Wikipedia:Reference desk/Archives/Science/2021 September 23

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September 23

Why ammeter get damaged if connected in parallel?

Whole point of Ammeter is to measure current, so why it get damaged if connected in parallel? If a bulb withstand parallel connection, why can't this measure device? I know that it should be low resistance. Rizosome (talk) 02:21, 23 September 2021 (UTC)

I googled the subject. This article contains an answer.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 23 September 2021 (UTC)

It says whatever connection is, ammeter will get damage: an ammeter connected in series or connected in parallel with a electrical circuit will probably blow the fuse, which can possibly damage the ammeter and cause injury. Rizosome (talk) 04:11, 23 September 2021 (UTC)

You are right; that is a rather curious mistake in the article. Where they write that the ammeter needs to be inserted into the circuit and become part of it, they clearly mean it needs to be connected in series with the other components of the circuit. Using the formulas given in Series and parallel circuits, it is easy to see that when connected in parallel the current in the ammeter will be very high, which may blow a fuse but will likely blow the ammeter before the fuse gets a chance. If the fuse blows first, it actually protects the ammeter. When connected in series, the current in the ammeter will be slightly lower than the current in the circuit (at the place of insertion) before it was inserted.  --Lambiam 05:30, 23 September 2021 (UTC)

Please specify: ...gets damaged if connected (into what circuit?) in parallel (to which part of the circuit?). The ammeter is designed to measure current. so it needs to be in the branch of the circuit in which you want the current measured. If you connect it directly into the supply, you make a circuit of a source and a meter. Ammeters should have minimum resistance (so they do not influence much the current they measure) so the current, equal voltage divided by (tiny) resistance, gets really big. --CiaPan (talk) 07:46, 23 September 2021 (UTC)

It will likely get damaged beyond repair if connected in parallel to the whole circuit; in the simple case of a one-resistor circuit (say a lamp) in parallel to that resistor. If there are several resistors, it may be harmless to connect it in parallel to one of them, but it never makes sense to connect an ammeter other than by serial insertion.  --Lambiam 12:11, 23 September 2021 (UTC)

Kirchhoff's circuit laws seems relevant background here regarding the measurement of voltage and current in a branching circuit. --Jayron32 15:32, 23 September 2021 (UTC)

As ammeter notes, an ammeter usually has low resistance so that it does not cause a significant voltage drop in the circuit being measured; this low resistance connected in parallel with elements with higher resistance, effectively causes a short circuit, with high current flowing through the ammeter. Klbrain (talk) 23:02, 24 September 2021 (UTC)

Bushy and straggly eyebrows

I've worn a beard for more than half my life, but otherwise I'm not noticeably hairy. Except, my eyebrows are taking on a life of their own. This only started happening in my mid-60s (I'm now 70).

• Why does this happen only at such a time in men's lives?
• Why does it happen to some men and not others?
• Why does it not happen to women (not that I've ever noticed, anyway)?

One other thing: I quite like the look of prominent bushy eyebrows on a senior gentleman, but mine are more straggly than bushy, so I need to keep trimming them. Is there anything I can do to promote bushiness rather than straggledom? -- Jack of Oz ^{[pleasantries]} 21:44, 23 September 2021 (UTC)

Re your third bullet point – many women in Western and other cultures routinely pluck, wax, thread and otherwise groom and modify their eyebrows to a far greater extent than men. {The poster formerly known as 87.81.230.195} 90.200.67.3 (talk) 23:52, 23 September 2021 (UTC)

Here is an article addressing some of these issues.  --Lambiam 09:30, 24 September 2021 (UTC)

• Just your eyebrows? Hahaha. Wait till your ears start getting hobbity and your nose sprouts wings. My ears have four different hairy places. Top of my head's a cue ball, mind you. --jpgordon^{𝄢𝄆𝄐𝄇} 00:22, 25 September 2021 (UTC)

  No, I have developed ear and nose hair as well, but they don't need regular trimming. -- Jack of Oz ^{[pleasantries]} 20:18, 25 September 2021 (UTC)

  Why fight it? Embrace your inner Andy Devine! ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:16, 25 September 2021 (UTC)

  I'm not fighting it per se. I'd be very happy to wear bushes above my eyes, but nature has seen fit to give me unsightly weeds. -- Jack of Oz ^{[pleasantries]} 21:23, 25 September 2021 (UTC)

For what it may be worth (there are a couple of relevant links), here's an old ref-desk thread on the old-age-hairiness question. Deor (talk) 14:55, 25 September 2021 (UTC)

I once mentioned to a friend that I trim my eyebrows. He was aghast. So for a couple of months I stopped trimming my right eyebrow, and the hairs ended up long enough that I could pull them over my eye down to the top of my cheek! I was in my mid-30s at the time. I'll turn 44 in a few days. I'm tempted to let them grow again to see how long they get. nagualdesign 19:29, 26 September 2021 (UTC)