A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently \$I=\frac{V}{R}\$)

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121 views

Why is there a resistor inline with switch in blender motor?

Our hand-held blender stopped working and I took it apart to see if I could fix it (no, as it turned out). The circuit was simple; a switch and a 0.47 Ohm (R47) resistor in series with a full bridge ...
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1answer
30 views

Analyzing this bode plot for frequency break point

So given this problem: The correct bode plot for it is: What I don't understand is how the -3db was measured. I know that -3db can be found through 20log(1/sqrt(2)), but how is it measured right ...
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1answer
93 views

Is there any pattern or standard to through-hole resistor sizes?

I've long been under the impression that a quarter-watt resistor has a standard package, and a half-watt resistor has a standard package, etc. But I've recently gotten through-hole resistors which are ...
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1answer
43 views

Missing steps to simplify this complex impedance

The problem is: How would you you simplify the equation to get down to \$716.97 - j450.47\Omega\$? I tried multiplying by the conjugate but that doesn't work.
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1answer
38 views

Finding Equivalent Thevenin Resistence

For the following circuit: I'm solving for the Rth at node 2. In the solution guide, it shows that the Rth = (10k || 10k). I don't understand how this is so, by following the resistence equivalent ...
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3answers
66 views

How to reduce maximum power rating of dishwasher for use with photovoltaics inverter? [closed]

I have a photovoltaic power system and an inverter with an overall power rating of 1500 Watts. I want to connect a dishwasher which consumes 2200 Watts when heating the water. Question: What is the ...
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2answers
299 views

Trouble finding the R(equivalent) in this circuit

I started studying Electric Circuits one week ago so this material is new to me. I was trying to solve this problem from the book but I had some difficulty: My analysis: The equivalent resistance ...
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2answers
314 views

For the resistor circuit shown in the picture, what must be the missing resistance to give a total resistance of 252 ohms?

After my calculations, I keep getting 1100 ohms, but the back of the book is saying 85 ohms. 85 seems to fit in better with the other numbers, but I can only get 1100 to add up. Here's my ...
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2answers
86 views

Changing the voltage of a power supply

I have an old laptop power supply which provides 3.5A at 20V. I want to re-purpose this for another project for which I require 3A at 5V. If I cut the output cable I'm assuming I'll find a +20V wire ...
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2answers
93 views

Does a circuit going into an Arduino pin/GND need a resistor? [closed]

If a circuit goes into an Arduino pin, even the GND pin, but does not use something a component that needs a resistor such as an LED, does it still need a resistor for the Arduino pin? Edit: To clear ...
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0answers
38 views

Microwave Oven Capacitor as replacement on a “Power Saver”'s capacitor

I've seen a lot of power saver circuit schematics online that uses a 10µf 400V AC capacitor. Can I use the MOT 2kV caps as a replacement for that? Will the high-resistance bleeder resistor inside the ...
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2answers
68 views

How to find current across a resistor using Thevenin Theorem

It's my first question here. How to find the current through 3 ohm resistor using Thevenin theorem?
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49 views

LDR resistance fluctuating slowly

I'm building a laser harp not unlike this, and part of it is a row of (rather cheap) LDRs to sense whether the beam has been broken. The LDRs, however, are doing something really weird - their ...
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6answers
750 views

Reducing voltage with resistors

I have been looking around for an easy way to convert 12v to 5v. I have seen some people saying that a simple resistor is all that is needed. ...
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2answers
81 views

Heat output element

I'm building a little quiz game in Arduino and I already have it displaying a multiple choice question and people can answer by pressing pushbuttons. But anyways now I wanted to know if it's possible ...
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0answers
47 views

How to get the value of a burned resistor on a PCB of Weanas® Plug Power Meter? [closed]

In my house electricity was shut down and came up again a several times during 5 seconds. After that my device - Power meter did not work. It was possible to turn on the device, but it was showing ...
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3answers
58 views

Miniature heater with more-or-less constant temperature. Need tip on element

I'm a software engineer with very basic knowledge of electronics. I have a project in which I want to make a small (cylinder of length about 100-150mm and diameter 20-30mm), localized heater that ...
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2answers
186 views

Learning transistor based circuits

simulate this circuit – Schematic created using CircuitLab In one of our electronic circuit tests, this question was asked: What is the output voltage of given circuit? This circuit ...
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0answers
30 views

thevenin equivalent using matrix method

Is it possible to determine the Thevenin equivalent of a linear network(of very high complexity) by using some matrix method?
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1answer
127 views

Does biasing of address pins require a resistor?

