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).
I am given that all the BJTs are the same.
First of all, when finding node voltages like Vref should I make the node voltage a voltage source first and then do circuit analysis? If so then I would use KVL but that does not give me Vref = 2Vbe.
I do know that Vref = Vb1 = Vb2. What am I doing...
I'm trying to maintain a spec requirement of less than 3% drop from farthest pin to closest pin from source.
I'used the entire layer for copper but my oart does not require such a large pour accept to handle high current.
So I'm considering there's a trade off that should meet inthe middle of...
I see that ##V_{ac}=V_{ab}+V_{bc}##, with ##V_{ab}=I_1R_1=I_2R_2## and ##V_{bc}=I_3R_3##.
However, I don't see how to express mathematically the maximum value of ##V_{ac}##. Could someone please help me with this task?
This is in python:
#ELECTRIC POTENTIAL
from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
import numpy as np
import matplotlib.pyplot as plt
dx = 0.1
dy = 0.1
xrange=np.arange(-1,1,dx)
yrange=np.arange(-1,1,dy)
X,Y = np.meshgrid(xrange, yrange)
max_dV = 10e-5
blockRadius = 3...
I don’t know the ratio of the CT. I’m just looking for an explanation on this. I thought in order to measure output voltage you need to pass the current through a resistor and read the voltage drop.
A co worker put 400a through the CT and measured 130v. Something just seems off to me. Can you...
Suppose I have a galvanic cell, where I've arbitrarily set the (-) anode to have a potential of zero volts and the (+) cathode to ##\epsilon## V. The electrodes are connected via the load, but also via the solutions and salt bridge in the centre. Edit: The two trailing wires are connected to a...
Good Day
Hi all,
I am doing a project with the standard lab about measuring equipotential surfaces with conductive paper, a voltmeter, and a power supply. I have a couple of questions about this project.
I attach a jpeg of the equations for voltage calculations in the file “Equations.jpeg”...
I was reading about ideal current and voltage amplifiers and the book says that an ideal current amplifier should have 0 input impedance and infinite output impedance while an ideal voltage amplifier should have an infinite input impedance and 0 output impedance.
I am not quite sure I...
Here are a few problems I have been trying which are shown below
Here is what I have done
The correct answers for these Q's are:
I'm not sure what I have done wrong for Q4, I assumed that all 12 cells were connected in series thus each individual emf sums up to 24V
Similarly the...
In my attempt, I tried
1) I1 = I2 + I3
Then set up these two equations based on Kirchhoff's second rule:
2) U1 = R1 (I2) + R3 (I3) and
3) U1 + U2 = R1 (I1) + R2 (I3).
From what we have
10 = 0.1* I_2 + 0.2 * I_3
22 = 0.1* I_2 + 0.02*I_3
I_3 = 50 - 0.5 I_2
That means
I_2 = 233.3 A
I_3 = -66.7A...
I really don't have any clue why the total voltage is equal to the voltage drop over the 3 Ω and 2 Ω resistors and independent of the 4 Ω resistor . Does it have to do with parallel circuits?
Hi everyone!
I ask some help in understanding better the concept of voltage. The voltage is a difference in electric potential between two points ##a## and ##b##. It is defined as
However, I'm a bit confused with the use of notation:
- Is ##V_{ab}## the same as ##\Delta{V}##, or rather...
In my idea the tension change after connecting the circuit to a battery is immediate, while the current takes some time before moving. That should be sufficient to prove my question but, so why in a RC circuit the opposite happens?
I honestly don't know how to quite even begin this problem.
Looking at Fig 3-2, the slopes of the graphs are 1/R, and hence where the slopes are 0, we have infinite resistance, in which case current wouldn't flow through that resistor and hence simplify the circuit. So I was trying to find...
From the circuit I have:
##-v_b + v_a + V = 0##
##v_b - V = v_a##
##i_1 = (v_b - V)/R_1##
##I + i_2 = i_1##
##(v_b - V)/R_1 = I + v_b/R_2##
From this last equation I get ##v_b = 10.8## and hence ##v_a = 5.8##.
