Electricity Study Guide

Electric current is a fundamental concept in physics, representing the rate at which electric charge flows past a point in a circuit. Imagine a hosepipe through which water is flowing; the current is like the amount of water passing a certain point per second. In electrical conductors, this charge is primarily carried by tiny particles called electrons. These electrons are negatively charged and are free to move within the material. When a potential difference (voltage) is applied across a conductor, it creates an electric field that pushes these free electrons, causing them to drift in a particular direction. This organised movement of electrons constitutes the electric current.

For charge to flow, two critical conditions must be met. Firstly, there must be a complete circuit. A circuit is like a continuous loop that allows electrons to travel from one terminal of a power source, through the components, and back to the other terminal. If there is any break or gap in the circuit, the flow of charge will stop. Secondly, there must be a source of potential difference, often called voltage, which provides the 'push' needed to make the charges move. This potential difference is supplied by components like batteries or power supplies. Without a potential difference, even in a complete circuit, the electrons would simply move randomly within the material without any net directional flow, meaning no current would be produced. Therefore, a complete circuit and a potential difference are essential for electric current to exist.

In a series circuit, all components are connected end-to-end, forming a single path for the electricity to flow. Imagine electrons as tiny cars moving along a single-lane road. If one car stops, all the cars behind it stop. Similarly, if one component in a series circuit breaks, the entire circuit is broken, and current stops flowing. Crucially, the amount of current flowing through every component in a series circuit is the same. This is because electric charge is conserved. Charge cannot be created or destroyed, nor can it accumulate at any point within a closed loop. Therefore, the rate at which charge flows (which is what current is) must be constant throughout the entire loop. If 2 Amperes (A) of current enter a resistor, then 2 Amperes must also leave it and continue flowing to the next component, and so on, until it returns to the power source. This principle is fundamental to understanding how series circuits behave and is a key concept in electrical circuits. This is why if you add more components in series, the total resistance increases, causing the total current to decrease, but the current through *each* component remains identical to the total current in that single loop.