47 votes

Is this an AC or DC signal?

DC + AC = DC Plainly put: No. It's AC with a DC offset, if you will. This is less about whether the sign changes (that sign is just relative to some arbitrarily defined reference), but about whether ...
mmmm's user avatar
  • 1,749
39 votes

Why do we use polarized capacitors?

The physical size of a capacitor is a function of the thickness of the dielectric (among other things). Early on, it was discovered that the oxides of certain metals (aluminum and tantalum in ...
Dave Tweed's user avatar
  • 172k
27 votes
Accepted

How to memorize a diode's polarity in symbol? (self-answered)

Two mnemonic technique I'll mention. Both technique I've learnt from someone else, many-years ago. We can easily remember, anode is abbreviated as A, and Cathode as K. That is standard, and easy to ...
Always Confused's user avatar
26 votes

Is this an AC or DC signal?

It has both AC and DC components. Which of these you regard as "the signal" depends on its intent (i.e. on the information content). If it is say analogue audio with some DC in there for ...
Guy Inchbald's user avatar
  • 1,455
24 votes
Accepted

What does the radiation from an antenna look like?

This image: Is just a drawing, it has no meaning. It does not represent the radiation pattern of an antenna in any way ! Basically all antennas radiate (and receive) the EM waves in all directions. ...
Bimpelrekkie's user avatar
  • 80.8k
20 votes
Accepted

Why do we use polarized capacitors?

Can I use a non-polarized capacitor with the same voltage and capacitance instead of these polarizing capacitors? Electrically speaking, non-polarized capacitor is always better than a polarized one. ...
Agent_L's user avatar
  • 1,725
18 votes
Accepted

Packaging polarity indication of a supercapacitor (polarity indicated by arrows)

Since the product you purchased has no background information, you can't be certain. However, the convention for these stacked-disk type capacitors is polarity mark points to negative lead. This is ...
user2943160's user avatar
  • 2,908
16 votes
Accepted

Can current flow both ways through a transistor?

A NPN transistor basically is a stack of three differently doped areas of a semiconductor. The first is N-doped, the middle P-doped and the last N-doped. So yes, on the first sight, you can swap ...
sweber's user avatar
  • 8,620
15 votes

Inductor polarity

Your mistake is that you're thinking the inductor is keeping the voltage constant, while it is in fact keeping the current flowing through it constant. (Or, more precisely, a voltage across an ...
Jonathan S.'s user avatar
  • 17.9k
14 votes
Accepted

Which of these wires is positive and which is negative?

tl;dr: this is an AC line voltage (230/240V) bulb, screwed into a socket. There’s no ‘positive’ or ‘negative’ but rather ‘hot’ and ‘neutral’. Being line voltage, it’s potentially dangerous to work ...
hacktastical's user avatar
  • 52.8k
13 votes

Is this an AC or DC signal?

The signal is changing direction with time (alternating), as well as continuously changing amplitude with time. I would call that an AC signal of 18 Vpp with a DC offset of +1 V.
Mitu Raj's user avatar
  • 10.9k
12 votes

Is this an AC or DC signal?

This is really a terminology question. For instance, Wikipedia has a classification under which your signal would be called either "Alternating" or "Pulsating": Clarify with your ...
Dmitry Grigoryev's user avatar
11 votes
Accepted

What is the polarity of this barrel plug with a double circle?

The outer cylinder is negative with the inner surface being positive. The tip connects to a Maxim One-Wire memory in the power supply that is read by the computer to obtain information such as power ...
Kevin White's user avatar
  • 32.9k
11 votes

Why is this 3-way speaker wired this way?

and 2. As I recall from some professional audio gear manual (made in 1980s) that I had to mess with, miswiring +/- at the speakers is the common reason for big "trenches" in the spectrum ...
fraxinus's user avatar
  • 8,981
9 votes
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Confusion about dot convention in an ideal transformer

Note that in case (a) the ratio of the currents is negative while in (b) it is positive but the secondary current arrows are reversed. They both, effectively, say the same thing. I've never seen it ...
Transistor's user avatar
  • 175k
9 votes

What does the radiation from an antenna look like?

