Voltage, electric potential difference, electromotive force (emf), electric pressure or electric tension is the difference in electric potential between two points, which (in a static electric field) is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage (potential difference) is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, and recently (2019) fundamental physical constants have been introduced for the definition of all SI units and derived units. Voltage or electric potential difference is denoted symbolically by ∆V, simplified V, or U, for instance in the context of Ohm's or Kirchhoff's circuit laws.
Electric potential differences between points can be caused physically by electric charge build up or imbalance (eg. well known "static" and electronic capacitor) also by electric current through a magnetic field, and by time-varying magnetic fields (eg. dynamo or generator), or some combination of these three. Additionally on a macroscopic scale potential difference can be caused by electrochemical processes (cells and batteries) and pressure induced piezoelectric effect and heat induced emf across metal junctions. These latter processes at microscopic level have the physical origins previously mentioned. A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often a common reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy (electromotive force) or lost, used, or stored energy (potential drop).
Hi PF,
I have a setup with two plates that are connected to two different voltages and separated by vacuum. In my case, one plate is set at -10kV, and the other plate is set at -7.5kV. I know the area of these plates, the separation of the plates (which is much smaller than the plate area), and...
[mod note: thread moved from homework forum]
I have this Mouser voltage regulator
https://www.mouser.com/ProductDetail/STMicroelectronics/L7912CV/?qs=sGAEpiMZZMug9GoBKXZ75xbXFDWiKqpmvrbz5I0HaKg%3D
Wired according to datasheet https://www.mouser.com/ds/2/389/l79-974159.pdf see insert photo...
Homework Statement
Why is my calculated total resistance of the circuit higher than the resistor used in series and the theoretical total resistance? In a series circuit I used a 100Ω resistor and measured the current at 1.0v intervals from 1.0-5.0v.
At 1.0v the current was 8.70mA using a 100Ω...
Homework Statement
If a Hall effect magnetic sensor is designed to operate at 40°C, how much temperature variation would be tolerable for a Hall voltage accuracy of ±5% -I have I graph of hall voltage vs the absolute temperature but I am not sure how to go about this
Homework Equations...
Homework Statement
All the data is on the sheet. I named the nodes V1 to V4, however I'm primarily evaluating in terms of V3 and V4. The x=V3 and y=V4 are for the systems solving I'm using. I've looked and looked at this problem, and seem to be hung up, but I suspect it is going to be on my...
hi,
i tried to simulate a simple capacitor and resistor charging circuit like this
i used an imaginary resistor value "10M ohm" the result as you see appear to be strange, why this happened? is capacitor's charge is relative to the voltage on the capacitor it self?
and i need some...
Homework Statement
For a circuit with 3 resistors in series (R1=1.00 kOhms, R2=2.50 kOhms, R3= 4.00 kOhms and Va=12.0 V). A voltmeter was placed across R2 and R3. Calculate the relative error in the voltage reading if the internal resistance of the voltmeter was a) 5000 ohms, b) 50 kOhms, C)...
So I was messing around and made a lemon battery using a zinc nail and a copper penny. I wired 4 of these lemons together and connected it to a 5mm red LED and got around 3.7V. It came on but was dim. However, when I wire my power supply and also set it to 3.7V, it is much brighter. Now i assume...
Homework Statement
A charged capacitor consists of two large flat plates, one with positive charge +Q and the other negative charge -Q. An external agent trans an electron from the positive plate to the negative and also transfers a proton from the negative plate to the positive plate. There is...
Homework Statement
http://www.chegg.com/homework-help/questions-and-answers/problem-2-variableh-resistor-r-circuit-fig-p224-adjusted-va-equals-60-v-find-value-r-q8083343
Homework EquationsThe Attempt at a Solution
Hi, I attached a pdf file with the problem. My question is, for the lower right...
Hello All, I work in an optical lab and am currently attempting to determine the voltage output of a subtractor circuit I've wired up (as I'd like to work back from my output voltage and FFT magnitudes to read out the value of a magnetic field using faraday magnetometry.)
So my circuit is as...
When does an N-ch Mosfet conduct when drain voltage varies from 0V to Vdd(like 5V).
In case of Source voltage changing between 0V to 5V, all you do is check if VGS > Vth, with Vdrain fixed at 5V.
But in case of Drain Voltage changing between 0V to 5V, how does it work?
Homework Statement
What is the relationship of charge polarity and voltage polarity?
I understand an anion has negative charge and cation ion has negative charge, but does an anion have a positive voltage and the cation have a negative voltage?
