The voltage required to light up the LED is less than 3.3V. This is often referred to as the forward voltage.

The forward voltage of my LED is 2.5V.

The Raspberry Pi's GPIO pins work at 3.3V.

My LED has a recommended forward current of 30 mA (milliamps are one-thousandth of an amp), which is the equivalent of 0.03A.

According to Ohm's Law:

R = V/I.

Pi supplies 3.3V.

the forward voltage of the LED: Total source volts - the LED volts:

3.3V - 3V = 0.3 V.

The current is the forward current of your LED. For me that is 0.03A.

by Ohm's Law:

0.3V / 0.03 A = 10Ω

Atoms are made of extremely tiny particles called protons, neutrons, and electrons.

Protons and neutrons are in the center of the atom, making up the nuleus.

Electrons surround the nucleus.

Protons have a positive charge.

Electrons have a negative charge.

Neutron is neutral.

30mA (milliamps are one thousandth of an amp), which is equivalent of 0.03A.

A battery converts chemical energy into electrical energy through a process called an electrochemical reaction.

When two different metals are immersed in a certain type of chemical, the metal atoms react with the chemical atoms to prudce charged particles.
Negative charges build up on one of the metal plats, while positive charges build up on the other metal plats.

The difference in charge across the two metal terminals (a terminal is just a piece of metal to which you can hook up wires) creates a voltage. That voltage is the force that electorons need to push them around a circuit.

To use a battery in a circuit, you connect one side of your load - for instance, a light bulb - to the negative terminal (known as the anode) and the other side of your load to the positive terminal (known as the cathode).

Your've created a path that allows the charges to move, and electrons flow from the anode, through the circuit, to the cathode.

Direct current (DC): A steady flow of electrons in one direction, with very little variation in the strength of the current. Cells (commonly knows as batteries) produce DC and most electronic circuits use DC.

Alternating current (AC): A fluctuating flow of electrons that changes direction periodically. Power companies supply AC to your electical outlets.

To electrons delivering energy to a light bulb or other device, the word "work" has real physical meaning. 

Work is a measure of the energy consumed by the device over some time when a force (voltage) is applied to a bunch of electrons in the device.

The more electrons you push, and the harder you push them, the more electrical energy is available and the more work can be done.

The total energy consumed in doing work over some period of time is known as power and is measured in watts. Power is calculated by multiplying the force (voltage) by the strength of the electron flow (current):

Power = voltage x current

The for that pushes electrons along is known as voltage, and it is measured in units called volts (abbreviated V). Apply enough voltage to a conductor, and the free electrons within it will move together in the same direction.

Voltage is electric pressure. The higher the voltage, the higher the pressure, the stronger the push.

A Coulomb, for example, is defined as the charge carried by 6.24 x 10^18 (that's 624 followed by 16 zeros) electrons. If a coulomb of charge moves past a point within a second, we say that the strength of the electric current is one ampere, or one amp (abbreviated as 1 A).

That's a whole lot of electrons at once, much more than are typically found in electronic systems.

There you'r more likely to see current measured in milliamps (mA). A milliamp is one one-thousandth of an amp.

A milliampere hour (mAh) is 1000th of an ampere hour ( Ah ). Both measures are commonly used to describe the energy charge that a battery will hold and how long a device will run before the battery needs recharging.

Insulator-Materials (such as air or plastic) that like to keep their electrons close to home are called insulators.

Conductors-Materials, such as copper, aluminum, and other metals, that contain loosely bound outer electrons are called conductors.

Electric charge is a property of certain particles, such as electrons, protons, and quarks, that describes how they interact with each other.

There are two different flavors of elctric charge, somewhat aribrarily named "positive" and "negative".

In general, particles carrying the same type of charge repel each other, whereas particles carrying different charges attract each other.

That is why electrons and protons find each other so attractive.

Quark

A quark is type of elementary particle and fundamental constituent of matter. Quarks combine to form composite particles call hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.

Electricity-do with how certain types of particles found in nature interact with each other when a bunch o them are hanging around in the same general area.

Electric charge: A fundamental property of certain particles that describes how they interact with each other. Two types:-positive and negative. Particles of the same type (positive or negative) repel each other, while particles of the opposite type at tract each other.

Electrical energy: A form of energy caused by the behavior of electrically charged particles. This is what you pay your electric company to supply.

Electric current: The flow of electrically charges particles.