What is the transfer speed of electricity?
Turn the switch on, the bulb lights up instantly, like the kind of electricity from the switch running to the bulb in no time at all. How fast is electricity!
Indeed like that, In the blink of an eye, you switch on the switch. The entire circuit quickly creates an electric field. There are many free electrons in the circuit. They are affected by electric fields, moving in one direction, forming an electric current. When the current passed through the bulb, the light immediately lit up. So the transmission speed of electricity is, in fact, the speed at which the electric field is formed in a circuit. It is equal to the speed of electromagnetic waves, that is, 300,000 km / s.
Here, we should not confuse the transmission speed of electricity with the electron movement speed in the conductor. Be aware that the electron’s speed moving in a certain direction in the conductor is less than 1 mm / s, even slower than the mechanism! It is like the case of a large number of people lined up in a long vertical line, with someone in front shouting “step by step” the voice command from the front to the tail only takes a little time while waiting for the team to go through it takes a very long time. Since the spreading speed of the voice chants and your walking speed were two things, the two differ greatly. The same situation is that free electrons are found everywhere; they are like hordes of people lined up in long vertical rows. The electron’s directional motion speed is similar to that of human walking. And the speed at which the electric field is created in the entire conductor is like the voice tag’s propagation speed. So, just turn on the switch. The electrons in the conductor subject to the electric field’s direction are almost simultaneously moving up, generating an electric current, making the lamp glow, not waiting for the electron to stay where the switch moves to the bulb before the light starts to glow.
We know that the electromagnetic waves emitted by radio and television stations are a kind of electromagnetic wave, with a propagation speed of 300,000 km / s. The electricity that travels in a conductor is the electric wave that travels in the conductor. The speeds of both are equal, i.e., 300,000 km / s. So why do electric waves broadcast by radio and television stations, when being spread in the air, do not need to rely on anything, and electricity must be in a closed circuit to spread, generating current electricity, make the electric light bulb light up?
That’s because their frequencies are different. Physics tells us that the electric wave’s radiant energy out of the conductor is proportional to the fourth power of the frequency. The frequency used by radio and television stations is from a few hundred kilohec or more, and the antenna easily emits electric waves. The frequency of conventional 220 V AC is only 50 Hz, much lower than the radiofrequency. So the waves in the transmission lines can not flow out but can only travel through the wires.