Questions tagged [voltage]
Voltage is the unit of measurement for electronic potential, from one point location to another.
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How can an electric field between two parallel plates be constant
How can electric field in general and more specifically between two parallel plates be constant, if E depends on distance, how can the electric field be constant. The equation deltaV=Ed, should E not ...
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2answers
30 views
Understanding the potential difference of a wire
I'm trying to understand the fundamentals of potential difference in circuits.
My understandings (from textbook and stackExchange):
Potential difference is created by a separation of charges.
A ...
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0answers
19 views
Photoelectric effect wow
The effect of electric potential on the threshold frequency in the Lenard's photoelectric experiment
I have been taught that electrons can ejected from the atom by applying strong electric field(...
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2answers
42 views
Electric field and potential [duplicate]
Suppose we consider a point dipole i.e. an ideal dipole. At the origin the potential:
$$ \phi(\mathbf r) = \frac{1}{4\pi\epsilon_0} \frac{\mathbf p\cdot\hat{\mathbf r}}{r^2}$$
is undefined due to ...
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1answer
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Method of Images conundrum
My lecturer and I have found separately valid solutions to Poisson's equation in the region of interest for the following problem:
Here is my interpretation of the boundary conditions:
$$V(x,y,z \to ...
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1answer
25 views
Combining two power sources to get voltage from one and current from another
For a project, I have to make a battery that output 5 V, 500 mA. However, each one of my cells can only produce 1 V, 80 mA. I can combine these cells in series and parallel to get the required ...
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0answers
44 views
Why does current not increase when the voltage increases in this case? [migrated]
When talking about BJT transistors, a very common graph is the one shown below, that plots (VCE,IC) as an ascending function. As far as I know, the BJT manages VCE so that IC is beta times IB, being
...
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0answers
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Safe amperage and voltage for humans [closed]
What are safe amperage and voltage for a human-being? Starting from what amperage and voltage can we feel? I want to make a trap for thief, but I do not want to injure him
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2answers
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What the voltage, electric field, and potential energy in the center of grounded concentric conductor spheres? [closed]
the a shell is charged with 120v
while the surfaces of b is grounded
What is the voltage in the center of shells (vo)?
The electric field in the center of shells?
The potential energy in the center ...
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3answers
76 views
Summing up very basic terms in basic electricity [closed]
My attempt to define following terms as per my understanding. I am currently at high school.
Electromotive force (EMF): Potential between two terminals when open circuited.
Wikipedia's ...
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4answers
80 views
What remains the same: voltage, current or resistance? [closed]
A current 1 ampere passed through a conductor which resistance is 10 ohms, if the current become 2 amperes, then will the resistance of the conductor will remain 10 ohms, and if not, then what is the ...
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2answers
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Potential in open branch of a parallel circuit with grounding [closed]
If the switch is still open, what will the electric potential at Q be, i.e. negative, positive or zero?
Is there a potential difference across the grounded point and point Q, or R3, even though the ...
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8answers
1k views
Does Ohm's law $V = IR$ mean voltage causes current, or does it just say that voltage and current are related?
I have read that Ohm's law, $V=IR ,$ just means that $V$ is equivalent to $IR ,$ not that voltage is the cause of current.
This is similar to the interpretation of Newton's second law, $\mathbf{F} = ...
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3answers
64 views
Can anyone tell me why the answer to this question is D? [closed]
I think the current will go through earth wire but my physics teacher told us the current will continue to flow through the circuit.
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2answers
31 views
Empty and fresh battery in series
If you have 2 (e.g. 1.5V) batteries in series and one is dead/empty, what is the reason why a device is not working? Lack of voltage (1.5 + 0 is simply not enough for the device to operate)? From my ...
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1answer
48 views
Why isn't electric potential infinite?
In my textbook, I've read that electric potential is the work performed to carry one unit of positive charge to electric field from infinite distance.
We know that, W = Fs
So here the distance is ...