Given the above is generally true, when is the...
Hi PF! Though I've lurked here for some time, this is the first time I've created an account.
I'm a volunteer in a country in West Africa. The school I teach at has a tiny library with 4 small dell PC's and a printer that were donated some time ago. A grant was used years ago to buy a battery...
I am trying to build a Voltage Doubler to use a motorcycle 6 Volt a.c. alternator's dedicated headlight coil (which presently runs a 36W incandescent headlight bulb) to provide 12 Volt d.c. to drive a commercially-bought 12V LED headlight unit (also rated at 36W). Frequency will be (1500 ~ 5000...
Homework Statement
Theses questions have been modified to solve my own inquiries. The originals can be found in the attached file.
A parallel plate capacitor has area A = 1 cm2, a plate separation of d = 0.01m, and is filled with air.(a) If the breakdown field is E0 = 3 × 106V/m, calculate...
Homework Statement
Consider the circuit
How long after the switch is closed does the voltage across the resistor drop to Vf = 20V. Answer in units of s.
Homework Equations
Tc = RC
Q=Qm(1-e-t/RC)
The Attempt at a Solution
[/B]
RC = .0003026
11 = 31(1-e-t/RC)
.3548 = 1-e-t/RC
1.3548 =...
I need help regarding piezolectric effect...
If I add DC voltage to piezoelectric crystal it will change its dimension (length) and vice versa: if I put pressure on piezoelectric crystal it willl produce DC voltage on its surfaces...
But I am wondering how long this voltage will last? If I keep...
Hello Everyone,
I am still trying to get my head around what a current to voltage converter (and vice versa) is. There is a section on my book, in the chapter about op amps, that discusses this topic.
Apparently, a current signal is less susceptible to noise than a voltage signal... But what...
I'm trying to understand what exactly it means in terms of the voltage of a battery. I know that the voltage in a battery is just the potential difference between the two terminals. But, is the negative terminal used as a relative point and seen as 0? If that's the case does 12V mean that the...
Hi, did you ever get to understand why a fuse installed in the Hot (Live) conductor of a circuit doesn't rupture when the AC Polarity reverses with the Neutral conductor bonded to Ground ? I still don't get it i.e. if current flows in both directions then the polarity is allowing the Hot wire...
Homework Statement
Q1: A power plant produces energy at a voltage of Vi = 18667 V. Before being sent along long distance power lines this electricity is sent through a transformer with 143 turns in the primary coil and 8971 turns in the secondary coil.
Voltage is calculated to be...
Homework Statement
Homework Equations
V = IR
And R becomes 2(r of one conductor) because of return path.
The Attempt at a Solution
V minimum is at third junction. At VD
Using KVL we get:
[/B]
Drop at AB = (10 + 20 + 50) * 2 * 0.1 = 16 V
Drop at BC = (20 + 50) * 2 * 0.08 = 11.2
Drop at CD =...
Homework Statement
Given the known quantities ##R, C, L##, ##k##, and the effective values of the voltages ##E_1=E_2=E_3=E## , ##w = \frac{1}{\sqrt{LC}}## of the direct-symmetrical 3-Phase system find the expressions for the effective values of ##U_{12}##, ##U## and ##I## and calculate the...
My question is whether voltage is actually a magnetic force that pushes electrons through the electrical circuit. My question arises from the fact that conductor passes through the magnetic field and if the circuit is closed we have the electron movement as some force pushes the electrons it...
I read online that insulation rating of the conductor depends on the voltage rating and not on the current. Can some one explain me how current doesn't contribute to insulation rating?
Am i missing something?
Kindly explain me
Homework Statement
A solid sphere with radius R=12 m has charge Q=3 nC distributed uniformly throughout its volume.
(a) Calculate the potential difference between a location at infinity and a location on the sphere’s surface.
(b) Calculate the potential difference between a location on the...
Homework Statement
For AC Circuit shown in the picture, ##C=60nF##, ##L=100uH##, ##X_3=-100Ω##, ##Z_2=50Ω## and ##Φ_2=\frac {\pi}{6}##. When the switch is closed the ammeter shows a current ##I_1=0.6A## and the voltmeter shows ##U_l=60V##. The measuring instruments mentioned are ideal...
Homework Statement
Homework Equations
I drew phasors and got the answer. Angle between V and I is 60 degrees. Cosine of 60 is 0.5. Then I multiplied V and I and divided it by 2.The Attempt at a Solution
I got answer 62.5. But I'm not sure if values of V and I given are rms values or maximum...
