Physics
Electrical Circuits
Quick fact
In a typical copper wire, electrons drift at a snail's pace—about 0.1 millimeters per second—yet the light turns on almost instantly because the energy travels via the electric field near the speed of light.
Why this is interesting
You flip a switch and a light bulb instantly glows—but what is actually happening inside that closed loop?
Read the full explanation
Understanding Electrical Circuits
Think of an electrical circuit like a water fountain. The pump (battery) creates pressure (voltage) that pushes water (electrons) through pipes (wires). The water flows through a closed loop back to the pump. If you block the pipe (break the circuit), the flow stops. The water wheel (light bulb) turns because of the moving water. In a circuit, electrons flow from the negative terminal of the battery, through the wires and components (like a resistor or bulb), and back to the positive terminal. This continuous path is the circuit. The flow of electrons is called current, measured in amperes. The 'push' that drives them is voltage, measured in volts. Any opposition to flow is resistance, measured in ohms.
A deeper explanation
A circuit works because of a fundamental principle: electrons move when there is a difference in electric potential (voltage) across a closed path. The source (e.g., a battery) provides this potential difference, creating an electric field that pushes electrons through the conductor. The field propagates almost instantly, so even though electrons drift slowly, the signal—the instruction to start moving—travels at nearly the speed of light. The circuit must be closed (a continuous loop) for electrons to flow from the source and return; an open circuit breaks the path and stops current. Components like resistors add controlled resistance, converting electrical energy into heat or light, while loads (like motors or LEDs) use the energy to do work. Without a closed loop, no steady current can exist, which is why switches are used to open and close the path deliberately.