# Search results

• Users: meBigGuy
• In Electromagnetism
• Order by date
1. ### How do I charge a small battery with a large battery?

looks like an interesting unit. The lm317 can do CC regulation, BTW. Just Google LM317 conctant current.
2. ### Question about potential energy in capacitors

which is a much better explanation!
3. ### Question about potential energy in capacitors

Intuitively you probably already understand the concept expressed in that equation. For a given increment of work you can move a given increment of charge with a particular voltage. If you increase the voltage, you can move less charge for the same amount of work. If you then move on to unit...
4. ### (New) Simple Question about unusual current!

A 9.8 ohm resistor? Obviously the voltage, current, or resistance measurements are incorrect, or any combination of the three. Not that I'm really telling you anything you don't already know. :) Are there any lab standards, recently calibrated supplies or meters, 1% or 0.1% resistors. Is...
5. ### What is meant by the input impedance of a voltage source?

I agree for the most part. I think the problem is probably referring to the input impedances as seen by the voltage sources. Think of the voltage sources as signal sources that would be loaded down by anything less that 100K ohms. They should probably still be modeled simply as ideal voltage...
6. ### Creating Electric Arcs?

Interesting, didn't know that. Guess that makes pulling the spark plug wire to check the spark a bad idea. I wasn't able to find any specifications for the secondary insulation breakdown voltage. The coils ranged from 30KV to 50 KV. Looks like they fire at around 15KV. There are numerous...
7. ### Creating Electric Arcs?

Is an old automobile ignition coil, a resistor and a switch considered too dangerous? It can easily do an inch or more. I thought it would be a good place to start.
8. ### AC Voltage Sources Riding A DC Voltage Source

I'm only being logical here. Doesn't it seem the average and peak voltages would be linear sums of the components? The RMS is different in that it is about power/energy and is proportional to the square of the voltage (Power = (V^2)/R ) I would guess that Vp = Vp(sine wave) + Vdc (that is...
9. ### AC Voltage Sources Riding A DC Voltage Source

How did you derive the equation for Vp? (yours only works for pure sine wave)
10. ### Tesla Coils & Vacuum

I am far from an expert in this field --- not even a novice --- I would appreciate hearing what you discover and whether I was on the right path.
11. ### Tesla Coils & Vacuum

I'm not positive that everything I'm saying is correct, but it seems to be in the correct general direction. Essentially you first bring the tesla coil to the glass such that the gasses inside ionize *AND GLOW*. when you near a leak the ionized path provides a path to ground (through the pump...
12. ### Creating Electric Arcs?

WOW --- never heard of the Kelvin Water Dropper. Amazing effect. Learn something every day here. Here is a video (see the last 6 minutes) http://www.youtube.com/watch?v=RQX8I9ZWtPQ&feature=relatedLecture The simplest arc would be with an old automobile ignition coil, resistor, and switch...
13. ### AC Voltage Sources Riding A DC Voltage Source

The RMS voltage of uncorrelated superimposed waveforms is the sum of the squares of the individual rms values. There is a nice derivation for the dc offset sine wave here: http://masteringelectronicsdesign.com/how-to-derive-the-rms-value-of-a-sine-wave-with-a-dc-offset/
14. ### Creating Electric Arcs?

The classic continuous, safe, long electric arc is the tesla coil. Of course even that can be unsafe if you overdo it or are careless. The simplest and cheapest arc generator would be with an automobile or motorcycle ignition coil driven by a 555/powerFet. That can be unsafe though, so be...
15. ### Which bulb is really more collision of electrons inparallel connection

Nice paper: Always learning :) It seems that (in the simple cases) the resistance is based more on the mean free path than on the number of collisions, which has a nice intuitive feel.
16. ### Which bulb is really more collision of electrons inparallel connection

First, explain electron collisions, and explain their significance. Also, explain, since you know the 1ohm resistor is equivilent to two 2 ohm resistors in parallel, what collisions have to do with anything.
17. ### The superposition theorem for electrical circuits

Here is a proof. Maybe it will cover the case you are interested in. http://users.ece.gatech.edu/mleach/papers/superpos.pdf
18. ### Use of electronic meters

Obviously you have played in school with an ammeter with calibrated shunts and think such an approach is applicable to random meters. In order for that to work one needs to properly match the shunts to the meter. If you are going to do that, it's much easier to just measure the voltage across...
19. ### Use of electronic meters

An ammeter appears as a short circuit from its input lead to its output lead. It's purpose is to measure the current passing through it as if it was not there. All ammeters have some very small resistance, and so cause some voltage drop. (That is a basic "instrumentation problem"). A...
20. ### Use of electronic meters

He said it is a 5A meter. Basically you just connect the ammeter in series with your load and it measures the current. If the current it too large for your meter, get another meter or measure it a different way. A shunt resistor across an ammeter? NO WAY. A series resistor you measure the...
21. ### Use of electronic meters

You connect the ammeter in series with your load. It measures the load current. You do not add resistors for the instrument. In fact, there will be a small voltage drop across your ammeter since they are not 0 ohms. If you put the ammeter across a battery it will draw a huge current. It is...
22. ### Use of electronic meters

You can get a multimeter with leads that works "fine" for \$5.00 at harbor freight. http://www.harborfreight.com/catalogsearch/result?q=multimeter
23. ### Physical intepretation of derivative in Maxwell equation?

The equations work both ways. B represents a vector magnitude and direction, so it's spatial characteristics are included. The dt derivitive indicates how it changes with time.
24. ### Need help with understanding resistance

Ok, I'm forced to use the water/hose analogy. Water flows in a hose, but the nozzle limits the flow. The more pressure, the more water flows out the nozzle. How does the water know there is a nozzle down stream. It's an analogy with flaws, but will help you think about it. "unless the...
25. ### Need help with understanding resistance

Assume that as many electrons enter as leave the resistors. The current flow is constant throughout the circuit. The applied potential can force a limited number of electrons through the resistors, and so there is a potential drop distributed across each resistor (resulting in dissipated...
26. ### How do I charge a small battery with a large battery?

Generally you build/buy a power supply that converts the car battery to the proper voltage for the device you want to operate. If you create the right voltage, and are capable of supplying the required current, then the system will work. This assumes you are powering a device which contains a...