# Tag Info

12

Because of electromagnetic forces, all of the electrons in the wire are displaced towards A with a certain velocity causing a positive current towards B. The electrons have a small drift velocity, not moving much. Although your light turns on very quickly when you flip the switch, and you find it impossible to flip off the light and get in bed ...

10

As the other answers point out, there are a vast number of electrons in a piece of wire, and no single electron must traverse the whole circuit for a current to flow. You can think of an ac current as more of a sea of electrons sloshing back and forth. I'll focus on your second question: How would the electron flow in DC circuits work if a bulb and a ...

5

Specially if length of the wire was large, say 3 * 10^8 meters, then would the movement of electrons on one end of the wire be "in sync" with movement of electrons on the other end? No, they wouldn't and this fact is crucial for understanding antenna operation. Note that even short conductors become electrically long if the frequency is high ...

5

Metals are good conductors of electricity because the outer (valence) electrons of the metal atoms are only loosely bound to the nucleus and form molecular orbitals known as the conduction band. Electrons can move more or less freely through the conduction band and so metals conduct electricity generally well. When a metal is chemically oxidised its outer ...

5

The electrons from the battery are not in the ends of the wires, no. The wires do contain electrons, however. Conductors have free electrons which can "float" around in the metal. There is an electric field between the two terminals of the battery. The electrons experience a force due to this field. When the wire is not connected, the electrons don't go ...

4

By capacitor charge is meant the absolute value of the charge on each capacitor plate: $\mid Q \mid$. If the battery generates the potential difference $V$ and you connect the capacitor to the battery through a conducting wire, as shown in your picture, once the equilibrium is reached each plate of the capacitor will have a charge $Q = CV$, where $C$ is ...

3

Any wire circuit will have inductance and capacitance between the "outbound" and "return" wires - this immediately follows from very basic laws of physics, and in fact is intimately related to the finite propagation velocity of the electrical signal. The expression $$u=\frac{1}{\sqrt{LC}}$$ would give an infinite velocity if either $L$ or $C$ was zero... ...

2

Lets do the arithmetic, as suggested by Energizer777 $$R= \frac{\rho L}{A}$$ $$\rho_{copper} = 10^{-8} \Omega m$$ $$\rho_{glass} = 10^{11} \Omega m$$ How wide a piece of glass would I need to have resistance (per meter length) equal to a very fine copper wire with a radius of 0.1 mm? The area of my copper wire is $\pi r^2 = 3.14 \times 10^{-8} m^2$ The ...

2

Sorry for a low-tech explanation. It is like a metal pipe filled with water. If you put more water in one end, it (almost) immediately comes out the other end, because the pipe cannot expand, so some water has to come out to make room for the water that goes in. When I say (almost) immediately, it depends on the speed of sound in water. It requires a ...

2

As long as you provide a power source to a circuit, whether it is closed or not, electrons will definitely begin to move to a small amount. There are two specific cases which I think would best demonstrate this point. Case 1: A circuit with a capacitor. A simple capacitor contains two electrically conducting plates separated by an insulator, which could ...

