Questions tagged [voltage]

Voltage, otherwise known as electrical potential difference (denoted ∆V and measured in volts) is the difference in electric potential between two points (adapted from Wikipedia). Voltage can be constant (DC) or varying (AC).

4,814 questions
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How current works

I apologize for the very basic question but I seem to be lacking some fundamental knowledge. I am using an infra red LED in a circuit and it seems like it is drawing around 15mA at 5v. I was told ...
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How to make a power supply cable for a 10.5V 4.3A laptop OR how much higher voltage can I use

Let me preface this by saying I've spent countless hours researching and learning what I can about electronics before asking this, and I cannot find a clear answer to this. So sorry if this seems like ...
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X Ray Transformer with Full Wave Rectifier Design

I current am in possession of a center tapped X-ray transformer that can supply 80 kV and 10 mA. However, I need this transformer to supply approximately 0 to -37 kV DC at around 8 mA. In order to ...
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What will be the real voltage along the line with a voltage source and a capacitor?

Take the following circuit: If I do a simulation of this circuit I get this graph: The strange thing is that in the simulator it gives the same voltage sine wave in the circuit, near the voltage ...
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No potential difference between the negative terminal of battery A and positive terminal of battery B?

I know that if you have two batteries, battery A and battery B, and connect the negative terminal of battery A to the positive terminal of battery B, there is no potential difference. If you consider ...
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High resistance, no current. What's the point of a potential then?

I am referring to this example: Why does it matter that the IC has a high resistance? What does this do for/to the IC? If there is a potential but no current, what is the point of using the IC when ...
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Connect 10 LEDs using 5 volt current

I have 10 yellow-colored LEDs and ten 220 ohm resistors. I don't have any power source except the Arduino's 5 volt itself. Is it possible to power all the 10 LEDs using the 5 volt equally? Or will ...
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Motor performance

If I was to run an electric motor rated at 24V 20A at 15V 10A and at 10V 15A what would the difference in performance be? Assuming everything is rated to safely handle more than that power.
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Open circuit voltage gain of JFET transistor circuit

So this is one of the questions from my previous past papers, I worked out my Vgs and Vds value correctly (-1.25v and 10v). However, when calculating my open circuit voltage gain, I use the equation ...
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Another Power Supply question [closed]

I am trying to troubleshoot a problem with a battery charger that accepts 11-18V DC input and can output up to 24V/8A/80W. The power supply I am using is rated for 12V10A, but if I select 10A 8.4V ...
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Circuit to tell Microcontroller when Voltage is Low

I would like to trip an input, similar to a button input to an microcontroller if the input voltage to the circuit/microcontroller is below a certain threshold. I have transistors and some zener ...
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How does the hot point-probe test affect p-type semiconductors?

In an n-type semiconductor if you place a hot probe close to a cold metal probe, the average thermal velocity of electrons near the hot probe increases which leads to a net electron motion from the ...
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Finding current of circuit in steady state

I am unsure if I did the KCL correctly. Also if I switched from rectangular to polar without mistakes. Excuse me if the work is a bit sloppy I am new to the polar and imaginary coordinates.
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Finding the voltage across a inductor in a charged RLC-circuit

Well, I've the following circuit: simulate this circuit – Schematic created using CircuitLab In the circuit I want to find the voltage $\text{V}_{\text{Y}_1}\left(t\right)$ as a function ...
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Inductor Symbol? What does this symbol indicate?

In the diagram below the symbol labeled L1 is described as: 1.5mH, Core: SM CM20 x 12 x 10 But what does this symbol show exactly? I have searched thoroughly and cannot find this symbol and am ...
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Using a 7.4 V LiPo Battery for an Arduino Feather 32u4

I am working on an Arduino project at the moment, with the following board: Adafruit Feather 32u4 And it says I need 3.7 V of LiPo to power it. However I also have a valve that I want to open and ...
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Voltage exceed source voltage over a coil when opening a switch

Well, I have the following circuit: simulate this circuit – Schematic created using CircuitLab When the switch is closed for a long time, the current that is flowing trough the resistor $R_1$...
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Understanding Mosfet Circuit with PWM

I am wanting to control a voltage range of 0-10v across a 10k load with PWM from a micro. Now I was told to use this circuit with an n channel mosfet: This is what I understand so far: R1 is to ...
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Maximum safe working voltage of capacitors

The answer is 30kV. My method led to an answer of 41KV, where did I go wrong? I believe I cant just add the Vmax(s) at the end, but what would I do instead and why?
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Limiting maximum voltage

I can't seem to find an answer to this, or the answers available are too advanced for me to understand. I have an AC source 0VAC-40VAC. I also have a buck converter rated at 6VDC-24VDC input, and 5V ...
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Help with determining the open circuit voltage

Can someone go through why Vxy= -84mV? Given the values off VB=180mv R1=22ohms R2=68ohms R3=150 ohms. Many thanks
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Voltage doubler using 555 timer

I found this circuit, a voltage doubler with 555. The duty cycle of the 555 is 50%. Does changing the duty cycle of the 555 timer affect the voltage output like in boost converter? Or does it not ...
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Confusion between the necessity of maximum voltage and maximum power transfer

This is a conceptual question therefore I want to ask with an example. I'm wondering in which cases impedance matching is used. For example, if one has a sensor which can be modeled as voltage ...
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How to findout the value of V(s)/V(e)?

