1. The Basic Idea Behind Current Electricity
When we talk about current electricity, we are simply talking about the movement of electric charges through a material. Every conductor (like a metal wire) already has free electrons that can move from one point to another when pushed by some driving force.
This movement of charges is what we call electric current. It is similar to water flowing through a pipe — the water moves only when there is a pressure difference. In the same way, charges move only when there is a potential difference across the ends of a conductor.
1.1. What Actually Flows in a Wire?
Inside a conductor, the particles that actually move are electrons. They are loosely bound to atoms and can drift from one point to another. When a potential difference is applied, these electrons start moving in an organised way, creating an electric current.
Even though electrons move, the direction of current is taken as the direction in which a positive charge would flow. This is called conventional current direction.
2. Why Do Charges Move?
Charges do not start moving on their own. They need a push. This push comes from an energy source such as a cell or a battery. These sources maintain a difference in electric potential between their terminals.
2.1. Electric Potential Difference (The Push)
Electric potential difference is the work done to move a unit positive charge from one point to another. It is this difference that makes charges move in a wire.
When we connect a wire across a battery, electrons inside the wire experience a force because one end becomes at a higher potential and the other at a lower potential. This force makes them flow.
2.1.1. A Quick Analogy
Imagine a water tank placed at some height. Water flows only because there is a difference in height (or pressure). Similarly, charges flow because there is a difference in electric potential.
3. What Do We Mean by Current?
Electric current tells us how fast charges are flowing. In simple terms:
Electric Current is the rate at which charge flows through a conductor.
3.1. The Mathematical Idea
The amount of charge flowing per unit time gives the current:
\( I = \dfrac{dq}{dt} \)
Here, I is current, dq is a small amount of charge, and dt is the small time interval.
3.1.1. Tiny Example
If a charge of \(2\,\text{C}\) passes through a wire in \(1\,\text{s}\), then the current is:
\( I = \dfrac{2}{1} = 2\,\text{A} \)
4. How Electricity Actually Flows
Even though electrons inside a conductor move randomly, the moment a potential difference is applied, they start drifting slowly in a particular direction. This organised movement is what forms a continuous flow of charge.
The surprising fact is: the drift speed of electrons is very slow, but the effect of electricity (like a bulb glowing) appears almost instant because the electric field inside the wire sets up very quickly.
4.1. Important Note
The wire does not carry electrons from the battery to the bulb. Instead, every part of the circuit already has charges. The electric field pushes them in an organised manner, making current appear immediately.
5. In Short — The Idea of Current Electricity
Current electricity is all about how charges move when there is a push (potential difference) applied across a conductor. Once a circuit is complete and a power source is connected, electrons drift in a systematic direction and create a steady flow of charge known as electric current.