Voltage is the unit of measurement for electronic potential, from one point location to another.

learn more… | top users | synonyms

21
votes
8answers
5k views

How can a battery charge up another battery to a higher percentage?

Say I have my phone on 5% and a large battery pack on 35% and I charge the phone. By the end the phone is on 100% and the pack is on 12%. How can the battery pack charge the phone up to a higher ...
0
votes
3answers
3k views

How is a potential difference created between two points?

I would like to know how potential difference is created between two points?Is potential difference created by adding more electrons at one side?If that's the case how to add more electrons at one ...
0
votes
0answers
15 views

Is it safe to use the USB ports of a 110v surge protector connected to a 220v socket? [on hold]

During my visit to the US, I have bought a surge protector with USB ports: Monster Power EXP 350 I'd like to know if it is safe to use while connected to a 220V european power socket, using a ...
0
votes
3answers
348 views

How does back-emf oppose the input-current?

A circuit, has current $A$ flowing at a certain $V$. When there is a change in magnetic-flux, based on Faraday's law of induction & Lenz's law, we know that there is change in Potential ...
0
votes
0answers
26 views

Measuring a capacitor accurately [on hold]

I want to accurately measure the value of an electrolytic capacitor at DC voltages, and accurately predict its voltage based on current drawn from it, or put the other way, accurately measure the ...
3
votes
2answers
175 views

Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
0
votes
1answer
38 views

Poisson's equation with point source

PDE's are not my thing, but I'm trying to calculate the voltage in a finite conducting sphere, based on a point current source. With Poisson's equation of $\nabla^2\Phi = -\frac{J}{\sigma}$, where $J$...
1
vote
1answer
56 views

Proof of Kirchoff's second law [closed]

There are 2 approaches I have stumbled to prove Kirchhoff's second law: Derive it from the conservation of energy. You can derive that from "integral of E*ds = 0". Can you show me a full or at ...
0
votes
2answers
26 views

Elementary derivation of $P = UI$ starting from the definition of voltage as work done per unit charge

Consider the following elementary derivation of the formula $P = VI$ for Joule heating of a resistor $R$ for the dissipated power $P$ where the voltage over the resistor is $V$ and the current $I$. ...
0
votes
1answer
126 views

Back EMF & Current, how can we make the current $I$ stable?

Lets assume we have a wire that has $10V$ across and $1$ $Amp$ flowing, now if this conductor is introduced to a changing magnetic field, $-EMF$ is induced, can we control our voltage to increase it ...
0
votes
1answer
77 views

Li-ion Battery charging

Why are constant current mode and constant voltage mode needed when charging Li-ion batteries? Why do we apply saturation charge even after the cell voltage reaches 4.2V? What exactly is 'I-sense' in ...
3
votes
0answers
55 views

Does charge injection from electrodes increases the total charge in a (semi)conductive channel?

When a (semi)conductor is connected to a voltage bias, a charge is injected by the electrodes. When steady state is reached (constant current flow), does the total charge of the (semi)conductor differ ...
5
votes
3answers
1k views

Measuring voltage drop from induced current

I'm having trouble connecting voltage drops and induced current. Imagine you have a triangular loop make up off three resistors. You place this loop in a constantly changing magnetic field. This ...
1
vote
1answer
43 views

Different voltage drops depending on the path

I was working through a problem in electromagnetic induction when I discovered that I have a fundamental ignorance of some sort that is puzzling me. Consider a circular wire, at rest, perpendicular ...
1
vote
1answer
25 views

Voltage in parallel and series connection

In series connection, voltage is said to be different and current constant across the circuit. How does it come about ? Is it due to the accumulation of electrons on one side due to resistors? Or, if ...
0
votes
2answers
726 views

What's the relation between output voltage and time to boil water given the same kettle?

