What is Potential difference: Definition and 699 Discussions
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).
Battery and Capacitor
For a battery (or capacitor), the potential increases by ##\mathcal{E}## (or ##\displaystyle\frac{q}{C}##) as we move from -ve to +ve terminal (or plate) regardless of the direction of the assumed current.
Resistor and Inductor
Suppose we are traversing the loop in the...
Hi.
I'm confused about the usage of "voltage". Some scripts I read introduce it in electrostatic as potential difference (where there's only the scalar potential), but continue using it when changing magnetic fields are present ("induced voltage"). Others make a clear distinction and introduce...
So far, here's what I have:
Taking the parallel-connected resistors alone, 1/Total effective resistance (R) = 1/3ohm + 1/6ohm = 1/2, so R = 2ohm
Replacing the 3 and 6 ohm resistors with a 2 ohm resistor, the total resistance will be 2+4 = 6ohm
Using V=IR,
I (current) = V(potential...
As the title says, i am struggling to understand how if the cell is only supplying 3V how 2 lamps in parallel both receive 3 volts (totalling 6)
I currently study a level physics and never really questioned how this works and just accepted it as the truth.
Can someone explain with a helpful...
In the given circuit, a transient current will flow and when this current finally stops at equilibrium, the charges ##q_1## and ##q_2## are assumed to deposit at the capacitor plates as shown below. The dashed line indicates an isolated system that will have it's total charge conserved.
If I...
(a) I think the top plate of C5 could end up with either + or - charge, and not necessarily + charge as shown. This is because the connected plates of C1, C5 and C3 form an isolated system to which we can apply the law of conservation of charge i.e. Total charge just before transient currents...
Hello everyone, thank you for taking your time to read this. I was assigned a homework task of multiple choice questions to do with gravitational fields. This is one of the last questions and I have been pondering over it for some time now. I don't understand how any sort of answer is...
(a)
I know some of the apparatus needed for the experiment, such as DC power supply, ammeter, voltmeter, maybe rheostat. But I don't know how to change the temperature of diode. What is the correct and safe way to change the temperature of diode?
Thanks
Electric potential = "absolute potential"
Textbooks usually connect both ends of two capacitors, of different voltages, in parallel. What would happen if we only connect one end of the capacitors? Perhaps we would have to solve for Maxwell's coefficients of potential for these two cases (to...
For this part(b) of this problem,
The solution is
However, I tried solving (b) like this:
Since ##Q_{total} = 363 \times 10^{-6} C## then ##Q_1 = 181.5 \times 10^{-6} C ## since the equivalent upper capacitor is in series with the equivalent bottom capacitor so should store the same amount...
The solution chooses the centre wire to determine the potential difference, where Va−(0.909 A)(2.00 Ω)=Vb and Vb - Va = -1.82
If I choose the top wire (passing through the 12 V battery and 4 Ω resistor), Va - 12 + (1.636 A)(4.00 Ω)=Vb, and Vb - Va is different (= -5.46 V). Why would this path...
I don't understand why the Uranium 238 ions are accelerated
I think ##\Delta V = -2000 V## to accelerate since the ion would be accelerated by more postive charges so ## V_i > V_f ##
This is the diagram provided in the question:
The ring is made of conducting material. I was originally asked to find the potential difference between ##a## and ##b##. I did so using the Hall effect (and assuming it would work as per normal in this situation). This got me ##\Delta V = vBl##...
In the case motional emf, there is a static magnetic field and a rectulgular loop that goes into the field region, then current is produced. There is no electric field, but there is an emf. However, Griffiths states that emf is equal to the potential difference between the source endpoints. But...
a) We know that ##Q_1=1,2\, \textrm{nC}## and ##Q_2=6\, \textrm{nC}##. By the TOTAL influence theorem:
$$-Q_1=Q_{2i}=-1,2\, \textrm{nC}$$
$$Q_2=Q_{2i}+Q_{2e}\rightarrow Q_{2e}=7,2\, \textrm{nC}$$
b) Electric potential difference crust:
$$V_A-V_\infty=$$
How was this potential difference thing...
The figure is:
I have the solution to this problem:
We have two distinct branches
$$V_a-V_b=\overbrace{(V_a-V_c)}^{\textrm{INI}-\textrm{FIN}}+\overbrace{(V_c-V_b)}^{\textrm{FIN}-\textrm{INI}}$$
They have different intensities: ##3\, \textrm{mA}## and ##2\, \textrm{mA}##
##V_A-V_C\rightarrow##...
(a) Using Gauss's Law ##E_P=\frac{q_1+q_2+q_3}{4\pi\varepsilon_0(R_1+R_2+R_3+d)^2};(b) V_3-V_1=\int_{R_3}^{R_2}\frac{q_1+q_2}{4\pi\varepsilon_0 r^2}dr+\int_{R_2}^{R_1}\frac{q_1}{4\pi\varepsilon_0 r^2}dr=\frac{q_2}{4\pi\varepsilon_0}\left(\frac{1}{R_3}-\frac{1}{R_2}\right).##
(c)...
I am able to get V1 = kq/a - 4kq/b
and V2 = kq/b + -4kq/b
For some reason the solution says it is V1-V2 as opposed to V2-V1.
Maybe has something to do with positive shell in the center and negative outer shell? I know the electric field goes from positive to negative, but I don't know how...
