What is Resistors: Definition and 603 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. V

    CIRCUITS: Four resistors and a voltage supply (very easy)

    Find v1 and v2 in the circuit shown. Also calculate i1 and i2 and the power dissipated in the 12-ohm and 40-ohm resistors: My work so far: i_1\,=\,\frac{N1\,-\,N2}{12\Omega} i_2\,=\,\frac{N2\,-\,0}{40\Omega} i_3\,=\,\frac{N1\,-\,N2}{6\Omega} i_4\,=\,\frac{N2\,-\,0}{10\Omega}...
  2. J

    Variable Resistors: Numeric Decade Resistors, 1-200 KOhms, 1 Ohm Resolution

    Hello all, I am working on a control circuit for a project that uses a 555 timer as a frequency controler. I need a variable resistor that has a range of 1-220 KOhms and I found some good 10-turn potentiometers that would seem to do the trick. But later, I was looking around on eBay and found...
  3. V

    CIRCUIT ANALYSIS: Use superposition - 2 Current source, 1 Voltage source, 4 resistors

    Using superposition, find v_0 in the following circuit. My work so far: v_1\,=\,2\,i_2\,+\,v_{0\,1} v_1\,=\,4\,i_1 v_{0\,1}\,=\,3\,i_3 v_{0\,1}\,=\,6\,i_4 KCL @ v1: 1\,A\,=\,i_1\,+\,i_2 i_2\,=\,i_3\,+\,i_4 Using these six equations, with 6 variables...
  4. V

    Engineering EECS: Find i_0 in a circuit with 4 resistors and 1 indep. current source

    (a) Using nodal analysis, determine i_0 in the circuit. (b) Now use linearity to find i_0. Work so far: i_0\,=\,\frac{v_1\,-\,0}{6\,\ohm}\,=\,\frac{v_1}{6\,\ohm} KCL@v_1: \frac{v_1\,-\,0}{3\,\ohm}\,+\,\frac{v_1\,-\,0}{6\,\ohm}\,+\,\frac{v_1\,-\,v_2}{2\,\ohm}\,=\,0 KCL@v_2...
  5. P

    Are resistors in series if there is a current source between them?

    are to reisistors considered in series if inbetween them is there is a wire supplying a current source not from the battery. for example if there was a wire giong up from point A to B and in that wire, there was a current source. A-----^^^(R1)----B----^^^(R2)
  6. F

    Finding Resistors Currents with Changing Resistance

    A 23 V battery is connected to terminals A and B below. (a) If R = 95 Ω, find the current in each resistor (/12, /55, /95). (b) Suppose the value of R is increased. For the 12 Ω resistor, does the current flowing through it increase or decrease? What about the 55 Ω resistor? What about...
  7. E

    Engineering Design a Circuit Using Diodes, Resistors and Voltage Sources

    Hello, I have this problem: design a circuit using diodes, resistors and voltage sources to obtain the input function. And the input function is Iin vs Vin plot with following points connected as straight lines: (2V,0mA), (3V,2mA), (4V,6mA). I guess I need a hint on what kind of topology...
  8. A

    Pullup Resistors & TTL Gates: Reducing Delay and Noise

    Is it true that a "high" input of a TTL gate shouldn't be left floating but instead connected to +Vcc through a pullup resistor because this way the propagation delay time is reduced and less noise is captured? If that's true, should a pullup resistor be used when connecting the input of a...
  9. G

    Finding current in a complex circuit with resistors

    I am given the following circuit: How do I find the current through the battery? I have trouble seeing which resistors are in series and which resistors are in parallel. I think I need to figure that out and then calculate R_eq accordingly. Then set I=V/R and solve for I. But which...
  10. R

    Solving Resistor Problems: How to Find Equivalent Resistances

    Is there a way to solve this mathmatically or do i have to draw out the 10 circuits and figure it out that way?
  11. D

    Troubleshooting Resistors in Series/Parallel Circuits

    I have a picture attached. Hopefully you guys are able to see it. The question is asking the following: Find the equivalent resistance Req between points A and B of the resistor network. I know you have to use the resistors in series/parallel approach. but which of these are in parallel...
  12. J

    What Current Corresponds to a 16 Ohm, 0.1 W Speaker?