However, apparently that is wrong. (And hence my answers to #2 were all wrong as...
I don't get this. Since we have analyzed the circuit separately for each source, adding them should give me the final values of I1, V2, I2, V1 etc. However, that's not quite true—from cases 1 and 2, I should have I1 = 4 + 5 = 9 mA, but it's 8mA. Hence, I thought that the black box consumes 1mA...
I am having a hard time solving this. Letting \$i\$ be the current flowing into ##R_3##, ##i_1## the current flowing through ##R_1## and ##i_2## the current through ##R_1##—and the node between R3 and R1 be e_1;
Using KVL and KCL, I've managed to find that
##i + I = i_1 + i_2##
Hence...
I have no problem getting the ##R_{TH}## since from the special element's POV, the resistors are in parallel, and that's the answer.
However, I don't really understand how to get ##V_{TH}##.
Ignoring the special element, it seems that I have the resistors in series this time. But I'm not too...
I don't really understand or see the correct way to approach this.
Letting the current in question be ##i_x## (as shown in Fig. 1), and the unknown (changing) resistance be $R_x$, I can write:
##-V_s + R_s i_s + i_x R_x = 0##, and ##R_p i_p = i_x R_x##. Hence we can also write ##-V_s + R_s i_s...
In a field effect transistor, does the threshold voltage decrease with increasing temperature? Imagine that there would be an increase in thermally generated carriers and thus the device would reach saturation faster? I realize the mobility would decrease, but the increase of thermal carriers...
The concepts of current and voltage are not difficult for me to understand. What I am having difficulty understanding, is what causes it? What causes there to be a potential difference so that when I plug my toaster in, electricity flows through it? How is there constantly a potential...
According to the attached image, the dielectric strength of Mylar film decreases with increasing film thickness. My question is if this trend is also present for when films are stacked or if the film can be stacked arbitrarily high with the same breakdown voltage as a single layer.
Hello,
I have been reading about impedance matching as being the main requirement to ensure maximum "power" transfer from one part of a circuit to another: the two electric systems ##A## and ##B## need to have complex conjugate impedance so only 50% of the energy is reflected back at their...
I assume that because there is a resistance, the polarity of the voltage must be the same as the charge flow, and thus the current, in order for energy to flow in the same direction.
For instance, could I use the example of a light bulb (the resistor) plugged into AC lines; we know that if the...
I need to create a powersupply that takes in a +5 and -5v and has an adjustable output that varies between -2 and +2 v using one potentiometer.
I already came up with a design myself but it did not work. I need some help figuring this out.
I think my idea for how to get specific positive or...
So something weird just happened along the way in my experiment, here is a little background of what I'm doing.
I have created a roughly 3x5mm inner diameter rectangular shaped channel for MHD liquid testing for one other project of mine, it's a simple conduction type MHD pump where the...
Summary:: What if you were calculating the voltage potential for a dipole, but underwater?
I'm making a predictive model (in R programming) for the voltage potential at any point around a dipole. I need to be able to change parameters, one being the k constant.
V=( kpcosѲ)/(r^2).
Where V is...
In a closed circuit the battery sets up a potential difference which causes charge to flow. I understand potential difference as the
measure of electric potential energy per unit charge, the amount of energy required to move a charge from one point to another per charge.
for example when a...
I already found ##I(t)## using Kirchhoff's laws, I got the equation ##V-RI-L\frac{dI}{dt}=0\Rightarrow L\frac{dI}{dt}=V-RI## then I solved the differential equation getting ##I(t)=\frac{V}{R}\left[1-e^{-\frac{R}{L}t}\right]##. My problem is founding the voltage as a function of time ##V(t)##, I...
So this is a problem from the legendary Razavi book "Design of Analog CMOS Integrated Circuits" (Specifically, it is the problem 7.7 (c)). I got the solutions online but when I try to calculate the noise expression myself, I don't arrive at the same result. Lambda is assumed zero for neglecting...
By combining the formula for the reactance of a capacitor with Ohm's Law for a capacitor, I can solve for angular frequency, and divide by 2π to find frequency.
