What is Electricity? Electrons, Charge, and Current
The Atom: Where It All Begins
Everything around us — air, iron, water, your body — is made of atoms. An atom is the smallest building block of matter, composed of:
- Protons: positively charged particles in the nucleus
- Neutrons: neutral particles in the nucleus
- Electrons: negatively charged particles orbiting the nucleus
In a neutral atom, the number of protons equals the number of electrons.
The Electron: The Star of the Show
The electron makes electricity possible because it is:
- Extremely light: 1/1836 the mass of a proton — easy to move
- Loosely bound in metals: outer electrons can detach and drift freely between atoms
- Field-sensitive: electric fields push electrons into directed, organized motion
In metals like copper and aluminum, outer electrons form a "sea" that floats freely between atoms. This is why metals are good conductors. Insulators like rubber hold electrons tightly — no current can flow. Semiconductors like silicon sit in between and can be controlled — the foundation of all transistors and computer chips.
Electric Current: Flowing Electrons
When an electric field is applied across a conductor, electrons stop wandering randomly and drift in one direction. This organized flow is electric current.
Unit: Ampere (A) — 1 A = 1 coulomb of charge per second passing a point
Historical note: by convention current flows from positive (+) to negative (-), but electrons actually move the other way. This convention dates to Benjamin Franklin, before electrons were discovered.
Voltage: The Driving Force
Voltage is the difference in electric potential energy between two points — the "pressure" that pushes electrons through a conductor.
Unit: Volt (V)
Common voltages:
- AA battery: 1.5 V
- Car battery: 12 V
- Household outlet: 110–240 V
- Industrial high-voltage line: 11,000–400,000 V
Resistance: The Opposition
Resistance measures how hard it is for current to flow through a material.
Unit: Ohm (Ω)
Resistance increases with: longer wire, thinner wire, higher temperature, and more insulating material composition.
Ohm's Law: The Master Equation
German physicist Georg Ohm discovered in 1827:
V = I × R
Where V = voltage (volts), I = current (amperes), R = resistance (ohms).
Examples:
- 10 Ω resistor on a 5 V battery: I = 5/10 = 0.5 A
- Need 2 A from 12 V: R = 12/2 = 6 Ω
Series vs Parallel Circuits
Series: same current through all elements, voltage splits. Total R = R1 + R2 + ...
Parallel: same voltage across all elements, current splits. 1/R_total = 1/R1 + 1/R2 + ...
Home appliances are wired in parallel so each gets the full mains voltage regardless of others.
Electric Power
P = V × I (Watts)
A 60 W bulb at 220 V draws 60/220 ≈ 0.27 A. A 3 kW motor at 380 V draws 3000/380 ≈ 7.9 A.
AC vs DC
- DC: electrons flow in one direction — batteries, solar panels, electronics.
- AC: electrons oscillate back and forth at a fixed frequency (50 or 60 Hz) — the power grid. AC is easier to transmit over long distances using transformers.
Summary
Electricity is electrons moving through conductors under voltage pressure, opposed by resistance. Ohm's Law ties all three together and is the foundation of every electrical device ever built — from a simple light bulb to a processor with billions of transistors.