I don't understand why there is potential difference between point A and O. Is there any change in magnetic flux experienced by the ring? I think the magnetic field passing through the ring's cross sectional area is constant
Thanks
So I have been given a uniform electric field ##\vec{E}=20 V/m## in the direction as show in the image. I have been told to calculate the potential difference ##VC - VA##. According to the teacher (on YouTube) the potential difference ##VC - VA = -10\sqrt{2}V##. But I say it's ##-20 V## as...
e=QxV
t=Q/I
p=(QxV)/(Q/I)
=V/I
The expression I came up with for a) is the potential difference divided by current to get power but I have no idea if that is even right if someone could just prompt me in the right direction that would be greatly appreciated
Hello there, I have derived the expressions for electric field and potential to be the ones above, then for continuity at ##x = 0## I set the electric fields and potentials to be equal to yield the expressions:
$$Sx_p^2 = Kx_n^2$$
$$V_{bi} = V_n - V_p = \frac {q}{3\epsilon} \left( Sx_p^3 +...
So Kirchoff's Loop law states that, The sum of all the potential differences encountered while moving around a loop or closed path is zero.
Ok so that is basically a statement of energy conservation. So I see why in the TYPED solution, they related all voltages in the circuit equal to zero. I...
So I know that E = -ΔV/Δs. If I wanted to solve for change in potential I could rearrange this equation and get Δ = -E*ds. With that information I believe I can solve the problem below. But in both solutions provided below, the negative sign goes away. Now I know I can pull the E out because it...
Hello,
I'm seriously confused on several things around how concretely
batteries create potential difference in order to force the electrons
circulate trought the circuit wire.
Almost all explanations I found (wikipedia, diverse tutorials, intro scripts, etc.) explain it in nearly
the same...
is this method accepted?
2V is split equally between the 2 5kohms resistor because they are of equal resistance.
2V=5kohms
2kohms= 0.8V
3kohms=1.2V.
p.d across P and Q= 1V-0.8V=0.2V
I understand phase voltage (phase to neutral) well, but I'm still confused by what exactly the potential difference is between any 2 phases in 3 phase power. If you were to try to find the potential difference where 2 sine wave phases cross, then at that instantaneous point, the potential...
When we have a resistor in electronic conductors, potential difference is created via surface charges which accumulate on conductor surface.
What about electrolytes?
I am not sure if electrolytes can create potential difference in the same way since surface in electrolytic conductors isn't as...
I tried following the formula but it wasn’t correct. I’m sure I could get it if I had an example as I’m sure this must be a simple question for other people I was just unsure if I was doing it correct.
Emf between the center of the disc and its rim
= ##- \frac{d \phi}{dt }##
= ##-B.A \frac{d \cos (\omega t)}{dt}##
=##\mu_0 \frac{N}{L} I A \omega \sin (\omega t)##
Potential difference across the ends of the solenoid = ##10\mu_0 \frac{N}{L} I A \omega \sin (\omega t)##
Is this correct? How to...
So, each capacitor must have a different potential difference, given by its capacity and charge... this would cause charge and current accordingly to flow in the circuit.
But how do I determine the final potential difference, which would of course be the same for both of them? I have tried...
So, having two parallel resistor ##R_{1}## and ##R_{2}## , the current flowing through the equivalent one will be ##I_{eq}=I_{1}+I_{2}##.
Now, it comes the point I'm not totally getting: why is ##V_{eq}=V_{1}=V_{2}##? These V's are the difference of potential measured between which points...
Specifically, I haven't really got all the "methods" through which you could calculate or derive the electric potential and in some situations, I cannot understand how and when to apply this concept.
Is it something caused by any charge, or must there be an interaction between the two to...
For the first part, since
$$ E(r) \propto \frac{1}{r} \hat{r}$$
by the principle of superposition the maximal electric field should be halfway in between the two wires.
Then I'm not sure how to go about the second part of the question. I understand that the total potential due to the two wires...
Is emf the work done to move a positive charge from LOWER potential to HIGHER potential to maintain the potential difference or else the charges move from higher potential to lower potential and will reach a point where the potential is the same between the two points and the charge will stop...
V at surface = k Q / r = 9 x 109 x (1 x 109 x (-1.6 x 10-19) / (1 x 10-2)
= - 144 V
V at a point far away = 0 V
From the sentence "electric potential difference between the surface of this sphere and a point far away" means that the question asks about V at surface minus V at far away so the...
A rod with a circular center in the middle (which causes the rod to change direction by 90 °) has an evenly distributed linear charge density 𝜆 of electrons along the entire rod. Determine the electrical potential of the red dot in the figure below which is at the center of the circular round...
I am working out an example problem from one of my textbooks and I am a bit confused on why a value is negative. The problem asks: Calculate the final speed of a free electron accelerated from rest through a potential difference of 100 V.
This is a conservation of energy problem. Ultimately you...
Imagine a container of salt water at 0V (Relative to ground),Now you've put in it 2 electrodes,one at +500V (Electrode A), The other at +250V(Electrode b), Normally positive ions should go to the negative electrode , and Negative ions should go to the positive electrode , But in our example the...
I'm not really sure what I need to find exactly. From what I'm seeing, I could give C1 the max potential difference of 125V because it has the lowest capacitance, and because V = Q/C, this means the capacitor with the highest potential difference across its plates will be the one with the lowest...
Firstly, I'm given this complicated circuit as shown below.
What I have to do first, is to simplify it, which I will need help in checking.
One question here: It's not possible to simplify this by adding resistors in series and capacitors in series am I, right? Or is it possible in this case...
Where does energy come from in potential difference appearing in Hall effect?It is magnetic force causes this potential.But we know that magnetic force does not do work on motion charge particles, then where is the energy come from?It seems contradiction that magnetic forces cause the potential...