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9 votes

In the Apollo 13 mission, how could the batteries have "no Volts" with two Amps of current?

The part of the movie transcript you're talking about (taken from here) is where Fred Halse says: Batt B, no volts, amps are okay. Batt C, s***. No volts, only two amps. They may die before the ...
Jodes's user avatar
  • 1,304
8 votes
Accepted

Short circuit in welding

No, this is not classed as a "short-circuit". This is a circuit with a designed current flow - ie a 60 to 150A range is common... A "short-circuit" is a circuit where the current flow is not ...
Solar Mike's user avatar
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5 votes
Accepted

In the equation for power as a function of current and resistance, what do the two factors for current represent?

Firstly, by temporal I think you mean spatial. Secondly if you consider acceleration, the units are m/s^2. Seconds-squared are not spatial, but they are temporal. But they needn't be either. Consider ...
Jodes's user avatar
  • 1,304
3 votes

Do piezoelectric materials produce a current flow or just an electric field?

the output signal of a stressed piezoelectric crystal is primarily a measurable voltage accompanied by an almost too-small-to-measure current flow. This is a general characteristic of high-impedance ...
niels nielsen's user avatar
3 votes

Are AC generators more efficient than DC generators?

You can have brushless DC as well, but its all a balancing game of cost over its lifetime. Efficiency only matters when the entirety of the process is considered. One high efficiency process can be ...
Abel's user avatar
  • 1,353
3 votes

Why is the Current to Motor less than Motor Rated Current?

The "rated" value is the maximum safe value for each parameter, not necessarily the actual value for any particular working condition. The current when the motor is running will depend on the load. ...
alephzero's user avatar
  • 12.5k
2 votes

Is there well known equation (formula) to calculate maximum practical current which copper wire of fixed diameter can handle

For whatever reason standards bodies seem to prefer to give a tabulated list of values without giving any rationale to how those figures were obtained. I once tried to do some first-principles ...
Peter Green's user avatar
2 votes

Is there well known equation (formula) to calculate maximum practical current which copper wire of fixed diameter can handle

There are tables by various standards authorities which give current ratings for various wire gauges based on their insulation, bundling, free-air, conduit, etc. If you find one of those and plot the ...
Transistor's user avatar
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2 votes
Accepted

Running a well pump rated for 230V on 208V power

The 1.5 HP motor is built to draw a specific amperage at full load at 240V. Because power equals voltage times current, a lower than rated voltage will draw more amps through the motor. So if your ...
Tiger Guy's user avatar
  • 6,901
2 votes
Accepted

Maximum amps from a switching voltage regulator

That is an oversimplification. From the data sheet http://www.ti.com/lit/ds/symlink/lm2596.pdf there are two relevant features, internal over-temperature protection and a maximum current limiter (...
alephzero's user avatar
  • 12.5k
2 votes
Accepted

Do piezoelectric materials produce a current flow or just an electric field?

The quartz or other Piezoelectric materials do not work under constant compression, they work under the varying pressure or vibration of the crystal. So they don't lose electrons. They produce an ...
kamran's user avatar
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1 vote
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AC/DC Laptop adapter power losses

Lenovo ADL170NLC3A has an Energy Star V (ES 2.0) rating. Energy Star states to get that rating for nameplate output power ($P_{no}$) > 45W, the Minimum Average Efficiency in Active Mode ≥ 87%. At ...
StainlessSteelRat's user avatar
1 vote

Why doesn't the work piece melt when arc welding if a lot of amperes run through our electrode?

The piece is big enough to not heat up. The rest of the piece is a lot larger than the weld point. The weld point is as thick as an electric arc. Heat (outside the arc) equals I2R. I is current (...
Tiger Guy's user avatar
  • 6,901
1 vote

Why doesn't the work piece melt when arc welding if a lot of amperes run through our electrode?

In arc welding, the local spot where the arc intersects the workpiece is small, so the heat addition is very concentrated right at that spot. This makes it get much hotter than the surrounding metal. ...
niels nielsen's user avatar
1 vote

Why doesn't the work piece melt when arc welding if a lot of amperes run through our electrode?

I assume you're imagining something like ice and water where when it seems to go straight from solid to thin liquid, right? Metals (or at least alloys) don't generally behave that way. You most easily ...
DKNguyen's user avatar
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1 vote

How to find pixel density in LED Display Board?

4875 pixels at 1 mm pitch gives a screen width of 4875 mm = 4.875 m = 15.99 feet (16 feet). 975 pixels at 5 mm pitch is also 4875 mm. 244 pixels at 20 mm pitch is 4880 mm so it's almost the same. How ...
Transistor's user avatar
  • 10.8k
1 vote

Heating pump/refrigerator - calculate efficiency

Efficiency = heat moved versus energy consumed. For a heat pump this is either SEER or Coefficient of Performance. Heat moved compared to energy used should be around 2 to 5 in equivalent units (COP)...
Tiger Guy's user avatar
  • 6,901
1 vote

Determining stability of a current souce from the datasheet. How to?

I suggest that you take a closer look at typical noise. I have highlight the area of the specification for you reference. The best method is to confirm is measure the output to confirm the output.
Mahendra Gunawardena's user avatar
1 vote

How can I get more power out from a windmill motor?

As far my knowledge a dynamo is a motor which provides electricity when the rotor shaft is rotated. A dynamo will give DC output. An alternator will give AC output. If I connect multiple dynamos ...
Transistor's user avatar
  • 10.8k
1 vote
Accepted

How can thin wire in generator windings carry the high output current?

My question was based on an appearance that the thin winding wire seemed to violate the laws of physics, so there might be some other factors at play. Neil_UK answers this in generator coils: max ...
fixer1234's user avatar
  • 146
1 vote

How can thin wire in generator windings carry the high output current?

Note: Small Gauge mean the wire can carry a significant amount of current. Example per the attach AWG 4-5 can carry 100A. There are lot other factors need to be considered before selecting a wire. ...
Mahendra Gunawardena's user avatar
1 vote

Why is the Current to Motor less than Motor Rated Current?

This can be due to the rated current is showing the initial start current which can be greater than the running current. The supply needs to be fused to cope with the start current as, if you put a ...
Solar Mike's user avatar
  • 15.8k
1 vote

Steel surface welding with high-frequency current

Look up ERW ( electric resistance welding ) , this is commonly used to weld steel pipe and tubes ( not necessarily round). Spot welding and projection welds have similar aspects.
blacksmith37's user avatar
  • 6,144
1 vote

Stall Torque of a DC Motor Less than Theoretical Values

Torque should be proportional to current, whether stalled or not. Measure the current at stall. Is it what you expected? It should be just the applied voltage divided by the DC resistance of the ...
Olin Lathrop's user avatar
  • 11.4k

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