Electric Charge
o Two kinds of electric charge: positive and negative
o Like charges repel; opposite charges attract
o Force is stronger when charges are close
o “neutral” matter is made of + and – charges!
o Friction can separate these charges
o Charge is free to move around in a conductor, its stuck in place on an insulator
o Unit of charge is the coulomb [C]
o Charge of electron (negative) or proton (positive) is
o ±𝑒, 𝑒 = 1.602 ∗ 10−19 𝐶
o Charge is quantized and conserved (can’t be created/destroyed)
o 𝑄 = ±𝑁𝑒
o Neutral matter is made of + and – charges in equal numbers. We say it has no net charge
Vectors
o A quantity that is fully described by a single number is called a scalar quantity (i.e., mass,
temperature, volume)
o A quantity having both a magnitude and a direction is called a vector quantity
o The geometric representation of a vector is an arrow with the tail of the arrow placed at
the point where the measurement is made
o We label vectors by drawing a small arrow over the letter that represents the vector