Electricity, Voltage, Current and Resistance

Electricity is the movement of electric charges and is part of electromagnetism. It allows us to use appliances such as defibrillators and batteries.

People often take electricity for granted, but it’s important to understand how it works. This way, we can better utilize it. Here are some of the basics:.

Voltage

Voltage is the “pressure” that makes electricity flow. It’s the energy difference between two points, measured in units called volts (or sometimes joules per coulomb).

Voltage generates the flow of electrons (electric current) in a circuit. It can either be direct, with the same polarity at all times, or alternating, with its polarity changing each second.

Electrical current flows from higher voltage to lower voltage, as shown in the diagram below. The resulting circuit has energy (power) equal to the product of current and voltage, which is called Ohm’s Law.

Electrical current at high levels can cause serious burns. This type of injury is often referred to as an electric shock. It can also result in medical and surgical problems that require monitoring over time, such as myoglobinuria, coagulopathy, and compartment syndromes. High voltage can also break down insulation, which is why special shoes, gloves, and tools are rated for specific voltage levels. The insulator must be able to resist the flow of electricity, and this resistance is usually indicated by an ampere rating.

Current

Current is the flow of electric charge and is measured in amperes. Current is important to understand because it affects the electrical system and is one of the causes of faults.

When a current flows through a conductor, it creates an electric field which forces free electrons to drift toward the positive terminal of the source. This is known as the “skin effect” and is one of the reasons why current density varies over the surface of a conductor.

Unlike voltage, which is stable over time, current is only an instantaneous value. This means that when you read a current measurement, you must use the lower-case letter “i” to symbolize that value as an instantaneous value rather than a constant (capital letters are used for variables that remain stable over time). In most cases, direct current will be described as having an instantaneous value of a coulomb of charge. This is because DC measurements are often made from very small time intervals.

Resistance

Resistance is a measure of how difficult it is for current to flow through a conductor. It is inversely proportional to the voltage in the circuit and directly proportional to the current density. It is expressed in ohms, named after German physicist Georg Simon Ohm who established the relationship between voltage, current and resistance.

Conductors that offer very little resistance to the flow of electrons are called conductors, while those that impede the flow of electrons more than others are known as insulators. In some cases, a substance’s resistance can be so high that it prevents current flow altogether.

Resistance is related to the geometry and material of a conductor, but it also depends on temperature. As the temperature of a conductor increases, its resistance tends to increase as well. The amount of energy required to move electrons through a conductor is also dependent on its resistance and can be used to determine the electrical properties of a material.

Power

The power system balances supply and demand in a vast network that is out of sight for most people. Yet, without it, our modern lives would be unrecognisable.

Over the past decade, the combination of weak economic recovery and stronger policies on energy efficiency has led to weaker-than-expected electricity demand in advanced economies. This has weakened the ability of utilities to invest in generation and transmission infrastructure with confidence about their returns.

Long rationing periods occur when systems operators have to reduce electricity supplies on a planned basis due to large deficits of power supply to meet demand. Examples include the rationing in Brazil following drought and the supply disruptions in Japan after the earthquake.

Voltage spikes are a significant threat to computers and other electronic devices. They occur when the voltage rises above a materials breakdown voltage and can damage circuitry. Star Plus Electrical