It really depends on the kind of antenna. Google will probably answer this with pictures better than I will (Google "antenna radiation pattern"). You will distinguish in shape of radiation mainly 2 ...
xgrimau's user avatar
  • 221
9 votes
Accepted

astable multivibrator: capacitor polarization

Good question. First off, the polarity of the capacitors in your picture is the wrong way around. The + terminal should not be connected to the base of the transistors. Why the circuit works (when ...
Nils Pipenbrinck's user avatar
9 votes

Why does this two terminal inductor have a polarity?

Murata has a site specifically about that "polarization" mark. It isn't so much polarization as that the chip its self is in some way asymmetrical so that it changes its electrical properties ...
JRE's user avatar
  • 71k
9 votes

Why do we use polarized capacitors?

Since you mention protection I'll add that polarized caps should not be used for reverse polarity protection. They will react on a reverse voltage very slowly (seconds or minutes), while typical ...
Dmitry Grigoryev's user avatar
9 votes

Footprint for Electrolytic Capacitor

Use the correct sized footprint and modify it so it has polarity markings on the silkscreen. Part of using CAD programs is making custom parts. Be sure the footprint you're pulling from the library ...
qrk's user avatar
  • 9,199
8 votes
Accepted

Troubleshooting why Powerbank Doesn't Charge Cell Phone

A device (phone) gets charged at optimal (high) rate only when it recognizes "charging port signature" on charger side. For Type-A port, there are several DIFFERENT port signatures that a charger port ...
Ale..chenski's user avatar
  • 40.1k
8 votes

Determining the correct polarity of a supposedly wrong polarized capacitor

That's funny, they actually added two plusses to the screen and they still put it in backwards. You could power it up and see which pin is more positive, but powering it up without the cap may also ...
Trevor_G's user avatar
  • 46.6k
8 votes
Accepted

Why is the electrolytic capacitor not polarity sensitive?

An aluminum electrolytic will handle a reverse polarity of about 1 volt or so. The cap probably never sees anything near that. This appnote from Nichicon shows that under 1V the capacitors don't ...
Robert Endl's user avatar
  • 2,197
7 votes

Does MOSFET let current flow through source to drain as it allows it from drain to source?

In case anyone else stumbles across this thread, the TLP175A (and plenty of others) is a single component which directly implements the circuit suggested in the above answers. That particular IC ...
Ody's user avatar
  • 171
7 votes

Why plug is polarized in the US? What are the benefits?

It's more than that -- polarized plug make cheap single-pole switches much safer. For example, look at the extension strip: With a polarized plug, it is perfectly safe to have a single-pole switch ...
theamk's user avatar
  • 3,203
7 votes

Inductor polarity

If you have a purely resistive load in series with your inductor, and provide a path for the current to return when the switch is turned off, you should see the behaviour you expect. The energy stored ...
Matt S's user avatar
  • 3,457
6 votes

What to do when a device doesn't specify it's DC polarity?

If the device has any metal part or other known ground point you can use the continuity test function of the multimeter ("the beep") to check if the center contact or the outer contact of the power ...
filo's user avatar
  • 8,931
6 votes
Accepted

rx_polarity inversion in USB3.x

The receiver inversion is available primarily for ease of PCB routing to maintain signal integrity. This feature is also available on PCI express. Consider an interconnect where you have this ...
Peter Smith's user avatar
  • 22.2k
6 votes

What does the radiation from an antenna look like?

Are you asking about the shape of the EM waves? Seems that way. The other answers do not show this. Instead they show the graphs of wattage versus direction (the "radiation pattern,") or graphs ...
wbeaty's user avatar
  • 10.9k
6 votes
Accepted

LED anvil and post are reversed!

The LED chip can be made to bond in a cathode up or anode up configuration. The pole that is down is typically bonded with a thermal epoxy that transports the heat from the die to the lead frame. The ...
Glenn W9IQ's user avatar
  • 5,574

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