    The little speaker in a portable radio is labeled 16 Ohm's , 0.1 W. To what current does that correspond? I'm kind of confused where to go with this one. what i know is this, 1 watt=1volt*1amp, but where do i go from there? Do I have to use Ohm's law somehow? V=IR. So does VI=.1 and...
  13. T

    Calculating Rate of Change in Parallel Resistors

    Hey Guys, I learning about Related rates and although I understand the basic concepts, I'm stuggling with this problem - When two resistors r1 and R2 are connected in parallel, the total resistance R is given by the equation 1/R=1/R1+1/R2. If R1 and R2 are increasing at rates of .01 ohm/sec...
  14. N

    Finding current across resistors

    I'm not quite sure how I'm supposed to be doing this problem. Consider the circuit shown in the figure below. R = 21.3 ohms http://east.ilrn.com/graphing/bca/user/appletImage?dbid=411814203 Find the current in the 21.3 ohm resistor. I combined (serial) R with the 5.85 ohm...
  15. M

    Connecting resistors in parallel

    When resistors are connected in parallel, which one , according to resistance value, carries the larger proportion of the currents? Does the ratio appear to be directly, or inversely, proportional to the ratio of the resistances?
  16. D

    How Many 8 Ohm Resistors Are Needed to Dissipate 5.6 Watts?

    You are given a number of 8 \Omega resistors, each capable of dissipating only 1.0 W without being destroyed. What is the minimum number of such resistors that you need to combine in series or in parallel to make a 8 \Omega resistance that is capable of dissipating at least 5.6 W? My approach...
  17. M

    Calculating Current and Voltage in a Series Resistor Circuit

    |------A------| |.....* R2 - Vs.....|B -.....| |.....* R1 |------C----- | Assuming that the above is a circuit (sorry for the bad drawing, ignore the dots), what would be Ia, Ib, Ic (currents), Va, Vb, Vc (voltages)? Initially, I thought that the current and the voltage would be the...
  18. J

    Why does the slope of a graph representing Ohm's Law equal the resistance value?

    I know that according to Ohm's Law that the voltage is directly proportional to the current in a resistor. Upon examing my graph that I have calculated in class, a resistor follows Ohm's Law because the slope was a straight line. The part I am confused about is why would the slope be equal to...
  19. P

    Finding the Voltage Drop Across a Capacitor in a Series Circuit

    I got a question that reads: Supoose a 10khz signal with an amplitude of 1 volt is applied across a 1k(ohm) trdidyot snf s 0.25 microF capacitor which are connected in series. What is the voltage drop across the capacitor? I tried to use the equation Vc(t) + Vco*cos(omega*t) in which i got...
  20. S

    Calculating Current, Voltage in Series Circuit with 25V Battery and 2 Resistors

    I have a series Circuit with a battery of 25 Volts and 2 Resistors, 1 is 250 Ohms and the other is 500 Ohms. What is wanted is a. I = _______mA b. V1 = _______ c. V2 = _______ To get I I took I = V 25 25 ______...
  21. D

    Probability Density Function of two Resistors in Parallel

    I have a problem where there are two resistors in parallel and I need to find the equivalent resistance. R1 = X and R2 = Y, and X and Y are independent random variables, uniform over the range of 100-120. If R equivalent = Z = XY/X+Y, what is probability density function of Z?
  22. D

    Probability Density Function of two Resistors in Parallel

    I have a problem where there are two resistors in parallel and I need to find the equivalent resistance. R1 = X and R2 = Y, and X and Y are independent random variables, uniform over the range of 100-120. If R equivalent = Z = XY/X+Y, what is probability density function of Z?
  23. M

    Question about variable resistors

    I'm building a circuit in one of my classes and it asks for a variable resistor. On the schematic it's value is 47kohms. On the circuit diagram I'm building this from, it says to adjust VR1 (variable resistor) until a diode comes on. First off, what exactly is a variable resistor? Second, how do...
  24. zeronem

    A Complex Three Loop Circuit with Resistors and two batterys only.

