49 votes
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Two resistors in series

It's the voltage rating on the resistors that is important here. They are powered from rectified 230 V AC and they need to have the correct voltage rating to suit their application. Two resistors in ...
Andy aka's user avatar
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44 votes

Not understanding why these two resistors are in parallel

It is entirely equivalent to the other answers, but sometimes it helps visualising to compress each connected segment down into a single node, as in the following diagram. I imagine lengths of solder,...
jonathanjo's user avatar
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36 votes

Parallel MOSFETs

MOSFETs are a bit unusual, in that if you connect several of them in parallel, they share the load quite well. Essentially, when you turn on the transistor, each one will have a slightly different on-...
Jack B's user avatar
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36 votes

How do solar inverter systems easily add AC power sources together?

Because UL 1741 does all the heavy lifting for you. That's what makes it "so easy". UL 1741 is a complicated spec for "grid-tie solar inverters". Aside from doing their usual inverter thing (...
Harper - Reinstate Monica's user avatar
35 votes
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White LED doesn't light up when a red LED is parallel to it

Welcome to EE.SE. The red LED has an operating voltage that is considerably lower than the white LED. When you connect the red LED in parallel the voltage across the white LED drops to a value that is ...
Graham Nye's user avatar
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31 votes
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What's wrong with parallel conductors?

Both configurations will conduct power to the loads. When trying to figure out what's 'illegal', and why, you need to understand what fault conditions the authorities are trying to prevent. There may ...
Neil_UK's user avatar
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25 votes
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How do capacitors stop voltage spikes?

The capacitor is not there to absorb voltage spikes. The purpose of the capacitor is to prevent the short-term variations in the load current from becoming voltage spikes. $$\Delta V = \frac{\Delta Q}{...
Dave Tweed's user avatar
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25 votes

Not understanding why these two resistors are in parallel

Each of the three resistors in question in the top right image have their right ends connected together and their left ends connected together, they are all in parallel. All they've done is draw it in ...
GodJihyo's user avatar
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22 votes

Why is the serial connection faster than the parallel connection?

The problem is keeping the signals on a parallel bus clean and in sync at the target. With serial "all you have to do", is be able to is extract the clock and as a result the data. You can help by ...
old_timer's user avatar
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21 votes
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Why do we use two parallel capacitors in a voltage regulator circuit?

Take a look at this graph: - http://electronicdesign.com/files/29/1478/figure_01.gif Capacitors have a resonant frequency due to the inherent small series inductance they have. The "generalized" ...
Andy aka's user avatar
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21 votes
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DC Parallel Breakers

No, you shouldn't do this. The problem is that the breakers won't share current equally because they're not totally identical and their contact resistance might vary[1]. This means that one of them ...
Jonathan S.'s user avatar
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21 votes
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What is the reasoning behind parallel memory pinouts?

That is for historical reasons how these evolved and the naming conventions were just extended as memory sizes grew and needed larger packages with more pins. First you had smaller RAMs which had less ...
Justme's user avatar
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20 votes

May I connect two open collector outputs in parallel

Yes, this is exactly the intended purpose. It's called a wired-OR or wired-AND, depending on your logic. (Or, as Tony points out, even a wired-NOR!) However - you should not do this if you just want ...
pipe's user avatar
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20 votes
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What is the reason to connect 4 resistors of the same value as 2s2p? (image)

Dissipation (4x) or pulse power capability (4x) since cost can go up much faster than those capabilities— or redundancy (no single failure will cause a short or open). The latter strategy is used in ...
Spehro Pefhany's user avatar
20 votes
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One of four MOSFET in parallel heating too much

You need to use an opamp for each MOSFET to ensure balancing. Each MOSFET should have an independent sense resistor feeding its own opamp for feedback. The opamps would all be driven from the filtered ...
Kevin White's user avatar
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20 votes

What is the reasoning behind parallel memory pinouts?

Take a look at this diagram to see how the EPROM pin-out evolved: - It evolved this way because that made sense (and still does). If you accept the ancient 2708's pin-out as being sensible then, ...
Andy aka's user avatar
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20 votes

Not understanding why these two resistors are in parallel

simulate this circuit – Schematic created using CircuitLab Figure 1. Another rearrangement. Using @GodJihyo's colour scheme we can rearrange the resistors as shown in Figure 1. Note that all the ...
Transistor's user avatar
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19 votes

Two resistors in series

Reasons someone might put two resistors in series in a volume design: A bit higher power was needed than what the commonly stocked parts can handle. Let's say a company standardizes on using 0805 ...
Olin Lathrop's user avatar
19 votes

Parallel MOSFETs to get more current (40A adjustable current source)

You have two problems Paralleling MOSEFTs in this mode is unstable. However, you could parallel the outputs of several totally independent current sources, each with its own power device, Rs and ...
Neil_UK's user avatar
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19 votes
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Is it true that on a modern processor, parallelism is possible on a single core?

It is indeed possible to have parallelism on a superscalar processor. A superscalar processor can execute multiple instructions at the same time by using multiple execution units. There are certain ...
user110971's user avatar
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19 votes

How does putting an LED in parallel with an 8-bit computer load affect the voltage/current of a circuit?

I agree with everything Jasen said, but I would add (stress?) that this circuit demonstrates extremely bad practice. The danger is remembering this circuit technique without remembering its ...
AnalogKid's user avatar
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18 votes
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Issue with parallel resistors in LTSpice

I tried to replicate, and I saw the same behavior. @SteveG did, too. After a few questions regarding the sanity of each of us, I think I found why, and it is pretty simple: Are you absolutely sure ...
dim's user avatar
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18 votes
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Two parallel wires with no resistance - why it's wrong?

Two parallel wires with no resistance - why it's wrong? This is wrong because there are no wires with no resistance. When trying to resolve Kirchhoff equations for this loop (or whatever their ...
Ale..chenski's user avatar
18 votes

White LED doesn't light up when a red LED is parallel to it

All diodes, LEDs included, have a forward voltage threshold, Vf, where they begin to conduct. Below the LED Vf threshold they won't light up (much, anyway.) Different LED colors have different Vf ...
hacktastical's user avatar
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17 votes
Accepted

Why is the serial connection faster than the parallel connection?

Why is the serial connection faster than the parallel connection? You're making wrong assumptions. Take any serial connection. Now place 10 in parallel and call that the parallel version. Which one ...
Bimpelrekkie's user avatar
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17 votes

Paralleling mosfets to reduce Rds On?

Yes. It does. Note that in general you can't blindly parallel transistors. You can parallel MOSFETs without special measures since as they get hotter they conduct less well which distributes the load ...
DKNguyen's user avatar
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17 votes
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Practical considerations when using a large number of capacitors in parallel

As DKNguyen pointed out it is important to "account for" or "manage" failures. We put capacitor banks on the 28 VDC power bus of spacecraft all the time. EVERY cap had its own fuse, so if the cap ...
xstack's user avatar
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16 votes

Why is the serial connection faster than the parallel connection?

The shift is from "parallel on a single clock" to "multiple serial links". Such as PCIe, where a card may have 1x to 16x "lanes". There are two factors involved, skew and size. Adding more ...
pjc50's user avatar
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16 votes
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Connecting two DC sources in parallel using diodes

When both sources are available, only S1 will power the load, D2 will be reverse biassed and S2 will remain idle. When S1 alone is available, considering D1 drops 0.51V and Regulator giving 75% ...
Neil_UK's user avatar
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