Quiz on capacitors

Hmm poorguy maybe it needs a dedicated thread as I find this stuff really interesting not only from a personal experience viewpoint but also from a historical one.
I might just post a thread in the chill out room just so that anyone who has interested in this subject / area can discuss what we have been doing already.

It certainly would not hurt for some of the software specialist folks to be able to understand some of the hardware and the properties of it because a lot of the old principles ie Ohms law will always pertain to what we are doing with electronics. I guess it is not everyone's cup of tea but certainly I find it interesting as you do and it has been a real treat going over stuff with you and Jeannie:)

Oops missed your post and well we did not have any money and what I got I had to save real hard for. For example the analogue meter was just the ducks guts when I eventually got it and the oscilloscope was just a dream.

I actually have a problem at the moment at my place (when I am there and not at my partners LOL!!) as the stereo I have hooked up to the TV and DVD player / recorder emits a loud hum meaning I cannot use anywhere near the volume I would really like.
Have earthed everything left right and centre , made sure there are no earth loops etc etc but no amount of fixing does anything.
Actually I am wondering if it has something to do with the TV and recorder being two pin power plugs and the stereo if I remember right being a three pin power plug. They all plug into the same surge / power board but like I said nothing seems to get rid of this hum. Any ideas mate??

John, does it hum with no sources connected to it at all? A Guy

I got 9/10 because one "answer" was incorrect.

"Is a camera's electronic flash powered by a battery or a capacitor?"
A capacitor is certainly charged to a high voltage and discharged but the flash is still powered by a battery. A flash unit with no batteries and just capacitors would be a hot seller.

ICit2lol said:

...Yep Jeannie I wonder why you missed the air caps in the quiz cos that was what you were using .
The tiny ones we called trimmers - I used to be fascinated by how one could "trim" with those things:)

Variable capacitor - Wikipedia, the free encyclopedia

As I explained earlier (or I think I did), I haven't seen air gap variable caps used in tuned circuits in fifty years and, back then, only the older style, tube powered equipment had them. Even trimmers had solid dielectrics, same as the tuning caps used in smaller radios. TV tuners had fixed tuned circuits that were switched in and out by being rotated on a drum and used solid dielectric trimmers to fine tune them. My old Heathkit didn't even use trimmer caps on the IF and other fixed circuits; you tuned them by screwing a ferrite core in and out of the coil.

During college, I was too busy trying stay afloat in my classes (I have ADHD, which nobody knew anything about back then; ironically I wound up majoring in Psychology) and, after college, I was too busy trying to make a living to be involved with electronics anymore. Being color blind really limited my ability to work in that field. I challenged the Basic Electricity class (took a test instead of actually taking the class: I did the same for Basic Woodworking Hand tools and aced that one), the only electricity class offered at the college I went to (I had planned on transferring after the first two years), and got only a C because I couldn't read the resistor and mica capacitor values because of my color blindness, even though I knew what the color code was. So, the only air gap caps I've seen in use for the last 50 years have been in antenna circuits for car radios and broadcast antennas and the question was asked in the present tense. As I said, the test was poorly laid out. The person who wrote that test would have flunked my college Psychology Tests and Measurements class.

ICit2lol said:

Oops missed your post and well we did not have any money and what I got I had to save real hard for. For example the analogue meter was just the ducks guts when I eventually got it and the oscilloscope was just a dream.

I actually have a problem at the moment at my place (when I am there and not at my partners LOL!!) as the stereo I have hooked up to the TV and DVD player / recorder emits a loud hum meaning I cannot use anywhere near the volume I would really like.
Have earthed everything left right and centre , made sure there are no earth loops etc etc but no amount of fixing does anything.
Actually I am wondering if it has something to do with the TV and recorder being two pin power plugs and the stereo if I remember right being a three pin power plug. They all plug into the same surge / power board but like I said nothing seems to get rid of this hum. Any ideas mate??

I got to "play" with oscilloscopes when I in High School but never got to own one. The most technical test equipment I ever had was a grid dip meter which I also rigged up to use as a variable test oscillator by making coupling coils for the various tuned circuits it used.

re: the hum. Have you tried plugging the two pin plugs into a different outlet? If the equipment have floating grounds or are grounded through the neutral, that could set up a ground loop. One 'trick" I used to use to get rid of hard to get rid of AC hum in speakers was to put in a bridge attenuator between the speakers and the amp (I used homemade ones but it's easier, and maybe cheaper, to just buy one now. That allowed me to run the amp at higher volume to drown out the hum. Sometimes, reducing the volume of the signal feeding the amp would allow one to crank up the volume to drown out hum but that failed more often than worked.

I haven't used discrete audio components in years; I've been using my computers for audio for the past six or seven years and get better quality than I used to get from the expensive stereo equipment and speakers I used to use in a tiny fraction of the space they used to occupy. The only thing I'm lacking is a radio tuner (for now; the TV tuners I'm planning on putting in my computer for recording OTA shows—and maybe satellite in the future—will be able to play and record FM) but there aren't any radio stations around here (or anywhere else, for that matter) I like well enough to want to bother with a separate one.

A Guy said:

John, does it hum with no sources connected to it at all? A Guy

No mate and the hum is volume related - a bit obvious I reckon and it is logarithmic hum as you might understand.
For example at 5% volume it is bearable at 30% volume - drowns the audio out.

mjf said:

I got 9/10 because one "answer" was incorrect.

"Is a camera's electronic flash powered by a battery or a capacitor?"
A capacitor is certainly charged to a high voltage and discharged but the flash is still powered by a battery. A flash unit with no batteries and just capacitors would be a hot seller.

Yes technically you are right MJ I guess the devil is in the detail but you have to say too that any cap has to have power before it can be discharged.
So if one was to interpret that the cap is powered up by the battery and the flash produced or in other words powered by the discharge.
In reality I suppose both answers are correct.:)

ICit2lol said:

A Guy said:

John, does it hum with no sources connected to it at all? A Guy

No mate and the hum is volume related - a bit obvious I reckon and it is logarithmic hum as you might understand.
For example at 5% volume it is bearable at 30% volume - drowns the audio out.

That's why an attenuator in the speaker line works (most of the time); it allows you to crank up the volume to drown out the hum without blowing out your eardrums and speakers (not to mention ticking off the neighbors). One downside is an attenuator will reduce bass response but that can usually be compensated for with an equalizer. Still, it's better to find the source of the hum and eliminate it there than to try to cover it up.