circuits with Resistors

    Homework Statement Homework Equations V=IR The Attempt at a Solution So far I haven't had any problems finding the Req. However, I am having trouble with the VIR chart. Can anyone confirm whether or not I did it correctly. My thought...
  23. YellowBelliedMarmot

    Engineering Simplifying a Circuit w/ Parallel Resistors

    The goal of this problem is to find the equivalent resistance of all the resistors. Each resistor shown in the image has a conductance of 1 mS which I believe is equal to 1000 ohms. I attached a picture of the circuit diagram in which I show some of my work in order to convey my erroneous...
  24. kamhogo

    Resistors (lightbulbs) Power & Brightness

    Homework Statement A 60 W lightbulb and a 100 W lightbulb are placed one after another ( in series, the 60 W battery closer to the positive terminal of the battery) in a circuit. The battery's emf is large enough that both bulbs are glowing. Which is the true statement? A. The 60 W bulb is...
  25. neilson18

    What is the voltage across battery terminals?

    Homework Statement [/B] Three resistors are connected to a real battery. The open circuit voltage of the battery is 4.5 Volts. The voltage across the 5 Ohm resistor is 2.5 Volts. A) What is the voltage across battery terminals? B) What is the internal resistance of the battery? Here's a...
  26. N

    Kirchoff's Loop Rule Involving 2 Resistors and a Capacitor

    A 5μF capacitor is connected in parallel with a 2MΩ resistor and the combination is then connected in series with a 1MΩ resistor through a switch to a 12V battery. Find the time taken for the voltage across the capacitor to rise from zero initial value to 2V after the switch is closed. From...
  27. A

    Find the resistance of a resistor using Ohm's Law?

    Hi, I have been at this problem for days and I can't seem to see what I am doing wrong. Here is the circuit layout along with my work As you can see I am running into problem getting values of current that do not add up equal to zero. My professor has never discussed how adding a wire like...
  28. marciokoko

    Help with current flow, voltage, resistors in basic circuit

    Im reading this stack exchange question: So there is a 5V circuit with 2-100 Ohm resistors that yields a voltage drop across the divide of 2.5V. The current through the circuit is 25mA...
  29. H

    Non Ideal Batteries in Electric Current

    Homework Statement A circuit is constructed with five resistors and one real battery as shown above right. We model. The real battery as an ideal emf V = 12 V in series with an internal resistance r as shown above left. The values for the resistors are: R1 = R3 = 57 Ω, R4 = R5 = 75 Ω and R2 =...
  30. S

    Engineering Series/Parallel Resistor Circuits (Diagonal Resistor)

    Homework Statement Homework Equations Kirchhoff's Current and Voltage Laws, Resistors in parallel and in Series. The Attempt at a Solution The main thing confusing me is the diagonal 6 Ohms, not too sure what it is parallel too and how...
  31. J

    Voltage drop for a charged capacitor

    Homework Statement What is the voltage drop across the 1000 Ohm resistor when capacitor is fully charged? Homework Equations V(t) = {V_i}*e^{-t/RC} = {V_i}*e^{-t/Tau} The Attempt at a Solution In RC circuit experiment, initial is 9V and final is 2V. The voltage drop should be difference...
  32. F

    Kirchoff's Law - Wire in parallel with light bulb

    Homework Statement If you measure the resistance of the three lightbulbs (independently) and get the following values. What is the equivalent total resistance of the circuit, and it’s uncertainty. R_1 = (50 \pm 7) \Omega, \ \ R_2 = (720 \pm 30) \Omega, \ \ R_3 = 140 \pm 20) \Omega Now you...
  33. N

    Determining current from ammeter

    Homework Statement The ammeter reads 5.0A. Find I1, I2, and ε Homework Equations ΔV=IR The Attempt at a Solution I've never dealt with ammeters before so I'm very confused. To start, I tried breaking this into loops, and then used Kirchhoff's Law. I started with the left side, since I...
  34. GoldWing

    Triangular Resistance Network

    Homework Statement Assuming R = R' in the network shown above, determine the net resistance between the points a and c. Express your answer as a number times R. b. Assuming R = R', determine the net resistance between the points a and b. c. Now suppose R' = 2.5R, and find the net resistance...
  35. M

    How do electrons know that there are other resistors?