I'm a total newbie fooling around with a project of mine. I want to use a MCP23071 I2C port extender (Data sheet) for my arduino project. The chip has three hardware pins that must be externally ...
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4answers
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Why do resistors still use color coding?

I always wondered why color coding is still used on resistors in 2014. Here is Wikipedia's word on the original reason why : Colorbands were commonly used (especially on resistors) because they ...
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0answers
49 views

E-series Enigma

I just found something that baffles me to no end. I programmatically calculated what should be the actual values for each number in the E-series from E6 to E48, and some of them do not match up with ...
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4answers
274 views

LEDs are burning. Cannot figure out why

I have a lamp that has LED driver producing 35 V (actually lamp driver says 16 - 28 V, but I've measured 35 V). On the lamp I have 7 LEDs (originally 5 + 2 I've added) with heatsinks that have burned ...
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1answer
45 views

Help compare my results to the maximum power transfer theorem and explain using algorithms

So below is an image of the relationship between efficiency of a circuit and the resistance of the load, as you can see the maximum efficiency occurs when the two resistances are equal. here is a ...
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5answers
698 views

Large Resistors?

Can there exist a resistor that can deal with current reaching up to 1000A or 10x time that value, and beyond? What about heat dissipation when massive amounts of current is required?
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1answer
62 views

Calculationg base-resistor between microcontroller and transistor

I'm curious, when connecting my 2N2222 transistor's base to a PWM output pin on my Arduino, I know the Arduino can deliver a maximum of 40mA current. The 2N2222 only requires around 5 to 10 mA on it's ...
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2answers
93 views

Slowing Down Capacitor Circuit discharge rate

I am currently trying to use a 5 Pin relay on a Motorcycle indicator circuit. The concept is I have a Daytime Running Light (DRL) that is in the same housing as the indicator. When the indicator is ...
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3answers
133 views

Identifying this resistor/capacitor

I'm having trouble to identify this (presumably broken) part for replacement: It was used in a broken LED power supply, with 220-240 V AC on the input and 120-200V DC on the output. I suspect this ...
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1answer
57 views

Motorised blind controller schematic - do I need to protect ICs with resistors?

I am making a simple motorised blind controller, which I want to have a "safety cut out" when it gets to its fully closed/fully open state. (So the user doesn't strain the motor keeping their finger ...
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1answer
87 views

Russian variable resistor datasheet

Can you please help me find datasheet for this 2.2 ohm variable resistor. I want to know if it can tolerate 20 amps. If you recognize the logo that would help a lot.
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98 views

Designing circuit with Arduino and optocoupler: beginners problem

Firstly, I am a beginning hobbyist starting doing some electronics and this is my absolutely first attempt in trying to automate something. Here is my circuit (or what I intend): I don't know if my ...
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2answers
66 views

Why increase in resistance of register used in circuit show lesser average power dissipation

I am working on 6 transistor full adder circuit. Red marked resistors (25k) are used to show all pattern of full adder correctly. But it show wired behavior. When I increase resistance from 25k to ...
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2answers
153 views

Resistor required for capacitor?

