# Tagged Questions

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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### Calculate expected voltage around a resistor [duplicate]

It's been a few years since I first studied the Ohm's law at school. Now I'm really getting into electronics, and I must admit a part of it still puzzles me. I know this is kind of a strange ...
218 views

### Are high power ceramic resistors waterproof?

I need to put some resistors on my jeep. I picked up 2x 22ohm, 10watt resistors at a local electronic store. They do the job well, but are they waterproof? Can they hold up to the elements? I ...
553 views

### How to amplify 3.3 volts to 8-9v?

I'm a total newbe in electronics but I like to make things up. All I want is to turn on a "black box" of leds (that operates at 8-9v) when my motion sensor is activated. The problem I've got is that ...
118 views

After assembling a simple emergency light kit, it's time to build the battery charger. Details: Most of the time, the battery won't be used and the circuit will be always connected to the energy ...
703 views

### Would plugging a 1M resistor into the outlet be bad?

Other then touching the leads and getting shocked, if I plug a 1M, 0.5W resistor into the 120V outlet, would it be bad? I calculated that $\frac{120 V}{1 M\Omega} = 0.12 mA$, which shouldn't do ...
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### What's wrong with this Phase Shift Oscillator?

I am trying to design a phase shift oscillator, using a CE Amplifier. I have a Vc of approximately 6V, gain of approximately 40(>29, as required). I aim for an oscillation frequency of 1.5 kHz. But ...
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### Is there any way that the Arduino board can get damaged by using a buzzer without a resistor?

I want to use a standard piezo buzzer on one of the Arduino Uno's analog pins without the use of a resistor. Will connecting this be a problem for the Arduino board? Why?
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### Power different types of lamps in single circuit

As homework, I have to design a circuit (in the form of a circuit diagram) to power three given lamps optimally (so that they receive the exact current and voltage they need) with any number of 1.5 V ...
112 views

### Planning of integrator and derivator circuit

I have to plan a circuit given by the series of an integrator and a derivator circuit. I haven't planned a circuit before, so I ask you if my reasoning is correct. The only condition that I have to ...
245 views

### Constructing a simple emergency light kit

This is my first adventure in the electronics world and, as I'm a CS student, you can expect a lot of associations that maybe aren't that right. The main feature of my circuit is: If there isn't ...
181 views

### Calculating current in a simple circuit

I am new to electronics and am trying to figure something out: I have a source putting out 12.6V and an unknown current. I know that I can calculate current by finding the voltage drop over a ...
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### R-EXT connection on the STP16CP05MTR LED sink driver

I'm planning to use a STP16CP05MTR LED sink driver to drive some LEDs in a matrix. The STP16CP05MTR supports constant current by the use of an external resistor ...
218 views

### Rise time for second order RC filter?

Can somebody help me in deriving the expression for rise-time for second order RC filter. simulate this circuit – Schematic created using CircuitLab
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### CMax: (New in circuits)

I've been working on circuits lately (still a beginner), and I was introduced to a "program" (i'm not sure of its actual name) CMax. Could anyone explain how the connections of wires/resistors/pot-s ...
190 views

### analog circuit to convert one resistance to another

I plan to have a thermistor attached to a CPU heatsink control the speed of a computer case fan. For temperatures below 30c (room temp) I want to stop the fan, and for temperatures at or above 60c, I ...
579 views

### Why doesn't the relocation of this resistor affect the circuit's total resistance?

Why does moving the 470Ω resistor in these examples have no effect on the total resistance between A and B? This is a new question regarding the answer given here by @helloworld992.
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### How to calculate a simple mixed parallel/series resistor circuit

I'm trying to understand how to calculate resistance in simple mixed parallel and series resister circuit. Below is a question from a worksheet I've been playing with to better understand the topic ...
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### Proper Component Testing (Specifically Resistors)

What is the best practice for testing small components such as resistors / capacitors before shipping? I buy these in bulk, and while it is easy to catch the duds that have already failed, sometimes ...
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### Is current the same coming out of an IC as it was going in?

This is my first diagram so keep that in mind. I've come up with this circuit because I've got some 74** series ICs and I want to be able to make them work. This example is a simple AND gate with ...
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### How do I know where to place resistors on my circuit?

Some of the books I have state that power comes from the negative terminal on the power supply.If that is the case, the circuit starts from the negative right? Say I have a simple circuit with a 6v ...
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### What is a good electronics kit for the everyday inventor [duplicate]

I am looking for a good electronics kit with lots of capacitors, trimmers, resistors, pots, diodes, transisters, leds and laser diodes, timers(like the 555), inductors ICs and common microchips, LOTS ...
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### How to find Thevenin resistance?

I've got a question, and I just keep getting myself confused when I try to solve it. I've attached the picture of the circuit (sorry it's so dodgy, paint is hard! :P) And the question is: replace ...
341 views

### Basic rules to calculate the equivalent resistance of a resistor circuit

I have a certain circuit only containing resistors of different values. There is one 'input' and one 'output' for the current. How do I calculate the equivalent resistance of the circuit? Are there ...
204 views

### Resistor values? [duplicate]

How can one see what value a resistor is given the colors? For example, what's the value of Red - Orange - Green - Gold?
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### Is Rg, calculated in the linked PDF calculating the pulldowm/pullup resistor for a MOSFET gate?

