# Current, Voltage and Resistance

Understanding Electricity

## What is Current?

An electrical phenomenon is caused by the flow of free electrons from one atom to another. The characteristics of current electricity are opposite to those of static electricity.

Wires are made up of conductors such as copper or aluminum. Atoms of metal are made up of free electrons, which freely move from one atom to the next. If an electron is added in the wire, a free electron is attracted to a proton to be neutral. Forcing electrons out of their orbits can cause a lack of electrons. Electrons, which continuously move in the wire, are called Electric Current. For solid conductors, electric current refers to directional negative-to-positive electrons from one atom to the next. Liquid conductors and gas conductors, electric current refers to electrons and protons flow in the opposite direction.

Current is the flow of electrons, but current and electron flow in the opposite direction. Current flows from negative to positive. Current is determined by the number of electrons passing through a cross-section of a conductor in one second. Current is measured in amperes, which is abbreviated “amps”. The symbol for amps is a letter “A”.

A current of one amp means that current pass through a cross-section of two conductors, which are placed in parallel 1 meter apart with 2×10-7 Newton per meter force occur in each conductor. It can also mean charges of one coulomb (or 6.24×1018 electrons) passing through a cross-section of a conductor in one second.

## What is voltage?

Electric current is the flow of electrons in a conductor. The force required to make the current flow through a conductor is called voltage and potential is the other term of voltage. For example, the first element has more positive charges, so it has higher potential. On the other hand, the second element has charges that are more negative so it has the lower potential. The difference between two points is called potential difference. Electromotive force means the force which makes current continuously flows through a conductor. This force can be generated from the power generator, battery, flashlight battery, and fuel cell, etc.

Volt abbreviated “V”, is the unit of measurement used interchangeably for voltage, potential, and electromotive force. One volt means a force which makes the current of one amp move through a resistance of one ohm

## What is resistance?

Electrons move through a conductor when electric current flows. All materials impede the flow of electric current to some extent. This characteristic is called resistance. Resistance increases with an increase of length or decrease of the cross-section of a material.

The unit of measurement for resistance is ohms and its symbol is the Greek letter omega (Ω). The resistance of one ohm means a conductor allows a current of one amp to flow with a voltage of one volt.

All materials are the difference in allowing electrons flow. Materials that allow many electrons to flow freely are called conductors such as copper, silver, aluminum, hydrochloric solution, sulphuric acid, and saltwater. In contrast, materials which allow few electrons to flow are called insulators such as plastic, rubber, glass and dry paper. Another type of materials, semiconductors have characteristics of both conductors and insulators. They allow electrons to move while being able to control the flow of electrons and examples are carbon, silicon, and germanium, etc.

The resistance of the conductor depends on two main factors as the followings:

1.             Types of material
2.             Temperature of material