The Science of Electricity -- The Learning Circuit 08

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Karen breaks down the science of how electricity works.  She’ll go over Coulomb’s law of electrostatic forces, use magnets to help visualize how polarity works, and break down how polarity works on an atomic level in an electrical circuit. She discusses electric current, voltage, and polarity and how it applies to a battery in a simple circuit.

We use electricity everyday in our homes. Devices plugged into the wall are powered by AC electricity.  Handheld devices like our smart phones are powered by DC electricity. Electricity for our devices comes from outlets in our walls and from batteries but how does that work?  How does electricity get from one point to another? To explain how electricity works, Karen starts with the most basic parts. Everything, all matter, is made up of atoms. Atoms are made up of particles consisting of protons and neutrons in the core, surrounded by electrons.  In an atom, protons are positively charged, while electronics are equally negatively charged.  Atoms normally contain the same number of protons and electrons.  If this is the case, these atoms are electrically neutral, having no charge.  However, this can be changed. An atom can gain or lose an electron by passing it to or from another atom.  This causes an atom to become an ion, meaning it has extra or is missing electrons.  If an ion has extra electrons it is negatively charged, while an ion with missing electrons is positively charged.  Charged ions exert force on each other.

You can look at Coulomb’s law of electrostatic forces to understand how these charges interact.  Coulombs’s law states that unlike charges attract each other whereas like charges repel each other.  Karen demonstrates this in action by using magnets.  The poles of magnets have opposing forces.  The opposing forces of the north and south poles of magnets interact the same way as the opposing forces of positive and negative ions. Coulomb’s law of electrostatic forces states that the force (F) of attraction or repulsion exerted between two charged bodies is directly proportional to the product of their charges (Q) and inversely proportional to the square of the distance (S) between them.  This means that two charged objects will repel or attract more or less proportionally to the amount of charge they have.  More charge, means a stronger charge, while less charge is a weaker force.  Once again, Karen uses magnets as a visual to understand this relationship. Karen has poured in some iron oxide power, a finer version of iron filament, into a bottle of baby oil.  The iron is attracted to the magnet. Placing the magnet to the side of the bottle allows you to see the size of the magnetic field.  The pull of the magnet is only strong enough to pull iron in at a close distance within this field.  You can also see how strength factors in, by comparing the strength of different types of magnets to the amount of charge in an atom.

Karen demonstrates how neodymium or rare earth magnets are stronger than ceramic magnets.  The rare earth magnets are only a quarter of the size of the ceramic magnets but are more than twice as strong.  They simply have more charge.  Less charge means weaker force while more charge means stronger force.  Unlike magnets, in electrical circuits, the distances are at the atomic level so you can’t even see them.  Atoms become ions when electrons pass form one atom to another.  This passing of electrons is called electric current.  Because of the way electrons are structured in an atom, electrons flow from one atom to another more easily in some substances than in others.  Substances in which electrons flow easily are called conductors while substances in which electrons do not flow easily are called insulators.

The amount of work needed for an electron to travel from one point to another is called potential energy or electric potential.  The difference in electric potential between two points is called voltage.  It’s also referred to as voltage drop, voltage difference, electromotive force, or EMF. Like magnets, batteries also have polarity. The electric potential between its positive pole and its negative pole, how much and how long the electrons will continue to flow, is the voltage of the battery. Because a circuit needs to have opposing charges to cause electrons to flow, you need to introduce something that has a polarity of an electric field. While you can use magnets to visualize how electrical polarity works, it doesn’t actually cause electrons to flow, therefore it doesn’t generate an electric current.  A battery has electrical polarity.  If you introduce a battery to circuit with an LED, the positive and negative poles of the battery will cause electrons to flow through the LED. The energy from the electrons flowing is what causes the LED to light up. That energy is the potential energy between the positive and negative ends of the battery and is measured in voltage.