Everything in the universe is either matter or energy.  We studied matter in the Chemistry unit; it is everything that we can touch, smell, taste, and see.  Energy is the ability to do work and it comes in many different forms. Forms of energy include: kinetic energy (energy of movement), light, heat, solar energy (from the Sun), geothermal energy (from the Earth), hydro power (from water falling through turbines), wind, and electricity. In order to study electricity, we have to take one more look at matter.  Do you remember what three particles make up an atom?  Protons, electrons, and neutrons.  Protons and neutrons are in the nucleus (center core) of the atom while electrons spin in energy levels (called orbits or shells) around the nucleus. Since electrons are not firmly held to the nucleus, they have the ability to leave atoms.  When electrons leave atoms, matter becomes charged.  When electrons are made to flow, electricity is generated. There are two types of electricity: static electricity and current electricity. The study of static electricity is called electrostatics.  Static electricity is when objects become charged.  The charges on these objects do not flow from one object to the other.  Objects become charged when they are rubbed together.  When two objects are rubbed together, electrons can jump from one object to the other. Current electricity is the type of electricity you are familiar with; this is when electricity flows through a specific path (called a circuit) that is usually made up of wires.  This is the type of electricity that powers electrical devices such as appliances.


Objects can exist in three different charged states: positively charged, negatively charged, or neutral (no charge). Most objects are neutral.  To understand this, let’s review the atomic particles in an atom of magnesium.  Magnesium has 12 protons (positively charged) and 12 electrons (negatively charged).  An atom of magnesium is considered neutral since (+12) + (-12) = 0 (no charge).  As soon as magnesium gains or loses electrons, it will have a charge on it.  For example, magnesium will lose two electrons to become a stable atom so that it will have 12 protons (+12) and 10 electrons (-10).

Therefore, the overall charge on an atom of magnesium that has lost two electrons is (+12) + (-10) = +2.  Therefore, magnesium is positively charged. Note that objects can only lose electrons.  Atoms are unable to lose protons because they are held very tightly within the atom’s nucleus. When two objects are rubbed together, electrons will leave one object and the other object will gain those electrons.  Therefore, every time objects are rubbed together, one will become positive and the other will become negative (since one must lose electrons and the other must gain electrons).


The Law of Electric Charges states that objects with the same charge (for example, two negatively charged objects) will always repel away from) each other while objects with different charges will always be attracted (move towards) each other.  Like charges repel, unlike charges attract. (move Neutral objects will always be attracted to positively or negatively charged objects as well.  Neutral objects will never be attracted or repelled from other neutral objects. Let’s summarize this information: Understanding the Law of Electric Charges can also help you determine the charge of unknown objects.  For example, what is/are the possible charge/s on the following unknown objects?


Once again, static electricity is when an object becomes charged (by gaining or losing electrons) from rubbing against another object.  Static electricity does not move. Current electricity is when electricity (or electrons) flow.  Current electricity travels along a path (known as a circuit) from where the electricity is generated.  For example, electricity in most of Ontario flows from Niagara Falls (where electricity is generated after water falls through turbines and powers generators) through power lines (like the ones you see in large hydro towers) to people all over North America.

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