Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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Does the Internal magnetic field inside of a current carrying conductor experience Lorentz force?
According to the most depictions of a Lorentz force I've found, Outer magnetic field of a wire reinforces the external magnetic field on the other side, and weakens it on the other, so the conductor ...
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1answer
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Will a generator turn a lamp on in open circuit if the lamp is connected to the earth which is greedy for electrons?
Consider the following thought experiment.
One end of a lamp is connected to one terminal of a power generator. The other end of the lamp is connected to the ground via a metal copper as follows. ...
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2answers
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Electromagnetic field around a conductor with current
According to this video https://www.youtube.com/watch?v=bHIhgxav9LY I have a question: If the glowing of a light bulb is the result of energy supplied from the electromagnetic field around a conductor,...
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2answers
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How do I find the current density vector in an electromagnet that has a time-varying current?
I know that the current $I$ is a scalar quantity, and to calculate current density $J$ , the cross sectional area $A$ is needed, to give us $J = IA$ .
$J$ also has other relations involving ...
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How do I make 500-1000 kV dc voltage? [closed]
I found some inverters that turn 9v into 1,000,000 volts ac, but I need something that turns 9v dc into 1,000,000 volts dc. Is there anything that makes 1,000 kV dc>
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4answers
357 views
What good reason to hang long cable carrying electric current high above the ground? [closed]
Assume no flooding or other natural disasters to damage the cable if it is laid beneath the ground, then what good reason for them to be suspended high above the ground? The cables are insulated and ...
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Creating an electric field
I'm trying really hard to finish making a Van de Graaff generator because I need an electric field to do a demonstration. I'm hoping it generates 500,000 volts. But I found some high volt generators ...
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1answer
40 views
Huge current flows when there is no resistance, consequently, the potential difference is 0 but no current flows if no cell is added to the circuit
If $R= 0$ , $V= 0$ and $I=$ $max$ (i.e. charges are flowing at a huge rate), but when there is no potential difference applied to a circuit, charges don't flow. That means huge current flows when ...
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Is potential difference required only to overcome resistance in a conductor?
In free space, a potential difference is required for the flow of a charge though there is no resistance. In a conductor, a potential difference is required only to overcome the resistance, am I right?...
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Current and voltage in series combination of resistors
In a series combination of resistors , current through each resistors is same but, how is it possible for current to be same if all the resistors have different resistance . the current has to apply ...
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28 views
Electrostatic attraction to electric circuit
Imagine a circuit with a $1$ $kV$ battery hooked up to a $100$ $k$$\Omega $ resistor. Let's also say I had a packing peanut with an overabundance of electrons, so it is negatively charged. Would this ...
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Efficiency of electric heaters
I was reading this question. A person was asking what is the efficiency of an electric heater, and to sum up, people were answering "All resistive heating, can be considered to have 100% ...
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What is the electric potential of a particle when it is initially released in a cyclotron?
Lets assume a positively charged particle in a cyclotron. When released it will move to a dee. Hence, does it move to an area of higher electric potential or lower electric potential?
In my ...
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4answers
271 views
Alternate explanation for energy flow in electricity as explained in this video
The question is about this video from a youtube channel called Veritasium. It is a popular physics/math youtube channel and topics discussed are usually fact checked and accurate.
The gist of the ...
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Capacitors with plates of opposite polarity connected at some voltage
Halliday/Resnick/Krane Vol. 2 contains the following problem: "A variable, air-filled capacitor of the type used in tuning radios is shown. Alternate plates are connected together, one group ...
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1answer
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How to solve the Biot-Savart Law?
I've currently trying to learn electromagnetism in depth and I tried to solve the Biot-Savart law, for a magnetic field generated by a current.
$$
\vec{B} = \frac{\mu_0}{4 \pi} \int{\frac{I \; \hat{r} ...
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4answers
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Are the "bird sitting on a live wire" answers wrong?
Long ago, my high school teacher wrote the popular question on board,
"Why doesn't a bird sitting on a live wire get electrocuted?"