    Okay,, I am going to try and give precise instructions on how to draw the circuit so you all can see what I am dealing with here. This is not a homework problem really. We just did a lab and worked on measuring the currents through resistors using the Ammeter. Anyways, we worked with two...
  25. V

    Please help me with resistors in parallel/series - with many variables

    Please help me with resistors in parallel/series - with many variables :) Three identical resistors are connected in parallel. The equivalent resistance increases by 700 W when one resistor is removed and connected in series with the remaining two, which are still in parallel. Find the...
  26. M

    How to Solve for Currents in a Circuit with Resistors and Voltage Sources?

    Cant quite get this one. What I think is that I3 and I1 add together to get I2 and I found this equation V1+v2=E1-E2 and V3+V2=E3-E2 and I was substituting IR in for all the V's and I3+I1 where I2 comes in and making two equaitons and solving but no dice any tips? Thanks. _________/\R3\/l l...
  27. N

    HELP Resistors Parallel/series

    Ok the question is: A resistor (resistance=R) is connected first in parallel and then in series with a 2.00 ohm resistor. A battery delivers five times as much current to the parallel combination as it does the series combination. Determine the two possible values for R. So let's see: I...
  28. O

    Reaction time of Light Dependant Resistors

    I am doing this bit of work on the reaction time of Light Dependant Resistors (LDR's) with different frequencys of light and i need to be able to get a graph out of it and I am not sure what to do for it. i was thinking of plotting reaction time vs. frequency but apart from making a graph and...
  29. T

    Resistors in series and parallel

    A 3 ohm resistor is connected in parallel with a 6 ohm resistor. This pair is then connected in series with a 4 ohm resistor. These resistors are connected to a battery. What will happen if the 3 ohm resistor breaks? I think that the power dissipated in the circuit will increase. The...
  30. T

    Currents and resistors and series and parallel you get the idea

    So this problem asks you to determine the magnitudes and irections of the currents in the resistors. I definitely understand how to determine directions, using Kirchhoff's Rules. But here is where I get stuck: the batteries have emfs of E1 = 9.0 V and E2 = 12.0 V and the resistors have vlaues...
  31. P

    Resistor Connections and Applications: Exploring Resistance in Circuits

    Guys I need your help about resistors... These are the questions: 1. You have 4 identical resistors, each with resistance of 5 ohms. Show how you will connect the four resistors to get an equivalent resistance of 5 ohms. (hint: there is more than one way) 2. As more doors are opened in a...
  32. A

    Electro question: Drop Voltage with 1 ohm resistors

    This might be a silly one, but I'm a bit stumped: Suppose you have a 6V battery and an unlimited supply of 1 ohm resistors. How do you drop the potential from 6V to 4V using the resistors? Off the top of my head I think you just put two of the resistors into a series attached to the...
  33. C

    Resistors, How to decode the resistance fom the color bands.

    OK, I know this is a stupid question, but I just plainly forgot how to decode the value of the resistance of standard resistors from the color coding. I know the last band is soemthing to do with tolerance of the resistance values, but what is the value of the tolerance related to a certain...
  34. G

    Finding Resistance in Infinite Chain of Resistors

    Consider the above infinite chain of resistors. Calculate the effective resistance, R in ohm of the network between the terminals A and B given that each of the resistances labelled r=4180 ohm. I've split the resistor and I've done R^2-Rr-r^2=0, solving for R and I don't get the right...
  35. quasar987

    Understanding Heat and Resistors: Explained for Non-Experts

    Griffith's saying that in a resistor, P = RI² is the rate at which heat is dissipated. Is that suposed to be intelligible to someone who has no knowledge in thermodynamics? Can someone explain this process to me. What is HEAT? And how does the rate at which work is being done by the...
  36. M

    Why do resistors in parallel not follow the trend?

    hi. ^_^ we recently did this experiment on measuring the actual resistances of resistors. every time, the actual resistance was less than the resistance on the label, except for the resistors arranged in parallel. the theoretical value for 100 ohm and 220 ohm resistors is 67.5 ohms, but...
  37. S

    Question regarding resistors and potentiometer

    I have spend many hours trying to solve this question but still can't figure out the answer.I hope that somebody will help me with this question.Thanks for anybody that spend some time on this question. I have my question and solution in the attachment followed.
  38. D

    What Resistance Does an Ohmmeter Read in an Infinite 2x2 Resistor Array?

