Electrical Laws and Circuits

By: Daniel Christie

Electricity Terms• Electricity – a fundamental form of energy observable in positive and

negative forms that occurs naturally (as in lightning) or is produced (as in a generator) and that is expressed in terms of the movement and interaction of electrons

• Circuit - A closed path followed or capable of being followed by an electric current

• Current – Flow of electrons• Electromagnetic Fields – The coupled electric and magnetic fields that

are generated by time-varying currents and accelerated charges.• Voltage – The electromotive force that is usually measured in Volts• Induction – The production of a potential difference (voltage) across a

conductor when it is exposed to a varying magnetic field

Circuit Symbols

Transistor

Transformer

Parts of a Circuit• Diode-semiconductor which allows electricity to flow in one direction• Circuit Breaker-automatic device for stopping the flow of current in an electric

circuit as a safety measure• Conductor-substance that conducts heat, light, sound, or an electric charge• Resistor-substance that resists the passage of heat, light, or an electric charge• Transistor-component that alters the flow of an electrical current• Transformer-static electrical device that transfers energy by inductive coupling

between its winding circuits• Inductor – a passive two-terminal electrical component that stores energy in its

magnetic field• Capacitor – a passive two-terminal electrical component used to store energy in

an electric field• Switch – an electrical component that can break an electrical circuit,

interrupting the current or diverting it from one conductor to another• Power Source - a device that supplies electric power to an electrical load• Node – connection point

Diode

Circuit Breaker

Conductor

Resistor

Transistor

Transformer

Inductor

Capacitor

The Difference Between Alternating Current and Direct Current

• The Main difference between Alternating Current (AC), and Direct Current (DC) is that with AC, the voltage and current varies over time. With DC, the voltage and current stays the same. We use AC most of the time because it is the most efficient of the two, although most electronics run on DC.

The Resemblance to the Body

• The circuit is closely related to the human body for all of the wires closely resemble the arteries, capillaries, and veins. The brain, the liver, the muscles and digestive system are all fueled by the battery, the heart. If a vein is disconnected from one of the organs, then the entire body will start to shut down. The body works like this and it closely resembles the circuit. There has to be a closed circuit in order for everything to work. If the circuit is open, however, everything will start to shut off.

How it all works• An electric circuit is like a pathway made of wires that

electrons can flow through. A battery or other power source gives the force that makes the electrons move. When the electrons get to a device, they give it the power to make it work. The wire must run from the power source, to the device that will be powered, and back to the power source again to work. Circuits should also have a switch. The switch would create a gap if the switch was open and electrons wouldn’t be able to go in a loop, which is required in a circuit for it to work. If the switch were to be closed, then the electrons would go in a loop and the circuit would be working perfectly fine.

Two Basic Types of Circuits

• The Power Circuit – Transmits energy and is used in power lines to power home appliance items. In between are transistors, resistors, and capacitors.

• The Electric Circuit – Transmits information. Think about phone lines, radio, and TVs.

• Although there are two basic circuits, a true circuit must do both.

Ohm’s Law

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Figuring Ohm’s Law is simple. First, have a look at Figure 1. It doesn’t matter which way you go, only if you think that the small slightly horizontal lines equal division symbols and the vertical line equals the multiplication symbol. Next, start out with the variable that you are looking for (V=,I=,R=), then do as I previously told you to do. If you started with V, you would end up with V equaling V=I*R, or V=R*I. This is Ohm’s law put in a simpler way.

Kirchhoff’s Current Law

• Kirchhoff made two laws that affect circuits deeply. He made Kirchhoff’s Current and Voltage Laws. The Current law states that at any node in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node. Simply, this means that the sum of the currents in a network of conductors meeting point is zero.

Kirchhoff’s Voltage Law

• Kirchhoff’s Voltage law is simply stated: the directed sum of the electrical potential differences around any closed network is zero, which simply means that if you were to go around a loop counting voltages and end up back at your starting point, then the voltage would be the same as you started out with, meaning that you started out with 0 volts.

Everyday Uses for Circuits

• All electronics run on circuits. It could be as small as your phone, to as big as an Aircraft Carrier. Every few years or so, circuits are getting smaller, and smaller, and soon, probably barely noticeable. They will be needed for the future of Mankind and help us develop.

Interview• I contacted a total of 3 people, all of which did not reply and their

names will be listed below:• Robert Nilssen• Johannes Skaar• Mr. Aucoin (couldn’t find his first name)• I was thinking hard and long about who I could interview when it hit

me. I could interview my dad, not only because he is my dad, but because he was chief engineer on a ship and knew about all of this material. He was responsible for generation & distribution of electrical power (providing electricity for weapons, sensors, lights, cooking, anything that ran on electricity). A fair amount of my information came from the interview and was put in the presentation.

Experiments

• All Experiments shown will be from the “Electronic Snap Circuits” kit by elenco.

References• “Cool Circuits” By Martineau, Susan and Nick Bushell, Windmill Books, 2012• “Electric Circuit Fundamentals” By Floyd, L. Thomas, Prentice Hall, 1998• http://www.eia.gov/kids/energy.cfm?page=electricity_science-basics “Science of

Electricity” US Energy Information Administration• http://www.choptankelectric.com/kids/energyfacts.html “Energy Facts” Choptank

Electric Cooperative, 2005• http://www.sciencefairadventure.com/ProjectDetail.aspx?ProjectID=154• http://

www.engineeringinteract.org/resources/siliconspies/flash/concepts/experimenting.htm• http://users.stargate.net/~eit/kidspage.htm#harmonics• http://science.howstuffworks.com/environmental/energy/circuit.htm• http://science.howstuffworks.com/environmental/energy/inside-transformer.htm• http://electronics.howstuffworks.com/circuit-breaker.htm• http://people.usd.edu/~schieber/psyc770/resistors/ohms4beginner.html• http://kids.discovery.com/tell-me/curiosity-corner/science/how-do-electric-circuits-wor

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Last Statements

• I don’t really know why, exactly I chose this topic. I thought it would be kind of fun, but later found out that it was a pain and took lots of time researching and trying to find out what in the world these electric laws meant. I would like to point out that there is much, much more on circuits out there. This is mostly just a simplified topic that I did. I hope you enjoy the upcoming demonstration.

Questions?