2

Let's think about the circuit you drew. It contains a battery, switch, bulb, and a very large inductor. In fact, the inductance of a wire that goes 10 times around the Earth can be calculated (I am going to assume an air core - in fact there is a piece of iron in the middle of the Earth which makes the resulting inductance greater). $$L\approx N^2 R \mu_0 ... 2 You can determine the charge of an electron from a static measurement in one frame. Another frame could determine the charge of an electron from a static measurement in their frame. And they might agree or disagree. We postulate they agree, but we had three options: We could postulate that whether or not something is an electron depends on your frame ... 1 "The frequency doesn't change" is only true when the core is perfectly linear. For a real transformer, there will be some nonlinear effects (saturation) meaning that the sinusoidal input waveform will create harmonics in the output - second harmonics and higher frequencies will appear. But if you ignore those, then the flux change will vary sinusoidally at ... 1 Two questions: How can the ammeter tell how much current is flowing the resistor? since it's "behind" the resistor? There at least several means that current can be measured using different technologies. The early ammeters used galvanometric technology where a coil in the galvanometer becomes part of the current path. The coil generates a magnetic ... 1 Why and how does a resistor limit the current flowing through the entire circuit? doesn't it limit only the current that is flowing past and after the resistor? First, this is a DC circuit (ignoring the switch) which is to say that the circuit voltages and currents are constant with time. Since that is the case, by conservation of electric charge, ... 1 If you are comparing two voltages with identical currents, you cannot be talking about the same bulb in both cases. This means that you are comparing two different bulbs, and there is no way to tell which will be brighter, since different bulbs can be designed for different luminous efficacy, which is light per unit power. For instance, a bulb can be ... 1 It is due to the electric field that is set up that will cause the electrons to move. The drift velocity of the electrons is much slower. There will be a delay in switching on the bulb, and it is equal to approximately l/c, l being the length of the wire. Your diagram is not exactly right, as it shows as if the electrons are being produced at one end and ... 1 Think of AC as something that starts out as a positive DC voltage. Then it starts going in the opposite direction. Then back again. And continues doing that over and over. Then smooth the current change out and make it sinusoidal. Now you have AC. 1 Its because of the fact that we are touching the Earth, so we have the same potential as the Earth. Without a human in the vicinity of a "patch" on Earth, all we have are equipotential lines of 226V per meter by your estimation. When a human arrives at that place, because of the fact that the Earth tends to make us have the same potential with it(it can ... 1 There is an error in your multiplication.$$ (9 \times 10^{9})(20 \times 10^{-9}) \neq 90\times20  (9 \times 10^{9})(20 \times 10^{-9}) = (9\times20)\times10^{0} = 9\times20 =180  This means that your answer is off by a factor of 10. Without the error your answer should be 3kV.

1

When the system reaches steady-state condition(things do not change with respect to time), then we have the same electric field inside the circuit. Before reaching the steady-state condition, then yes, the forces exerted on the electrons(or voltage difference between some points) is not the same at every point in the circuit. But, as Griffiths puts it in his ...

1

Because no charge is accumulated at any point anywhere when you have a steady current! If water is flowing in a pipe, you maybe have 1 cubic meter passing every second. Every part of the pipe system MUST get $1\;\mathrm{m^3}$ in every second and MUST also send $1\;\mathrm{m^3}$ out every second. If not - if for example more enters than what leaves every ...

1

9v batteries are made from 6 small 1.5v cells connected in series. So it has a very high internal resistance which limits how much current you can draw from one (and why they aren't used in high power devices) The resistance of your tongue is complicated, depends on how wet it is and the resistance changes as the current causes chemical changes. So you ...

1

1 amp current means 1 coloumb charge per second flows through the circuit. (1/1.6*10^-19) gives the electrons flowing through a point /second The above value * the total time (3600 seconds ) will give you the answer.

1

(1) The voltage across a capacitor is proportional to the charge $Q$ (where it is understood that there is $+Q$ charge on one plate and $-Q$ charge on the other plate). (2) The voltage across the capacitor is initially zero so the $Q$ is initially zero. (3) The voltage across the battery is not zero so, if the battery and capacitor are connected together, ...

1

Here's a surefire solution: Get one of these, and fasten it to something conducting on the treadmill and around your wrist. If you mind the cord very much, there are cordless one that work by ionizing the air. However, most ESD wriststraps advertised as "cordless" are a complete sham, so buyers beware. You can order one and open it up. If it has a piece of ...

1

There are two velocities to consider here. Firstly there is the velocity of propagation of the electromagnetic wave. As soon as you get a force on the first row of electrons on the cable, their displacement will create a force on the second row and so on. This chain reaction travels at the speed comparable with the speed of light (between 0.42c and 0.72c) ...

1

The short and simple answer is that railguns utilize a version of the Lorentz force with the term $\mathbf{j} \times \mathbf{B}$ as the main driver. They then take advantage of Faraday's law when a paramagnetic material like aluminium is exposed to a rapidly changing magnetic flux so that the $\mathbf{j} \times \mathbf{B}$-term can impart an impulse on the ...

1

It sounds as though you're on the right track: if I understand correctly, you're saying that once you have found the voltage across the pair $R_1 and R_4$ (equal to the voltage across $R_2$ and $R_3$), presumably by lumping $R_1,\,R_2\,R_3\,R_4$ together through parallel addition of $R_1 +R_4$ and $R_2+R_3$, then you simply work out $V_o$ thinking of ...

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