We take electricity for granted these days. But think of everything we do with electricity. We cook our food, light our homes, keep our families warm with it. It powers our vehicles. And it keeps many of our waking hours filled with entertainment. But do you know how electricity works?
Electricity is one of most of the impactful technologies to human existence.
How does electricity work?
Is the electric shock we receive from staticky socks the same as power coming into our television and computer? If they aren’t, how do they relate to each other? And what about batteries? Also, how does the power stored there relate to those other kinds of power?
In simplest terms, the power in your socks, in batteries, and coming into your home are all the same. Each one has electric current moving particles from areas of a different charge. It doesn’t matter whether we’re talking about annoying static, a charge hidden in batteries, or high voltage lines. In each case, there is a discharge occurring as the system tries to find a balance between positively and negatively charged electrons. Read more below.
What is Current
Electrical current refers to the flow of an electrical charge. The currents we use today are one of two types: direct current (DC) or alternating current (AC.) The names of the currents are big hints about how they act. Direct current flows in only one direction, while alternating current changes direction. Batteries are examples of DC current. However, DC current is not efficient over long distances. And we use AC current for high voltages that are capable of long transmission distances.
Series and Parallel Circuits
Most electrical circuits are series or parallel circuits.
In a series circuit, the current flowing through each component is the same., The voltage across the circuit is the sum of the voltage drops across each component.
If you’ve ever had old-fashioned Christmas lights where, when one bulb goes out the whole string goes out, that is an example of a series circuit. When one device in the circuit breaks, the entire circuit stops working.
A series circuit with three resistance units and a single voltage source.
Current in series circuits can be found through I=I1=I2=….In, as the current is the same for all elements.
Voltage in a series circuit can be found through V=V 1 +V2…+Vn as the voltage is the sum of voltage drops of each individual component.
When two or more components connect in parallel, they have the same difference of voltage from end-point to end-point. This creates a parallel circuit. The total current of a parallel circuit is the sum of the currents through the individual components. This is known as Kirchhoff’s Current Law(see below.)
Voltage of a parallel circuit can be found through
V = V1 = V2 = … Vn, as voltage is the same across the circuit
Current can be found using Ohms Law (see below.)
Ohm’s Law
Ohm’s law is one of the most fundamental laws of electricity. It states V=IR. Translated, this means the voltage is equal to current, which is measured in Amperes, times Resistance, which is measured in Ohms, represented by Ω.
- Voltage is the difference in electric potential between two reference points.
- Amperes or Amps are units of electric current. Each Amp is equal to a flow of one coulomb per second.
- Resistance is a measure of how the material restricts or allows an electric current to flow through it.
Resistance in a circuit creates friction, which produces heat. Everyone reading this has seen resistance in action, in the form of a light bulb. When the bulb’s filament heats up, it also creates light.
This friction/heat connection is also evident in resistors. Resistors are commonly used on circuit boards to reduce current flow or adjust signal levels. Secondarily, they produce heat. This partially explains why your laptop gets so warm.
We have a whole post on resistors and how to determine their value using their color bands.
Impedance in an AC current is typically expressed as a complex number Z. Z=R+jX, where R stands for the resistance of the load and X is its reactance. Impedance is the AC equivalent of resistance and is used in the AC version of Ohm’s Law:
Vcomplex= IcomplexZ
Impedance is also measured in Ohms (Ω).
People you Should Know
Here’s a list of some important people to know when it comes to electricity.
- Benjamin Franklin (1706-1790) American polymath, statesman, and scientist, Franklin conducted many experiments on electricity and invented the lightning rod.
- Alessandro Volta (1745-1827) A physics professor, Volta invented the first electric battery.
- Andre-Marie Ampere (1775-1836) A French physicist who invented both the solenoid and the electrical telegraph.
- Michael Faraday (1791-1867) English scientist who studied electromagnetism and electrochemistry. An early experiment on static electricity with an ice pail led to a shielding effect now known as a Faraday cage.
- Ernst Werner Siemens (1816-1892) German electrical engineer and industrialist. His name (siemens) is a unit of electric conductance that is redundantly equal to the reciprocal of one ohm ( S (= Ω−1).)
- James Prescott Joule (1818-1889) English physicist who studied the nature of heat and its relationship to mechanical energy. Helped develop the first law of thermodynamics.
- William Thomson, 1st Baron Kelvin (1824-1907) Irish-Scottish physicist and engineer who helped formulate the first and second laws of thermodynamics.
- George Westinghouse (1846-1914) American businessman and engineer who patented the first practical transformer to “step up” and “step down” AC power.
- Thomas Alva Edison (1847-1931) American inventor known for multiple inventions including the light bulb. He also developed direct current (DC) power delivery systems. AC systems eventually replaced DC power delivery systems.
- Nikola Tesla (1856-1943) Serbian-American inventor, mechanical engineer, and electrical engineer. Tesla created the modern alternating current (AC) electricity supply system we use today.
For more study about electricity, consider learning about:
- Kirchoff’s Current Law (KCL)
- Kirchoff’s Voltage Law (KVL)
- Transformers
- Ampere’s circuital law
- Watt’s Law
- Faraday’s Law
- Right-hand rule
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