I have wired in series: + of 9V battery --- + of 1000 uF capacitor --- 660 Ohm resistor --- + of a green LED --- - of the 9V battery. Remark: the 9V battery is a bit depleted 7.8 V unconnected.
Voltage drop across the capactor is 6.5V, across the LED is 1.5V but 0V across the resistor. Why...
Homework Statement
Homework EquationsThe Attempt at a Solution
This is a solved example given in my Physics textbook . I am not understanding a couple of things .
1) How is Iin calculated as Vin/Rin ?
Why is the book not taking potential difference between Base Emitter into consideration...
Homework Statement
Homework EquationsThe Attempt at a Solution
Output voltage and output current of an OP-Amp
Taking the OP-Amp as an ideal OP-Amp, the voltage at terminal 1 is 0 with respect to ground.
The voltage at B is ## V_B = - 0.5 V ##
## i_{in} ## is from A to B.
There is...
I have a 5.5v .22F capacitor and I plan on using a 6v led on it for a project. Since I am not going to need to use it much and I am willing to do minor damage to the capacitor could I do that. By the way its for a school project so I will likely use it once or twice then keep it but never use it...
It's written in my book that if you have two points having the same voltage then you'll cancel the resistance between them ... how can I know if the voltages of the two points are equal ...( The resistances are given in the circuit .)
Hello!
I've been working on a few soil based MFCs and I have been monitoring my voltage and energy output for a week now. I've made the electrodes by covering stainless steel metal meshes with activated carbon using epoxy. I've gotten some funky results as attached.
As you can see... the...
Ok, so I am am trying to make a homemade capacitor that is 4700pf and 15kv. polyester at 125 micrometers thick can withstand 15kv so were good. here is the equation i used
C=ε0 K A / D
Where C = capacitance, ε0 is epsilons constant, K = dielectric constant, A = area of aluminum foil, and D is...
Homework Statement
There is a conductor with the square-shaped area. the Radii are r1 , r2 with width b and resistivity ## \rho_R##.
Find the resistance R between A and B
2. Homework Equations
##I = \iint_A\vec J \cdot d \vec A##
## \vec J = \kappa \vec E ##
## \vec E = \rho \vec J##
## V =...
Homework Statement
the capacitance of each capacitors and the cell voltage
Homework EquationsThe Attempt at a Solution
I got the total capacitance = 8028/5333 uF
total voltage = 36v
total charge=289008/5333 uC
Homework Statement
Homework EquationsThe Attempt at a Solution
I can't seem to figure out the answer. Apparently, the right method involves saying that Vs is actually equal to the voltage Vgs + voltage across R1. I don't understand how Vs could be voltage across R1?
This is what I have so...
This is a problem from my midterm that I'm trying to understand before my final. The question is;
A voltage phasor is given by V = 12∠70° and the frequency is 60 Hz. What is the time-domain voltage at t = 1 ms?
a. 1.47 V
b. 5.11 V
c. -0.335 V
d. -4.73 V
As far as i know, the only equation...
Homework Statement
hello, just came across this type of question for first time.
A voltmeter with a range of 0-30volts is to be used to measure a 120 volt circuit. calculate the value of the resistor to be placed in series with the meter. the sensitivity of the meter is 1000 ohms per volt ...
Hello
How do I calculate the induced voltage in a passive signal cable that runs parallel to a 1 phase power cable?
Cable A is the power cable I = 500 A
Cable B passive signal cable
where:
D= 209.65 mm: distance between wires ( center wire to center wire)
r= 10 mm: radios of each wire
f=60...
Given two sets of load resistances and output voltages:
Rload = 108 ohms - Vout = 9.6V
Rload = 10 Ohms - Vout = 2.3V
Find the source voltage and the output voltage when R1 and R2 are equal.
When the resistance is very large, the voltage seems to be around 9.6. My assumption was that then the...
Hey everyone, I'm hoping that you guys will be able to help me with some calculations. I was on YouTube and came across this:
I then began to wonder if I could make a solenoid using bitter disk as in the video, granted no where near as powerful. I would say 1 tesla using an iron core. After...
Homework Statement
Two parallel plates located at a distance "L" from each other they maintain a potential difference "V" because of a battery (as shown in the picture). Through a small hole, made in bottom plate, electrons get into system (with mass "m" and charge "-e"), with velocity "v" and...
Hello,
I was thinking that using AC to supply power to a lamp would cause it to flicker, considering that the potential difference keeps changing signs.
This would mean that the current supplies voltage to the lamp, only to take it back after a really small amount of time. Voltage say's...