# Questions tagged [current]

Flow of electric charge - typically movement of charge carriers, such as electrons. Measured in amperes (A).

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53 views

### Why currents in the circuit of BJT change like that?

Why don't the currents in those two circuits change the same way when I change voltage of the voltage sources?
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### Meaning of “short circuit current” in datasheets

This a general question regarding what should we understand when we see the term "short circuit current" in a given device datasheet. Does it always exactly mean the output current when we short the ...
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### Do Smart Home Wifi controlled socket adaptors wear out when used with a conductive current appliance like a dryer? [closed]

I am designing a PAYG dryer using a smart phone for payment. However I am trying to keep it simple and inexpensive. The route I have gone down is this: Smart Socket adaptor between dryer and wall - ...
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### How long will a 32v 15A (500Wh) e-bike battery last outputting at 5V 1A?

I hope it's okay to ask this here My e-bike has a Lithium Ion battery (32 Volts, 15 Amps), and it has a USB-A output, marked as 5V and 1A, I have 3 questions: How long will this battery last while ...
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### Charge and negative current

Consider the following charge-time graph : If we need to calculate the current in the interval 8 to 12 seconds the current will be negative (since the current is the differentiation of the charge ...
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### DC Current Density and Voltage in a Finite-Length Conductor

Assume you have a rectangular bar of copper with finite length L. You apply a voltage difference at two points on the top surface of the bar; (x1,y1) and (x2,y2). Because the bar is finite in length,...
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### Node analysis: estimating variable current branches

Is there a way to get the number of potential currents that could be in a circuit? (Note: in the following circuits ignore the Resistor value, I've just added a resistor with the default schematic ...
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### What exactly is this question asking us to do?

Based on the model and circuit shown in Fig. 2, draw a circuit model of the path of current through the human body for a person touching a voltage source with both hands who has both feet at the same ...
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### Nodal analysis for resistive circuit

Given the following circuit: I know that I1 = I2 + I3, but what would be the relationship between I2,I3,I4, and I5? I would assume if there are 5 unknowns, we'd ...
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### What is causing a white scale buildup at copper pin connection on LED light sticks and how can they be cleaned?

Can someone explain what is causing this white scale to appear on the copper pins and on the block of this LED light connection? The seal at the connection is supposed to be watertight. On occasion, ...
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### If I have a device drawing 300mA @5V and I need to use a 15V PSU what current rating do I need for the PSU?

I have an application with multiple components and multiple voltages in use and current calculations are giving me a headache. A simplified version of my application would include: 1x device ...
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### bipolar current mirror, unified control

I'm trying to obtain a high impedance, several decades current pump for charging a capacitor from 1uA to 10mA, swing +/-5V. I arranged two current mirrors like this and is working acceptable for ...
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### How to sense a small current while handling larger ones

For one of the projects I'm working on, I need to monitor a DC power line for reverse current; the solution has to output a 24V signal when around 10A or more of current is flowing in reverse through ...
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### Current calculations

Emergency lighting solution Continuing from the previous post above. Firstly I know how to calculate current in a DC situation. However, since I am using an inverter that produces 220V at its output ...
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### Calculating total voltage/current for 3-phase?

Consider I have a 3-phase generator with the following measurements: Phase 1 (A): 22.8828A Phase 2 (A): 22.9922A Phase 3 (A): 22.9219A Phase 1 (V): 239.7656V Phase 2 (V): 241.8594V Phase 3 (V): 245....
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### Amplifying photodiode current with BJT transistor

I'm trying to develop a kind of light detector. To do that, I'm going to use a photodiode and a bjt transistor to amplify its current. I found a circuit in this tutorial: which explains how the ...
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### How to calculate voltage and current of this circuit?

I already know the answer of question 1, 2 and 3. 1) 448 ohm 2) 1.6 V 3) 0.13 V About the question 4, why 6V/300 = 0.02A = 20mA is wrong? Can I use current divider like 0.01339 * (3.3 * 10^3 / (...
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### Electrical components that modify current

Are there any electrical components that 'consume' current? That is, the current coming out of the component is different than the current going into it? For example, the following components consume ...
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### solving circuit using mesh equations

Im trying to solve this circuit.I think ive got something wrong because the results are a little different than what i was expecting.Any help would be very much apreciated.Ive got this so far. -20 + ...
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### How to active limit the current from a DC source

I have a source with variable power output during the time because it is shared with another devices and this source has not enough power to feed my load (a battery charger for a 1 cell 4.2V lipo) so ...
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### Question regarding supermesh

So im trying to solve the folowing circuit using mesh analysis but i cant get the right results.Im trying to find the currents of mesh 4(down to the right) and mesh 1(left on the upperside).Ive ...
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### Finding free electron concentration to check authors' calculations for electron drift velocity

I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5.1 How the Shape of a Conductor Affects Resistance presents the following image: I ...
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### What's the maximum current at every output of this driver?