The resulting equation is:
f = I/(2π VC)
Using the given values, I end up with 5.2 kHz, instead of the correct answer of 5.2 MHz. I...
Homework Statement: Figure shows two mutually coupled coils, for which
L11= L22 = 3 + 2/3x (mH)
L12 = L21 = 1/3x (mH)
where x is in meters, (a) If i1 = 5 A dc and i2 = 0, what is the mutual electrical force between the coils at x = 0.01 m? ( b ) If i1 = 5 A dc and the second coil is...
I tried to solve it by loop currents. So on the left mesh the loop current ##I_1## goes clockwise and on the right mesh the loop current ##I_2## goes counterclockwise.
I ended up with the following equations:
1) ##V_1-R_1(I_1+I_2)-R_2I_1=0##;
2) ##V_2-R_3I_2-R_1(I_1+I_2)=0##.
To find the...
Hello,
Here's the example I'm looking at now.
I am wondering if I swap ground and Node C... will this still be correct? I can see how it's more useful to have ground where it is above, but I'd still like to know if it would work for a swap of C and GND.
Here's my work trying this:
Does...
I've recently had a discussion with fellow technicians in the automotive industry about spark plugs and some systems having "opposite polarity" on the ignition coils. (specifically the secondary coil which sends the high voltage pulse to the plug which sparks the fuel)
Common sense tells me...
In this circuit a battery,Capacitor,and a resistance are in series.
For simplicity assume that there is a +4V in the positive terminal of the battery and -4V in the negative one and let A be the capacitor plate connected to the positive terminal and B the capacitor plate connected to the...
When you say ##i = \frac{dq}{dt}## it makes sense since current is the flow of charge over time. But why was voltage defined as
##v = \frac{dw}{dq}## ? What made physicians define it in this way? Is there a mathematical way that can lead to this definition or
did they define voltage just on the...
I made a permanent magnet alternator out of a 3hp 3 phase induction motor. I am getting voltage, but no current at all. The alternator is wired delta and feeds a capacitor bank wired in a wye, to create a neutral. I have even tied the neutral into the alternator and still no current. I connected...
The open loop voltage gain is given as :
$$ u(s) = \frac{u_o}{1+\frac{s}{w_o}} = \frac{100}{1 + \frac{s}{40}}$$
Where u_o is the d.c. voltage gain and w_o is the pole.
The op amp that is given is:
And I am told to use the non ideal op amp model as follows:
Well my guess is that I can find the...
I'm trying to find Vth (and then Rth). My work and results don't seem to agree with what my circuit simulation (done on LTSpice) shows. Can anyone point out what may be wrong here?
As I`` m learning for an upcoming exam I found an electrodynamics problem I struggle with.
In the first task I need to calculate the magnetic dipole moment of a uniformly charged,thin disk with the Radius R and a total charge Q which rotates with a angular speed omega round its symmetry axis...
Summary: Facing a circuit with 2 parallel resistors and 2 current sources (1 dependent, 1 independent). Trying to find the current, voltage, power delivered by the independent current source and power delivered by the dependent current source.
I'm trying to start by finding the current i0 but...
I'm really unsure about how to solve this because I am not given the total voltage between the plates. The voltage given (693V) is at a point that is 7.85 cm away from the zero volt plate. If I was given the total voltage between the complete distance between the plates (10 cm), then I could...
i connected a diode to a 4 volt battery. in 1 direction the diode passes 4 volts. in the other direction the diode passes 1.9 volts. is this normal? shouldn't the diode pass 0 volts in the other direction?
so when I did this problem I did nodal analysis to find the voltage across the 40k resistor, and found it to be 16V. From there I did two source transformations, combined the sources and did some equivalent resistance to get the answer as seen below:
However this differed from the answer he...
I am so sorry if I am posting this in the wrong forum; it is just not a homework problem, and I can't find the right place - it's more of a study help question.
Can anyone explain how to go about this? I don't understand the solution, which says:
A) Find the equivalent resistance (10 ohms). Find the voltage of the current source (4.2*10 = 42 V). Use a voltage divider to find vo = 42*(20/(10+20))=28V. My question is why do we need to add 10, which is R...