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

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1answer
14 views

Unidirectional current and bi-directional voltage device

Which is that device which can take in current in one direction irrespective of the voltage polarity across it? ( We can rule solid state switches - diode, SCRs etc).
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votes
1answer
50 views

How to draw constant current independent of voltage for capacitor testing

I have a 150 farad 2.7 volt super-capacitor. I want to test the cap under various loads, .1 amps, .5 amps, and 1 amp. I will be creating a graph of the voltage over time. How can I constantly draw ...
1
vote
3answers
64 views

Can't find the correct voltage and current source

I'm trying to self-study this problem but I got stuck. What I tried to do: The equivalent resistor R1 for the 12 and 4 ohm resistors is 3 (12x4/12+4). The equivalent resistor R2 for the 4 and 12 ...
0
votes
1answer
41 views

Max Current Output [duplicate]

Looking around at a couple of power supplies that I own such as a guitar pedal adapter that says it puts out 9V and 1700mA max, how does a power supply like this work so that it doesn't put out too ...
0
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2answers
53 views

For the circuit shown, use exponential model of diode to find value of R for which v=80mv

I know how to do this if the diodes were ideal, however here, they aren't. I've tried. Please help out. I've gone this far: log (iL/i1) = (v/vT) i2/i1 = e^3.345 (assuming vT = 25.4mv) i2/i1 = 23.31 ...
0
votes
4answers
81 views

Can voltage be controlled in a fixed DC circuit?

If resistance is fixed in a DC circuit, can voltage still be controlled and changed from one value to another? Imagine this circuit, that has a fixed resistance of 1 Ohm, and the desired current is ...
4
votes
4answers
547 views

How does this constant current sink actually work?

So I have implemented a constant current source and it works wonderfully, but I was just hoping to try and understand it a little bit more! Here is the circuit in question: I have tried doing some ...
3
votes
1answer
70 views

Continuous current capacity of this conductor?

How much current can a copper conductor that is 2 meters long, 0.003m thick, and 0.00045m wide continuously carry? Also, the resistance is about 0.02 Ohms.
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0answers
24 views

Problem with DAC with current mirrors

I'm trying to design curent steering DAC with binary weighted inputs - I'm using M4, M5, M6, M7 to copy the reference current flowing in M8 with coefficients of 1,2,4,8. The idea is to put either 0 or ...
1
vote
1answer
117 views

Do these LED's have a constant current driver built in?

I bought these LED's of eBay and connected them all (5) in parallel with a 4.7Ohm series resistor each. This should have given me a total current draw of 1.7A. However, when I measured it, I was only ...
1
vote
0answers
45 views

at89c51 power supply [duplicate]

I am making a project using at89c51. I used my mobile charger (output: 5V, 1A) as the power supply. Will my IC get damaged due to the high current? I asked cause, without loading the program I ...
0
votes
0answers
33 views

How to calculate current boosting ratio in CMOS technology

In the following picture: The \$I_{out}/I_{in}\$ equals \$(1+C_2/C_1)\$. But I can't calculate it. \$I_{out} = g_{m}\cdot V_{GS}\$ for MOSFET \$\text{M}_2\$, but how to find out the voltage of ...
0
votes
1answer
31 views

Repairing (possible) earthing/ground issue in computer PSU? [closed]

I've got a computer that will no longer power on. It used to be willing to power on quite randomly, and ran fine when it did. I'm not an electronics savvy person, but i've done a manual check on the ...
0
votes
1answer
37 views

Cutoff and Conducting diodes

Why is D1 considered cutoff and D2 considered conducting ? Note : I am working with constant voltage model where the diode voltage is 0.7v and I need to figure out I and V. Please explain why D1 is ...
-7
votes
0answers
93 views

Resistance in series [closed]

An electric kettle has coils A and B. When only A is switched on the water boils in 10 minutes and when only B is switched on water boils in 20 minutes. Calculate time taken by same amount of water ...
1
vote
2answers
75 views

How to choose a transistor for amplification

I've been trying to find information on choosing an NPN transistor but everything I've found seems to apply to saturated transistors only. I'm basically trying to amplify the current given from a 3mm ...
1
vote
1answer
33 views

Checking my understanding of “branch in parallel current” warning

A datasheet for a power connector I was looking at tonight has this warning: Note: Do not branch in parallel current which exceeds the rated current. If branched in parallel, current ...
0
votes
2answers
57 views

Convert a ringing telephone voltage of 90V AC to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing?