I'm currently working on some simple circuits to learn about circuitry, and being a Physics major I have a pretty good grasp of the mathematics and concepts, but I'm a little confused about ...
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2answers
104 views

Understanding resistors on inputs/outputs of op amps

I was looking at the schematic for Dave Jones' uCurrent, and I can't seem to make sense of why there are 270 ohm resistors on the inputs and outputs of the op amps in his circuit. The resistance is ...
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5answers
121 views

Which resistor to use for this LED

I'm looking to buy resistors for a Raspberry Pi project, but am getting conflicting information on which resistance to use for my LEDs. I will have three LEDs. The voltage from the RPi GPIO pins is ...
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3answers
109 views

Low power serial bluetooth module with Arduino

I plan to use the HC-06 serial bluetooth module with an Arduino Leonardo. To my knowledge, the Arduino's serial pins output at 5V with 40mA of current. The HC-06's datasheet says it will accept input ...
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3answers
216 views

Why resistor values are non-linear? What makes sense in 470 ohm? [duplicate]

I never figured that out. Why do we have 220 ohm and 470 ohm, rather than 100 ohm, 200 ohm, 300 ohm? Any particular reason? maybe it's just legacy from old manufacturing process.
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70 views

Calculate delay in long line

Assume we are connecting a lamp to a source but line (wire) is so long (for example 20Km): Will the lamp bright after connecting the source immediately? how much time it will be? Can we calculate ...
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1answer
246 views

Not sure if my calculation is correct, can anyone check this RC circuit for me?

Hello everyone, so in my book I decided to do this practice question but failed to notice that the answer was not given in the back of the book. If anyone can help me confirm my answer I would much ...
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3answers
191 views

Accuracy in translating voltages to currents for shunt resistors

I apply a constant 4ma current I to a resistor R and I measure a voltage V across. so the resistor \$ R = \dfrac{V}{I}\$. But when I apply \$ I_2=20ma\$ to the same resistor R and I obtain the ...
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3answers
240 views

Meaning of temperature coefficient for resistors

Is temperature coefficient of a resistor about the temperature of the resistor or ambient temperature or are they the same thing? What I mean to ask is that: Lets say I have a resistor and I have no ...
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1answer
689 views

What are the advantages of a shunt resistor vs. a hall effect sensor?

I'm constructing a boost converter, and I need to measure both the input current and the output current. Currents range anywhere from 25A to 200A, depending on the model. My controller is referenced ...
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2answers
52 views

Resistor Magnitudes in Voltage Dividers

I recently made a voltage divider that uses a 10 ohm (top) and ~90 ohm (bottom) to divide a source voltage of 5v to 4.5v. The resistor values I used was somewhat arbitrary, in that I just picked a ...
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3answers
202 views

Measuring Voltage across a resistor

I am taking my first steps into learning about electronics as a hobbyist and I am struggling to understand something about resistance. I have read about Ohm's law and it seems fairly straightforward ...
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2answers
73 views

Resistors in series current question

According to Wikipedia, the current of resistors in series will be Vin/R1+R2. Now I could be over thinking this but is that the current that you'll get out or is that just used for determining the ...
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1answer
150 views

Resistor in series and capacitor in parallel to ground

Could somebody tell me why someone would need circuit like that in supply rails? I assume it is for making DC voltage smoother by parallel capacitor. However, my 24V power supply has 500mA output ...
5
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5answers
2k views

Why are there so many resistors in a typical schematic?

I know that some resistors cause pull-up or pull-down or work as a voltage divider and/or current divider. But sometimes I cannot understand their function in some simple circuits: Take this motor ...
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2answers
290 views

Grounding unused leg of bussed resistor?

I've got a bussed resistor: The package I'm using has 13 inputs and 1 output, tied to ground. I'm only using 11 of the inputs. Do I need to worry about the floating end of the two unused inputs? ...
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3answers
148 views

A series resistor behind a reverse biased zener diode

simulate this circuit – Schematic created using CircuitLab If the Zener is rated at 4V, and the resistors R1 R2 are both 300ohm, may I know what is the value for Vout? I know this is a ...
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3answers
281 views

3 Watt LEDs in Series - Using constant voltage Source

I have searched everywhere for an answer to this question but I think its probably so simple that no one has felt the need to answer it. Basically I have 20 x 3 Watt LEDs and have a 80W Constant ...