# Tag Info

12

If, say, 3 charges enter each second then also 3 charges must leave each second for a steady state current. If more leave than enter each second, then where would the extra leaving charges come from? This is not possible. If fewer leave than enter each second, then some charges are staying behind within the conductor. Over time the net charge in the ...

10

I believe your question is about how a current can remain constant after passing through a conductor. The water analogy introduced by Roger Vadim reminds me of another explanation. A kid asks HC Verma, a renowned Indian physicist, Why does current not decrease on passing through a resistance. HC Verma's explanation is in some sense a "Proof by ...

8

I think your question seems to imply that you think that charges at one end of the wire are "fired" through the wire with some initial kinetic energy and and the resistance slows it down. The electric field inside a wire is constant so at each point in the wire charges experience a force Eq the resistive forces inside the wire are proportional to ...

8

I was wondering about this as well. This is not an answer, but reasons why I am confused about the video. Veritasium made the point that electrons in a wire do not carry energy around the circuit. The energy is carried by the electric and magnetic fields generated by currents in the wire. So when these fields reach the light bulb, energy has been transported ...

7

No one who knows what they're talking about would ever say "1/c seconds". A commenter called this a minor thing, but I would call it a useful shibboleth. It's a sign that the writer of the video isn't exactly playing fourth-dimensional chess, and a sophisticated analysis of their claim probably isn't necessary. Another sign that he may not be not ...

4

The charge conservation (often expressed by the continuity equation, $\partial_t\rho + \nabla\cdot\mathbf{j}=0$ means that, the difference between the charge entering the conductor and the charge exiting it, is accumulated as charge within this conductor. So in your scenario, the charge of the conductor should grow to infinity. What is misleading here is ...

4

When you abruptly turn on a voltage source $V$, the leading edge of a voltage step function propagates out into the wires either direction ($V/2$ from one side, $-V/2$ from the other) at the effective speed of light. This effective speed is determined by things like the geometry of the wire/waveguide and the permittivity and permeability of the surrounding ...

3

Copper at room temperature is a lattice of positive copper ions whose positions are relatively fixed, superimposed with a gas of conduction electrons. The conduction electrons have motion in random directions, with typical kinetic energy \begin{align} \frac12 mv^2 &\approx kT \approx 25\,\mathrm{meV} \text{ (at room temperature)} \\ \frac{v^2}{c^2} &...

2

It is my understanding that an electrical current (electromagnetic waves) moving inside of an electrical conductor, such as a copper wire, typically travels at about 1/100th of the speed of light. Your understanding is incorrect. First, an electric current is not an electromagnetic wave. Electric currents are movements of charged particles. Electric current ...

2

Will electric field change ? Yes If yes then why Because you kept the potential the difference the same but increase the distance over which it is dropped. electric field is produced by the battery having some potential difference, it is only related to the battery i.e. $\Delta V = -\int \vec E.d\vec r$ or $E = -\frac{\Delta V}{\Delta r}$ $\Delta r$ ...

2

Electrons are not billiard balls. They are not isolated particles bouncing around in the wire. They interact with one another via electrostatic forces. If you put two electrons in an area, they repel each other. If you push electrons into a conductor (from a battery) without letting them out, the electrostatic forces will push the electrons apart. This ...

1

This is simple, and done all the time in high-powered vacuum tube circuits (audio amplifiers and RF amplifiers). You obtain a step-up transformer which takes the mains voltage up to a high voltage, send it through a diode rectifier, and then filter the resulting pulsating DC to obtain a smooth, constant high voltage DC source. All the components needed to ...

1

Electrons are accelerated by electric fields. But the story of what happens in a wire is a little bit more complicated. Electrons have thermal energy, and the free electrons in a conductor are moving randomly quite rapidly. At room temperature, electrons are moving somewhere on the order of 10^5 meters/sec. By comparison, the speed of light is about 3 x 10^8 ...

1

The way I understand voltage vs current is that voltage is the potential energy (or force) of the current. The voltage $V$, or potential difference, between two points is the work required per unit charge to move the charge between the two points. It is the potential energy per unit charge, not the total potential energy or force of the current. And the ...

1

If kinetic energy increase then the current must be increase . . . . is not true. You can think of the free (mobile) electrons as having two types of motion. A random component due to their thermal energy and a directed component, often called the drift velocity, produced by the electric field and hence the flow of charges (current). Increasing the ...

1

You're forgetting that there is a driving force behind the current - in a steady state, the force causing the motion of (e.g.) electrons must be the same as the force that resists their motion. This force is related to the charge. If an individual electron were to slow down, it would get closer to the other like charges, increasing the force that repels them ...

1

Bead Necklace This idea of charges going into a resistor moving faster than charges going out makes sense if the pool of incoming charges and outgoing charges aren't directly connected...like a river flowing into a narrow channel, which then drains into the ocean. This would be like charge from a cloud traveling through the air to the ground in a lightning ...

1

One part of an electrical circuit can influence another mainly in two ways: The first part influences the local current or voltage, and this influence propagates along the wires to the second part. The first part influences the local electric and magnetic field around the wires, and this influences propagates outwards through the space around the circuit, ...

1

There are three stages: Before the switch is closed, the circuit is inert. Under a charitable interpretation of Veritasium's simplifying assumptions, there's no residual currents or stray electromagnetic fields interfering with the setup, the wire is a superconductor, and the bulb is hyperefficient (i.e. it will "turn on" as soon as any current ...

1

Microwave ovens use a magnetron that produces the microwaves, that inside the oven create standing waves. Because of this, there exists points of constructive and destructive interference. So this means there will be hot regions and cooler regions inside the oven. What the turntable does then is allow whatever is being cooked to rotate so that the whole ...

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