An electric kettle rated 220V, 2000W needed 10 minutes to boil water when it is half filled with water in Singapore where the output voltage is 220V. Estimate the amount of time needed to do the same ...
-1
votes
1answer
19 views

Why do proportionality constants come on only one side?

We know that voltage is directly proportional to current. Then if we change proportionality to equality, we get $V=IR$. Why not $I=RV$??
1
vote
2answers
4k views

How can be the neutral wire at 0 volts when current flowing through it?

Voltage is potential difference, and current flows because of voltage. So if the voltage is zero, how can current flow through the neutral wire.
0
votes
1answer
26 views

How SPAD work over Break Down voltage?

SPAD (Single Photon Avalanche Detector) works beyond Breakdown Voltage which is mentioned as Geiger Mode. But how this actually working. When bias voltage aceede breakdown voltage, generally high ...
0
votes
1answer
122 views

How is a variable potential divider able to reduce current/voltage through a component to zero, unlike a variable resistor?

For example, the diagram in my text book shows a filament lamp, in series with a uniform resistive wire, which can have its voltage and current varied by moving the sliding contact, e.g., a ...
1
vote
1answer
158 views

Spherical magnet inside a solenoid

When passing a bar magnet through a long solenoid why is it that the induced emf when the magnet is in the middle of the solenoid is zero? And if a spherical magnet is put inside the solenoid, will ...
1
vote
1answer
26 views

Electrical gradient

I'm a zoology minor and I'm trying to understand electrical gradient. I found this explanation in an authentic website but cannot undertand it fully. An unequal distribution of charges across the ...
1
vote
3answers
166 views

How does voltage divided by EMF show efficiency?

I get that electromotoric force (emf) is energy per coulomb supplied and that voltage is energy per coulomb used but I don't get what it means when we say that the voltage divided by the emf gives the ...
1
vote
1answer
81 views

What is the current in a circuit with two voltage sources in series? [closed]

What happens? We have 2 voltage sources and 2 currents. When I2 and I3 come together (they have opposite sides), what happens? I tried writing down the voltage relations but I'm stuck because I don't ...
1
vote
5answers
13k views

Relation between Power, Voltage and Current when one or more of them is amplified?

$$\text{Power}(P) = \text{Voltage}(V) \cdot \text{Current}(I)$$ If voltage or current is amplified or multiplied what happens to power and current. Does this affect in increase or decrease in power ...
-2
votes
1answer
49 views

Why does there have to be an electric field if there is potential difference?

I read in a few books that there is always an electric field if there is an electric potential. I went through this but the question on this page only states that there is an electric field and it is ...
-1
votes
1answer
38 views

How does voltage produce current?

I am studying electric current and i dont understand how does voltage(potential difference )produce current? PS : I am a 10th grade student so please avoid complicated terminologies.
-1
votes
1answer
33 views

Solar cell efficiency

What is the relation between open circuit voltage and efficiency of the solar cell? Let say that I include the graph of Voc and efficiency in my result. How to relate them both? Thanks :)
1
vote
2answers
163 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
0
votes
1answer
199 views

Current and Resistance-Effects of the Length of the Wire

Two wires of the same material are both connected to a 9-V ideal battery. They have the same cross section area but wire 2 is twice longer than wire 1. Compare the following quantities by answering if ...
1
vote
2answers
354 views

Which power equation to use: $P = I^2 * R$ or $P = V^2 / R$?

Given are ideal max voltage $V = 200\;\mathrm{V}$ and max current $I = 5\;\mathrm{A}$. Therefore: ideal resistance is $$R = \frac VI = \frac{200 \;\mathrm{V}}{5\;\mathrm{A}} = 40 \;\mathrm{\Omega}$$...
0
votes
4answers
246 views

Transformers and DC voltage

Ok, if I have a transformer with 100 coils of the primary and 200 coils on the secondary and I connect a 9 volt battery to the primary, how many volts should I expect from the secondary coil? I know ...
1
vote
2answers
176 views

The Zero Electric Potential of the “Earth”

I know its the potential differences that matter and generally we define the zero of the electric potential according to our convenience. I would like you to look at this standard problem: Charge $-...
0
votes
1answer
15 views

Relyance of plate distance on the capacitor equation

I am studying capacitors and i cannot seem to understand why the increase/ decrease in voltage and distance between the plates would affect the capacitor's abillity to store charge. Can anyone help??
3
votes
1answer
124 views

What does a voltmeter actually measure?