He gave us four options (I don't remember all of them) ...
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1answer
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Asking for proof for total voltage is equal to the sum of the voltages of the resistors (connected at series pattern) [closed]
Recently I was taught that when a set of resistors are connected as a series pattern the total voltage of the resistors is equal to the sum of the voltages of each resistor. I know how to prove this ...
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3answers
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I have trouble understanding why two different capacitors should have the same amount of charge on each side of a circuit
There is a rhombus with four different capacitors. There's a voltage between the point $a$ and the point $b$, but there is no voltage between the point $c$ and the point $d$. Apparently, assuming that ...
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0answers
17 views
Motion of electric charge as seen from non inertial frame of reference [closed]
Consider a charge Q resting at point A . If the observer watch the charge from non inertial frame of reference, will that charge acquire kinetic charge from the perspective of the non inertial ...
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4answers
75 views
Why is current = 0 in open circuit?
This is an open circuit. Now , a chemical reaction happens in the cell which makes the current to flow in the wire. Then , the current has no other place to go , so it just gets grounded. It is ...
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Will an induced electric field reduce the reaction time between two substances?
I've built a Van de Graaff generator that can generate 500,000 volts. When I tried pushing co2 from a tank into a flask of sodium hydroxide solution, it took approximately 3 minutes before the co2 and ...
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Is the terminal voltage twice the EMF when the battery is being charged and short circuited?
So, I know V terminal= E- Ir during discharging of a battery. 'E' is the EMF, 'r' is internal resistance of the battery and 'I' is current.
If the battery is short circuited, 'I' becomes = E/r because ...
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2answers
71 views
Does any time dilation take place within an electrical conductor when electricity is flowing through it?
I am curious to know if any time dilation takes place within an electrical conductor when electricity is flowing through it.
It is my understanding that an electrical current (electromagnetic waves) ...
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Does the height of a Van de Graaff generator matter?
I'm interested in building a van de Graaff generator as a science project, but when I found some websites that showed how to make one, the height of the housing pipe was tall. If I reduce the height ...
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2answers
169 views
Magnetising a needle with static electricity using silk cloth
A nautical navigation textbook on my table says that we can magnetise a non-magnetised needle by rubbing it with a silk cloth. I decided to cross check on the internet, and found some experts calling ...
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1answer
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Load of a device in circuit
This question is based on the answer in my previous question:
Current vs voltage in high voltage transmission lines
Suppose we have a system that consists of a primary circuit and secondary circuit, ...
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2answers
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Can you please help me understand how Electric Potential and Electric Potential Energy work?
Considering the image we observe the following:
$r_A<r_B \Rightarrow \frac{1}{r_B}<\frac{1}{r_A} \Rightarrow \frac{K(+Q)}{r_B}<\frac{K(+Q)}{r_A}$ (if $0<Q$) and thus
$$\frac{K(+Q)}{r_B}=V(...
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2answers
23 views
Force on a current-carrying loop due to a uniform electric field
Why does a closed current carrying coil experience no force when placed in a uniform electric field, whereas a charge moving with constant velocity through a uniform electric field does?
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1answer
54 views
Definition of Power in electrical terms
The following definition of power is given in Engineering Circuit Analysis by Hayt, Kemmerly and Durbin, 8th edition
Also, as they say that they have already defined power, their earlier definition ...
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1answer
32 views
How do I find the electric field at the middle point in a thin long strip whose cross section is a semicircle?
A thin long strip whose cross-section is a semicircle carries a uniform surface charge of density s on
its inner surface. Find the electric field at a point O located midway on its axis.
Link of ...
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The relationship between impedance, resistance and resistivity and which are purely material properties
The resistivity of a wire, $\rho$, is purely a material property. For a wire of length, $l$, and cross-sectional area, $A$, the resistance, $R$, is given by
$$
R=\frac{\rho l}{A}
$$
which depends on ...
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24 views
Why the lightening flash happens from the ground up?
In a cloud-to-ground lightening, once a step leader meets a positive streamer, there is an electric discharge from the cloud to the ground. I understand that we can't see the electrons moving ...