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2answers
34 views
Potential drop in slide wire (Potentiometer Experiment)
While doing the potentiometer experiment I was taught that the galvanometer will show opposite deflection on opposite ends of the slide wire.
My questions are as follows:
Why does this happen?
In ...
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2answers
331 views
When the voltage is increased does the speed of electrons increase or does the electron density increase?
I am just a high school student trying to self study, please excuse me if this question sounds silly to you.
I know that current is a product of the speed of electrons and the electron density.When ...
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1answer
41 views
How does a load/resistor affects a Transformer?
If a resistor is connected on the secondary let's say 2 Ohms, this would have an overall effect on the primary & secondary circuit of a Transformer. It is obvious that the resistor would affect ...
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4answers
68 views
Why isn't there any current in the Primary if Secondary circuit is opened in a Transformer?
Assume an ideal transformer, with no load/resistor attached on the Secondary (Open Circuit), it is said that the Primary would act as if it is an open circuit too, thus no current flows through the ...
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1answer
48 views
How do we know how much charge is in an object?
It's a little science history question but I really wonder how did peoples measured the amount of charge in an ball or something or like in coulombs case how did he measured the electrical force ...
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2answers
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Why did a 12V battery affect my motor more than two 9v batteries in series?
In class, we made a coil of wire and used it to make a simple electric motor with a magnet. I put two square 9v batteries in series for a total of 18v to power the motor.
I then used a larger 12v ...
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3answers
63 views
Why is the current same after and before passing through a resistor? [closed]
•Why is the current same after and before passing through the resistor ?
•Why is a voltage drop across the resistor ?
Explanation in terms of electron flow and electric field will be really helpful.
...
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1answer
40 views
Physics of Neuroscience - Action potential
I am confused about how to understand action potential in the context of physics.
Are action potential and potential difference synonymous? If so why is it stated that an action potential 'travels' ...
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4answers
665 views
How does resistance convert voltage to current? [closed]
This is a statement that I read mainly on books about electronics.
Could someone explain why after the resistance current is what makes things work and not voltage?
Example from the Art of ...
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4answers
41 views
Find relationships between the voltage difference across capacitor and resistor
I'm trying to learn kirchhoff's law. but im stuck on how to solve for a circuit that has both a resistor and a capacitor. How would you proceed?
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3answers
53 views
Question about full wave bridge rectifier
Sorry if this is a stupid question, what I know is when a diode is forward biased, it conducts current, when it is reverse biased, it acts as an open branch if its $ PIV \geq V_{in}$
But in this ...
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1answer
56 views
Resistor Capacitor circuits
I am a high school physics teacher and came across some issues today that I am unable to explain.
We made a circuit with an $11$ V power source connected to a $100~k\Omega$ resistor and $100~\mu F$ ...
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1answer
24 views
Why do we subtract the voltage of the resistor from the emf voltage to find the terminal voltage?
I attached an image of a question from homework.
I calculated the current in step 1) and then I calculated the voltage of the resistor. But why do I need to subtract that voltage from the emf voltage ...
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2answers
33 views
Voltage when lamp burns out [closed]
In the question below, shouldn't the voltmeter read zero V because the circuit is broken and there is no current flowing? (the answer in the text is 12v)
0
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1answer
35 views
Why is a specific voltage limit needed to light a bulb in an electric circuit
The battery provides a potential difference between its terminals that allow acceleration of the electrons in the circuit, i.e the potential energy gets converted to kinetic energy, these electrons ...
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1answer
41 views
A voltmeter is connected in parallel across the load. Why? [duplicate]
Voltmeter is connected in parallel across the load. Why?
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2answers
42 views
Equipotential lines around two parallel charged wires
I'm studying electric potential, and I'm trying to follow the derivation of equipotential lines surrounding two parallel, oppositely charged wires, found here. But I feel like the source is skipping a ...
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1answer
34 views
Which law is true at the transformator?
