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Physics: Electricity

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A series of free Online High School Physics Video Lessons.

In this lesson, we will learn

  • Electric Potential
  • Electrons - Quantization of Electric Charge
  • Conductors
  • Insulators

Electric Potential

Electric potential is the ratio of electric potential energy and test charge. The concept of test charge is explained in electric fields. Positive charges prefer high electric potential while negative charges prefer low electric potential. The unit of electric potential is the volt, or 1 Joule/Coulomb.
Understanding Electric Potential and Potential Difference
A brief overview of electric potential difference and electric potential energy

Electrons - Quantization of Electric Charge

Electric charge is the transfer of electrons from one material to another. So negative charge means that there is an excess of electrons while positive charge is a deficiency of electrons. Quantization of charge means that when we say something has a given charge, we mean that that is how many times the charge of a single electron it has. Because all charges are associated with a whole electron, this is possible.

Understanding quantization of charge
This video explains how electric charge is quantized and how the smallest unit of charge is 1.6x10-19 C, or the elementary charge. Robert Millikan discovered the elementary charge using the oil drop experiment. Electrons have a negative elementary charge and protons have a positive elementary charge.


Conductors have a flow of charge through the conduction band. Metals are extremely good conductors. In general, charge congregates at sharp points. Conductivity is related to electric fields by the equation "charge flow = conductivity x electric field".
Conductors and insulators. An explanation and examples.
Why conductors allow electrons to flow

Conductors and Insulators

Insulators also called dielectrics, don't conduct charge. In insulators, there is no conduction band so charge does not move to any appreciable extent. Dielectric strength, also called breakdown voltage, is the amount of voltage you need to apply to an insulator for it to conduct electricity
Why insulators don't allow electrons to flow
This video discusses the difference between electrical conductors and electrical insulators and describes the different ways to charge them as well as how that charge behaves on them.

Try the free Mathway calculator and problem solver below to practice various math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.
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