Just need a clarification here, how the current is produced due to the movement of electrons, in an external circuit,having a very slow drift speed.
Normally in a battery there is high potential terminal and low potential. Using these two terminals the external circuit is closed. Now within the battery the direction of the current flow and the electron flow is opposite to that of the external circuit. If I consider that positive current is flowing from the positive terminal to the negative terminal of the battery through the external circuit then we can say that positive terminal is at higher potential then the negative terminal of the battery.
Now when we are closing the switch of an external circuit, in that case the electrons are moving from negative terminal to positive terminal of the battery, through the external circuit. But we also know that the drift speed is very slow, of the electron. But when we
switch on some of the electrical devices, within a fraction of second the device starts working. If drift sped of electron is low, so how the device is working so fast ,(near about the speed of light,I guess), as we know that current flows due to the flow of the electrons.So how it is possible, in spite of electrons are having such a low drift speed ?
Please help me guys !!!!!
Best Answer
Am I correct that you can rephrase your question to 'electrons move so slow, how come that when I flip the light switch the light comes on basically instantly?'?
It's true that the electrons travel very slowly. But these electrons don't have to travel across the wire to power your light bulb.
In electromagnetism, we have the continuity equation $\nabla J = 0$. It says that current can't 'heap up' somewhere in the wire. So when you flip the switch, all electrons in the wire start moving simultaneously.
It's analogous to a bicycle - when you start pedalling, the entire chain starts moving rather than the links closest to the pedals.