# Questions tagged [current]

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

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### What is the optimal current for charging two 12V batteries in series?

I have to charge two 12 V, 184 Ah lead-acid batteries in a series circuit. I have read that the provided current should be the 10% of the Ah rating of the battery, e.g. in this case it would be 18.4 A ...
117 views

### How to calculate the lethal amount of current for given amount of output voltage?

I have some electrical parts that I was planning to reuse, things like laptop chargers and some parts from a printer. I searched google for what's the lethal amount of current and they mention 10ma is ...
392 views

### TPM 3VSB power capabilities

I have a question about Trusted Platform Module header on PC motherboards. I want to install ESP8266 (standalone) inside of my PC, I know of 5VSB the the PSU supplies, but after looking at my mobo ...
727 views

### Professor said no current flows to ground

According to the professor, adding the ground at 0V has no effect on the current flow and current flows in this circuit as if the grounding point did not exist so the answer is E. How have people died ...
489 views

### Powering 10 m of WS2812B RGBs

I wanted to make sure that my solution would work before wiring it physically and I felt that all the great minds here would be able to do that. So I have two WS2812B 5 m LED strips, each containing ...
259 views

### Energy meter neutral current measurement

I was reviewing an energy meter specification and I came across neutral current measurement. What is the importance of neutral current measurement in an energy meter for three phase power supply? I ...
33 views

### TRIAC control of inductive load. Current ringing at higher power causes TRIAC to remain on

Here is the circuit I am using to control the motor. L2 is meant to represent the motor and C3 is the capacitor that comes with the motor. It is a single phase AC motor found here. This circuit is ...
837 views

### VSD (Inverter) current measurement on 3 motor phases

I'm working on a project to build a rig for testing various sized Variable Frequency Drives (VSD's / inverters), the kind that you'd use to run a squirrel cage induction motor. The range would be from ...
69 views

### Is the reversal of time another way to interpret negative resistance? [closed]

Or, restated... What is the correct equation for the reversal of time in an overunity circuit? (Not this equation...) $$Vc=(Vx)(e^\frac{-t}{RC})$$ In this differential equation, the negative current ...
25 views

### Repelling charges and current flow

The electrostatic force between two like charges is repelling. This concept is fairly clear to me with Coulomb's law and electric fields. So two electrons will repel each other. Given this statement, ...
56 views

### Computer SMPS overload protection and Low current shut down [closed]

What i have : i have a zebronics 450w smps (those generic things like this) . *which is rated for 12 v 15a max *it is a old PC so now I dont need it anymore, so I decided to take the psu out and turn ...
29 views

### Calculating battery life considering the capacity drops depending on load current (2 x 4 AA-packs in parallel)

This is a very recurrent question, about calculating the battery life given certain circuit current usage. This example will be similiar to this one in terms of the battery used and the consideration ...
60 views

### Meanwell LRS-350-12 power supply spec'ed input current amperage confusion

I have an LRS-350-12 and am trying to understand how much AC current it can draw. Everything I've read tells me it should basically be its rated DC wattage divided by input current, divided by ...
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### Are 4N35 optocouplers clamped at 22V?

I am trying to detect mains with an ESP32, for that I started testing this circuit: I bought a 4N35 optocoupler and 110kΩ resistors. My first test was using 2 resistors in series, so R1 = 220kΩ. The ...
188 views

### MCP73871 Low Charge Current

I am trying to make some GameBoys use rechargeable LiPo batteries. I wanted to utilize a circuit that would allow me to play and charge at the same time and so I settled on the MCP73871. https://ww1....
202 views

### How does one know that the current is flowing downwards through the $8 \ \Omega$ resistor?

I'm currently studying the textbook Fundamentals of Electric Circuits, 7th edition, by Charles Alexander and Matthew Sadiku. Chapter 1.7 Problem Solving gives the following example: Example 1.10 ...
156 views

### What is the relation between reverse saturation current and leakage current in a BJT?

I have been studying Studying Donald Neamen's Electronic Circuits 4th edition and Sedra Smith's Microelectronics 7th edition for quite some time now. I have been self studying. After searching ...
178 views

### Questions from a current regulating and measuring circuit

In my previous question I asked about a simple topology suggestions for regulation of highish currents(around 10A) especially for resistive heating elements in 1...10 Ohm range. I concluded to use a ...
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### How to find the Thevenin equivalent of this circuit?

This is what I've got so far, but not sure what to do from here.
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### How can a current be constant and there still be a voltage drop

I'm having trouble understanding how this can be possible. Obviously, I'm missing something but I'm not sure what it is. The amount of voltage at a point depends on the electrical potential energy at ...
42 views

### Electric field in a circuit and potential drop

With reference to the above image: Here the battery produces a constant (will it be constant? pl. explain) electric field across the length of the wire, lets say its value is $\vec E$ . This field ...
43 views

### Measuring output impedance of current mirror

I am working on a current mirror circuit using BJTs. I have managed to calculate all the values from the given problem (Sedra book). I am having issues with the simulation. I have calculated my output ...
1k views

### Calculate Power Dissipation of 0ohm resistor

I have a 0 Ohm resistor here. Can someone tell me how the power dissipation will be calculated for this type of 0 ohm resistor. The part says it has a power rating of 0.1W. But, if we use either V ...
29 views

### Source Transform [closed]

I am doing source transformation and I arrived at this setup. Elements in series with a current source can be removed. So should I remove R2,V2,R1 and V1 immediately or should I add first V3 and V1, ...
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### DC motor: why is torque NOT DEPENDENT on the angle of rotation?