According to Faradays law The changing flux will generate voltage in the secondary winding/circuit, so if the N2 = 2*N1, then the U2 =2*U1, and according to conservation of energy in that case I1 = 2*...
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2answers
94 views
How do voltmeters measure work done over a component?
In my physics class, we were shown the picture below to measure the current and potential difference through a component. We were told that the resistance of the ammeter is as low as possible, and the ...
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4answers
63 views
How can there will be current in purely inductive circuit? [closed]
In a purely inductive circiut there are two emf's one is applied and other is induced
applied emf and induced emf are equal and opposite, then how can there will be current in a purely inductive ...
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1answer
33 views
If voltage across a capacitor GROWS till maximum in finite time then, is it possible that the capacitor also reaches maximum charge in finite time?
When a dc-voltage V is applied to a capacitor C, the charge on it takes infinite time to reach maximum value ...
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3answers
67 views
General Definition of Potential in Circuits with Time-dependent Fields?
Electric potential is a very common observable to measure (especially in electro-engineering fields). It is measured using a multimeter, and thought of as the energy per charge that one charged ...
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6answers
1k views
Does the resistance of the voltmeter affect the behavior of this circuit?
I have this setup.
It consists of a battery of no internal resistance with voltage $V$ and a resistor with resistance $R$. It also consists of a voltmeter of some (not so large) resistance as good ...
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1answer
80 views
Influence of an external electric field on an uncharged capacitor
Influence of an external electric field on an uncharged capacitor.
Fig A shows an uncharged capacitor with no external electrical field. There is no net charge on each of the plates. Since the ...
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1answer
55 views
How do I calculate voltage in a loop antenna?
How do I calculate the effective source voltage applied to the loop by assuming that the loop is perpendicular to the wave magnetic field and that the transmitter transmits the wave evenly in each ...
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2answers
61 views
Car headlight voltage
If I put a higher voltage bulb in my car headlight, what will happen? I haven't tried it yet, but I'm wondering if it would matter. The bulb has the same wattage but a different voltage.
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3answers
57 views
Why would Low Voltage produce HIGH current with the same resistance? Transformers
We always see in Ohm's law that $v=IR $. So if $R$ is fixed for a wire, how can the electrons with High P.D have low current. Isn't it the electrons bumping into the resistor that creates the heat? ...
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2answers
26 views
Wording clarification about the concept of electric potential
So I am struggling with trying to understand what electric potential is and I wondering if this statement is correct based on my readings:
"Electric potential is the electric potential energy a ...
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1answer
23 views
Uncertainty estimation of a quantity after its calibration
I have to calibrate power output of a diode to its input voltage. The voltage source has negligible error but the power meter has significant uncertainty (a couple %). I take a number of power ...
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2answers
32 views
Electrical vs Heating Insulation
Let's say we have a 120V cable and a 600V cable, this means that the 600V needs more electrical insulation to prevent the insulator from exceeding its dielectric strength. But in the other case, the ...
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3answers
53 views
Brightness of lamp
Brightness of lamp (power) depends on two factors:
Current which flows through the lamp.
voltage (p.d) across the lamp.
In the figure:
When the variable resistance increases, what happens to the ...
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1answer
53 views
Voltage between two points in circuit
Calculate the voltage between terminals a and b.
I am confused about a problem. I've tried to solve this using the second Kirchoff's rule, but my solution is equal to 0. What am doing wrong? E=5V R1=...
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1answer
40 views
Calculate the voltage between terminals a and b [closed]
Calculate the voltage between terminals a and b before and after connecting the external resistance R, then calculate absolute and relative difference of these voltages.
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2answers
58 views
Why High Voltage Power Lines need more Insulation than a low one?
"A 400 kV cable requires less insulation than a 240V cable."
This was regarded as False in one of my question papers, but why? Doesn't a higher voltage means, lower current(P=V. I) and a lower ...
