Electrical Theory

Electricity is a form of energy that can be used by electrical devices to perform work For electricity to flow there must be a circuit An electrical circuit contains, at minimum, a voltage source, a load, and conductors to carry the electrical current The atomic theory explains the construction and behavior of atoms

The atom is the smallest part of an element that enters into a chemical change, but it does so in the form of a charged particle – these particles are called ions There are positive and negative ions Positive is positively charged Negative is negatively charged They repel each other

A proton is positively charged An electron is negatively charged Protons repel protons Electrons repel electrons Protons attract electrons The outer shell of an atom is called the valence shell

Electrons found in the valence shell are called valence electrons These electrons determine an atoms ability to gain or lose electrons Valence electrons are most concerned with electricity because they are the easiest to break loose from their parent atom

Conductors – easily conduct the flow of electricity - usually have three or less valence electrons Insulators – do not conduct electricity to a great degree – usually have five or more valence electrons Transformers – step the voltage down to lower levels

Voltage we get at home (from the power company) is usually about 220 volts At wall outlets the voltage is about 120 volts The basic unit that current is measured is ampere or amp (A) The force that causes electrons to move is called voltage or volts (V)

Resistance is an opposition to current A resistor is a device that resists current flow Resistance is measured in ohms (R) Ohm’s law defines the relationship between current, voltage, and resistance

Series circuit - provides only one path for current flow and is a voltage divider – one goes out they all go out Parallel circuit – each load is connected directly to the voltage source – the voltage is the same through all loads and current is divided between the loads – one goes out others stay on

Kirchhoff’s voltage law states that the algebraic sum of the voltages around any closed path is zero The sum of the voltage drops around the circuit must equal the voltage applied to the circuit