I'm using the driver DS26LV31T and need to know what is the maximum output current for the output pins (P,N, for example pins 2,3). I'm confused because I'm not sure where to take that information ...
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### How can different voltages produce the same short circuit current?

I hope I’m not just thinking past something trivial but I can’t make sense of this. In this video, https://m.youtube.com/watch?v=XDf2nhfxVzg , variable voltages from .1-20V are used and when he shorts ...
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### Why does this circuit cut out when an extra load is added?

I have a circuit that consists of an Arduino controlling a small PAM8403 based amplifier which is powered via an L7805CV voltage regulator. When I press a button the arduino sends an audio signal to ...
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### Calculating voltage through unknown resistor

I'm asked to get the voltage Ix and Vx, as you can see in the image, the voltage is on an unknown resistor, through loop analysis I got that Ix should be equal to 1. by KVL( Kirchhoff's Voltage Law) I ...
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### Plastic Plugs in Surge Protectors or UPS

Would plugging 4 out of 7 outlets in a surge protector or UPS with plastic “safety plugs” to keep out dust/dirt harm the product in any way? I know that plastic is an insulator and it might affect ...
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### Howland source, MAX current output?

How would one determine the maximum current output you could achieve from an improved Howland source given a specific Op-Amp? ie. What do I need to look at in the Opamps datasheet? (I am using a ...
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### what is the Lt1086-5 Vin min?

I have LT1086 5V regulator what is the Vin min to provide 5V output?( assume load current 500mA -800mA) I tested it worked for 6V Vin, but datasheet does not mention anything about Vin min https://...
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### BQ297xy Overcurrent protection

Can someone explaine to me how dose this overcurrent protection works and how to calculate it? BQ297xy Schematics
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### What is the ampere of a piezo material

The voltage generated by piezo materials varies but does ampere also vary? Are there any sources where I can find this out? I might add that I’m not so much at home in the electrical world but I’m ...
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### What is the difference between pulling up multiple digital IC pins to Vdd with a single resistor vs. one resister per pin?

I am not very good at understanding current, so I was hoping someone could help calrify the difference between pulling up multiple digital IC pins to Vdd with ...
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### I'm struggling finding everything I need to know to pick out a pot

I'm trying to make a color mixer with 3 potentiometers and a lightstrip. Each potentiometer will control a LED, one red, one green, and one blue. The voltage requirement for the strip is 5v I think, ...
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### When does a transistor turn on

I am having a very hard time understanding when exactly a transistor turns on. For example in the following circuit from Everycircuit: Why does the transistor turn on when the push button is off, but ...
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### How to generate 100 A at 20 kHz?

I have interesting problem to overcome and seek some advice. I need to test different hall effect sensors and magnetic cores. I am currently stack at issue of bandwidth. I tested sensors at DC using ...
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### What is a Current Source? [duplicate]

In EveryCircuit, they have a component called a "Current Source". For example, here is a circuit I've created with a 2A current source: Is there a such thing as a 'current source' in the real world, ...
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### Generating a current between 0 - 250 mA for a load up to 40 ohms

I'm trying to use a howland current source to generate stable current for a load which is =<40 ohms. The load does not need to be connected to groud. I can work with a DAC to supply the Vin (V3 in ...
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### BLDC motor current sensing for load torque

I would like to control 14V BLDC motor of battery powered drill. What I want to do remake the drill to nut runner (torque wrench), so I need to sense a motor current which is proportional to motor ...
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### Current Probe with 1mA precision [closed]

I've designed this circuit for a 1 mili amp precision current probe, what change should I apply to it?
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### How to wire digital voltmeter/ammeter to measure arduino battery consumption

I'm not sure if you can tell but I'm a bit of a beginner, I want to wire up an digital voltmeter/ammeter combo to measure arduino power consumption. I found the following device which seems suitable ...
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### Help regarding Ac current limiting using resistor

I've 12v(Vrms) 1A AC transformer. I need to regulate it to 1to 4ma maximum output without having much voltage drop. Output load is an animal skin which has resistance in it. Can I just use a ...