For time varying fields (even quasistatic ones) the electric field is given by $${\bf E} = - \nabla \Phi - \frac{\partial {\bf A}}{\partial t}$$ So what does a voltmeter measure? Does it measure a ...
0
votes
1answer
153 views

Why is current shared in a parallel circuit but not a series circuit?

Electricity test coming up. It's not clear to me why current is shared in a parallel circuit but not a series circuit.
1
vote
2answers
340 views

Why is the voltage output equal to the voltage drop?

I have a very basic question about measurement of voltage output on some simple circuits. Considering the circuits of the figure: Supposing one wants to measure the voltage output $V_2$, on the ...
1
vote
1answer
34 views

Is it possible to determine how many electrons there are in a plate from its voltage?

We've just stared doing voltage in school, and so I wondered if this is possible :) If I charge an insulated metal plate using an EHT to something like 5kV, then I've added electrons to the plate. My ...
-1
votes
2answers
28 views

AC circuit having a capacitor

Consider a parallel plate capacitor connected to an AC. The current in the circuit leads the emf by $\pi /2$. My question is, what does it mean that the current lead the emf by $\pi/2$? Does it ...
1
vote
1answer
34 views

Ohm's law deviation

In terms of superconductivities and diodes (I do not know anything else except these), Ohm's law deviate from a linear relation. I search many titles or tags for this but I did not understand properly ...
0
votes
3answers
49 views

EMF or terminal voltage?

I have a doubt that is: What does this statement mean: "a 6 V battery". Does this mean that the EMF of the battery is 6 V or the terminal voltage of the battery is 6 V? If the battery has internal ...
0
votes
2answers
54 views

Why don't capacitor charging graphs look like other exponential growth graphs?

Sorry if this question is stupid, but I can't find any answers for this online. Physics websites show that capacitors charge and discharge exponentially. The discharging graphs of charge against time ...
0
votes
4answers
41 views

Light bulbs in Series

In physics we were learning about how in series the current is the same through each resistor. So that the lightbulbs will all have the same brightness but dimmer than if there was just one bulb on ...
0
votes
0answers
26 views

Charge Magnitude Based on Isoline Spacing

Suppose we have two positive charges of unknown magnitudes. We are given the isoline map (the equipotential lines) for the two-charge system. One has isolines more "squashed together" (more closely ...
0
votes
1answer
29 views

If a battery is open on one end but connected on the other, does it raise the potential on the connected end?

If a battery has one end open and other end connected to a circuit will the battery increase the potential at the point of connection?
2
votes
1answer
80 views

What do the batteries actually do to the electrons?

I am plagued by this simple question that what force exactly causes the motion of an electron in the middle of a lattice of electrons of a wire? a. Is it an electric field created inside a wire due to ...
1
vote
2answers
119 views

Why does internal resistance increase as current decreases?

Our class conducted and experiment to investigate internal resistance and terminal pd, using a cell, fixed resistor and variable resistor. The results were as follows: As the resistance of the ...
1
vote
4answers
240 views

Voltage - Energy drop

I'm having a hard time understanding the nature of voltage and am hoping you guys can help. The main issue is the concept of the voltage drop. Take the following circuits : In regard to the first, ...
-1
votes
2answers
75 views

How do we get 25kV at power stations? [closed]

Could anyone tell how we get a potential difference of 25000v at power stations? Is it due to the number of electrons present or the speed of the turbine or the large induced emf generated by the ...
1
vote
0answers
19 views