"The field due to the battery sets up a surface charge in the wire. The surface charge is negative near the negative pole of the battery, and positive near the positive terminal, and varies more or less linearly along the wire. The surface charge in turn sets up inside the wire an electric field which is constant across the diameter of the wire, and along the length. This field accelerates electrons"
If there are charges being set up in the wire, the charges (electrons) have mass and cannot move at $c$. How then do they not affect the speed of electricity and gives us its speed to be equal to $c$?
Do electrons in a wire (load) affect the speed of electricity due to their own velocity?
Think about a circuit with a 5 V battery and a very long resistor with two switches at its end. So, when both switches were open there was no charge setup inside resistors. When we close both switches then, the charge will setup and the signal travel at the speed of $c$ inside that resistor. How?
Doesn't the charge being set up and their own electric fields being created slow down the signal's speed?
Best Answer
They do affect the speed.
The speed of the signal in a cable or other communication channel is given by the velocity factor which is the speed of the signal expressed as a percentage of c. This is 100% for a radio wave in vacuum, but it is about 75% for CAT 7 twisted pair cable. The velocity factor primarily depends on the insulator rather than the conductor. So a coaxial cable with air as the insulator might propagate signals at 93% of c, while one using polyethylene might have a velocity factor of around 80%.
The velocity factor is sometimes considered to be the speed of light in the material as opposed to c which is the speed of light in vacuum. However, it is a little complicated since the structure is not just a simple homogenous material (the dielectric) but a complicated waveguide.