ch32_eawf

32.1 Electrical Forces and Charges Chapter 32 is about **electrostatics**, or electric forces at rest**. Electrical forces** are billions of times stronger than gravitational forces, however unlike gravity, there is an opposite force acting on you the same time, repelling the first force. Electrical forces arise from atoms- electrons attract protons but repel other electrons. This behavior is known as **charge**. Electrons are negatively charged while protons are positively charged, and like particles repel while opposite particles attract to one another. 32.2 Conservation of Charge

Based on the net number of protons/electrons, an atom is neutral, positive, or negative. A charged atom is called an ion. Even if an atom looses or gains an electron or proton, they are not created or destroyed. **Conservation of charge** applies meaning an electrical charge cannot be created or destroyed.

32.3 Coulomb’s Law

Electrical force between any two objects is similar to the inverse square relationship with gravity. This is known as **Coulomb’s Law** which states that for charged particles or objects that are small compared to the distance between them, the force between the charges varies directly as the product of the charges and inversely as the square of the distance between them. Or mathematically: F = k (q1∙q2 / d^2) D is the distance between charged particles, q1 represents the quantity or charge of one particle along with q2, and k is the proportionality constant. In scientific notation, k = 9.0 x 10^9 N∙m^2/C^2. 32.4 Conductors and Insulators

Since electrons are not anchored to the nucleus in some materials like most sub atomic particles, they roam freely through the material. These are good **conductors**. Metals are good conductors because their electrons are loose. But in other material, such as wood glass or rubber, electrons are not free to move making them good **insulators**. Whether an item is a conductor or an insulator depends on how tightly their electrons are held, but when an item is altered such as silicone which is a good insulator in its pure crystalline form, and an electron is added the conductivity increases ten million fold. These are called **semiconductors**. At temperatures near absolute zero, certain materials can conduct infinitely creating **SUPERCONDUCTERS!**

32.5 Charging by Friction and Contact

Electrons can be transferred from one object to another through contact – called charging by contact. If it is a good conductor the charge will spread throughout, but if it is an insulator, it may have to be touched a few times along the surface to create a universal charge throughout. 32.6 Charging by Induction

Changing an electric charge without touching an object with another is called **induction**. Since every electrical force needs an opposite and equal force, induction can positively and negatively charge multiple objects. The charge can be indefinitely held or transferred, but when it comes into contact with an object that has a practically infinite potential for holding a charge, the ground, the object loses it’s charge. This is known as **grounding** an object.

32.7 Charge Polarization

In insulators, there are no free electrons to migrate throughout the material. But the material instead rearranges of positions of charges within the atoms. One side is induced as positive, the other negative. If one side is slightly more than the other the object is said to be **electrically polarized.** This explains why paper can be attracted to another object. Another common example is if you were to rub a balloon on your head and hang it on the wall.