    ... | ... R ... | -R- --R ... | ... R Suppose you have an infite array (2by2) of resistors, each of value let's 1k. If you place the an ohmeter accres one resistor, what resistance will the ohmeter read?
  39. L

    Electrical Can DIY Resistors Create an Effective Portable Heater?

    DIY heater with resistors??! help please Hi physics gurus, I have some questions I'm hoping someone with a kind enough heart can answer for me! I am trying to build a small circular heater (similar to a dew heater for a telescope) with resistors. Basically I have 22 gauge rated 300volts...
  40. M

    Explain to me what resistors do?

    Can someone please explain to me what resistors do? And why we use them. Thank you.
  41. T

    Two capacitors, two resistors and a battery

    Hey guys I am a bit stuck as to what to do here... we haven't covered much on RC circuits yet and id like to learn how to do this properly. Two 6.0µF capacitors, two 2.2 kiloOhm resistors, and a 12 V source are connected in SERIES. Starting from the uncharged state how long does it take for...
  42. K

    Sizing a Potentiometer and padding resistors

    Hello I have an Electronic control unit supplying +5volts and 15mA to a Potentiometer. The control unit needs to have padding resistors that need to be sized correctly so the output of the potentiometer is 0.5 volts to 4.5 volts. Can anyone help me figure out how to size the potentiometer and...
  43. K

    Kirchhoff Circuit: Current, Resistors, Voltage

    Circuit Current I have the circuit below (also attached as an image): Note: ^^^^ & <<<< = resistors [-]=power supply ...=just space (-) & (+) indicates + & - side of battery A,B represent the junctions |-----^^^^------A-----^^^^------| |......|......| <......<......(-)...
  44. O

    Resistors in series and parallel

    Resistors in series and parallel (fixed) ___^^^^_____ |````````````| x````````````|___ `` __^^^^___|```| x`|``````````````| |`|``````````````| |_|``````````````| ``|__^^^^_______| Can someone explain why this is a series - parallel circuit? I don't understand why when starting from...
  45. C

    Resistors connected in parallel and series

    Hi there, I've another problem... as you can see I'm new to all these... pls forgive! senario: point A to B... across A and B there're 2 resistors R(1) and R(2) connected in parallel and R(3) in series to (R(1) and R(2))... Questions: 1) assume R(1)=5ohm, R(3)=2ohm and find R(2)...
  46. P

    Circuits: find current in the resistors

    Ok, so what i got here is a drawing of a circuit. It's rectangular, with points a & b making up one side of the rectangle. It's a symetrical diagram-use your imagination... 7 4 __w__ 9 __w__| |__w__ | |__w__| | |...
  47. M

    Calculating Shunt Resistor for Galvanometer to Ammeter Conversion

    A galvonometer has a coil resitance of 460 ohms and a full scale deflection current of of 100^10*-6 A What shunt resistor is needed to convert this galv.. into an ammeter which has a full scale deflection current of 200 ^10*-3 A? What is the resitance of the ammeter when it is completed? What...
  48. A

    Resistance of parallel resistors

    If resistors of 5 ohm, 20 ohm, 40 ohm, and 50 ohms are parallel with each other, the equivalent resistance would most nearly be how many ohms?
  49. K

    Problem with current and parallel resistors.

    Problem with current and parallel resistors. Please help! Ok, I've got this homework problem that I'm somewhat stuck with. The problem relates to the picture below: I've got to figure out the total resistivity (done that), total current (done that), the current through the 21 ohm resistor...
  50. M

    Solve Series Resistor Problems: 7, 11 & 13

    Problem 7. A(n) 5.0 ohm resistor is connected in series with another resistor and a 6.0 V battery. The current in the circuit is 0.64A. Calculate the value of the unkonwn resistance. Answer in ohms. Note: I don't how to slove this problem. Problem 11. A 6.0V battery is connected...
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