I stumbled upon the following paper while looking for ways to calculate a specific value for the pullup/pulldown resistor for the gate of a MOSFET. I see several calculations for Rg. Is that the ...
982 views

### Do I need to use a resistor with a microswitch to limit current for an Arduino Uno?

I'm using an Arduino Uno to control a small robot and I'm starting to add micro-switches as bump-sensors. I know that when I'm creating a circuit with LEDs I need to use resistors to limit the current ...
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### Calculating the pulldown resistance for a given MOSFET's gate

I searched and read many similar questions, but did not find a specific answer for how to calculate the correct value for a pulldown resistorn for a MOSFET's floating gate. Seems like everyone dodges ...
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How can I achieve 10k resistance? I just got my photocell in the mail, totally forgot the 10k resistor. The thing is I have a lot of different resistors in the span 1, 10, 27, 37,56, 68, 82, 100. Is ...
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### Discharging RLC. Kirchhoff's second law

I have been trying to solve this homework problem for who-knows how many hours. I could break it down enough as to specify the problem I'm facing into a single question: For the following circuit ...
120 views

### Finding RC output voltage to a sine input?

So I have a simple RC series circuit with a sine input with -1 dc and amplitude A. I'm trying to find the value of the output voltage across both the R and C elements. The problem is, the sine wave ...
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### Conversion of voltage of battery [closed]

I have 9 volts battery. What resistance do I need to have 5 volts. And how to calculate?
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### how to calculate total resistance in circuit with parallel and series resistors connected

A battery of EMF 8.0 V and internal resistance r = 1.0 – is connected to an external circuit as shown: I need to find out the total resistence and my problem is that I dont know which resistors ...
186 views

### What easily acquirable material changes its resistance when heated?

I'm trying to build a Resistance Thermometer that varies current/voltage output when heated. It has to be DYI, I don't want to buy anything done, only something like a light bulb, and this has to be ...
349 views

### How do I calculate the required value for a pull-down resistor in a PWM circuit?

I'm using 74HC595 with SoftPWM to control some LED's. When the 74HC595 is off, its outputting about 0.57v, enough to turn my LED's on somewhat. How do I work out the value of the pull-down resistor ...
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I'm trying to answer following question: In the ladder circuit in figure 3, find the current, I, if $V_s = 7V$. Use the fact that the circuit is linear. This can be done by assuming that ...
169 views

### Parallel resistor not affecting rest of the circuit

I have been asked the following question: The resistance, r, is not known in fig(1a), why does its value not affect potential at b? By Thévenin's theorem, any arbitrary voltage source can be ...
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### Why Johnson's noise is not uniform when plotted in log mode?

I have a 2 resistors of 1000 k each , I have connected them in series and biased one end with +9 V and other end with +9 V. The output is taken from connection point of two resistors and I have given ...
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### What is the power lost per foot?

This question seems trivial and i think i am overlooking something but for whatever reason i cant figure it out. A city requires 1010W of power at 110V. Assuming 1 foot diameter transmission cables ...
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### Reset pin on ATtiny84/85/2313 clarification

I have two questions that I was hoping someone could clarify with a quick True/False. When using the ATtiny85/85/2313 the reset pin is connected to a 10k resistor which is connected to VCC. When ...
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Please refer to the attached Images. Dimensions: Hieght and Breadth: 42mm Thickness: 25mm I know its PT 1k Ohm resistor(Positive Temperature Coefficient) and its two connecting wires are ...
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### DS1307-breakout-board

I want to build an RTC clock for the Raspberry Pi. Adafruit has a guide to accomplish this with Dallas DS1307. On the schematic they put a 2.2K resistor between VCC and SCL and do the same for VCC and ...
279 views

### Gain on a Differential Amplifier

For the past hour, I've been trying to calculate the gain of a differential amplifier in the following form: $\frac{V_{out}}{V_{in}} =$ some function of resistors I went to this site and tried to ...
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### Static-sensitive high-precision resistor?

I just received some 10K .1% precision resistors from Digikey (part number PTF10KECT-ND). Unlike all their other passive components, which come in a normal plastic bag, these came in a metalized bag ...
327 views

### Nulling Offset Voltage [duplicate]

I am using a ua741 op-amp. My question is, how can I use a potentiometer to null the output offset voltage? I believe if I'm correct, that output offset voltage means the output voltage provided by ...
276 views

### What is the function of resistors in this flip-flop circuit?

Here's the link to the circuit: http://rustamaji.net/resource/images/flip-flop2.swf From the simulation, when the 22k resistors are removed the LEDs stop blinking because the current flowing only ...
419 views

### Help with custom motorbike tail lights

About a week ago, I have been soldering exactly 29 LEDs to a PCB in an effort to replace my old, custom taillight bulb that came with my motorbike since I bought it. I have successfully managed to ...
176 views

### Changing a Pot's Adjustment Range [duplicate]

I want to put 24 VDC through a 10 k pot but limit the output on the wiper to 2.5 V. Could you advise me what value and where to put the resistors please? There is no load on the circuit as it's just a ...
182 views

### Arduino Question regarding the resistor

I was instructed to set up a resistor on the negative side of the LED and pulling it to ground. I'm confused why we are implementing a resistor on the backside (negative end) of the LED. I always ...