Basic Concepts

Electricity is the form of energy that results from the presence and flow of electrons. An electric circuit is a closed pathway or loop that allows electric charge to flow from one point to another. It consists of various electrical components, such as wires, resistors, capacitors, inductors, switches, and more, connected in a specific arrangement.

In order to understand electricity and electrical circuits, there are a few basic concepts to grasp.

Electric Charge

An electric charge is the fundamental property of matter that results from an imbalance in the number of negatively charged electrons and positively charge protons within an object. Objects can carry a positive, negative, or neutral charge depending on the balance of electrons and protons.

Electric charges alone produce electric fields, and moving electric charges additionally produce magnetic fields.

Electric charge is measured in units of coulombs ($C$), which is defined as the amount of charge 1 amp delivers in 1 second. It is equal to the charge of $6.242 \times 10^{18}$ electrons.

Voltage

Voltage, often referred to as electric potential or electromotive force (EMF), is a measure of the difference in potential energy between two points.

Voltage is measured in volts ($V$) and is the force that causes electric charges to move in a circuit.

Current

Electric current is the flow of electric charge through a conductor.

By convention, current is said to flow from points of higher voltage to points of lower voltage. In actuality, electrons flow in the opposite direction, but conventional current flow remains the convention used by scientists and engineers today.

Current is measured in amperes ($A$, also called amps) and represents the rate at which charge moves through a circuit.

Resistance

Resistance is the property of a material to oppose the flow of electric current.

Resistance is measured in units of ohms ($\Omega$) and represents how much opposition is present against a current.