How can I convert and step down a ringing telephone voltage of 90VAC current to 3.3V 1000mAh DC current so that it only triggers when the telephone is ringing? Bridge rectifier? Inductor? Step Down ...
0
votes
1answer
71 views

Does coil require extra resistor before connecting mains?

I am planning to build diaphragm air pump. For this instead of using an AC motor, I am planning to connect an aluminium rod to diaphragm, and put a permanent magnet on it that will be pulled and ...
0
votes
4answers
179 views

Why does a 10A fuse blow at 10A and 5V or 10A and 500V?

Something that's always puzzled me: Wire and fuses can handle a given max current, pretty much regardless of voltage. A 10A fuse will blow if you exceed 10A, if the voltage is 5V or 500V. Why is ...
0
votes
2answers
68 views

How to find current across a resistor using Thevenin Theorem

It's my first question here. How to find the current through 3 ohm resistor using Thevenin theorem?
8
votes
3answers
788 views

Flow of electrons in a wire

Electricity is "flow of electrons". My child asked me if this is so, then ultimately the copper wire should disappear/vanish/finish because the matter is moving from one place to the other. I am not ...
0
votes
1answer
48 views

Powering a load with specified maximum current of 300mA. Is it safe to use a matching voltage power supply with a higher current rating? [duplicate]

I just bought a guitar amp that can be powered by a 9v battery or a 9v power supply. The instructions that came with the amp specify that the power supply should deliver 300mA maximum. As far as I ...
-3
votes
2answers
104 views

Why does AC Current exists? [closed]

I need to know why does AC Current exists? And why not only DC current exists? Most devices needs DC current. I know that DC current is much dangerous then AC current. because of it is alternating ...
0
votes
1answer
87 views

How much current actually passes along household neutral?

My home has 3-wire single-phase supplied from the power company (Massachusetts, US). Red and black are separated by 180°. Both are 120 V from neutral (white). And in my electrical panel, neutral ...
0
votes
1answer
42 views

Increasing USB 5V current the right way

USB2 is limited to 500mA. If you want more current you need an external PSU to pump in more juice. What would be the proper way to add another 5V PSU to the system? Connect the 5V from the PSU to ...
0
votes
1answer
45 views

Known voltage/current source

I am working on an EVM for an electricity meter. Its manual says the EVM requires a known voltage and current source for the calibration. I bought a power supply and measure the output of the PSU by ...
-2
votes
1answer
57 views

Circuit breaker vs. electric heaters

Let's have a household with 230 Volt AC supply. What happens with the current if I start to gradually activate more and more (purely) resistive loads, like electric heaters and ovens? Because I=U/R, ...
1
vote
0answers
39 views

Small overdose in current — dangerous? [duplicate]

(I have a feeling that this question may be off-topic here because it is so utterly, enormously basic, and hardly related to engineering at all. Please bear with me...) My phone came with a power ...
0
votes
1answer
84 views

Calculate current using compensation

simulate this circuit – Schematic created using CircuitLab Okay, first I'd like to apologize if this question seems stupid, but I'm preparing for an exam, and don't know how to solve this ...
0
votes
1answer
62 views

Supply voltage drops AFTER connecting to device [closed]

I have a 19V 2.1 amp (power mentioned is 45 watt) laptop adapter connected to a 19V 2 amp laptop (in description power mentioned 10.2 watt). When I plug the adapter, the multimeter shows the rated ...
2
votes
3answers
62 views

Current drawn by a permanent magnet DC motor

I have been working with PMDC motors for a while now. In these motors, as the load increases current drawn by the motor also increases. I was just wondering what is the theoretical reason behind this ...
-3
votes
1answer
59 views

Ohm's Law Calculation

Just a quick quesiton. How much current if Voltage is 12 with 2 Ohm resistor's? If you can explain to me how you get the answer, that'd be great. Thanks.
1
vote
1answer
62 views

What is the current gain of this op-amp circuit?

