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Questions tagged [current]

32 questions
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1 answer

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

In the movie Apollo 13 there's a scene when the LEM is losing power; when they switch the module on, one of the astronauts reads the levels and says that one battery has no Volts but 2 Amps. What did he mean?
user6396
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1 answer

How does conductivity $\sigma$ of salt-water depend on salinity?

In what way does the electrical conductivity $\sigma$ (or conversely, resistivity $\rho = 1/\sigma$) depend on the salinity $S$ of the saline- (or sea-) water? I know they must be in some way proportional since the more free charge carriers (ions…
Harry Smith
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3
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1 answer

Short circuit in welding

All I know about welding is it is a technique in which electrode is connected to one terminal and the gripper connected to workpiece is in connection with the other terminal. As current passes and when the electrode is touched to the workpiece,an…
Shwetha
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3
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1 answer

What materials or techniques can I use to reduce this electrical effect when building spotwelding tables?

I have been experimenting with building various support tables around press-type spot-welders. These are relatively simple fixures; think of a tabletop with legs under it and devices like sliding gibs, pins, clamps, rollers, etc mounted to the…
Mike
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2
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5 answers

Ice Bank Cooling

Ice Bank Cooling A century ago when mechanical refrigeration was just coming into use, Ice Banks were a common way to cool large infrequently used areas. Large tanks of water were located in special ice bank rooms in basements and compressors…
Richard Illyes
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Overcurrent protection, limit for nominal current or stall?

Background: I'm currently working on a robotics design that will drill through soil. I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the motor with a microcontroller and motor…
gunter
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1 answer

Maximum amps from a switching voltage regulator

Looking at a part like this LM2596 It is rated for 3Amps with a voltage range from 3.3-12 volts. Does that mean that this voltage regulator will only output a maximum of 3amps?
eestudent
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1 answer

Stall Torque of a DC Motor Less than Theoretical Values

I have an unknown DC motor with specifications I was testing. I used a Prony Brake setup and scale to evaluate torque, a tachometer for RPM, and multimeters for voltage and current. I get a linear graph relating torque and RPM. However, when I…
yma3
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1 answer

Will AC Motor Maintain Speed of Descending Object

Suppose we have an AC motor which needs to lower an object at a set speed. We use a PID loop to determine and correct positional errors. Presumably the PID loop will keep the current low as most of the work will be done by gravity. By lowering or…
M-R
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3 answers

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

I am recently learning the theory of Manual Arc Welding. So far I have seen that our electrodes are connected to a machine that outputs hundreds of amps. The work pieces is electrically connected through a clamp connected to the current source, and…
AB2
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Household 3 phase devices

So, I'm not sure if this is the right place to ask this, but have been working on modifying a lawn mower robot that has, for roughly 3 years now been stored under less than favorable conditions. As a result, the motor driver is broken, and I don't…
Mat NX
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2 answers

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

I was watching a video https://www.youtube.com/watch?v=uvT3XvDSSQw about piezoelectric materials. They mentioned that "a current can flow when a pressure is applied to the material". I have a problem with this expression. I'm not sure if my…
user134613
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Understanding the RMS noise for a given bandwidth

I would like to ask a technical question regarding the current source Keithley Series 2400 Model 2450. I am looking for a high stability current source capable of feeding some Hall probes with a nominal current of 10 mA. According to the 2450's…
jeb
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2 answers

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

I found many online calculators or tables which can give maximum current for the wire. Like 1 mm diameter can handle up to 10 Amperes, 2 mm diameter wire can handle up to 30 Amperes, etc. Is there any practical equation (formula) for this which will…
Zlelik
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1 answer

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

I have a well with a 1.5 HP pump. The pump is rated for 240V input. At the moment, the only nearby available power is 4-wire 208Y 3phase. I am considering connecting two of the three phases to the well pump, so it receives 208V where it is expecting…
Diogenes Creosote
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