    If there is only one resistor, the voltage drop is equal to the potential of the positive terminal. The voltage drop across more than one resistor is directly proportional to the value of each resistor. But the total drop in potential difference must be equal to the potential of the positive...
  36. E

    RESISTORS problem

    Could you solve this?
  37. B. Vane

    RCL Circuit: 2 Resistors, 1 Capacitor, 2 Inductors

    Homework Statement NOTE: Image uploaded with thread shows problem in clearest possible form. V = (45v)sin(80[pi] t) Resistors 1 and 2 = 50 Ohms Inductor 1 = 20 mH Inductor 2 = 2.5 mH Capacitor = 50 uF a) Find the power dissipated by each resistor. b) At what frequency will both resistors...
  38. F

    Ammeter from parallel to series, current change

    Homework Statement In the circuit shown, a student mistakenly connects a perfect ammeter(i.e. One of negligible resistance), in parallel with one of two identical resistors. The ammeter reads 0.40A. What would the reading have been if he had correctly connected the ammeter in series with the...
  39. G

    Unknown value of added resistor in parallel

    Homework Statement Picture provided. The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 14.00 Ω, R2 = 142.00 Ω, and R3 = 24.00 Ω. The voltage is V = 11 V. With this information, what...
  40. L

    Finding an Unknown Resistance

    Homework Statement The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 70.00 Ω, R2 = 50.00 Ω, and R3 = 62.00 Ω. The voltage is V = 15 V. With this information, what is the value of...
  41. S

    Calculate the equivalent resistance

    Homework Statement Ignore the internal resistance of the battery and assume it is merely a battery. Calculate the equivalent resistance of the circuit. Homework Equations 1/Req = 1/R + 1/R ... (parallel) Req = R + R ... (series) The Attempt at a Solution I know this is fairly simple but I...
  42. C

    What is the correct way to analyze a circuit with resistors?

    Homework Statement [/B] R1 = 42 Ω R2 = 124 Ω R3 = 119 Ω R4 = 105 Ω Rx = ? I4 = O A Homework Equations R = IV V = V1 = V2 for parallel Resistors Iequiv = I1 +I2 for parallel Resistors Vequiv = V1+V2 for series Resistors Iequiv = I1= I2 for series Resistors The Attempt at a Solution I have...
  43. E

    RC Circuit Help

    Homework Statement There is a circuit with a battery of voltage V and resistor R, then splits into two branches one with a capacitor C, and one with a resistor 2R. The answers for the questions can only depend on R, C, V, and t. When a switch only allows current to flow through the capacitor...
  44. C

    Power dissipation limit for a resistor

    I am confused about the concept of a power dissipation limit for a resistor. Basically for a resistor the product of the current through it and the potential across it should not exceed 0.25 watt otherwise it starts to heat up and act in a non-linear fashion. Is this value just a constant or is...
  45. C

    The current through an individual resistor

    The following circuit has been modeled using some modelling software (Micro-Cap 11). I was wondering why current is only shown at the source and not in R1, R_Unknown and R3. I know current is meant to be the same in series although I am confused by the effects of the resistors. (This is not a...
  46. G

    Finding Unknown Currents in a Two-battery Complex Circuit

    Homework Statement Look at the circuit given in figure 1. Solve for the three currents, I1,I2,I3. Homework Equations KVL: Sum of voltages in a closed loop equals zero KCL: Sum of currents entering a junction equals the sum of currents exiting a junction Ohm's Law: V=IR NOTE: Nodal analysis...
  47. davidbenari

    Internal resistence: chicken and egg misconcpetion

    I feel like have a chicken and egg type of problem regarding internal resistences because of the following problem: The voltage across a battery with internal resistence is given by the equation EMF-Ir=V Given the voltage across the battery then the voltage in the circuit is V=IR So, if I have...
  48. A

    Finding the Effective resistance of a tree of resistors

    1. A) Find the Effective resistance of a tree of resistors that bifurcates 3 times. B) Find the effective resistance of a tree of infinite resistors. (if the tree below went on to infinity) Homework Equations Ohm's Law The Attempt at a Solution I have no idea how to start this. There was no...