I just happened to see this circuit in some lecture slides and I thought I could solve it. Unfortunately, I've been trying to check my result with an ideal simulation in LTspice and all my attempts ...
2
votes
8answers
590 views

How do households get their power?

I'm a little confused about the whole kilowatt hour thing. I get its 1000 watts in 1 hour but I don't get how you figure out how much voltage and current is running through the house. I did a little ...
0
votes
0answers
20 views

How to rectify the power line for leakage current based electrical shocks? [duplicate]

In May 2014, I had purchased Samsung LCD TV with two pin mains cord. I used to get electric shock like feeling when I touched the metal body part of it or the HDMI port (any other connected ungrounded ...
1
vote
0answers
40 views

Analyse data discrepancies: Efficiency of wire vs current

Please help me explain why the efficiency of the wire does not follow a distinct path (ie R^2 value is low). Graph 1 Efficiency of wire vs current: http://postimg.org/image/p49bzm4ab/ Is is to do ...
0
votes
1answer
41 views

How to provide enough current for my GSM circuit, and still use a LiOn battery?

I am very new to electronics. I am building a simple GPS tracker prototype circuit that uses a 3.7 volt 500mah lithium ion rechargeable battery. The circuit has 2 major components: a simple ...
1
vote
1answer
86 views

Don't understand spec sheet

I'm planning to buy a photo-interrupter, and I had a look at the spec sheet, but I didn't see much on the current/voltage of the device. I was thinking that it could run on 20mA, but I am confused ...
0
votes
1answer
62 views

Measure 208v single phase with Current Transformer

I have a single phase 208v circuit that I want to measure the amps on. What is the proper way to measure the amps? This is for a connection with 2 hots and a ground wire, no neutral coming from a ...
1
vote
4answers
212 views

How many LEDs can you chain in serial?

Theoretically, on a 12v with a max of 10w power line, how many LED's could you chain in serial before the LEDs further down the chain begin to dim? Where the LEDs have a forward voltage of 3.2 - 3.5 ...
-2
votes
1answer
80 views

Battery Current Stabilizing [duplicate]

So, from I can tell from the answers I received to my previous questions, if I want to lower the output current from a battery, I could put a resistor in series with my circuit. But wouldn't that ...
-1
votes
1answer
78 views

How to increase current output of a multiplexer for activating a relay

I want to make a multiplexer for my project which needs 24v dc to operate. I am using an OR Gate IC for generating an output. My 4 gate inputs are connected to 6V battery power and I am getting a 6V ...
0
votes
3answers
99 views

Current flow through a battery

So this might be a stupid question and I really should know the answer to it but I am having difficulties with a circuit I have made to drain a battery. The basic idea of this circuit is that I have ...
0
votes
1answer
70 views

Controlling current in a PWM circuit

I have a PSOC Cypress board which generates a 5V PWM signal to drive a laser diode. The idea is to design a programmable pulse which I could control the on-time period and current in the pulse. The ...
0
votes
2answers
71 views

Maximum op-amp output current

Im looking to drive an LED, but am not sure if i should use an op-amp or bjt configured as a switch. Is it possible for an op-amp to source roughly 10mA; the current needed to drive an LED in series ...
1
vote
4answers
162 views

KVL loop current direction convention--should be same in all loops?

Do we have to take the same sense of direction for loop current, like clockwise, in each loop when applying KVL to a circuit or can we take different directions in different loops? If we must take ...
0
votes
1answer
35 views

Current Injection Via Jumper Design Help

I am currently designing a circuit that uses a 5V 2A power brick. The circuit requires a current source and I have seen good efficiency with Ohm's Law. The current is variable through a 2k ...
0
votes
3answers
104 views

Current capacity of batteries wired in parallel

I'm wondering what would happen to the mAh when I connect 2 5000mAh batteries in parallel. Would the mAh over all be 10000mAh?! simulate this circuit – Schematic created using CircuitLab
0
votes
1answer
47 views

Understanding the input specifications for a laptop adapter [closed]

The sticker on my laptop adapter claims the input should be INPUT: 100-240V~ 2.5A(2,5A) 50-60Hz What does all this mean? Here are a couple specific questions: Can the adapter accept anywhere ...