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1answer
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Running electrolysis on inside surface of a tube
I use electrolysis for rust removal and electroplating. I notice that when one of the electrodes is a closed tube or has other topological holes with a sufficiently large height:diameter ratio, the ...
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What is the Lorentz force due to a single point charge?
The Biot-Savart law as applied to a single point charge is described to be:
as retrieved from here.
Now we consider the following system of 2 similar charged particles:
By this definition, the B ...
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1answer
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Is there a theoretical efficiency limit for thermoelectric generators?
Typical Thermoelectric/Seebeck generators operate at 5-8% efficiency.
Is there an upper limit to the conversion of heat flux (temperature differences) directly into electrical energy?
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1answer
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Ebonite rod charged with fur is brought together with an acetate rod charged with silk
What would happen if an ebonite rod charged with fur is brought together with an acetate rod charged with silk?
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Anyone know what this physics lab equipment, found in the storage room, are? A resistivity kit or an optic bench? Any ideas? No identifying brand seen
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These equipment were found in the physics storage room. Unsure of how old they are or of their usage. They might be part of a resistivity kit or some sort of optic bench. Any ...
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Definition about Electric potential
Hello I have a question:
Question
It is often said that if a point A has a potential
higher than a point B, then A has a positive potential and
B a negative potential.
Is it forcibly concluded that a ...
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1answer
30 views
How to calculate current given voltage sources, resistors, and current direction [closed]
I am self-studying circuit analysis, and got the following question incorrect.
I thought the answer was (a) since I know current is equal to voltage divided by resistance. I summed the resistors ...
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1answer
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Is electric potential gradient a scalar or vector quantity?
It's an image from my textbook where it's written that EPG is scalar but at some sites I read that it is vector.
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Random Walk of Thermal Electrons
The drift velocity of electrons in a typical electronic circuit might be measured in mm per second. In contrast, the thermal velocity of electrons is in the vicinity of km per second.
Because of the ...
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5answers
873 views
Why does a comb rubbed through hair not attract paper if it's been left alone for some time?
In childhood we did an activity with a comb and paper pieces to understand electrostatic force. I noticed that after rubbing the comb in hair it attracts paper pieces very well, but when trying again ...
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1answer
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How does a resitance affect electric current in a circuit...??(series)
Consider the following circuit:
Let the resistance of the lamp be $R_1$, and the potential difference across it be $V$. Let the current that flows through the circuit be $I$ in this situation. Say you ...
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3answers
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What is the resistance of an (an ideal) ohmmeter?
For the sake of expirementing, as far as I have tested (with simulators online) connecting an ohmmeter in parallel with the single component in a closed circuit with a generator short circuits, ...
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Why do we reduce only current to prevent power loss? Why not voltage?
In power transmission lines current is kept low and voltage is kept high to reduce the power loss. This is because $P = I^{2}R$ and $P = VI$. In order to reduce power loss we have to reduce $I$ since $...
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1answer
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Energy of each electron in a lightning bolt
I have read that lightning bolts have a difference of potential of 300 Mega Volts. Does it mean that the electrons in the cloud have an energy of 300MeV each? I found that astonishing since that ...
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2answers
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Electric current and potential difference
I have lots of doubts regarding electrical energy, electric current and voltage. I have tried to understand as much I can but every time I try to completely clear my concept, I encounter a dilemma! So ...
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1answer
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How can we take dielectric medium kept between the capacitor plates as capacitors in series and solve for effective capacitance?
My book says that the charge induced on the dielectric slab kept between the parallel plates is given Qp=Q(1-1/K) where K is the dielectric constant and Q is the charge on the capacitor.
I have seen ...
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1answer
47 views
Potential difference between two hollow spheres and amount of current flow
If two Hollow Spheres with radius $r_1$ and $r_2$ have charge $q_1$ and $-q_2$ in them respectively(charges are evenly distributed in the surfaces).The spheres are separated by a distance d .Now We ...
