1. How Slowly Do the Particles in a Wire Really Move?
In a copper wire, some electrons are free to wander between the copper atoms, while the atoms themselves stay in place [1]. When a current flows, these free electrons slowly drift in one direction. The average drift speed depends on how many electrons are available, how thick the wire is, and how much current you push through.
Using the formula for drift speed and a typical textbook figure of about 8.5 × 1028 free electrons per cubic meter of copper (an assumed value, not one I checked on that page), I worked out an example: a wire with a cross-section of 1 square millimeter carrying 1 ampere has electrons drifting at about 0.07 millimeters per second. At that pace, an electron would need roughly four hours to travel one meter. (The formula is from the HyperPhysics page [1]; the number for this wire is my own calculation, so treat it as a typical size rather than a measured record.)
The wires in a house may be a different thickness from the wire in this example, and a hair dryer pulls far more current than 1 ampere. But the lesson holds: the drift is slow. HyperPhysics puts it plainly. Your light turns on very quickly when you flip the switch, yet the actual drift speed of electrons through copper wires is very slow [1].
Wall outlets add another twist. Many countries supply alternating current, which reverses direction many times each second (more on that in section 4). With such a current, each electron mostly shuffles back and forth in place rather than traveling toward your lamp.
2. Why the Light Still Comes On Right Away: The Push Arrives Long Before the Particles
The answer is that the wire already contains free electrons along its length, and so does the bulb's filament, before you touch the switch. What travels fast is not an electron from the power plant. It is the change, the "signal," that tells all the electrons to start moving. HyperPhysics says this signal propagates along wires at essentially the speed of light [1].
A garden hose gives a rough picture. If the hose is already full of water, turning on the tap makes water come out of the far end almost at once, even though any single drop moves slowly. The push passes along the water much faster than the water itself moves. This is only an analogy: electrons are not water, and the energy of electricity is carried in a more complicated way than the hose suggests. But it shows how a quick effect can come from slow movers.
That leaves a bigger question. If the electrons are already in the wire, what is pushing them?
3. Where Does the Push Come From? Faraday Found That Moving a Magnet Can Do It
For years in the 1820s, the English scientist Michael Faraday tried to find out how to make electricity from magnetism. He succeeded on 29 August 1831, in his basement laboratory at the Royal Institution in London [2].
His apparatus was an iron ring with two separate coils of insulated copper wire wound on opposite sides. When he sent a current through one coil, a current appeared in the other coil, but only for a very brief moment [2]. The ring made the effect easy to see, and the lesson was surprising: a steady current in one coil did nothing to the other. A change was needed.
A few months later, in October 1831, Faraday built a simpler device based on this idea. It used a coil of wire and a bar magnet. When he moved the magnet back and forth through the coil, the needle of a current-detecting instrument called a galvanometer jumped, showing that a current was flowing. The Royal Institution notes that the same apparatus would light a bulb if you swapped the galvanometer for one [3].
That is the heart of nearly all electric power today. The Royal Institution says virtually all electric power is produced using Faraday's principles. Whether the original energy source is coal, oil, gas, nuclear, hydro or wind, the fuel is used to drive a generator, which makes the current [3]. In plain terms, a power plant is mostly a way to keep a magnet and a coil moving past each other. The push on the electrons in your house starts there.
4. Why Power Plants Must Make Electricity at the Same Moment You Use It
Here is a catch. Electricity is, by its nature, hard to store in large amounts, so supply has to match demand very closely at every moment [4]. This job is called grid balancing. When you plug in a kettle or switch on a lamp, the grid as a whole has to supply that little extra, almost immediately.
On an alternating-current grid, frequency is a way to see whether the balance is right. The current's frequency, the number of times per second it reverses direction, is tied to how fast the generators spin. As long as supply and demand are in balance, the frequency stays steady at its target, which is 50 or 60 hertz depending on the country. When there is a mismatch, the generators speed up or slow down a little, and the frequency rises or falls [4].
The frequency cannot drift too far. According to the source, many units of electrical equipment can be damaged by a frequency that is out of bounds, so they disconnect automatically to protect themselves, which can potentially trigger a blackout [4]. Unlike water stored in a reservoir, electricity on the grid has to be generated about as fast as it is used. The people who run a grid are always adjusting the amount made to match the amount used.
5. Why Outlets and Plugs Are Different in Other Countries
The electricity at the outlet differs around the world. According to a table compiled from national standards, most of the world gets a supply of 220 to 240 volts at 50 hertz. Some places, including the United States, instead use about 120 volts at 60 hertz. Plug and socket shapes vary too, and the table cautions that a plug fitting a socket does not guarantee the voltage, frequency or grounding will match [5].
For that reason, many phone chargers are built to accept a wide range of input voltages, and the label says so. A device that works at only one voltage can be damaged or become unsafe if plugged into the wrong one. Whether a given device can travel is written on the device itself.
6. How You Can Check This Yourself Safely
With an adult, take a phone charger that is unplugged and cool, and look at the tiny print on its body. Find the line marked "Input." It lists the voltage range it accepts, such as "100-240V," and the frequency, such as "50-60Hz." Do not open the charger, and do not touch plugs with wet hands. Leave appliances such as refrigerators plugged in.
Then look for a number followed by "W" (watts) on a kettle, a hair dryer and a lamp. When an appliance runs as rated, a larger number means it uses electrical energy faster, that is, more each second. If you want to read more, the Royal Institution pages on Faraday's apparatus [2] [3] are a good place to see where the idea began.