There is some confusion here:
What is measured in Amperes is NOT the speed of electricity but the intensity of the current, proportional to the number of electrons per second . If a four-lane highway allows twice as many cars per minute to enter the city than a two-lane highway would, this means twice as many "Amperes", yet the cars don't run faster. Also, an electromagnetic wave is NOT the same as electricity.
While the speed of an electrical signal is generally close to the speed of light, the speed of individual electrons depends on the medium but also on the strength of electrical field, which is proportional to the force that the field exites on each electron. Imagine an astronaut on the moon (or Earth) that lets a metal ball fall in a glass of honey (or water). The thickness of the honey slows the ball, but also the Earth's strong gravitational field makes the balls fall faster on Earth.
To compute the strength of the field, divide the voltage with the length of the wire. If the cable for your desktop lamp is two meters and the voltage is 110 Volt, the field strength is 110/2=55 Volts per meter. A Volt per meter is 0.00000000000000000016 Newton per electron.
You can get these figures with google calculator, e.g. "1 (electron volt per meter) in newtons". If you want American units, you can Google on e.g. "1 (electron volt per foot) in pound force"