I am reading a book on control systems where they take an example of an armature controlled DC motor. Because the goal is to describe constructing a block diagram from the system equations, the ...
413 views

### What is the maximum charge current and discharge current of R5460 Series IC?

I am using "R5460N214AF" IC for 2 cell Li-Ion battery protection. According to datasheet, excess discharge current threshold is 0.2 V and excess charge current threshold is -0.2 V. I would like to ...
90 views

### Make a circuit to make sure a device only gets a maximum of 1A

I'm making my own smart home device with a Raspberry Pi. I will power the Pi on the same circuit as our bell. Now the bell transformer is 8V, 1A and the bell itself uses 0.5A. I'm thinking to replace ...
55 views

### Why is the polarity of the $3 \ \text{V}$ source necessary to calculate the current flowing through the $8 \ \Omega$ resistor?

I'm currently studying the textbook Fundamentals of Electric Circuits, 7th edition, by Charles Alexander and Matthew Sadiku. Chapter 1.7 Problem Solving gives the following example: Example 1.10 ...
36 views

### Calculate the integral of a saw tooth wave

My question is with reference to this question over here Suppose, I have a saw tooth current source with peak value from 0A to 1A with a frequency of 1kHz and I need to calculate the charge of the ...
14 views

### Bias Tee scale for current of 500mA, 1A, 2A, 3A, 5A

Before I start excuse my ignorance but I am new to this topic. I have been asked a question regarding Bias Tees. The Bias Tee is supposed to have a frequency range of 1-30MHz and then we need to scale ...
2k views

### 12V fans in series with 25 A supply

I'm trying to set up a relayed cooling mechanism for a mass spectrometer (i.e. cooling fans turn on when the MS exceeds a certain temperature). I have a 24V DC/25A power supply which converts 100-120V ...
44 views

### Effect of Internal ADC capacitor in Microcontroller

The input pin mentioned in the below image is the input pin of the microcontroller. It explains that the internal capacitor of A/D peripheral of MCU should be very much less than the external ...
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### Why is there EMF present when there is no current?

Current means the rate of flow of charge. Electrons are the ones that carry charge in current. From the definition of EMF (electromotive force), When no current is drawn from cell, the potential ...
332 views

### Battery failing. Oscilloscope?

The question is - is there an inexpensive oscilloscope I can use to measure DC voltage and current to see why my battery pack is failing to power a DSLR? In order to take long time lapse photos with ...
138 views

### Average value and RMS value

I am trying to understand the concept of RMS value. From whatever I have read and the tutorials I have seen, I have seen them derive the RMS value only considering the first positive half cycle of the ...
187 views

### 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 ...
4k views

### How does this current limiting circuit work?

A tutorial electronicsArea explains a transistor based current limiting circuit. Problem is that I am not able to understand how T1 gets switched on in the fist place. To make T1 on it needs a ...
47 views

### DC current rating of copper wire (SWG)

I want to use SWG-sized copper wire but I am a little bit confused about the following: On the internet I found different charts with different maximum current ratings for the same wire diameter. The ...
1k views

### With enough copper wire, can I attach one end to one side of a 9V battery, then circle the earth and connect it back?

This is a dead serious question I have not been able to find an answer to: if I had enough wire, could I make electricity pass through if I connected one end to a small 9V battery and then circled the ...
2k views

### What is the difference between a linear regulator and an LDO

Can someone tell me what the difference between linear regulators and LDOs is? From what I have read and understood, it is that linear regulators and LDOs don't use switching elements, but I think ...
61 views

### The current that an AC3 contactor can support

I am constructing an ATS (Automatic Transfer Switch) for a diesel generator with a max current of 300 A. Now I already have an AC3 contactors with Ith = 100 A and I don't want to waste the money on ...
3k views

### LM358 differential voltage and amplifier circuit

I designed a circuit that's rather common: simulate this circuit – Schematic created using CircuitLab And I have a problem. I have got few LM358s, some from ST, some from other companies. (I ...
152 views

### How to control proportional valve (pvq13-5l-03-m5-a) with arduino

I would like to know how to control this specific proportional valve with arduino. The valve operates with a constant 12V and driven by current of a range of 0-170mA. Could you help me with what ...
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### How important is it for a device (laptop) to identify wattage of a charger? [closed]

I have several "old" Thinkpads. Recently I came across that Type-C PD mod to replace charge port with Type-C one. Description said: Please pay attention what you order because normally your ...
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### What is the formula or any method to calculate the value of the output capacitor and inductor in a buck converter

I have using a buck converter whose output is 5V and 1A. Can someone tell me whether these is any formula to calculate the value of the output capacitor? Like, without involving the switching ...
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### Two directional FET switch. Is it possible?

Is it possible to have a high side MOSFET switch that will allow any direction of current? I was trying to design one but without the success. Or should I use a relay?
3k views

### How does the Ring doorbell get powered?

The Ring doorbell is a pretty simple and useful product. I was wondering: how does the Ring doorbell get power without activating the chime? As far as I know, a doorbell works by shorting two wires ...
612 views

### Resistor values on a 12v 10a circuit with LT3045 LDO

I am currently working on a project that aims to provide 12v 10a in the final output. I am quite new to EE and wasn't quite sure if I have choose the correct resistors value as highlighted in the ...