How to findout the value of V(s)/V(e)? Is it correct? \dfrac{Vs}{Ve} = \dfrac{\dfrac{R2 \cdot \dfrac{1}{j\omega C}}{R2 + \dfrac{1}{j\omega C}}}{R1 + \dfrac{R2 \cdot \dfrac{1}{j\omega C}}{R2 + \...
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Voltage isolation at IC pin when Vcc=0V

I recently started a project that utilizes a piezo sensor to sense vibrations. The piezo signal is fed to a uC in order to detect vibrations above a certain threshold. However, the piezo's high ...
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USB cable for power delivery max voltage

I have a USB cable with the following markings on it AWM 80°C 30V VW-1 28AWGX1P 24AWGX2C Inside the cable there are 4 wires. I would like to use the VCC and GND ...
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Peak open-circuit current and applied voltage of transformer function

I know that the back-EMF equation tells shows that the peak flux density is proportional to the AC supply voltage. But what is the explanation for that the open-circuit current increases non linearly ...
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does a higher amperage source help prevent voltage sag?

I'm currently troubleshooting my car's ongoing electrical issues and during the troubleshooting process so far I have gone through multiple OEM alternators and multiple OEM & non-OEM batteries. ...
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do the voltage and amperage applied to a motor matter as long as the wattage stays at what its rated for?

I have an electric 180w motor from an electric go cart which currently runs on lead acid batteries but I want to convert it to have a 18650 battery pack for a power supply but I cant find the rated ...
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Capacitor circuit simplification

I am unsure if I have simplified this circuit correctly, therefore I am unsure how to write Vo in terms of V1. Please let me know if I have simplified this correctly.
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Why does the base-emitter voltage in NPN transistor become constant?

The setup above shows the experiment that I have been working with. During the experiment, the current $i_c$ and the voltage $V_{be}$ were measured for increasing $V_{in}$. At some point, the ...
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Current Transformers

I have a question about current transformers being used to measure AC currents. Say for example, we have a 50/5 amp current ratio, meaning that when there's 50 amps on the primary, there will be 5 ...
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Mathematical help with Wheatstone bridge

This is a homework, so I won't ask for a complete solution, but can anyone tell me how should I approach this? I've been sitting now for hours without any progress, all that I know is the answer ...
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How to account for the low voltage when designing a Step Down Switching Regulator

Datasheet: http://www.ti.com/lit/ds/slvs569f/slvs569f.pdf Design procedure: **Essentially my question is say I have an input voltage that can range from 7-15V. When designing this converter (must ...
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Solving for open ckt voltage and short circuit current

I am unsure if I did the KCL for node A for the short circuit diagram correctly. I used the ia value from the open circuit and used it to find iy. Please let me know if I am on the right path or if ...
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Why is there a positive body voltage when grounded, but none when not?

So after reading about earthing and earthing mats, I decided to make myself a very basic one for cheap to test the concept before jumping in with purchasing more sophisticated products. Here's what I ...
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Confused on voltage potential

I’ve been doing much research the last couple of days about electricity. I have a pretty good understanding of Watts, Joules, Coulombs, Amperes, Ohms, and I know Ohms law finding voltage and all and I ...
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Directional Coupler Terminals

I have a basic question about directional couplers. In this scheme each port is represented by one wire. What does it mean? The other terminal of each port is GND for all?
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No Output Voltage On Power Mux

I am building a board based on a working reference design. I've obtained the assembled board based on my design but the '3V3_OUT' signal is failing to carry power anywhere on the board. The issue ...
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Replace 3.7V flat tablet battery with a 18650 cell

I am building a device using cheap Chinese tablet. One of the problems I have is weak built-in battery. I'd like to replace it with a few 18650 cells. As far as I know, 18650 cell can be charged up ...
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Stepping down voltage 120 VAC to either 110 VAC or 117 VAC

I'm a vintage radio collector and I have on my benchtop a Variac that I use for testing out radios. I wonder if there's a way I can put together something that I can either put inside the radio ...
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Regulating VAC transformer voltage

Good day all, I was wondering if there are ways to stabalize the AC voltage between 220 - 230VAC (standard mains voltage in Europe) if the mains output voltage drops say for example 200VAC? I am ...
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Solving capacitor voltage with Laplace

I saw this example and I got confused. The example shows: $V_{C}(s)=\dfrac{R\parallel\frac{1}{sC}}{sL+R\parallel\frac{1}{sC}}V_{in}(s)$ . Isn't it enough to express $V_{C}(s)$ with the voltage ...
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DC Voltage drop multiplier confusion

I have half a meter of 18 AWG (1.02mm diameter) stranded copper wire and I am planning to run 12 volts with a maximum 6 amp load. Determining the cross sectional ...
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modify schematic to work at 5V (solar panel sun tracking system)

I have this schematic and I want to know: if it will work at 5V (my solar panel is 5V-6V) modifications required to command (clockwise/anticlockwise rotation) the motor directly with the final ...
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LED driver putting out more voltage than rated?

The Background I bought a 200W magnetic LED driver with hopes of replacing the 40W Philips-supplied driver that came with my set of Hue Lily outdoor lights. Each fixture requires 8W at 24v. This new ...
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What happens if we force a voltage on Vbe of a bjt transistor

I'm wondering what happens in a BJT transistor if we force a voltage bigger than 0.7V on Vbe. A colleague of mine said that if we put on Vbe, let's say, 5V the transistor would be saturated. I ...
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Supply white/blue led with 3V3 at constant current

I need to drive a white/blue led at low constant current (about 10mA.) To do that I usually use the schematic below, but in my case I can only supply the LED with 3V3. Since the typical forward ...