I have been guilty of measuring voltage with an ammeter. But I was probably 12 years old. Those types of lessons cost a bit of tuition but they stick with you.
Sent from my iPhone > On Nov 8, 2019, at 5:33 AM, Mark Radabaugh <m...@amplex.net> wrote: > > For our EE power class (motors, generators, etc.) they decided we should > take a lab exam. My exam time was for the second session. When the > elevator door opened on the lab floor the burnt electrical smell was pretty > obvious. Professor comes walking out of the exam with an armful of > equipment heading for the tech repair shop shaking his head and muttering > something about “this was a really bad idea”. > > One would think senior level electrical engineering students would know not > to yank banana plug patch cords out of DC motors running at full speed. Or > not try to uncouple a paralleled generator by adjusting the power factor to 0 > (for those of you not EE’s that leads to two generators trying to rip > themselves apart). Or measure voltage with a ammeter. > > Mark > >> On Nov 7, 2019, at 2:27 PM, <ch...@wbmfg.com> <ch...@wbmfg.com> wrote: >> >> In our motor lab someone asked the prof something similar like reversing >> polarity to a DC motor that was fully wound up. >> I don’t remember the exact question or exactly what he did but I do remember >> the result. >> >> The motor tore itself from its moorings and launched across the room.. >> >> From: Ken Hohhof >> Sent: Thursday, November 7, 2019 12:15 PM >> To: 'AnimalFarm Microwave Users Group' >> Subject: Re: [AFMUG] OT: Induction coil voltage >> >> I was an EE undergrad long enough ago that we had a required course called >> “Electromechanical Devices”, and popularly referred to as “Motors”. It had >> a lab, and none of the professors wanted to teach Motors Lab, so it usually >> fell to the most junior prof, who didn’t want to be there. >> >> We had one whose standard answer to all questions was “Let’s find out.” >> >> Student: What happens if you open the field coil on a running DC motor? >> Professor: Let’s find out. >> >> Student: What happens if you short the output of the generator in a >> motor/generator pair? >> Professor: Let’s find out. >> >> Who can guess what we found out? >> Hints: a high pitched whirr, and a sudden thunk, were involved. >> >> >> From: AF <af-boun...@af.afmug.com> On Behalf Of ch...@wbmfg.com >> Sent: Thursday, November 7, 2019 12:53 PM >> To: af@af.afmug.com >> Subject: Re: [AFMUG] OT: Induction coil voltage >> >> I used to have a flashlight that had a coil and magnet just like this. >> Shake it for a while and charge a cap that is used to light the light. >> Can’t remember if you could shake it and make light in real time. >> >> But yeah, you can certainly use a rectifier and cap to make DC for a DC >> motor. >> >> From: Adam Moffett >> Sent: Thursday, November 7, 2019 11:47 AM >> To: af@af.afmug.com >> Subject: Re: [AFMUG] OT: Induction coil voltage >> >> A future project is going to be a primitive motor powered by a battery....I >> wonder if I can shake this bugger to make the motor spin. >>> On 11/7/2019 1:41 PM, ch...@wbmfg.com wrote: >>> Yes, it is one cycle of AC. >>> >>> From: Adam Moffett >>> Sent: Thursday, November 7, 2019 11:26 AM >>> To: af@af.afmug.com >>> Subject: Re: [AFMUG] OT: Induction coil voltage >>> >>> So by the way, this activity works with a 4oz (800+ feet) roll of 30AWG >>> wrapped around the paper towel tube. >>> My next point of confusion is this: >>> An LED obviously has a polarity. If I connect one LED to the coil and drop >>> the magnet through, the LED lights for a moment. I expected that if I drop >>> the magnet N first and S first that it would light up one way and not the >>> other. Instead the LED blinks whichever way I drop the magnet. So does >>> that mean I am getting A/C power with this? Do I get current in one >>> direction with the leading edge of the magnetic field passing through the >>> coil and then current the other direction as the trailing edge of the field >>> passes? >>> I ran out of time last night before I got to the point of hooking up both >>> LED's. So if this is A/C then the difference would be which color blinks >>> first I suppose. >>> The point of this was to teach the kids something about electricity, but >>> it's turning out that my knowledge on these fundamentals is pretty >>> superficial. >>> -Adam >>> >>> >>>> On 11/3/2019 12:19 PM, Adam Moffett wrote: >>>> I wanted to do this science experiment with the kids. My problem is my >>>> LED's don't light up. It's from a discontinued textbook. Apparently they >>>> sold a kit with the materials for all the projects, but that's no longer >>>> available so I'm scrounging in the garage. >>>> I put a volt meter on the rig and I was only getting 6mV when I dropped >>>> the magnet. I doubled the number of coils on the tube and then doubled the >>>> number of neodymium magnets and I'm getting closer to 30mV now, but I need >>>> closer to 2V to light up an LED, so I'm wondering what would increase the >>>> voltage by two orders of magnitude. Is it based on the number of turns in >>>> the coil? >>>> >>>> <image001.png> >>> >>> -- >>> AF mailing list >>> AF@af.afmug.com >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >>> >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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