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9

does this mean that Ohm's law just fails in this case Ohm's law is not universal. The ideal resistor circuit element is defined by Ohm's law but not all circuit elements obey Ohm's law; Ohm's law only applies to ohmic devices. Physical resistors and conductors approximately obey Ohm's law but, for example, semiconductor diodes, transistors, ...


9

If there was nothing in the way then an electron leaving the anode of a 4 volt battery would have a kinetic energy of 4 electronvolts by the time it reached the cathode. However the mean free path of electrons in metal wires is exceedingly short so electrons never build up anything like this velocity. The end result is that the electron velocities are ...


5

The term Resistance does not come into play while dealing with Photoelectric Effect. The latter is related to the emission of electrons when the surface of a metal(or any substance) is hit by photon particles(photon is the unit particle making up the light that we talk of). Here the more important concept is that of Work Function, i.e. the minimum amount of ...


4

To be precise, current is a scalar quantity. Although current has a specific direction and magnitude, it does not obey the law of vector addition. Let me show you. Take a look at the above picture. According to Kirchhoff's current law, the sum of the currents entering the junction should be equal to sum of the currents leaving the junction( no charge ...


3

We may say that the average power dissipated in the circuit is as follows: But the equation following that isn't true. In AC circuit analysis, the voltage and current are represented as phasors. Further, $p=v \cdot i$ is the formula for instantaneous power in the time domain. The average power, over some time $T$ in the time domain, is given by ...


2

There is a commonly used analogy for electric circuits called the hydraulic analogy. This imagines the electrons as water and the wires as pipes. The voltage is equivalent to the water pressure and the current is equivalent to the water flow rate. Start with a DC current and imagine the water is doing work by flowing through a water wheel: This is all ...


2

The answer is positive. This is due to the fact that the equations describing how currents generate the field are linear. The solution is obtained by a suitable inverse of the linear operator associating currents to fields. It is fundamental to observe that this inverse operator is linear because the boundary conditions satisfy the superposition principle ...


2

Check out this post over at NASA. It's directed towards kids but it gives a good overview. Most relevantly, "In space, batteries must work in both very hot and very cold conditions. They must withstand a lot of radiation from the Sun. They must work in a vacuum without leaking or blowing up! They must be rugged enough to withstand the severe vibrations ...


2

The reason that you typically think of it as a scalar, is because we confine the current to travelling along one path ( the wire ). This is clearly a special case. Why? Because we have a wire that predefines the path of the electricity for us. For more general situations, we don't assume a particular path, and this lets us apply vector analysis to the ...


2

The confusion is because the $V$ in: $$ W = IVt $$ is the voltage drop across the transmission line not the supply voltage. If the power station generates some high voltage $V_0$, then at your local transformer the voltage will have fallen slightly to $V_1 = V_0 - \Delta V$ due to the resistance of the transmission lines. The voltage drop is: $$ \Delta V ...


2

For starters, when we talk about voltage as energy per unit charge, is this energy manifest simply as the kinetic energy of the electron? Voltage is potential energy per unit charge. An analogy: voltage is to charge as altitude (as on the surface of Earth) is to mass. So if you lift a 1kg rock off the ground by a height of 1m, you've added some ...


1

For starters, when we talk about voltage as energy per unit charge, is this energy manifest simply as the kinetic energy of the electron? No, not at all. Recall that, in electric circuits especially, voltage is not measured at a point (in general, the potential at a point is not physically meaningful - only the difference in potential of two points ...


1

Do not equate potential with kinetic energy. How fast electrons flow in a conductor has very little to do with their potential. You need to consider the current and the charge carrier density for that. Depending on the material you can have a few fast electrons or many more slower ones. In semiconductors the carrier velocity will be higher - which is why the ...


1

Flow is a good word. Current in a sheet is described as flow, which is the same as a field and that means in general, partial DEQs. When constrained to a wire current is like water in a pipe. You don't worry about a vector field unless you get into turbulence or some other complication. The rate alone (scalar) is good enough for a lot of problems. ...


1

Short answer is: If you heat up the whole material, then no. If you heat up the material in on end (an iron bar e.g.), then yes. The thermoelectric effect will cause a small current to flow between the two ends of different temperature. It looks like you are mistakenly assuming that electromagnetic induction causes heating, which should then be possible ...


1

To start with one could have an ac current never grounded anywhere , for a household generator for example. The reason one grounds at the generator is for safety so the ground can pick up any miss chance, as it is a practically infinite sink for electrons. Only one of the two lines can be grounded of course :). It was found though that due to capacitences ...



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